DoEasy 函数库中的图形（第七十四部分）：由 CCanvas 类提供强力支持的基本图形元素

内容

• 概述
• 改进库类
• 基于画布的所有函数库图形对象的基准对象
• 测试
• 下一步是什么？
  

概述

在前一篇文章中，我开始研究处理图形的大型函数库章节。 即，我着手开发交互窗对象，它基于 CCanvas 标准库类，将作为所有函数库图形对象的主对象。 我还测试了一些机制，并为进一步开发做好了准备。 然而，经过仔细分析发现，所选概念与构建函数库对象概念不同，交互窗对象比基准对象复杂得多。

我将针对画布上的基准图形对象引入“元素”概念。 这个概念将用于构建其余的图形对象。 例如，交互窗对象也是在程序中绘制图形结构的最低限度对象，但它业已能够作为一个独立的对象参与设计。 它已经拥有绘制对象框架、各种形状和文本的能力。 对比之下，元素对象作为创建函数库“图形”层次结构中所有后续对象的基础，例如：

• 基准图形对象 是 CObject 的衍生后代。 在终端中可用于构建的图形对象包含一些固有属性；
  
• 画布上的 Element 对象所拥有的对象属性均基于画布对象；
  
• Form 对象为设计元素对象外观提供了附加属性和功能；
  
• Window 对象 是基于元素和交互窗对象的复合对象；
  
• 诸如此类。

基于这个新概念，我将重新设计 CGBaseObj 函数库图形对象的基类，并创建一个新的“图形元素”对象，它完全重复了构建基准函数库对象的整个概念。 稍后，这种方式将令我们能够快速搜索所需的图形对象，针对它们进行排序，管理它们的行为，并渲染。

改进库类

在 MQL5\Include\DoEasy\Data.mqh 里，加入新的消息索引:

   MSG_LIB_SYS_FAILED_CREATE_STORAGE_FOLDER,          // Failed to create folder for storing files. Error: 
   MSG_LIB_SYS_FAILED_ADD_ACC_OBJ_TO_LIST,            // Error. Failed to add current account object to collection list
   MSG_LIB_SYS_FAILED_CREATE_CURR_ACC_OBJ,            // Error. Failed to create account object with current account data
   MSG_LIB_SYS_FAILED_OPEN_FILE_FOR_WRITE,            // Could not open file for writing
   MSG_LIB_SYS_INPUT_ERROR_NO_SYMBOL,                 // Input error: no symbol
   MSG_LIB_SYS_FAILED_CREATE_SYM_OBJ,                 // Failed to create symbol object
   MSG_LIB_SYS_FAILED_ADD_SYM_OBJ,                    // Failed to add symbol
   MSG_LIB_SYS_FAILED_CREATE_ELM_OBJ,                 // Failed to create the graphical element object

以及与新添加的索引对应的文本：

   {"Не удалось создать папку хранения файлов. Ошибка: ","Could not create file storage folder. Error: "},
   {"Ошибка. Не удалось добавить текущий объект-аккаунт в список-коллекцию","Error. Failed to add current account object to collection list"},
   {"Ошибка. Не удалось создать объект-аккаунт с данными текущего счёта","Error. Failed to create account object with current account data"},
   {"Не удалось открыть для записи файл ","Could not open file for writing: "},
   {"Ошибка входных данных: нет символа ","Input error: no "},
   {"Не удалось создать объект-символ ","Failed to create symbol object "},
   {"Не удалось добавить символ ","Failed to add "},
   {"Не удалось создать объект-графический элемент ","Failed to create graphic element object "},

对于 \MQL5\Include\DoEasy\Defines.mqh 中的新“图形元素”对象，将其类型添加到图形对象类型的枚举列表之中，以及其整数型和字符串型属性：

//+------------------------------------------------------------------+
//| The list of graphical element types                              |
//+------------------------------------------------------------------+
enum ENUM_GRAPH_ELEMENT_TYPE
  {
   GRAPH_ELEMENT_TYPE_ELEMENT,                        // Element
   GRAPH_ELEMENT_TYPE_FORM,                           // Form
   GRAPH_ELEMENT_TYPE_WINDOW,                         // Window
  };
//+------------------------------------------------------------------+
//| Integer properties of the graphical element on the canvas        |
//+------------------------------------------------------------------+
enum ENUM_CANV_ELEMENT_PROP_INTEGER
  {
   CANV_ELEMENT_PROP_ID = 0,                          // Form ID
   CANV_ELEMENT_PROP_TYPE,                            // Graphical element type
   CANV_ELEMENT_PROP_NUM,                             // Element index in the list
   CANV_ELEMENT_PROP_CHART_ID,                        // Chart ID
   CANV_ELEMENT_PROP_WND_NUM,                         // Chart subwindow index
   CANV_ELEMENT_PROP_COORD_X,                         // Form's X coordinate on the chart
   CANV_ELEMENT_PROP_COORD_Y,                         // Form's Y coordinate on the chart
   CANV_ELEMENT_PROP_WIDTH,                           // Form width
   CANV_ELEMENT_PROP_HEIGHT,                          // Form height
   CANV_ELEMENT_PROP_RIGHT,                           // Form right border
   CANV_ELEMENT_PROP_BOTTