DoEasy 函数库中的图形（第七十五部分）：处理基本图形元素图元和文本的方法

MetaTrader 5 — 示例 | 29 七月 2021, 13:36

1 879

Artyom Trishkin

内容

概述

我继续开发基本图形元素对象类，用作创建更复杂函数库图形对象的基础。在上一篇文章中，我提出了构建基准图形对象的概念，创建了图形元素，并已赋予它设置、修改和接收的基本属性。
由于 CCanvas 类意为在“在画布上”绘图，因此它提供了处理图形基元和文本的方法。在本文中，我将创建元素对象方法，允许我们访问和处理绘图的 CCanvas 类方法。这些方法很简单。它们将用于在元素对象类的衍生后代对象中创建高级绘图方法。

除了创建操控基元的方法之外，我还将创建操控文件的方法。我们的图形对象是自定义程序的 GUI 元素，理应“记住”它们在图表上的属性、状态和位置，例如在切换到另一个时间帧时。为达此目的，我将对象属性保存到文件中。而在构造对象时，会从文件中读取属性。不过，由于文件应在图形对象集合类中处理，而我尚未开发它，我将简单地添加保存和上传图形对象属性的方法。而在创建图形对象集合类时，我们将会用到此处为图形元素对象开发的保存和上传属性的方法。

此外，我将需要操控颜色的类。我打算把它添加到函数库之中。
该类将取自 Dmitry Fedoseev 开发并提交至 MQL5.com 代码库社区的代码。

最终结果是图形元素会准备好，可作为将来利用函数库图形对象的基础。

改进库类

如果我们需要清除一个带有透明度的 CCanvas 类对象，我们应调用 Erase() 方法，默认接收零：

   //--- clear/fill color
   void              Erase(const uint clr=0);

在我们的例子中，这是一个不正确的解决方案。在用零值清除画布时，我们看不到它的 alpha 通道（颜色透明度通道），这会最终导致以这种方式清除 alpha 通道的情况下，在画布上绘图时会出现残影。
为了清除画布的 alpha 通道，需用 0x00FFFFFF 替代零值。
这是 ARGB 格式的完全透明的黑色（Alpha = 0，Red = 255，Green = 255，Blue = 255）。

在 \MQL5\Include\DoEasy\Defines.mqh 里，添加指定此类颜色的宏替换：

//--- Canvas parameters
#define PAUSE_FOR_CANV_UPDATE          (16)                       // Canvas update frequency
#define NULL_COLOR                     (0x00FFFFFF)               // Zero for the canvas with the alpha channel
//+------------------------------------------------------------------+

当利用 TextOut() 方法在画布上显示文本时，我们可以设置文本消息的锚点角度（文本对齐点）— 矩形边界，相对于消息的定位。需要用六个标志来设置锚点 — 两两标志的组合，所有这些都如下所列：

水平文本对齐标志：

TA_LEFT — 矩形边界左侧的锚点
TA_CENTER — 矩形边界中间的水平锚点
TA_RIGHT — 矩形边界右侧的锚点

垂直文本对齐标志：

TA_TOP — 矩形边界顶部的锚点
TA_VCENTER — 矩形边界中间的锚点
TA_BOTTOM — 矩形边界底部的锚点

这些标志的可能组合，和设置锚点的方法如下所示：

为了避免混淆哪个标志先出现，只需设置一个自定义枚举，指定所有可能的标志组合，以及相对于其锚点的文本对齐：

//+------------------------------------------------------------------+
//| Data for handling graphical elements                             |
//+------------------------------------------------------------------+
//+------------------------------------------------------------------+
//| List of anchoring methods                                        |
//| (horizontal and vertical text alignment)                         |
//+------------------------------------------------------------------+
enum ENUM_TEXT_ANCHOR
  {
   TEXT_ANCHOR_LEFT_TOP       =  0,                   // Text anchor point at the upper left corner of the bounding rectangle
   TEXT_ANCHOR_CENTER_TOP     =  1,                   // Text anchor point at the top center side of the bounding rectangle
   TEXT_ANCHOR_RIGHT_TOP      =  2,                   // Text anchor point at the upper right corner of the bounding rectangle
   TEXT_ANCHOR_LEFT_CENTER    =  4,                   // Text anchor point at the left center side of the bounding rectangle
   TEXT_ANCHOR_CENTER         =  5,                   // Text anchor point at the center of the bounding rectangle
   TEXT_ANCHOR_RIGHT_CENTER   =  6,                   // Text anchor point at the right center side of the bounding rectangle
   TEXT_ANCHOR_LEFT_BOTTOM    =  8,                   // Text anchor point at the bottom left corner of the bounding rectangle
   TEXT_ANCHOR_CENTER_BOTTOM  =  9,                   // Text anchor point at the bottom center side of the bounding rectangle
   TEXT_ANCHOR_RIGHT_BOTTOM   =  10,                  // Text anchor point at the bottom right corner of the bounding rectangle
  };
//+------------------------------------------------------------------+
//| The list of graphical element types                              |
//+------------------------------------------------------------------+

在此我们为每个文本锚点级别设置了三个标志：

顶部垂直锚点 (TA_TOP) — 0:
- 左侧水平锚点 (TA_LEFT) — 0,
- 中间水平锚点 (TA_CENTER) — 1,
- 右侧水平锚点 (TA_RIGHT) — 2.
中间垂直锚点 (TA_VCENTER) — 4:
- 左侧水平锚点 (TA_LEFT) — 0,
- 中间水平锚点 (TA_CENTER) — 1,
- 右侧水平锚点 (TA_RIGHT) — 2.
底部垂直锚点 (TA_BOTTOM) — 8:
- 左侧水平锚点 (TA_LEFT) — 0,
- 中间水平锚点 (TA_CENTER) — 1,
- 右侧水平锚点 (TA_RIGHT) — 2.

每个 ENUM_TEXT_ANCHOR 枚举值对应于上述设置标志的正确组合：

TEXT_ANCHOR_LEFT_TOP = (TA_LEFT | TA_TOP) = 0,
TEXT_ANCHOR_CENTER_TOP = (TA_CENTER | TA_TOP) = 1,
TEXT_ANCHOR_RIGHT_TOP = (TA_RIGHT | TA_TOP) = 2,
TEXT_ANCHOR_LEFT_CENTER = (TA_LEFT | TA_VCENTER) = 4,
TEXT_ANCHOR_CENTER = (TA_CENTER | TA_VCENTER) = 5,
TEXT_ANCHOR_RIGHT_CENTER = (TA_RIGHT | TA_VCENTER) = 6,
TEXT_ANCHOR_LEFT_BOTTOM = (TA_LEFT | TA_BOTTOM) = 8,
TEXT_ANCHOR_CENTER_BOTTOM = (TA_CENTER | TA_BOTTOM) = 9,
TEXT_ANCHOR_RIGHT_BOTTOM = (TA_RIGHT | TA_BOTTOM) = 10.

我在将来会用此枚举来指定相对于其锚点的文本对齐方式。

由于我目前正在开发函数库的图形部分，因此我需要各种操控颜色的方法。
MQL5.com 源代码库提供了卓越的操控颜色的函数库，由 Dmitry Fedoseev 友情提供，供一般使用。

我们稍微改进 CColors 类 — 令其成为静态，从而可以不必设置类对象，而是直接用上下文解析运算符 (::) 访问其方法，例如：

class_name::variable

因此，函数库中包含的 CColors 类允许我们在代码中的任何位置（包括自定义程序）访问类方法，例如两种颜色混合 — 不透明度为 128 的蓝色和不透明度为 64 的红色：

CColors::BlendColors(ColorToARGB(clrBlue,128),ColorToARGB(clrRed,64));

将类文件保存在函数库目录 \MQL5\Include\DoEasy\Services\，文件是 Colors.mqh。

//+------------------------------------------------------------------+
//|                                                       Colors.mqh |
//|                                  Copyright 2021, MetaQuotes Ltd. |
//|                             https://mql5.com/en/users/artmedia70 |
//+------------------------------------------------------------------+
#property copyright "Copyright 2021, MetaQuotes Ltd."
#property link      "https://www.mql5.com/en/users/integer"
#property version   "1.00"
#property strict    // Necessary for mql4
//+------------------------------------------------------------------+
//| Class for working with color                                     |
//+------------------------------------------------------------------+
class CColors
  {
private:
   static double     Arctan2(const double x,const double y);
   static double     Hue_To_RGB(double v1,double v2,double vH);
public:
//+--------------------------------------------------------------------+
//| The list of functions from http://www.easyrgb.com/index.php?X=MATH |
//+--------------------------------------------------------------------+
   static void       RGBtoXYZ(const double aR,const double aG,const double aB,double &oX,double &oY,double &oZ);
   static void       XYZtoRGB(const double aX,const double aY,const double aZ,double &oR,double &oG,double &oB);
   static void       XYZtoYxy(const double aX,const double aY,const double aZ,double &oY,double &ox,double &oy);
   static void       YxyToXYZ(const double aY,const double ax,const double ay,double &oX,double &oY,double &oZ);
   static void       XYZtoHunterLab(const double aX,const double aY,const double aZ,double &oL,double &oa,double &ob);
   static void       HunterLabToXYZ(const double aL,const double aa,const double ab,double &oX,double &oY,double &oZ);
   static void       XYZtoCIELab(const double aX,const double aY,const double aZ,double &oCIEL,double &oCIEa,double &oCIEb);
   static void       CIELabToXYZ(const double aCIEL,const double aCIEa,const double aCIEb,double &oX,double &oY,double &oZ);
   static void       CIELabToCIELCH(const double aCIEL,const double aCIEa,const double aCIEb,double &oCIEL,double &oCIEC,double &oCIEH);
   static void       CIELCHtoCIELab(const double aCIEL,const double aCIEC,const double aCIEH,double &oCIEL,double &oCIEa,double &oCIEb);
   static void       XYZtoCIELuv(const double aX,const double aY,const double aZ,double &oCIEL,double &oCIEu,double &oCIEv);
   static void       CIELuvToXYZ(const double aCIEL,const double aCIEu,const double aCIEv,double &oX,double &oY,double &oZ);
   static void       RGBtoHSL(const double aR,const double aG,const double aB,double &oH,double &oS,double &oL);
   static void       HSLtoRGB(const double aH,const double aS,const double aL,double &oR,double &oG,double &oB);
   static void       RGBtoHSV(const double aR,const double aG,const double aB,double &oH,double &oS,double &oV);
   static void       HSVtoRGB(const double aH,const double aS,const double aV,double &oR,double &oG,double &oB);
   static void       RGBtoCMY(const double aR,const double aG,const double aB,double &oC,double &oM,double &oY);
   static void       CMYtoRGB(const double aC,const double aM,const double aY,double &oR,double &oG,double &oB);
   static void       CMYtoCMYK(const double aC,const double aM,const double aY,double &oC,double &oM,double &oY,double &oK);
   static void       CMYKtoCMY(const double aC,const double aM,const double aY,const double aK,double &oC,double &oM,double &oY);
   static void       RGBtoLab(const double aR,const double aG,const double aB,double &oL,double &oa,double &ob);
//+------------------------------------------------------------------+
//| Other functions for working with color                           |
//+------------------------------------------------------------------+
   static void       ColorToRGB(const color aColor,double &aR,double &aG,double &aB);
   static double     GetR(const color aColor);
   static double     GetG(const color aColor);
   static double     GetB(const color aColor);
   static double     GetA(const color aColor);
   static color      RGBToColor(const double aR,const double aG,const double aB);
   static color      MixColors(const color aCol1,const color aCol2,const double aK);
   static color      BlendColors(const uint lower_color,const uint upper_color);
   static void       Gradient(color &aColors[],color &aOut[],int aOutCount,bool aCycle=false);
   static void       RGBtoXYZsimple(double aR,double aG,double aB,double &oX,double &oY,double &oZ);
   static void       XYZtoRGBsimple(const double aX,const double aY,const double aZ,double &oR,double &oG,double &oB);
   static color      Negative(const color aColor);
   static color      StandardColor(const color aColor,int &aIndex);
   static double     RGBtoGray(double aR,double aG,double aB);
   static double     RGBtoGraySimple(double aR,double aG,double aB);
  };
//+------------------------------------------------------------------+
//| Class methods                                                    |
//+------------------------------------------------------------------+
//+------------------------------------------------------------------+
//| Arctan2                                                          |
//+------------------------------------------------------------------+
double CColors::Arctan2(const double x,const double y)
  {
   if(y==0)
      return(x<0 ? M_PI : 0);
   else
     {
      if(x>0)
         return(::atan(y/x));
      if(x<0)
         return(y>0 ? atan(y/x)+M_PI : atan(y/x)-M_PI);
      else
         return(y<0 ? -M_PI_2 : M_PI_2);
     }
  }
//+------------------------------------------------------------------+
//| Hue_To_RGB                                                       |
//+------------------------------------------------------------------+
double CColors::Hue_To_RGB(double v1,double v2,double vH)
  {
   if(vH<0)
      vH+=1.0;
   if(vH>1.0)
      vH-=1;
   if((6.0*vH)<1.0)
      return(v1+(v2-v1)*6.0*vH);
   if((2.0*vH)<1.0)
      return(v2);
   if((3.0*vH)<2.0)
      return(v1+(v2-v1)*((2.0/3.0)-vH)*6.0);
//---
   return(v1);
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into XYZ                                       |
//+------------------------------------------------------------------+
void CColors::RGBtoXYZ(const double aR,const double aG,const double aB,double &oX,double &oY,double &oZ)
  {
   double var_R=aR/255;
   double var_G=aG/255;
   double var_B=aB/255;
//---
   if(var_R>0.04045)
      var_R=::pow((var_R+0.055)/1.055,2.4);
   else
      var_R=var_R/12.92;
//---
   if(var_G>0.04045)
      var_G=::pow((var_G+0.055)/1.055,2.4);
   else
      var_G=var_G/12.92;
//---
   if(var_B>0.04045)
      var_B=::pow((var_B+0.055)/1.055,2.4);
   else
      var_B=var_B/12.92;
//---
   var_R =var_R*100.0;
   var_G =var_G*100.0;
   var_B =var_B*100.0;
   oX    =var_R*0.4124+var_G*0.3576+var_B*0.1805;
   oY    =var_R*0.2126+var_G*0.7152+var_B*0.0722;
   oZ    =var_R*0.0193+var_G*0.1192+var_B*0.9505;
  }
//+------------------------------------------------------------------+
//| Conversion of XYZ into RGB                                       |
//+------------------------------------------------------------------+
void CColors::XYZtoRGB(const double aX,const double aY,const double aZ,double &oR,double &oG,double &oB)
  {
   double var_X =aX/100;
   double var_Y =aY/100;
   double var_Z =aZ/100;
   double var_R =var_X*3.2406+var_Y*-1.5372+var_Z*-0.4986;
   double var_G =var_X*(-0.9689)+var_Y*1.8758+var_Z*0.0415;
   double var_B =var_X*0.0557+var_Y*(-0.2040)+var_Z*1.0570;
//---
   if(var_R>0.0031308)
      var_R=1.055*(::pow(var_R,1.0/2.4))-0.055;
   else
      var_R=12.92*var_R;
//---
   if(var_G>0.0031308)
      var_G=1.055*(::pow(var_G,1.0/2.4))-0.055;
   else
      var_G=12.92*var_G;
//---
   if(var_B>0.0031308)
      var_B=1.055*(::pow(var_B,1.0/2.4))-0.055;
   else
      var_B=12.92*var_B;
//---
   oR =var_R*255.0;
   oG =var_G*255.0;
   oB =var_B*255.0;
  }
//+------------------------------------------------------------------+
//| Conversion of XYZ into Yxy                                       |
//+------------------------------------------------------------------+
void CColors::XYZtoYxy(const double aX,const double aY,const double aZ,double &oY,double &ox,double &oy)
  {
   oY =aY;
   ox =aX/(aX+aY+aZ);
   oy =aY/(aX+aY+aZ);
  }
//+------------------------------------------------------------------+
//| Conversion of Yxy into XYZ                                       |
//+------------------------------------------------------------------+
void CColors::YxyToXYZ(const double aY,const double ax,const double ay,double &oX,double &oY,double &oZ)
  {
   oX =ax*(aY/ay);
   oY =aY;
   oZ =(1.0-ax-ay)*(aY/ay);
  }
//+------------------------------------------------------------------+
//| Conversion of XYZ into HunterLab                                 |
//+------------------------------------------------------------------+
void CColors::XYZtoHunterLab(const double aX,const double aY,const double aZ,double &oL,double &oa,double &ob)
  {
   oL =10.0*::sqrt(aY);
   oa =17.5*(((1.02*aX)-aY)/::sqrt(aY));
   ob =7.0*((aY-(0.847*aZ))/::sqrt(aY));
  }
//+------------------------------------------------------------------+
//| Conversion of HunterLab into XYZ                                 |
//+------------------------------------------------------------------+
void CColors::HunterLabToXYZ(const double aL,const double aa,const double ab,double &oX,double &oY,double  &oZ)
  {
   double var_Y =aL/10.0;
   double var_X =aa/17.5*aL/10.0;
   double var_Z =ab/7.0*aL/10.0;
//---
   oY =::pow(var_Y,2);
   oX =(var_X+oY)/1.02;
   oZ =-(var_Z-oY)/0.847;
  }
//+------------------------------------------------------------------+
//| Conversion of XYZ into CIELab                                    |
//+------------------------------------------------------------------+
void CColors::XYZtoCIELab(const double aX,const double aY,const double aZ,double &oCIEL,double &oCIEa,double &oCIEb)
  {
   double ref_X =95.047;
   double ref_Y =100.0;
   double ref_Z =108.883;
   double var_X =aX/ref_X;
   double var_Y =aY/ref_Y;
   double var_Z =aZ/ref_Z;
//---
   if(var_X>0.008856)
      var_X=::pow(var_X,1.0/3.0);
   else
      var_X=(7.787*var_X)+(16.0/116.0);
//---
   if(var_Y>0.008856)
      var_Y=::pow(var_Y,1.0/3.0);
   else
      var_Y=(7.787*var_Y)+(16.0/116.0);
//---
   if(var_Z>0.008856)
      var_Z=::pow(var_Z,1.0/3.0);
   else
      var_Z=(7.787*var_Z)+(16.0/116.0);
//---
   oCIEL =(116.0*var_Y)-16.0;
   oCIEa =500.0*(var_X-var_Y);
   oCIEb =200*(var_Y-var_Z);
  }
//+------------------------------------------------------------------+
//| Conversion of CIELab into ToXYZ                                  |
//+------------------------------------------------------------------+
void CColors::CIELabToXYZ(const double aCIEL,const double aCIEa,const double aCIEb,double &oX,double &oY,double &oZ)
  {
   double var_Y =(aCIEL+16.0)/116.0;
   double var_X =aCIEa/500.0+var_Y;
   double var_Z =var_Y-aCIEb/200.0;
//---
   if(::pow(var_Y,3)>0.008856)
      var_Y=::pow(var_Y,3);
   else
      var_Y=(var_Y-16.0/116.0)/7.787;
//---
   if(::pow(var_X,3)>0.008856)
      var_X=::pow(var_X,3);
   else
      var_X=(var_X-16.0/116.0)/7.787;
//---
   if(::pow(var_Z,3)>0.008856)
      var_Z=::pow(var_Z,3);
   else
      var_Z=(var_Z-16.0/116.0)/7.787;
//---
   double ref_X =95.047;
   double ref_Y =100.0;
   double ref_Z =108.883;
//---
   oX =ref_X*var_X;
   oY =ref_Y*var_Y;
   oZ =ref_Z*var_Z;
  }
//+------------------------------------------------------------------+
//| Conversion of CIELab into CIELCH                                 |
//+------------------------------------------------------------------+
void CColors::CIELabToCIELCH(const double aCIEL,const double aCIEa,const double aCIEb,double &oCIEL,double &oCIEC,double &oCIEH)
  {
   double var_H=Arctan2(aCIEb,aCIEa);
//---
   if(var_H>0)
      var_H=(var_H/M_PI)*180.0;
   else
      var_H=360.0-(::fabs(var_H)/M_PI)*180.0;
//---
   oCIEL =aCIEL;
   oCIEC =::sqrt(::pow(aCIEa,2)+::pow(aCIEb,2));
   oCIEH =var_H;
  }
//+------------------------------------------------------------------+
//| Conversion of CIELCH into CIELab                                 |
//+------------------------------------------------------------------+
void CColors::CIELCHtoCIELab(const double aCIEL,const double aCIEC,const double aCIEH,double &oCIEL,double &oCIEa,double &oCIEb)
  {
//--- Arguments from 0 to 360°
   oCIEL =aCIEL;
   oCIEa =::cos(M_PI*aCIEH/180.0)*aCIEC;
   oCIEb =::sin(M_PI*aCIEH/180)*aCIEC;
  }
//+------------------------------------------------------------------+
//| Conversion of XYZ into CIELuv                                    |
//+------------------------------------------------------------------+
void CColors::XYZtoCIELuv(const double aX,const double aY,const double aZ,double &oCIEL,double &oCIEu,double &oCIEv)
  {
   double var_U =(4.0*aX)/(aX+(15.0*aY)+(3.0*aZ));
   double var_V =(9.0*aY)/(aX+(15.0*aY)+(3.0*aZ));
   double var_Y =aY/100.0;
//---
   if(var_Y>0.008856)
      var_Y=::pow(var_Y,1.0/3.0);
   else
      var_Y=(7.787*var_Y)+(16.0/116.0);
//---
   double ref_X =95.047;
   double ref_Y =100.000;
   double ref_Z =108.883;
   double ref_U =(4.0*ref_X)/(ref_X+(15.0*ref_Y)+(3.0*ref_Z));
   double ref_V =(9.0*ref_Y)/(ref_X+(15.0*ref_Y)+(3.0*ref_Z));
//---
   oCIEL =(116.0*var_Y)-16.0;
   oCIEu =13.0*oCIEL*(var_U-ref_U);
   oCIEv =13.0*oCIEL*(var_V-ref_V);
  }
//+------------------------------------------------------------------+
//| Conversion of CIELuv into XYZ                                    |
//+------------------------------------------------------------------+
void CColors::CIELuvToXYZ(const double aCIEL,const double aCIEu,const double aCIEv,double &oX,double &oY,double &oZ)
  {
   double var_Y=(aCIEL+16.0)/116.0;
//---
   if(::pow(var_Y,3)>0.008856)
      var_Y=::pow(var_Y,3);
   else
      var_Y=(var_Y-16.0/116.0)/7.787;
//---
   double ref_X =95.047;
   double ref_Y =100.000;
   double ref_Z =108.883;
   double ref_U =(4.0*ref_X)/(ref_X+(15.0*ref_Y)+(3.0*ref_Z));
   double ref_V =(9.0*ref_Y)/(ref_X+(15.0*ref_Y)+(3.0*ref_Z));
   double var_U =aCIEu/(13.0*aCIEL)+ref_U;
   double var_V =aCIEv/(13.0*aCIEL)+ref_V;
//---
   oY=var_Y*100.0;
   oX=-(9.0*oY*var_U)/((var_U-4.0)*var_V-var_U*var_V);
   oZ=(9.0*oY-(15.0*var_V*oY)-(var_V*oX))/(3.0*var_V);
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into HSL                                       |
//+------------------------------------------------------------------+
void CColors::RGBtoHSL(const double aR,const double aG,const double aB,double &oH,double &oS,double &oL)
  {
   double var_R   =(aR/255);
   double var_G   =(aG/255);
   double var_B   =(aB/255);
   double var_Min =::fmin(var_R,::fmin(var_G,var_B));
   double var_Max =::fmax(var_R,::fmax(var_G,var_B));
   double del_Max =var_Max-var_Min;
//---
   oL=(var_Max+var_Min)/2;
//---
   if(del_Max==0)
     {
      oH=0;
      oS=0;
     }
   else
     {
      if(oL<0.5)
         oS=del_Max/(var_Max+var_Min);
      else
         oS=del_Max/(2.0-var_Max-var_Min);
      //---
      double del_R =(((var_Max-var_R)/6.0)+(del_Max/2.0))/del_Max;
      double del_G =(((var_Max-var_G)/6.0)+(del_Max/2.0))/del_Max;
      double del_B =(((var_Max-var_B)/6.0)+(del_Max/2.0))/del_Max;
      //---
      if(var_R==var_Max)
         oH=del_B-del_G;
      else if(var_G==var_Max)
         oH=(1.0/3.0)+del_R-del_B;
      else if(var_B==var_Max)
         oH=(2.0/3.0)+del_G-del_R;
      //---
      if(oH<0)
         oH+=1.0;
      //---
      if(oH>1)
         oH-=1.0;
     }
  }
//+------------------------------------------------------------------+
//| Conversion of HSL into RGB                                       |
//+------------------------------------------------------------------+
void CColors::HSLtoRGB(const double aH,const double aS,const double aL,double &oR,double &oG,double &oB)
  {
   if(aS==0)
     {
      oR=aL*255;
      oG=aL*255;
      oB=aL*255;
     }
   else
     {
      double var_2=0.0;
      //---
      if(aL<0.5)
         var_2=aL*(1.0+aS);
      else
         var_2=(aL+aS)-(aS*aL);
      //---
      double var_1=2.0*aL-var_2;
      oR =255.0*Hue_To_RGB(var_1,var_2,aH+(1.0/3.0));
      oG =255.0*Hue_To_RGB(var_1,var_2,aH);
      oB =255.0*Hue_To_RGB(var_1,var_2,aH-(1.0/3.0));
     }
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into HSV                                       |
//+------------------------------------------------------------------+
void CColors::RGBtoHSV(const double aR,const double aG,const double aB,double &oH,double &oS,double &oV)
  {
   const double var_R   =(aR/255.0);
   const double var_G   =(aG/255.0);
   const double var_B   =(aB/255.0);

   const double var_Min =::fmin(var_R,::fmin(var_G, var_B));
   const double var_Max =::fmax(var_R,::fmax(var_G,var_B));
   const double del_Max =var_Max-var_Min;
//---
   oV=var_Max;
//---
   if(del_Max==0)
     {
      oH=0;
      oS=0;
     }
   else
     {
      oS=del_Max/var_Max;
      const double del_R =(((var_Max-var_R)/6.0)+(del_Max/2))/del_Max;
      const double del_G =(((var_Max-var_G)/6.0)+(del_Max/2))/del_Max;
      const double del_B =(((var_Max-var_B)/6.0)+(del_Max/2))/del_Max;
      //---
      if(var_R==var_Max)
         oH=del_B-del_G;
      else if(var_G==var_Max)
         oH=(1.0/3.0)+del_R-del_B;
      else if(var_B==var_Max)
         oH=(2.0/3.0)+del_G-del_R;
      //---
      if(oH<0)
         oH+=1.0;
      //---
      if(oH>1.0)
         oH-=1.0;
     }
  }
//+------------------------------------------------------------------+
//| Conversion of HSV into RGB                                       |
//+------------------------------------------------------------------+
void CColors::HSVtoRGB(const double aH,const double aS,const double aV,double &oR,double &oG,double &oB)
  {
   if(aS==0)
     {
      oR =aV*255.0;
      oG =aV*255.0;
      oB =aV*255.0;
     }
   else
     {
      double var_h=aH*6.0;
      //---
      if(var_h==6)
         var_h=0;
      //---
      int    var_i =int(var_h);
      double var_1 =aV*(1.0-aS);
      double var_2 =aV*(1.0-aS*(var_h-var_i));
      double var_3 =aV*(1.0-aS*(1.0-(var_h-var_i)));
      double var_r =0.0;
      double var_g =0.0;
      double var_b =0.0;
      //---
      if(var_i==0)
        {
         var_r =aV;
         var_g =var_3;
         var_b =var_1;
        }
      else if(var_i==1.0)
        {
         var_r=var_2;
         var_g=aV;
         var_b=var_1;
        }
      else if(var_i==2.0)
        {
         var_r=var_1;
         var_g=aV;
         var_b=var_3;
        }
      else if(var_i==3)
        {
         var_r=var_1;
         var_g=var_2;
         var_b=aV;
        }
      else if(var_i==4)
        {
         var_r=var_3;
         var_g=var_1;
         var_b=aV;
        }
      else
        {
         var_r=aV;
         var_g=var_1;
         var_b=var_2;
        }
      //---
      oR =var_r*255.0;
      oG =var_g*255.0;
      oB =var_b*255.0;
     }
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into CMY                                       |
//+------------------------------------------------------------------+
void CColors::RGBtoCMY(const double aR,const double aG,const double aB,double &oC,double &oM,double &oY)
  {
   oC =1.0-(aR/255.0);
   oM =1.0-(aG/255.0);
   oY =1.0-(aB/255.0);
  }
//+------------------------------------------------------------------+
//| Conversion of CMY into RGB                                       |
//+------------------------------------------------------------------+
void CColors::CMYtoRGB(const double aC,const double aM,const double aY,double &oR,double &oG,double &oB)
  {
   oR =(1.0-aC)*255.0;
   oG =(1.0-aM)*255.0;
   oB =(1.0-aY)*255.0;
  }
//+------------------------------------------------------------------+
//| Conversion of CMY into CMYK                                      |
//+------------------------------------------------------------------+
void CColors::CMYtoCMYK(const double aC,const double aM,const double aY,double &oC,double &oM,double &oY,double &oK)
  {
   double var_K=1;
//---
   if(aC<var_K)
      var_K=aC;
   if(aM<var_K)
      var_K=aM;
   if(aY<var_K)
      var_K=aY;
//---
   if(var_K==1.0)
     {
      oC =0;
      oM =0;
      oY =0;
     }
   else
     {
      oC =(aC-var_K)/(1.0-var_K);
      oM =(aM-var_K)/(1.0-var_K);
      oY =(aY-var_K)/(1.0-var_K);
     }
//---
   oK=var_K;
  }
//+------------------------------------------------------------------+
//| Conversion of CMYK into CMY                                      |
//+------------------------------------------------------------------+
void CColors::CMYKtoCMY(const double aC,const double aM,const double aY,const double aK,double &oC,double &oM,double &oY)
  {
   oC =(aC*(1.0-aK)+aK);
   oM =(aM*(1.0-aK)+aK);
   oY =(aY*(1.0-aK)+aK);
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into Lab                                       |
//+------------------------------------------------------------------+
void CColors::RGBtoLab(const double aR,const double aG,const double aB,double &oL,double &oa,double &ob)
  {
   double X=0,Y=0,Z=0;
   RGBtoXYZ(aR,aG,aB,X,Y,Z);
   XYZtoHunterLab(X,Y,Z,oL,oa,ob);
  }
//+------------------------------------------------------------------+
//| Getting values of the RGB components                             |
//+------------------------------------------------------------------+
void CColors::ColorToRGB(const color aColor,double &aR,double &aG,double &aB)
  {
   aR =GetR(aColor);
   aG =GetG(aColor);
   aB =GetB(aColor);
  }
//+------------------------------------------------------------------+
//| Getting the R component value                                    |
//+------------------------------------------------------------------+
double CColors::GetR(const color aColor)
  {
   return(aColor&0xff);
  }
//+------------------------------------------------------------------+
//| Getting the G component value                                    |
//+------------------------------------------------------------------+
double CColors::GetG(const color aColor)
  {
   return((aColor>>8)&0xff);
  }
//+------------------------------------------------------------------+
//| Getting the B component value                                    |
//+------------------------------------------------------------------+
double CColors::GetB(const color aColor)
  {
   return((aColor>>16)&0xff);
  }
//+------------------------------------------------------------------+
//| Getting the A component value                                    |
//+------------------------------------------------------------------+
double CColors::GetA(const color aColor)
  {
   return(double(uchar((aColor)>>24)));
  }
//+------------------------------------------------------------------+
//| Conversion of RGB into const color                               |
//+------------------------------------------------------------------+
color CColors::RGBToColor(const double aR,const double aG,const double aB)
  {
   int int_r =(int)::round(aR);
   int int_g =(int)::round(aG);
   int int_b =(int)::round(aB);
   int Color =0;
//---
   Color=int_b;
   Color<<=8;
   Color|=int_g;
   Color<<=8;
   Color|=int_r;
//---
   return((color)Color);
  }
//+------------------------------------------------------------------+
//| Getting the value of the intermediary color between two colors   |
//+------------------------------------------------------------------+
color CColors::MixColors(const color aCol1,const color aCol2,const double aK)
  {
//--- aK - from 0 to 1
   double R1=0.0,G1=0.0,B1=0.0,R2=0.0,G2=0.0,B2=0.0;
//---
   ColorToRGB(aCol1,R1,G1,B1);
   ColorToRGB(aCol2,R2,G2,B2);
//---
   R1+=(int)::round(aK*(R2-R1));
   G1+=(int)::round(aK*(G2-G1));
   B1+=(int)::round(aK*(B2-B1));
//---
   return(RGBToColor(R1,G1,B1));
  }
//+------------------------------------------------------------------+
//| Blending two colors considering the transparency of color on top |
//+------------------------------------------------------------------+
color CColors::BlendColors(const uint lower_color,const uint upper_color)
  {
   double r1=0,g1=0,b1=0;
   double r2=0,g2=0,b2=0,alpha=0;
   double r3=0,g3=0,b3=0;
//--- Convert the colors in ARGB format
   uint pixel_color=::ColorToARGB(upper_color);
//--- Get the components of the lower and upper colors
   ColorToRGB(lower_color,r1,g1,b1);
   ColorToRGB(pixel_color,r2,g2,b2);
//--- Get the transparency percentage from 0.00 to 1.00
   alpha=GetA(upper_color)/255.0;
//--- If there is transparency
   if(alpha<1.0)
     {
      //--- Blend the components taking the alpha channel into account
      r3=(r1*(1-alpha))+(r2*alpha);
      g3=(g1*(1-alpha))+(g2*alpha);
      b3=(b1*(1-alpha))+(b2*alpha);
      //--- Adjustment of the obtained values
      r3=(r3>255)? 255 : r3;
      g3=(g3>255)? 255 : g3;
      b3=(b3>255)? 255 : b3;
     }
   else
     {
      r3=r2;
      g3=g2;
      b3=b2;
     }
//--- Combine the obtained components and return the color
   return(RGBToColor(r3,g3,b3));
  }
//+------------------------------------------------------------------+
//| Getting an array of the specified size with a color gradient     |
//+------------------------------------------------------------------+
void CColors::Gradient(color &aColors[],   // List of colors
                       color &aOut[],      // Return array
                       int   aOutCount,    // Set the size of the return array
                       bool  aCycle=false) // Closed-loop cycle. Return array ends with the same color as it starts with
  {
   ::ArrayResize(aOut,aOutCount);
//---
   int    InCount =::ArraySize(aColors)+aCycle;
   int    PrevJ   =0;
   int    nci     =0;
   double K       =0.0;
//---
   for(int i=1; i<InCount; i++)
     {
      int J=(aOutCount-1)*i/(InCount-1);
      //---
      for(int j=PrevJ; j<=J; j++)
        {
         if(aCycle && i==InCount-1)
           {
            nci =0;
            K   =1.0*(j-PrevJ)/(J-PrevJ+1);
           }
         else
           {
            nci =i;
            K   =1.0*(j-PrevJ)/(J-PrevJ);
           }
         aOut[j]=MixColors(aColors[i-1],aColors[nci],K);
        }
      PrevJ=J;
     }
  }
//+------------------------------------------------------------------+
//| One more variant of conversion of RGB into XYZ and               |
//| corresponding conversion of XYZ into RGB                         |
//+------------------------------------------------------------------+
void CColors::RGBtoXYZsimple(double aR,double aG,double aB,double &oX,double &oY,double &oZ)
  {
   aR/=255;
   aG/=255;
   aB/=255;
   aR*=100;
   aG*=100;
   aB*=100;
//---
   oX=0.431*aR+0.342*aG+0.178*aB;
   oY=0.222*aR+0.707*aG+0.071*aB;
   oZ=0.020*aR+0.130*aG+0.939*aB;
  }
//+------------------------------------------------------------------+
//| XYZtoRGBsimple                                                   |
//+------------------------------------------------------------------+
void CColors::XYZtoRGBsimple(const double aX,const double aY,const double aZ,double &oR,double &oG,double &oB)
  {
   oR=3.063*aX-1.393*aY-0.476*aZ;
   oG=-0.969*aX+1.876*aY+0.042*aZ;
   oB=0.068*aX-0.229*aY+1.069*aZ;
  }
//+------------------------------------------------------------------+
//| Negative color                                                   |
//+------------------------------------------------------------------+
color CColors::Negative(const color aColor)
  {
   double R=0.0,G=0.0,B=0.0;
   ColorToRGB(aColor,R,G,B);
//---
   return(RGBToColor(255-R,255-G,255-B));
  }
//+------------------------------------------------------------------+
//| Search for the most similar color                                |
//| in the set of standard colors of the terminal                    |
//+------------------------------------------------------------------+
color CColors::StandardColor(const color aColor,int &aIndex)
  {
   color m_c[]=
     {
      clrBlack,clrDarkGreen,clrDarkSlateGray,clrOlive,clrGreen,clrTeal,clrNavy,clrPurple,clrMaroon,clrIndigo,
      clrMidnightBlue,clrDarkBlue,clrDarkOliveGreen,clrSaddleBrown,clrForestGreen,clrOliveDrab,clrSeaGreen,
      clrDarkGoldenrod,clrDarkSlateBlue,clrSienna,clrMediumBlue,clrBrown,clrDarkTurquoise,clrDimGray,
      clrLightSeaGreen,clrDarkViolet,clrFireBrick,clrMediumVioletRed,clrMediumSeaGreen,clrChocolate,clrCrimson,
      clrSteelBlue,clrGoldenrod,clrMediumSpringGreen,clrLawnGreen,clrCadetBlue,clrDarkOrchid,clrYellowGreen,
      clrLimeGreen,clrOrangeRed,clrDarkOrange,clrOrange,clrGold,clrYellow,clrChartreuse,clrLime,clrSpringGreen,
      clrAqua,clrDeepSkyBlue,clrBlue,clrFuchsia,clrRed,clrGray,clrSlateGray,clrPeru,clrBlueViolet,clrLightSlateGray,
      clrDeepPink,clrMediumTurquoise,clrDodgerBlue,clrTurquoise,clrRoyalBlue,clrSlateBlue,clrDarkKhaki,clrIndianRed,
      clrMediumOrchid,clrGreenYellow,clrMediumAquamarine,clrDarkSeaGreen,clrTomato,clrRosyBrown,clrOrchid,
      clrMediumPurple,clrPaleVioletRed,clrCoral,clrCornflowerBlue,clrDarkGray,clrSandyBrown,clrMediumSlateBlue,
      clrTan,clrDarkSalmon,clrBurlyWood,clrHotPink,clrSalmon,clrViolet,clrLightCoral,clrSkyBlue,clrLightSalmon,
      clrPlum,clrKhaki,clrLightGreen,clrAquamarine,clrSilver,clrLightSkyBlue,clrLightSteelBlue,clrLightBlue,
      clrPaleGreen,clrThistle,clrPowderBlue,clrPaleGoldenrod,clrPaleTurquoise,clrLightGray,clrWheat,clrNavajoWhite,
      clrMoccasin,clrLightPink,clrGainsboro,clrPeachPuff,clrPink,clrBisque,clrLightGoldenrod,clrBlanchedAlmond,
      clrLemonChiffon,clrBeige,clrAntiqueWhite,clrPapayaWhip,clrCornsilk,clrLightYellow,clrLightCyan,clrLinen,
      clrLavender,clrMistyRose,clrOldLace,clrWhiteSmoke,clrSeashell,clrIvory,clrHoneydew,clrAliceBlue,clrLavenderBlush,
      clrMintCream,clrSnow,clrWhite,clrDarkCyan,clrDarkRed,clrDarkMagenta,clrAzure,clrGhostWhite,clrFloralWhite
     };
//---
   double m_rv=0.0,m_gv=0.0,m_bv=0.0;
//---
   ColorToRGB(aColor,m_rv,m_gv,m_bv);
//---
   double m_md=0.3*::pow(255,2)+0.59*::pow(255,2)+0.11*::pow(255,2)+1;
   aIndex=0;
//---
   for(int i=0; i<138; i++)
     {
      double m_d=0.3*::pow(GetR(m_c[i])-m_rv,2)+0.59*::pow(GetG(m_c[i])-m_gv,2)+0.11*::pow(GetB(m_c[i])-m_bv,2);
      //---
      if(m_d<m_md)
        {
         m_md   =m_d;
         aIndex =i;
        }
     }
//---
   return(m_c[aIndex]);
  }
//+------------------------------------------------------------------+
//| Conversion into gray color                                       |
//+------------------------------------------------------------------+
double CColors::RGBtoGray(double aR,double aG,double aB)
  {
   aR/=255;
   aG/=255;
   aB/=255;
//---
   aR=::pow(aR,2.2);
   aG=::pow(aG,2.2);
   aB=::pow(aB,2.2);
//---
   double rY=0.21*aR+0.72*aG+0.07*aB;
   rY=::pow(rY,1.0/2.2);
//---
   return(rY);
  }
//+------------------------------------------------------------------+
//| Simple conversion into gray color                                |
//+------------------------------------------------------------------+
double CColors::RGBtoGraySimple(double aR,double aG,double aB)
  {
   aR/=255;
   aG/=255;
   aB/=255;
   double rY=0.3*aR+0.59*aG+0.11*aB;
//---
   return(rY);
  }
//+------------------------------------------------------------------+

所有进行的修改都归结到为每个方法设置'static' 修饰符，以及一些符合我的编码风格的纯粹外观更改（除了方法参数中的变量名称）。此外，我还添加了 RGBtoLab() 方法，可将 RGB 颜色模型转换为 Lab。该方法只是将 RGB 模型转换为 XYZ，然后将其转换为 Lab 颜色模型。这个问题曾在 Anatoli Kazharski 的文章 "Graphical Interfaces IX: The Color Picker Control (Chapter 1)" 中进行过研究：

CColors 类中没有合适的方法可以将 RGB 格式转换为 Lab。因此，在需要转换 RGB->Lab 的地方，需要通过颜色主模型 XYZ 进行双重校正：RGB->XYZ->Lab。

我简单地遵守作者的建议。

若要令 CColors 类在整个函数库和基于它的程序里可见，需将类文件包含到 \MQL5\Include\DoEasy\Services\DELib.mqh 中的函数库服务函数文件当中：

//+------------------------------------------------------------------+
//|                                                        DELib.mqh |
//|                        Copyright 2020, MetaQuotes Software Corp. |
//|                             https://mql5.com/en/users/artmedia70 |
//+------------------------------------------------------------------+
#property copyright "Copyright 2020, MetaQuotes Software Corp."
#property link      "https://mql5.com/en/users/artmedia70"
#property strict  // Necessary for mql4
//+------------------------------------------------------------------+
//| Include files                                                    |
//+------------------------------------------------------------------+
#include "..\Defines.mqh"
#include "Message.mqh"
#include "TimerCounter.mqh"
#include "Pause.mqh"
#include "Colors.mqh"
//+------------------------------------------------------------------+
//| Service functions                                                |
//+------------------------------------------------------------------+

我在这里不需要这个类，但稍后我将在创建图形元素对象衍生后代类时开始用它。

至少为每个图形对象提供了尺寸和在图表上的位置坐标。此外，我们的对象还拥有许多可在程序运行时更改的属性。但如果我们重新启动程序或切换时间帧，程序运行时对图形对象所做的所有修改都会被重置。为了让每个对象记住其属性的状态，我们需要将它们保存在外部。在这种情况下，重新启动程序后，所有在其操作期间构造和更改的图形对象都会从文件中读取它们的相应属性（与重置时刻相关），并恢复它们。为了达此目的，我们需要在图形元素对象类里添加两个方法 — 将对象属性写入文件的方法，和从文件读取对象属性的方法。

为了读写对象属性，我将对象属性保存到结构中，而利用 StructToCharArray() 和 CharArrayToStruct() 标准函数结构既可以保存到文件中，也可以从文件读取。

每个图形对象都提供了将属性保存到文件和从文件中读取它们的方法，因为基于画布的每个图形对象都是图形元素对象的后代，而在其中已经设置了方法。因此，如果对象是复合的（即它由基于图形元素的其他对象组成），我们可以根据从属对象列表中的对象索引（索引存储在元素对象属性的 ENUM_CANV_ELEMENT_PROP_INTEGER 枚举的 CANV_ELEMENT_PROP_NUM 常量中），逐一恢复它的所有状态。

在本文中，我不会将属性保存到文件/从文件中读取它们，因为这应在图形对象集合类中完成。我稍后会考虑 — 在创建图形元素之后。无论如何，写和读的方法都会加在这里。

由于图形元素是所有 CGBaseObj 函数库图形对象的基准对象的衍生后代，首先我们在对象类文件 (\MQL5\Include\DoEasy\Objects\Graph\GBaseObj.mqh) 里设置从对象属性中创建结构的虚拟方法，和从受保护部分中的结构恢复对象属性的虚拟方法：

protected:
   string            m_name_prefix;                      // Object name prefix
   string            m_name;                             // Object name
   long              m_chart_id;                         // Chart ID
   int               m_subwindow;                        // Subwindow index
   int               m_shift_y;                          // Subwindow Y coordinate shift
   int               m_type;                             // Object type

//--- Create (1) the object structure and (2) the object from the structure
   virtual bool      ObjectToStruct(void)                      { return true; }
   virtual void      StructToObject(void){;}

public:

这些方法在这里什么都不做 — 它们应在类的衍生后代中重新定义。该类的最接近的衍生后代是 \MQL5\Include\DoEasy\Objects\Graph\GCnvElement.mqh 中的图形元素对象类。在其受保护部分声明相同的虚拟方法：

//+------------------------------------------------------------------+
//| Class of the base object of the library graphical objects        |
//+------------------------------------------------------------------+
class CGCnvElement : public CGBaseObj
  {
protected:
   CCanvas           m_canvas;                                 // CCanvas class object
   CPause            m_pause;                                  // Pause class object
//--- Return the cursor position relative to the (1) entire element and (2) the element active area
   bool              CursorInsideElement(const int x,const int y);
   bool              CursorInsideActiveArea(const int x,const int y);
//--- Create (1) the object structure and (2) the object from the structure
   virtual bool      ObjectToStruct(void);
   virtual void      StructToObject(void);

private:

在私密部分，声明存储所有对象属性的结构、含结构类型的对象和对象结构数组：

private:
   struct SData
     {
      //--- Object integer properties
      int            id;                                       // Element ID
      int            type;                                     // Graphical element type
      int            number;                                   // Element index in the list
      long           chart_id;                                 // Chart ID
      int            subwindow;                                // Chart subwindow index
      int            coord_x;                                  // Form's X coordinate on the chart
      int            coord_y;                                  // Form's Y coordinate on the chart
      int            width;                                    // Element width
      int            height;                                   // Element height
      int            edge_right;                               // Element right border
      int            edge_bottom;                              // Element bottom border
      int            act_shift_left;                           // Active area offset from the left edge of the element
      int            act_shift_top;                            // Active area offset from the top edge of the element
      int            act_shift_right;                          // Active area offset from the right edge of the element
      int            act_shift_bottom;                         // Active area offset from the bottom edge of the element
      uchar          opacity;                                  // Element opacity
      color          color_bg;                                 // Element background color
      bool           movable;                                  // Element moveability flag
      bool           active;                                   // Element activity flag
      int            coord_act_x;                              // X coordinate of the element active area
      int            coord_act_y;                              // Y coordinate of the element active area
      int            coord_act_right;                          // Right border of the element active area
      int            coord_act_bottom;                         // Bottom border of the element active area
      //--- Object real properties

      //--- Object string properties
      uchar          name_obj[64];                             // Graphical element object name
      uchar          name_res[64];                             // Graphical resource name
     };
   SData             m_struct_obj;                             // Object structure
   uchar             m_uchar_array[];                          // uchar array of the object structure
   
   long              m_long_prop[ORDER_PROP_INTEGER_TOTAL];    // Integer properties
   double            m_double_prop[ORDER_PROP_DOUBLE_TOTAL];   // Real properties
   string            m_string_prop[ORDER_PROP_STRING_TOTAL];   // String properties

在类的公开部分，声明从文件中写入和读取对象属性的方法：

public:
//--- Set object (1) integer, (2) real and (3) string properties
   void              SetProperty(ENUM_CANV_ELEMENT_PROP_INTEGER property,long value)   { this.m_long_prop[property]=value;                   }
   void              SetProperty(ENUM_CANV_ELEMENT_PROP_DOUBLE property,double value)  { this.m_double_prop[this.IndexProp(property)]=value; }
   void              SetProperty(ENUM_CANV_ELEMENT_PROP_STRING property,string value)  { this.m_string_prop[this.IndexProp(property)]=value; }
//--- Return object (1) integer, (2) real and (3) string property from the properties array
   long              GetProperty(ENUM_CANV_ELEMENT_PROP_INTEGER property)        const { return this.m_long_prop[property];                  }
   double            GetProperty(ENUM_CANV_ELEMENT_PROP_DOUBLE property)         const { return this.m_double_prop[this.IndexProp(property)];}
   string            GetProperty(ENUM_CANV_ELEMENT_PROP_STRING property)         const { return this.m_string_prop[this.IndexProp(property)];}

//--- Return the flag of the object supporting this property
   virtual bool      SupportProperty(ENUM_CANV_ELEMENT_PROP_INTEGER property)          { return true; }
   virtual bool      SupportProperty(ENUM_CANV_ELEMENT_PROP_DOUBLE property)           { return false;}
   virtual bool      SupportProperty(ENUM_CANV_ELEMENT_PROP_STRING property)           { return true; }

//--- Compare CGCnvElement objects with each other by all possible properties (for sorting the lists by a specified object property)
   virtual int       Compare(const CObject *node,const int mode=0) const;
//--- Compare CGCnvElement objects with each other by all properties (to search equal objects)
   bool              IsEqual(CGCnvElement* compared_obj) const;

//--- (1) Save the object to file and (2) upload the object from the file
   virtual bool      Save(const int file_handle);
   virtual bool      Load(const int file_handle);

//--- Create the element

由于对象没有实数型属性，故返回对象支持实数型属性标志的虚方法应返回 false。

在类主体之外实现所声明的方法。

在类主体之外实现所声明的方法。

//+------------------------------------------------------------------+
//| Create the object structure                                      |
//+------------------------------------------------------------------+
bool CGCnvElement::ObjectToStruct(void)
  {
//--- Save integer properties
   this.m_struct_obj.id=(int)this.GetProperty(CANV_ELEMENT_PROP_ID);                            // Element ID
   this.m_struct_obj.type=(int)this.GetProperty(CANV_ELEMENT_PROP_TYPE);                        // Graphical element type
   this.m_struct_obj.number=(int)this.GetProperty(CANV_ELEMENT_PROP_NUM);                       // Eleemnt ID in the list
   this.m_struct_obj.chart_id=this.GetProperty(CANV_ELEMENT_PROP_CHART_ID);                     // Chart ID
   this.m_struct_obj.subwindow=(int)this.GetProperty(CANV_ELEMENT_PROP_WND_NUM);                // Chart subwindow index
   this.m_struct_obj.coord_x=(int)this.GetProperty(CANV_ELEMENT_PROP_COORD_X);                  // Form's X coordinate on the chart
   this.m_struct_obj.coord_y=(int)this.GetProperty(CANV_ELEMENT_PROP_COORD_Y);                  // Form's Y coordinate on the chart
   this.m_struct_obj.width=(int)this.GetProperty(CANV_ELEMENT_PROP_WIDTH);                      // Element width
   this.m_struct_obj.height=(int)this.GetProperty(CANV_ELEMENT_PROP_HEIGHT);                    // Element height
   this.m_struct_obj.edge_right=(int)this.GetProperty(CANV_ELEMENT_PROP_RIGHT);                 // Element right edge
   this.m_struct_obj.edge_bottom=(int)this.GetProperty(CANV_ELEMENT_PROP_BOTTOM);               // Element bottom edge
   this.m_struct_obj.act_shift_left=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_LEFT);    // Active area offset from the left edge of the element
   this.m_struct_obj.act_shift_top=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_TOP);      // Active area offset from the top edge of the element
   this.m_struct_obj.act_shift_right=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT);  // Active area offset from the right edge of the element
   this.m_struct_obj.act_shift_bottom=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM);// Active area offset from the bottom edge of the element
   this.m_struct_obj.opacity=(uchar)this.GetProperty(CANV_ELEMENT_PROP_OPACITY);                // Element opacity
   this.m_struct_obj.color_bg=(color)this.GetProperty(CANV_ELEMENT_PROP_COLOR_BG);              // Element background color
   this.m_struct_obj.movable=(bool)this.GetProperty(CANV_ELEMENT_PROP_MOVABLE);                 // Element moveability flag
   this.m_struct_obj.active=(bool)this.GetProperty(CANV_ELEMENT_PROP_ACTIVE);                   // Element activity flag
   this.m_struct_obj.coord_act_x=(int)this.GetProperty(CANV_ELEMENT_PROP_COORD_ACT_X);          // X coordinate of the element active area
   this.m_struct_obj.coord_act_y=(int)this.GetProperty(CANV_ELEMENT_PROP_COORD_ACT_Y);          // Y coordinate of the element active area
   this.m_struct_obj.coord_act_right=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_RIGHT);        // Right border of the element active area
   this.m_struct_obj.coord_act_bottom=(int)this.GetProperty(CANV_ELEMENT_PROP_ACT_BOTTOM);      // Bottom border of the element active area
//--- Save real properties

//--- Save string properties
   ::StringToCharArray(this.GetProperty(CANV_ELEMENT_PROP_NAME_OBJ),this.m_struct_obj.name_obj);// Graphical element object name
   ::StringToCharArray(this.GetProperty(CANV_ELEMENT_PROP_NAME_RES),this.m_struct_obj.name_res);// Graphical resource name
   //--- Save the structure to the uchar array
   ::ResetLastError();
   if(!::StructToCharArray(this.m_struct_obj,this.m_uchar_array))
     {
      ::Print(DFUN,CMessage::Text(MSG_LIB_SYS_FAILED_SAVE_OBJ_STRUCT_TO_UARRAY),(string)::GetLastError());
      return false;
     }
   return true;
  }
//+------------------------------------------------------------------+

此处的一切都很简单：每个整数型结构字段接收相应的对象属性，而对象字符串型属性保存在结构的相应 uchar 数组之中。接下来，简单地调用 StructToCharArray() 将新创建的对象属性结构保存到 uchar 数组。如果将结构保存到数组失败，则通知错误，并返回 false。结果就是，返回 true。

从结构中恢复对象属性的方法：

//+------------------------------------------------------------------+
//| Create the object from the structure                             |
//+------------------------------------------------------------------+
void CGCnvElement::StructToObject(void)
  {
//--- Save integer properties
   this.SetProperty(CANV_ELEMENT_PROP_ID,this.m_struct_obj.id);                                 // Element ID
   this.SetProperty(CANV_ELEMENT_PROP_TYPE,this.m_struct_obj.type);                             // Graphical element type
   this.SetProperty(CANV_ELEMENT_PROP_NUM,this.m_struct_obj.number);                            // Element index in the list
   this.SetProperty(CANV_ELEMENT_PROP_CHART_ID,this.m_struct_obj.chart_id);                     // Chart ID
   this.SetProperty(CANV_ELEMENT_PROP_WND_NUM,this.m_struct_obj.subwindow);                     // Chart subwindow index
   this.SetProperty(CANV_ELEMENT_PROP_COORD_X,this.m_struct_obj.coord_x);                       // Form's X coordinate on the chart
   this.SetProperty(CANV_ELEMENT_PROP_COORD_Y,this.m_struct_obj.coord_y);                       // Form's Y coordinate on the chart
   this.SetProperty(CANV_ELEMENT_PROP_WIDTH,this.m_struct_obj.width);                           // Element width
   this.SetProperty(CANV_ELEMENT_PROP_HEIGHT,this.m_struct_obj.height);                         // Element height
   this.SetProperty(CANV_ELEMENT_PROP_RIGHT,this.m_struct_obj.edge_right);                      // Element right edge
   this.SetProperty(CANV_ELEMENT_PROP_BOTTOM,this.m_struct_obj.edge_bottom);                    // Element bottom edge
   this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_LEFT,this.m_struct_obj.act_shift_left);         // Active area offset from the left edge of the element
   this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_TOP,this.m_struct_obj.act_shift_top);           // Active area offset from the upper edge of the element
   this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT,this.m_struct_obj.act_shift_right);       // Active area offset from the right edge of the element
   this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM,this.m_struct_obj.act_shift_bottom);     // Active area offset from the bottom edge of the element
   this.SetProperty(CANV_ELEMENT_PROP_OPACITY,this.m_struct_obj.opacity);                       // Element opacity
   this.SetProperty(CANV_ELEMENT_PROP_COLOR_BG,this.m_struct_obj.color_bg);                     // Element background color
   this.SetProperty(CANV_ELEMENT_PROP_MOVABLE,this.m_struct_obj.movable);                       // Element moveability flag
   this.SetProperty(CANV_ELEMENT_PROP_ACTIVE,this.m_struct_obj.active);                         // Element activity flag
   this.SetProperty(CANV_ELEMENT_PROP_COORD_ACT_X,this.m_struct_obj.coord_act_x);               // X coordinate of the element active area
   this.SetProperty(CANV_ELEMENT_PROP_COORD_ACT_Y,this.m_struct_obj.coord_act_y);               // Y coordinate of the element active area
   this.SetProperty(CANV_ELEMENT_PROP_ACT_RIGHT,this.m_struct_obj.coord_act_right);             // Right border of the element active area
   this.SetProperty(CANV_ELEMENT_PROP_ACT_BOTTOM,this.m_struct_obj.coord_act_bottom);           // Bottom border of the element active area
//--- Save real properties

//--- Save string properties
   this.SetProperty(CANV_ELEMENT_PROP_NAME_OBJ,::CharArrayToString(this.m_struct_obj.name_obj));// Graphical element object name
   this.SetProperty(CANV_ELEMENT_PROP_NAME_RES,::CharArrayToString(this.m_struct_obj.name_res));// Graphical resource name
  }
//+------------------------------------------------------------------+

此处，每个整数型对象属性都接收来自相应结构字段的值，同时调用 CharArrayToString() 将相应 uchar 数组结构的内容读取到对象字符串型属性之中。

该方法将对象保存到文件：

//+------------------------------------------------------------------+
//| Save the object to the file                                      |
//+------------------------------------------------------------------+
bool CGCnvElement::Save(const int file_handle)
  {
   if(!this.ObjectToStruct())
     {
      ::Print(DFUN,CMessage::Text(MSG_LIB_SYS_FAILED_CREATE_OBJ_STRUCT));
      return false;
     }
   if(::FileWriteArray(file_handle,this.m_uchar_array)==0)
     {
      ::Print(DFUN,CMessage::Text(MSG_LIB_SYS_FAILED_WRITE_UARRAY_TO_FILE));
      return false;
     }
   return true;
  }
//+------------------------------------------------------------------+

该方法接收保存对象属性的文件句柄。然后使用上面研讨过的 ObjectToStruct() 方法将对象属性保存在结构之中。调用 FileWriteArray() 把构造结构时创建的 uchar 数组写入文件，并返回 true。若失败，该方法会在日志中显示错误消息，并返回 false。

该方法从文件加载对象属性：

//+------------------------------------------------------------------+
//| Upload the object from the file                                  |
//+------------------------------------------------------------------+
bool CGCnvElement::Load(const int file_handle)
  {
   if(::FileReadArray(file_handle,this.m_uchar_array)==0)
     {
      ::Print(DFUN,CMessage::Text(MSG_LIB_SYS_FAILED_LOAD_UARRAY_FROM_FILE));
      return false;
     }
   if(!::CharArrayToStruct(this.m_struct_obj,this.m_uchar_array))
     {
      ::Print(DFUN,CMessage::Text(MSG_LIB_SYS_FAILED_CREATE_OBJ_STRUCT_FROM_UARRAY));
      return false;
     }
   this.StructToObject();
   return true;
  }
//+------------------------------------------------------------------+

该方法接收保存对象属性的文件句柄。接下来，调用 FileReadArray() 将文件中的对象属性加载至 uchar 数组。调用 CharArrayToStruct() 将加载的属性复制到结构之中。调用上述 StructToObject() 方法把来自文件中的数据填充到设置对象属性的结构，并返回 true。如果从文件读取，或将得到的数组复制到结构时以错误结束，则该方法会通知，并返回 false。

简化的访问对象属性的方法模块，接收方法返回的右侧和底部元素边缘的方法，设置和返回元素背景颜色的方法，返回元素 ID 的方法，以及返回其在复合对象元素列表中的索引的方法：

//+------------------------------------------------------------------+
//| The methods of simplified access to object properties            |
//+------------------------------------------------------------------+
//--- Set the (1) X, (2) Y coordinates, (3) element width, (4) height, (5) right (6) and bottom edge,
   bool              SetCoordX(const int coord_x);
   bool              SetCoordY(const int coord_y);
   bool              SetWidth(const int width);
   bool              SetHeight(const int height);
   void              SetRightEdge(void)                        { this.SetProperty(CANV_ELEMENT_PROP_RIGHT,this.RightEdge());           }
   void              SetBottomEdge(void)                       { this.SetProperty(CANV_ELEMENT_PROP_BOTTOM,this.BottomEdge());         }
//--- Set the shift of the (1) left, (2) top, (3) right, (4) bottom edge of the active area relative to the element,
//--- (5) all shifts of the active area edges relative to the element, (6) the element background color and (7) the element opacity
   void              SetActiveAreaLeftShift(const int value)   { this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_LEFT,fabs(value));       }
   void              SetActiveAreaRightShift(const int value)  { this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT,fabs(value));      }
   void              SetActiveAreaTopShift(const int value)    { this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_TOP,fabs(value));        }
   void              SetActiveAreaBottomShift(const int value) { this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM,fabs(value));     }
   void              SetActiveAreaShift(const int left_shift,const int bottom_shift,const int right_shift,const int top_shift);
   void              SetColorBG(const color colour)            { this.SetProperty(CANV_ELEMENT_PROP_COLOR_BG,colour);                  }
   void              SetOpacity(const uchar value,const bool redraw=false);
   
//--- Return the shift (1) of the left, (2) right, (3) top and (4) bottom edge of the element active area
   int               ActiveAreaLeftShift(void)           const { return (int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_LEFT);       }
   int               ActiveAreaRightShift(void)          const { return (int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT);      }
   int               ActiveAreaTopShift(void)            const { return (int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_TOP);        }
   int               ActiveAreaBottomShift(void)         const { return (int)this.GetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM);     }
//--- Return the coordinate (1) of the left, (2) right, (3) top and (4) bottom edge of the element active area
   int               ActiveAreaLeft(void)                const { return int(this.CoordX()+this.ActiveAreaLeftShift());                 }
   int               ActiveAreaRight(void)               const { return int(this.RightEdge()-this.ActiveAreaRightShift());             }
   int               ActiveAreaTop(void)                 const { return int(this.CoordY()+this.ActiveAreaTopShift());                  }
   int               ActiveAreaBottom(void)              const { return int(this.BottomEdge()-this.ActiveAreaBottomShift());           }
//--- Return (1) the background color, (2) the opacity, coordinate (3) of the right and (4) bottom element edge
   color             ColorBG(void)                       const { return (color)this.GetProperty(CANV_ELEMENT_PROP_COLOR_BG);           }
   uchar             Opacity(void)                       const { return (uchar)this.GetProperty(CANV_ELEMENT_PROP_OPACITY);            }
   int               RightEdge(void)                     const { return this.CoordX()+this.m_canvas.Width();                           }
   int               BottomEdge(void)                    const { return this.CoordY()+this.m_canvas.Height();                          }
//--- Return the (1) X, (2) Y coordinates, (3) element width and (4) height,
   int               CoordX(void)                        const { return (int)this.GetProperty(CANV_ELEMENT_PROP_COORD_X);              }
   int               CoordY(void)                        const { return (int)this.GetProperty(CANV_ELEMENT_PROP_COORD_Y);              }
   int               Width(void)                         const { return (int)this.GetProperty(CANV_ELEMENT_PROP_WIDTH);                }
   int               Height(void)                        const { return (int)this.GetProperty(CANV_ELEMENT_PROP_HEIGHT);               }
//--- Return the element (1) moveability and (2) activity flag
   bool              Movable(void)                       const { return (bool)this.GetProperty(CANV_ELEMENT_PROP_MOVABLE);             }
   bool              Active(void)                        const { return (bool)this.GetProperty(CANV_ELEMENT_PROP_ACTIVE);              }
//--- Return (1) the object name, (2) the graphical resource name, (3) the chart ID and (4) the chart subwindow index
   string            NameObj(void)                       const { return this.GetProperty(CANV_ELEMENT_PROP_NAME_OBJ);                  }
   string            NameRes(void)                       const { return this.GetProperty(CANV_ELEMENT_PROP_NAME_RES);                  }
   long              ChartID(void)                       const { return this.GetProperty(CANV_ELEMENT_PROP_CHART_ID);                  }
   int               WindowNum(void)                     const { return (int)this.GetProperty(CANV_ELEMENT_PROP_WND_NUM);              }
//--- Return (1) the element ID and (2) index in the list
   int               ID(void)                            const { return (int)this.GetProperty(CANV_ELEMENT_PROP_ID);                   }
   int               Number(void)                        const { return (int)this.GetProperty(CANV_ELEMENT_PROP_NUM);                  }

//+------------------------------------------------------------------+

所有这些方法只返回相应的元素对象属性。

操控基元的方法

CCanvas 类为在画布上绘制各种图形基元提供了充分的机会。我们既能够读取每个像素的颜色，也可为其设置所需的颜色和透明度。除了简单地为像素设置颜色之外，该类还提供了逐个像素（无需平滑）或借助各种平滑方法绘制不同图形的工具。

图形元素对象类可为用户提供访问 CCanvas 类的绘制方法。我们的方法只会稍微简化 CCanvas 类方法的调用。简化实际上在于颜色以通常的方式设置 — 通过在颜色格式中指定必要的颜色，并设置颜色不透明度（0 — 透明，255 — 完全不透明），而 CCanvas 类方法“要求”立即以 uint ARGB 格式指定颜色，这只是一个数字。并非每个人都喜欢以这种格式指定所需的颜色（半透明灰色：0x7F7F7F7F）。后续自图形元素对象继承的类中，我会在每个所创建的类中添加更便利的固有功能来扩展绘图功能的范围。在同一个类中，这是创建其余图形对象的基础，故绘制方法应该简单明了。

简化访问对象属性的方法模块随后是新的代码模块。我尝试根据它们的目的分派它们。数据接收方法以 “Get” 开头，而数据设置方法以 “Set” 开头。

该方法接收指定坐标点的颜色：

//+------------------------------------------------------------------+
//| The methods of receiving raster data                             |
//+------------------------------------------------------------------+
//--- Get a color of the dot with the specified coordinates
   uint              GetPixel(const int x,const int y)   const { return this.m_canvas.PixelGet(x,y);                                   }

//+------------------------------------------------------------------+

此处返回调用 CCanvas 类的 PixelGet() 方法的结果。该方法返回 ARGB 格式颜色。

该方法填充、清除和更新栅格数据：

//+------------------------------------------------------------------+
//| The methods of filling, clearing and updating raster data        |
//+------------------------------------------------------------------+
//--- Clear the element filling it with color and opacity
   void              Erase(const color colour,const uchar opacity,const bool redraw=false);
//--- Clear the element completely
   void              Erase(const bool redraw=false);
//--- Update the element
   void              Update(const bool redraw=false)           { this.m_canvas.Update(redraw);                                         }
   
//+------------------------------------------------------------------+

Update() 方法调用 CCanvas 类的 Update() 方法来简单地更新对象和图表。

Erase() 方法则在类主体之外实现：

//+------------------------------------------------------------------+
//| Clear the element filling it with color and opacity              |
//+------------------------------------------------------------------+
void CGCnvElement::Erase(const color colour,const uchar opacity,const bool redraw=false)
  {
   this.m_canvas.Erase(::ColorToARGB(colour,opacity));
   if(redraw)
      ::ChartRedraw(this.m_chart_id);
  }
//+------------------------------------------------------------------+
//| Clear the element completely                                     |
//+------------------------------------------------------------------+
void CGCnvElement::Erase(const bool redraw=false)
  {
   this.m_canvas.Erase(NULL_COLOR);
   if(redraw)
      ::ChartRedraw(this.m_chart_id);
  }
//+------------------------------------------------------------------+

这是两个重载的方法。
在第一个里，我们传递所需的颜色和不透明度，并在 CCanvas 类的 Erase() 方法的帮助下填充整个元素。请注意，该方法调用 ColorToARGB() 函数将该值转换为 ARGB 格式，并把所应用的颜色和不透明度级别传递给 CCanvas 类的 Erase() 方法。我会在所有绘图方法中做到这一点。在第二个方法中，我们简单地用完全透明的黑色填充整个背景。其值以前是用 NULL_COLOR 宏替换定义的。
每个方法都会收到一个标志，指示需要重新绘制图表。如果设置了标志，则重新绘制图表。

接下来，在无需平滑的情况下绘制图元的方法模块。所有方法都雷同，并调用 CCanvas 类的相应方法。这些方法接收指定的参数，并把传递给方法的颜色和透明度值转换为 ARGB 格式：

//+------------------------------------------------------------------+
//| The methods of drawing primitives without smoothing              |
//+------------------------------------------------------------------+
//--- Set the color of the dot with the specified coordinates
   void              SetPixel(const int x,const int y,const color clr,const uchar opacity=255)
                       { this.m_canvas.PixelSet(x,y,::ColorToARGB(clr,opacity));                                                       }
                       
//--- Draw a segment of a vertical line
   void              DrawLineVertical(const int x,                // X coordinate of the segment
                                      const int y1,               // Y coordinate of the segment first point
                                      const int y2,               // Y coordinate of the segment second point
                                      const color clr,            // Color
                                      const uchar opacity=255)    // Opacity
                       { this.m_canvas.LineVertical(x,y1,y2,::ColorToARGB(clr,opacity));                                               }
                       
//--- Draw a segment of a horizontal line
   void              DrawLineHorizontal(const int x1,             // X coordinate of the segment first point
                                        const int x2,             // X coordinate of the segment second point
                                        const int y,              // Segment Y coordinate
                                        const color clr,          // Color
                                        const uchar opacity=255)  // Opacity
                       { this.m_canvas.LineHorizontal(x1,x2,y,::ColorToARGB(clr,opacity));                                             }
                       
//--- Draw a segment of a freehand line
   void              DrawLine(const int x1,                       // X coordinate of the segment first point
                              const int y1,                       // Y coordinate of the segment first point
                              const int x2,                       // X coordinate of the segment second point
                              const int y2,                       // Y coordinate of the segment second point
                              const color clr,                    // Color
                              const uchar opacity=255)            // Opacity
                       { this.m_canvas.Line(x1,y1,x2,y2,::ColorToARGB(clr,opacity));                                                   }
                       
//--- Draw a polyline
   void              DrawPolyline(int &array_x[],                 // Array with the X coordinates of polyline points
                                  int & array_y[],                // Array with the Y coordinates of polyline points
                                  const color clr,                // Color
                                  const uchar opacity=255)        // Opacity
                       { this.m_canvas.Polyline(array_x,array_y,::ColorToARGB(clr,opacity));                                           }
                       
//--- Draw a polygon
   void              DrawPolygon(int &array_x[],                  // Array with the X coordinates of polygon points
                                 int &array_y[],                  // Array with the Y coordinates of polygon points
                                 const color clr,                 // Color
                                 const uchar opacity=255)         // Opacity
                       { this.m_canvas.Polygon(array_x,array_y,::ColorToARGB(clr,opacity));                                            }
                       
//--- Draw a rectangle using two points
   void              DrawRectangle(const int x1,                  // X coordinate of the first point defining the rectangle
                                   const int y1,                  // Y coordinate of the first point defining the rectangle
                                   const int x2,                  // X coordinate of the second point defining the rectangle
                                   const int y2,                  // Y coordinate of the second point defining the rectangle
                                   const color clr,               // color
                                   const uchar opacity=255)       // Opacity
                       { this.m_canvas.Rectangle(x1,y1,x2,y2,::ColorToARGB(clr,opacity));                                              }
                       
//--- Draw a circle
   void              DrawCircle(const int x,                      // X coordinate of the circle center
                                const int y,                      // Y coordinate of the circle center
                                const int r,                      // Circle radius
                                const color clr,                  // Color
                                const uchar opacity=255)          // Opacity
                       { this.m_canvas.Circle(x,y,r,::ColorToARGB(clr,opacity));                                                       }
                       
//--- Draw a triangle
   void              DrawTriangle(const int x1,                   // X coordinate of the triangle first vertex
                                  const int y1,                   // Y coordinate of the triangle first vertex
                                  const int x2,                   // X coordinate of the triangle second vertex
                                  const int y2,                   // Y coordinate of the triangle second vertex
                                  const int x3,                   // X coordinate of the triangle third vertex
                                  const int y3,                   // Y coordinate of the triangle third vertex
                                  const color clr,                // Color
                                  const uchar opacity=255)        // Opacity
                       { m_canvas.Triangle(x1,y1,x2,y2,x3,y3,::ColorToARGB(clr,opacity));                                              }
                       
//--- Draw an ellipse using two points
   void              DrawEllipse(const int x1,                    // X coordinate of the first point defining the ellipse
                                 const int y1,                    // Y coordinate of the first point defining the ellipse
                                 const int x2,                    // X coordinate of the second point defining the ellipse
                                 const int y2,                    // Y coordinate of the second point defining the ellipse
                                 const color clr,                 // Color
                                 const uchar opacity=255)         // Opacity
                       { this.m_canvas.Ellipse(x1,y1,x2,y2,::ColorToARGB(clr,opacity));                                                }
                       
//--- Draw an arc of an ellipse inscribed in a rectangle with corners at (x1,y1) and (x2,y2).
//--- The arc boundaries are clipped by lines from the center of the ellipse, which extend to two points with coordinates (x3,y3) and (x4,y4)
   void              DrawArc(const int x1,                        // X coordinate of the top left corner forming the rectangle
                             const int y1,                        // Y coordinate of the top left corner forming the rectangle
                             const int x2,                        // X coordinate of the bottom right corner forming the rectangle
                             const int y2,                        // Y coordinate of the bottom right corner forming the rectangle
                             const int x3,                        // X coordinate of the first point, to which a line from the rectangle center is drawn in order to obtain the arc boundary
                             const int y3,                        // Y coordinate of the first point, to which a line from the rectangle center is drawn in order to obtain the arc boundary
                             const int x4,                        // X coordinate of the second point, to which a line from the rectangle center is drawn in order to obtain the arc boundary
                             const int y4,                        // Y coordinate of the second point, to which a line from the rectangle center is drawn in order to obtain the arc boundary
                             const color clr,                     // Color
                             const uchar opacity=255)             // Opacity
                       { m_canvas.Arc(x1,y1,x2,y2,x3,y3,x4,y4,::ColorToARGB(clr,opacity));                                             }
                       
//--- Draw a filled sector of an ellipse inscribed in a rectangle with corners at (x1,y1) and (x2,y2).
//--- The sector boundaries are clipped by lines from the center of the ellipse, which extend to two points with coordinates (x3,y3) and (x4,y4)
   void              DrawPie(const int x1,                        // X coordinate of the upper left corner of the rectangle
                             const int y1,                        // Y coordinate of the upper left corner of the rectangle
                             const int x2,                        // X coordinate of the bottom right corner of the rectangle
                             const int y2,                        // Y coordinate of the bottom right corner of the rectangle
                             const int x3,                        // X coordinate of the first point to find the arc boundaries
                             const int y3,                        // Y coordinate of the first point to find the arc boundaries
                             const int x4,                        // X coordinate of the second point to find the arc boundaries
                             const int y4,                        // Y coordinate of the second point to find the arc boundaries
                             const color clr,                     // Line color
                             const color fill_clr,                // Fill color
                             const uchar opacity=255)             // Opacity
                       { this.m_canvas.Pie(x1,y1,x2,y2,x3,y3,x4,y4,::ColorToARGB(clr,opacity),ColorToARGB(fill_clr,opacity));          }
                       
//+------------------------------------------------------------------+

该方法模块绘制无需平滑的填充图元：:

//+------------------------------------------------------------------+
//| The methods of drawing filled primitives without smoothing       |
//+------------------------------------------------------------------+
//--- Fill in the area
   void              Fill(const int x,                            // X coordinate of the filling start point
                          const int y,                            // Y coordinate of the filling start point
                          const color clr,                        // Color
                          const uchar opacity=255,                // Opacity
                          const uint threshould=0)                // Threshold
                       { this.m_canvas.Fill(x,y,::ColorToARGB(clr,opacity),threshould);                                                }
                       
//--- Draw a filled rectangle
   void              DrawRectangleFill(const int x1,              // X coordinate of the first point defining the rectangle
                                       const int y1,              // Y coordinate of the first point defining the rectangle
                                       const int x2,              // X coordinate of the second point defining the rectangle
                                       const int y2,              // Y coordinate of the second point defining the rectangle
                                       const color clr,           // Color
                                       const uchar opacity=255)   // Opacity
                       { this.m_canvas.FillRectangle(x1,y1,x2,y2,::ColorToARGB(clr,opacity));                                          }

//--- Draw a filled circle
   void              DrawCircleFill(const int x,                  // X coordinate of the circle center
                                    const int y,                  // Y coordinate of the circle center
                                    const int r,                  // Circle radius
                                    const color clr,              // Color
                                    const uchar opacity=255)      // Opacity
                       { this.m_canvas.FillCircle(x,y,r,::ColorToARGB(clr,opacity));                                                   }
                       
//--- Draw a filled triangle
   void              DrawTriangleFill(const int         x1,      // X coordinate of the triangle first vertex
                                      const int         y1,      // Y coordinate of the triangle first vertex
                                      const int         x2,      // X coordinate of the triangle second vertex
                                      const int         y2,      // Y coordinate of the triangle second vertex
                                      const int         x3,      // X coordinate of the triangle third vertex
                                      const int         y3,      // Y coordinate of the triangle third vertex
                                      const color clr,           // Color
                                      const uchar opacity=255)   // Opacity
                       { this.m_canvas.FillTriangle(x1,y1,x2,y2,x3,y3,::ColorToARGB(clr,opacity));                                     }
                       
//--- Draw a filled polygon
   void              DrawPolygonFill(int &array_x[],              // Array with the X coordinates of polygon points
                                     int &array_y[],              // Array with the Y coordinates of polygon points
                                     const color clr,             // Color
                                     const uchar opacity=255)     // Opacity
                       { this.m_canvas.FillPolygon(array_x,array_y,::ColorToARGB(clr,opacity));                                        }
                       
//--- Draw a filled ellipse inscribed in a rectangle with the specified coordinates
   void              DrawEllipseFill(const int x1,                // X coordinate of the top left corner forming the rectangle
                                     const int y1,                // Y coordinate of the top left corner forming the rectangle
                                     const int x2,                // X coordinate of the bottom right corner forming the rectangle
                                     const int y2,                // Y coordinate of the bottom right corner forming the rectangle
                                     const color clr,             // Color
                                     const uchar opacity=255)     // Opacity
                       { this.m_canvas.FillEllipse(x1,y1,x2,y2,::ColorToARGB(clr,opacity));                                            }
                       
//+------------------------------------------------------------------+

该方法采用平滑绘制图元：

//+------------------------------------------------------------------+
//| The methods of drawing primitives using smoothing                |
//+------------------------------------------------------------------+
//--- Draw a point using AntiAliasing algorithm
   void              SetPixelAA(const double x,                   // Point X coordinate
                                const double y,                   // Point Y coordinate
                                const color clr,                  // Color
                                const uchar opacity=255)          // Opacity
                       { this.m_canvas.PixelSetAA(x,y,::ColorToARGB(clr,opacity));                                                     }
                       
//--- Draw a segment of a freehand line using AntiAliasing algorithm
   void              DrawLineAA(const int   x1,                   // X coordinate of the segment first point
                                const int   y1,                   // Y coordinate of the segment first point
                                const int   x2,                   // X coordinate of the segment second point
                                const int   y2,                   // Y coordinate of the segment second point
                                const color clr,                  // Color
                                const uchar opacity=255,          // Opacity
                                const uint  style=UINT_MAX)       // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.LineAA(x1,y1,x2,y2,::ColorToARGB(clr,opacity),style);                                           }
                       
//--- Draw a segment of a freehand line using Wu algorithm
   void              DrawLineWu(const int   x1,                   // X coordinate of the segment first point
                                const int   y1,                   // Y coordinate of the segment first point
                                const int   x2,                   // X coordinate of the segment second point
                                const int   y2,                   // Y coordinate of the segment second point
                                const color clr,                  // Color
                                const uchar opacity=255,          // Opacity
                                const uint  style=UINT_MAX)       // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.LineWu(x1,y1,x2,y2,::ColorToARGB(clr,opacity),style);                                           }
                       
//--- Draws a segment of a freehand line having a specified width using smoothing algorithm with the preliminary filtration
   void              DrawLineThick(const int   x1,                // X coordinate of the segment first point
                                   const int   y1,                // Y coordinate of the segment first point
                                   const int   x2,                // X coordinate of the segment second point
                                   const int   y2,                // Y coordinate of the segment second point
                                   const int   size,              // Line width
                                   const color clr,               // Color
                                   const uchar opacity=255,       // Opacity
                                   const uint  style=STYLE_SOLID, // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                   ENUM_LINE_END end_style=LINE_END_ROUND) // Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.LineThick(x1,y1,x2,y2,::ColorToARGB(clr,opacity),size,style,end_style);                         }
 
//--- Draw a vertical segment of a freehand line having a specified width using smoothing algorithm with the preliminary filtration
   void              DrawLineThickVertical(const int   x,         // X coordinate of the segment
                                           const int   y1,        // Y coordinate of the segment first point
                                           const int   y2,        // Y coordinate of the segment second point
                                           const int   size,      // Line width
                                           const color clr,       // Color
                                           const uchar opacity=255,// Opacity
                                           const uint  style=STYLE_SOLID,  // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                           const ENUM_LINE_END end_style=LINE_END_ROUND)  // Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.LineThickVertical(x,y1,y2,::ColorToARGB(clr,opacity),size,style,end_style);                     }
                       
//--- Draw a horizontal segment of a freehand line having a specified width using smoothing algorithm with the preliminary filtration
   void              DrawLineThickHorizontal(const int   x1,      // X coordinate of the segment first point
                                             const int   x2,      // X coordinate of the segment second point
                                             const int   y,       // Segment Y coordinate
                                             const int   size,    // Line width
                                             const color clr,     // Color
                                             const uchar opacity=255,// Opacity
                                             const uint  style=STYLE_SOLID,  // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                             const ENUM_LINE_END end_style=LINE_END_ROUND)  // Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.LineThickHorizontal(x1,x2,y,::ColorToARGB(clr,opacity),size,style,end_style);                   }

//--- Draws a polyline using AntiAliasing algorithm
   void              DrawPolylineAA(int        &array_x[],        // Array with the X coordinates of polyline points
                                    int        &array_y[],        // Array with the Y coordinates of polyline points
                                    const color clr,              // Color
                                    const uchar opacity=255,      // Opacity
                                    const uint  style=UINT_MAX)   // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.PolylineAA(array_x,array_y,::ColorToARGB(clr,opacity),style);                                   }
                       
//--- Draws a polyline using Wu algorithm
   void              DrawPolylineWu(int        &array_x[],        // Array with the X coordinates of polyline points
                                    int        &array_y[],        // Array with the Y coordinates of polyline points
                                    const color clr,              // Color
                                    const uchar opacity=255,      // Opacity
                                    const uint  style=UINT_MAX)   // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.PolylineWu(array_x,array_y,::ColorToARGB(clr,opacity),style);                                   }
                       
//--- Draw a polyline with a specified width consecutively using two antialiasing algorithms.
//--- First, individual line segments are smoothed based on Bezier curves.
//--- Then, the raster antialiasing algorithm is applied to the polyline built from these segments to improve the rendering quality
   void              DrawPolylineSmooth(const int   &array_x[],   // Array with the X coordinates of polyline points
                                        const int   &array_y[],   // Array with the Y coordinates of polyline points
                                        const int    size,        // Line width
                                        const color  clr,         // Color
                                        const uchar  opacity=255, // Opacity
                                        const double tension=0.5, // Smoothing parameter value
                                        const double step=10,     // Approximation step
                                        const ENUM_LINE_STYLE style=STYLE_SOLID,// Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                        const ENUM_LINE_END   end_style=LINE_END_ROUND)// Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.PolylineSmooth(array_x,array_y,::ColorToARGB(clr,opacity),size,style,end_style,tension,step);   }
                       
//--- Draw a polyline having a specified width using smoothing algorithm with the preliminary filtration
   void              DrawPolylineThick(const int     &array_x[],  // Array with the X coordinates of polyline points
                                       const int     &array_y[],  // Array with the Y coordinates of polyline points
                                       const int      size,       // Line width
                                       const color    clr,        // Color
                                       const uchar    opacity=255,// Opacity
                                       const uint     style=STYLE_SOLID,         // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                       ENUM_LINE_END  end_style=LINE_END_ROUND)  // Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.PolylineThick(array_x,array_y,::ColorToARGB(clr,opacity),size,style,end_style);                 }
                       
//--- Draw a polygon using AntiAliasing algorithm
   void              DrawPolygonAA(int        &array_x[],         // Array with the X coordinates of polygon points
                                   int        &array_y[],         // Array with the Y coordinates of polygon points
                                   const color clr,               // Color
                                   const uchar opacity=255,       // Opacity
                                   const uint  style=UINT_MAX)    // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.PolygonAA(array_x,array_y,::ColorToARGB(clr,opacity),style);                                    }
                       
//--- Draw a polygon using Wu algorithm
   void              DrawPolygonWu(int        &array_x[],         // Array with the X coordinates of polygon points
                                   int        &array_y[],         // Array with the Y coordinates of polygon points
                                   const color clr,               // Color
                                   const uchar opacity=255,       // Opacity
                                   const uint  style=UINT_MAX)    // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.PolygonWu(array_x,array_y,::ColorToARGB(clr,opacity),style);                                    }
                       
//--- Draw a polygon with a specified width consecutively using two smoothing algorithms.
//--- First, individual segments are smoothed based on Bezier curves.
//--- Then, the raster smoothing algorithm is applied to the polygon built from these segments to improve the rendering quality. 
   void              DrawPolygonSmooth(int         &array_x[],    // Array with the X coordinates of polyline points
                                       int         &array_y[],    // Array with the Y coordinates of polyline points
                                       const int    size,         // Line width
                                       const color  clr,          // Color
                                       const uchar  opacity=255,  // Opacity
                                       const double tension=0.5,  // Smoothing parameter value
                                       const double step=10,      // Approximation step
                                       const ENUM_LINE_STYLE style=STYLE_SOLID,// Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                                       const ENUM_LINE_END   end_style=LINE_END_ROUND)// Line style is one of the ENUM_LINE_END enumeration values
                       { this.m_canvas.PolygonSmooth(array_x,array_y,::ColorToARGB(clr,opacity),size,style,end_style,tension,step);    }
                       
//--- Draw a polygon having a specified width using smoothing algorithm with the preliminary filtration
   void              DrawPolygonThick(const int  &array_x[],      // array with the X coordinates of polygon points
                                      const int  &array_y[],      // array with the Y coordinates of polygon points
                                      const int   size,           // line width
                                      const color clr,            // Color
                                      const uchar opacity=255,    // Opacity
                                      const uint  style=STYLE_SOLID,// line style
                                      ENUM_LINE_END end_style=LINE_END_ROUND) // line ends style
                       { this.m_canvas.PolygonThick(array_x,array_y,::ColorToARGB(clr,opacity),size,style,end_style);                  }
                       
//--- Draw a triangle using AntiAliasing algorithm
   void              DrawTriangleAA(const int   x1,               // X coordinate of the triangle first vertex
                                    const int   y1,               // Y coordinate of the triangle first vertex
                                    const int   x2,               // X coordinate of the triangle second vertex
                                    const int   y2,               // Y coordinate of the triangle second vertex
                                    const int   x3,               // X coordinate of the triangle third vertex
                                    const int   y3,               // Y coordinate of the triangle third vertex
                                    const color clr,              // Color
                                    const uchar opacity=255,      // Opacity
                                    const uint  style=UINT_MAX)   // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.TriangleAA(x1,y1,x2,y2,x3,y3,::ColorToARGB(clr,opacity),style);                                 }
                       
//--- Draw a triangle using Wu algorithm
   void              DrawTriangleWu(const int   x1,               // X coordinate of the triangle first vertex
                                    const int   y1,               // Y coordinate of the triangle first vertex
                                    const int   x2,               // X coordinate of the triangle second vertex
                                    const int   y2,               // Y coordinate of the triangle second vertex
                                    const int   x3,               // X coordinate of the triangle third vertex
                                    const int   y3,               // Y coordinate of the triangle third vertex
                                    const color clr,              // Color
                                    const uchar opacity=255,      // Opacity
                                    const uint  style=UINT_MAX)   // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.TriangleWu(x1,y1,x2,y2,x3,y3,::ColorToARGB(clr,opacity),style);                                 }
                       
//--- Draw a circle using AntiAliasing algorithm
   void              DrawCircleAA(const int    x,                 // X coordinate of the circle center
                                  const int    y,                 // Y coordinate of the circle center
                                  const double r,                 // Circle radius
                                  const color  clr,               // Color
                                  const uchar opacity=255,        // Opacity
                                  const uint  style=UINT_MAX)     // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.CircleAA(x,y,r,::ColorToARGB(clr,opacity),style);                                               }
                       
//--- Draw a circle using Wu algorithm
   void              DrawCircleWu(const int    x,                 // X coordinate of the circle center
                                  const int    y,                 // Y coordinate of the circle center
                                  const double r,                 // Circle radius
                                  const color  clr,               // Color
                                  const uchar opacity=255,        // Opacity
                                  const uint  style=UINT_MAX)     // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.CircleWu(x,y,r,::ColorToARGB(clr,opacity),style);                                               }
                       
//--- Draw an ellipse by two points using AntiAliasing algorithm
   void              DrawEllipseAA(const double x1,               // X coordinate of the first point defining the ellipse
                                   const double y1,               // Y coordinate of the first point defining the ellipse
                                   const double x2,               // X coordinate of the second point defining the ellipse
                                   const double y2,               // Y coordinate of the second point defining the ellipse
                                   const color  clr,              // Color
                                   const uchar opacity=255,       // Opacity
                                   const uint  style=UINT_MAX)    // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.EllipseAA(x1,y1,x2,y2,::ColorToARGB(clr,opacity),style);                                        }
                       
//--- Draw an ellipse by two points using Wu algorithm
   void              DrawEllipseWu(const int   x1,                // X coordinate of the first point defining the ellipse
                                   const int   y1,                // Y coordinate of the first point defining the ellipse
                                   const int   x2,                // X coordinate of the second point defining the ellipse
                                   const int   y2,                // Y coordinate of the second point defining the ellipse
                                   const color clr,               // Color
                                   const uchar opacity=255,       // Opacity
                                   const uint  style=UINT_MAX)    // Line style is one of the ENUM_LINE_STYLE enumeration values or a custom value
                       { this.m_canvas.EllipseWu(x1,y1,x2,y2,::ColorToARGB(clr,opacity),style);                                        }

//+------------------------------------------------------------------+

所有添加方法的逻辑都是完全透明的。所有传递给方法的参数都已签名。每种方法的目的都已在注释中说明。所以，我相信这里一切都很清晰明了。无论如何，欢迎您参与评论部分。

操控文本的方法

CCanvas 类会记住上次显示文本的设置，包括其字体、颜色、透明度、等等。为了查找文本大小，我们可以调用 TextSize() 方法应用当前字体设置来测量文本边界矩形的宽度和高度。我们可能需要在多种情况下这样做，例如使用背景颜色覆盖之前的文本，并用新坐标重写 — 文本偏移。在这种情况下，我们不仅需要文本坐标，还需要文本锚点（左上、中上、右上、等等）。我们需要确切给出文本边界矩形的锚点角度，否则设置的擦除矩形坐标将不正确。为达此目的，我们需要添加类成员变量存储最后指定锚点。

在类的私密部分声明变量：

   long              m_long_prop[ORDER_PROP_INTEGER_TOTAL];    // Integer properties
   double            m_double_prop[ORDER_PROP_DOUBLE_TOTAL];   // Real properties
   string            m_string_prop[ORDER_PROP_STRING_TOTAL];   // String properties
   
   ENUM_TEXT_ANCHOR  m_text_anchor;                            // Current text alignment

//--- Return the index of the array the order (1) double and (2) string properties are located at
   int               IndexProp(ENUM_CANV_ELEMENT_PROP_DOUBLE property)  const { return(int)property-CANV_ELEMENT_PROP_INTEGER_TOTAL;                                 }
   int               IndexProp(ENUM_CANV_ELEMENT_PROP_STRING property)  const { return(int)property-CANV_ELEMENT_PROP_INTEGER_TOTAL-CANV_ELEMENT_PROP_DOUBLE_TOTAL;  }

在参数型类构造函数的最开始，初始化对象类型和文本锚点：

//+------------------------------------------------------------------+
//| Parametric constructor                                           |
//+------------------------------------------------------------------+
CGCnvElement::CGCnvElement(const ENUM_GRAPH_ELEMENT_TYPE element_type,
                           const int      element_id,
                           const int      element_num,
                           const long     chart_id,
                           const int      wnd_num,
                           const string   name,
                           const int      x,
                           const int      y,
                           const int      w,
                           const int      h,
                           const color    colour,
                           const uchar    opacity,
                           const bool     movable=true,
                           const bool     activity=true,
                           const bool     redraw=false)
                                          
  {
   this.m_name=this.m_name_prefix+name;
   this.m_chart_id=chart_id;
   this.m_subwindow=wnd_num;
   this.m_type=element_type;
   this.m_text_anchor=0;
   if(this.Create(chart_id,wnd_num,this.m_name,x,y,w,h,colour,opacity,redraw))
     {

在由 Type() 虚方法返回的 m_type 父类变量里，添加构造函数参数中传入的对象类型，而 m_text_anchor 变量则采用默认值进行初始化 — 边界矩形的左上角。

在类主体的最后（即，在操控基元的代码块之后），添加操控文本的代码块：

//+------------------------------------------------------------------+
//| The methods of working with text                                 |
//+------------------------------------------------------------------+
//--- Return text the alignment type (anchor method)
   ENUM_TEXT_ANCHOR  TextAnchor(void)                       const { return this.m_text_anchor;                                         }

//--- Set the current font
   bool              SetFont(const string name,                   // Font name. For example, "Arial"
                             const int    size,                   // Font size
                             const uint   flags=0,                // Font creation flags
                             const uint   angle=0,                // Font slope angle in tenths of a degree
                             const bool   relative=true)          // Relative font size flag
                       { return this.m_canvas.FontSet(name,(relative ? size*-10 : size),flags,angle);                                  }

//--- Set a font name
   bool              SetFontName(const string name)               // Font name. For example, "Arial"
                       { return this.m_canvas.FontNameSet(name);                                                                       }

//--- Set a font size
   bool              SetFontSize(const int size,                  // Font size
                                 const bool relative=true)        // Relative font size flag
                       { return this.m_canvas.FontSizeSet(relative ? size*-10 : size);                                                 }

//--- Set font flags
//--- FONT_ITALIC - Italic, FONT_UNDERLINE - Underline, FONT_STRIKEOUT - Strikeout
   bool              SetFontFlags(const uint flags)               // Font creation flags
                       { return this.m_canvas.FontFlagsSet(flags);                                                                     }

//--- Set a font slope angle
   bool              SetFontAngle(const float angle)              // Font slope angle in tenths of a degree
                       { return this.m_canvas.FontAngleSet(uint(angle*10));                                                            }

//--- Set the font anchor angle (alignment type)
   void              SetTextAnchor(const uint flags=0)      { this.m_text_anchor=(ENUM_TEXT_ANCHOR)flags;                              }

//--- Gets the current font parameters and write them to variables
   void              GetFont(string &name,                        // The reference to the variable for returning a font name
                             int    &size,                        // Reference to the variable for returning a font size
                             uint   &flags,                       // Reference to the variable for returning font flags
                             uint   &angle)                       // Reference to the variable for returning a font slope angle
                       { this.m_canvas.FontGet(name,size,flags,angle);                                                                 }

//--- Return (1) the font name, (2) size, (3) flags and (4) slope angle
   string            FontName(void)                         const { return this.m_canvas.FontNameGet();                                }
   int               FontSize(void)                         const { return this.m_canvas.FontSizeGet();                                }
   int               FontSizeRelative(void)                 const { return(this.FontSize()<0 ? -this.FontSize()/10 : this.FontSize()); }
   uint              FontFlags(void)                        const { return this.m_canvas.FontFlagsGet();                               }
   uint              FontAngle(void)                        const { return this.m_canvas.FontAngleGet();                               }

//--- Return the text (1) width, (2) height and (3) all sizes (the current font is used to measure the text)
   int               TextWidth(const string text)                 { return this.m_canvas.TextWidth(text);                              }
   int               TextHeight(const string text)                { return this.m_canvas.TextHeight(text);                             }
   void              TextSize(const string text,                  // Text for measurement
                              int         &width,                 // Reference to the variable for returning a text width
                              int         &height)                // Reference to the variable for returning a text height
                       { this.m_canvas.TextSize(text,width,height);                                                                    }

//--- Display the text in the current font
   void              Text(int         x,                          // X coordinate of the text anchor point
                          int         y,                          // Y coordinate of the text anchor point
                          string      text,                       // Display text
                          const color clr,                        // Color
                          const uchar opacity=255,                // Opacity
                          uint        alignment=0)                // Text anchoring method
                       { 
                        this.m_text_anchor=(ENUM_TEXT_ANCHOR)alignment;
                        this.m_canvas.TextOut(x,y,text,::ColorToARGB(clr,opacity),alignment);
                       }

  };
//+------------------------------------------------------------------+

此处的一切都类似于处理基元。所有方法都有注释，公告了其目的、输入和输出。
我想说明一下设置当前字体参数的方法：

//--- Set the current font
   bool              SetFont(const string name,                   // Font name. For example, "Arial"
                             const int    size,                   // Font size
                             const uint   flags=0,                // Font creation flags
                             const uint   angle=0,                // Font slope angle in tenths of a degree
                             const bool   relative=true)          // Relative font size flag
                       { return this.m_canvas.FontSet(name,(relative ? size*-10 : size),flags,angle);

此处的 size 指定字体大小，并且总是根据我们要在普通 OBJ_LABEL 文本标签对象的帮助下显示文本时的字体大小来设置。大小设置为正整数值。与此对比，在画布上绘制文本时，字体大小的设置方式与 TextSetFont() 函数中的设置方式相同：

字体大小可用正值或负值进行设置。符号定义文本大小是否取决于操作系统设置（字体比例）。

如果大小为正数值，则逻辑字体显示为物理字体时，将其转换为设备物理单位（像素）。大小对应于可用字体的符号单元格的高度。在利用 TextOut() 函数和 OBJ_LABEL（“文本标签”）图形对象显示文本的情况下，不建议这样做。
如果大小为负值，则假定设置为逻辑点的十分之一（值 -350 等于 35 个逻辑点），并除以 10。所得数值转换为设备的物理单位（像素），及对应于可用字体的字符高度的绝对值。为了获得屏幕上 OBJ_LABEL 对象大小的文本，请将对象属性中指定的字体大小乘以 -10。

在方法中检查字体相对大小标志。如果已设置（默认情况下），则将大小值乘以 -10，以便用正确的数值指定字体，并将其传递给 CCanvas 类的 FontSet() 方法。

在参数型类构造函数中，加入字体初始化（设置其默认名称和大小）：

//+------------------------------------------------------------------+
//| Parametric constructor                                           |
//+------------------------------------------------------------------+
CGCnvElement::CGCnvElement(const ENUM_GRAPH_ELEMENT_TYPE element_type,
                           const int      element_id,
                           const int      element_num,
                           const long     chart_id,
                           const int      wnd_num,
                           const string   name,
                           const int      x,
                           const int      y,
                           const int      w,
                           const int      h,
                           const color    colour,
                           const uchar    opacity,
                           const bool     movable=true,
                           const bool     activity=true,
                           const bool     redraw=false)
                                          
  {
   this.m_name=this.m_name_prefix+name;
   this.m_chart_id=chart_id;
   this.m_subwindow=wnd_num;
   this.m_type=element_type;
   this.SetFont("Calibri",8);
   this.m_text_anchor=0;
   if(this.Create(chart_id,wnd_num,this.m_name,x,y,w,h,colour,opacity,redraw))
     {

这些就是我为本文计划的所有改进。我们测试一下结果。

测试

我们有一个来自前一篇文章中的 EA，在图表上显示两个图形元素对象。我们借用同一 EA，将其保存在新文件夹 \MQL5\Experts\TestDoEasy\Part75\ 中，命名为 TestDoEasyPart75.mq5，并执行以下操作：

单击第一个（顶部）对象时，我们将在其上交替绘制一个矩形和一个圆。每次单击对象时，矩形的大小在每条边侧均减少 2 个像素，圆的半径也减少 2 个像素。矩形以通常的方式绘制，而圆则运用平滑绘制。每单击一次，对象的不透明度就会从 0 增加到 255 循环。

单击第二个（底部）对象时，在其锚点上显示交替更化的文本。在文本中写入锚点名称。对象透明度保持不变。

指定所创建元素的数量:

//+------------------------------------------------------------------+
//|                                             TestDoEasyPart75.mq5 |
//|                                  Copyright 2021, MetaQuotes Ltd. |
//|                             https://mql5.com/en/users/artmedia70 |
//+------------------------------------------------------------------+
#property copyright "Copyright 2021, MetaQuotes Ltd."
#property link      "https://mql5.com/en/users/artmedia70"
#property version   "1.00"
//--- includes
#include <Arrays\ArrayObj.mqh>
#include <DoEasy\Services\Select.mqh>
#include <DoEasy\Objects\Graph\GCnvElement.mqh>
//--- defines
#define        ELEMENTS_TOTAL (2)   // Number of created graphical elements
//--- input parameters
sinput   bool  InpMovable  = true;  // Movable flag
//--- global variables
CArrayObj      list_elements;
//+------------------------------------------------------------------+

为避免每次时间帧变更时都创建相同的对象，创建新对象之前清除在 OnInit() 处理程序中已创建的对象列表：

//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
  {
//--- Set the permissions to send cursor movement and mouse scroll events
   ChartSetInteger(ChartID(),CHART_EVENT_MOUSE_MOVE,true);
   ChartSetInteger(ChartID(),CHART_EVENT_MOUSE_WHEEL,true);
//--- Set EA global variables

//--- Create the specified number of graphical elements on the canvas
   list_elements.Clear();
   int total=ELEMENTS_TOTAL;
   for(int i=0;i<total;i++)
     {
      //--- When creating an object, pass all the required parameters to it
      CGCnvElement *element=new CGCnvElement(GRAPH_ELEMENT_TYPE_ELEMENT,i,0,ChartID(),0,"Element_0"+(string)(i+1),300,40+(i*80),100,70,clrSilver,200,InpMovable,true,true);
      if(element==NULL)
         continue;
      //--- Add objects to the list
      if(!list_elements.Add(element))
        {
         delete element;
         continue;
        }
     }
//---
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+

由于我还没有图形对象集合类来检查是否需要创建具有指定名称的新对象，此处我将简单地重新创建这些对象，故需预先清除先前创建的对象列表。

OnChartEvent() 处理程序接收在两个已创建对象上的鼠标点击：

//+------------------------------------------------------------------+
//| ChartEvent function                                              |
//+------------------------------------------------------------------+
void OnChartEvent(const int id,
                  const long &lparam,
                  const double &dparam,
                  const string &sparam)
  {
//--- If clicking on an object
   if(id==CHARTEVENT_OBJECT_CLICK)
     {
      //--- In the new list, get the element object with the name corresponding to the sparam string parameter value of the OnChartEvent() handler
      CArrayObj *obj_list=CSelect::ByGraphCanvElementProperty(GetPointer(list_elements),CANV_ELEMENT_PROP_NAME_OBJ,sparam,EQUAL);
      //--- If the object is received from the list
      if(obj_list!=NULL && obj_list.Total()>0)
        {
         static uchar try0=0, try1=0;
         //--- Get the pointer to the object in the list
         CGCnvElement *obj=obj_list.At(0);
         //--- If this is the first graphical element
         if(obj.ID()==0)
           {
            //--- Set a new opacity level for the object
            uchar opasity=obj.Opacity();
            if((opasity+5)>255)
               opasity=0;
            else 
               opasity+=5;
            //--- Set a new opacity to the object
            obj.SetOpacity(opasity);
            //--- Set rectangle and circle coordinates
            int x1=2,x2=obj.Width()-3;
            int y1=2,y2=obj.Height()-3;
            int xC=(x1+x2)/2;
            int yC=(y1+y2)/2;
            int R=yC-y1;
            //--- Draw a rectangle at each first click
            if(try0%2==0)
               obj.DrawRectangle(x1+try0,y1+try0,x2-try0,y2-try0,clrDodgerBlue,obj.Opacity());
            //--- Display the circle smoothed using AntiAliasing at each second click
            else
               obj.DrawCircleAA(xC,yC,R-try0,clrGreen,obj.Opacity());
            //--- If the number of clicks on the object exceeds 30
            if(try0>30)
              {
               //--- Clear the object setting its current color and transparency
               obj.Erase(obj.ColorBG(),obj.Opacity());
               //--- Re-start the click number countdown
               try0=0;
              }
            //--- Update the chart and the object, and display the comment featuring color values and object opacity
            obj.Update(true); // 'true' is not needed here since the next Comment command redraws the chart anyway
            Comment("Object name: ",obj.NameObj(),", opasity=",obj.Opacity(),", Color BG: ",(string)obj.ColorBG());
            //--- Increase the counter of mouse clicks by object
            try0++;
           }
         //--- If this is the second object
         else if(obj.ID()==1)
           {
            //--- Set the font parameters for it ("Calibri" size 8)
            obj.SetFont("Calibri",8);
            //--- Set the text anchor angle corresponding to the click counter by object
            obj.SetTextAnchor((ENUM_TEXT_ANCHOR)try1);
            //--- Create the text out of the anchor angle name
            string text=StringSubstr(EnumToString(obj.TextAnchor()),12);
            //--- Set the text coordinates relative to the upper left corner of the graphical element
            int xT=2,yT=2;
            //--- Depending on the anchor angle, set the new coordinates of the displayed text
            //--- LEFT_TOP
            if(try1==0)       { xT=2; yT=2;                                   }
            //--- CENTER_TOP
            else if(try1==1)  { xT=obj.Width()/2; yT=2;                       }
            //--- RIGHT_TOP
            //--- since the ENUM_TEXT_ANCHOR enumeration features no 3, increase the counter of object clicks by 1
            else if(try1==2)  { xT=obj.Width()-2; yT=2; try1++;               }
            //--- LEFT_CENTER
            else if(try1==4)  { xT=2; yT=obj.Height()/2;                      }
            //--- CENTER
            else if(try1==5)  { xT=obj.Width()/2; yT=obj.Height()/2;          }
            //--- RIGHT_CENTER
            //--- since the ENUM_TEXT_ANCHOR enumeration features no 7, increase the counter of object clicks by 1
            else if(try1==6)  { xT=obj.Width()-2; yT=obj.Height()/2; try1++;  }
            //--- LEFT_BOTTOM
            else if(try1==8)  { xT=2; yT=obj.Height()-2;                      }
            //--- CENTER_BOTTOM
            else if(try1==9)  { xT=obj.Width()/2; yT=obj.Height()-2;          }
            //--- RIGHT_BOTTOM
            else if(try1==10)    { xT=obj.Width()-2; yT=obj.Height()-2;       }
            //--- Clear the graphical element filling it with the current color and transparency
            obj.Erase(obj.ColorBG(),obj.Opacity());
            //--- Display the text with the calculated coordinates in the cleared element
            obj.Text(xT,yT,text,clrDodgerBlue,255,obj.TextAnchor());
            //--- Update the object and chart
            obj.Update(true); // 'true' is not needed here since the next Comment command redraws the chart anyway
            Comment("Object name: ",obj.NameObj(),", opasity=",obj.Opacity(),", Color BG: ",(string)obj.ColorBG());
            //--- Increase the counter of object clicks
            try1++;
            if(try1>10)
               try1=0;
           }
        }
     }
  }
//+------------------------------------------------------------------+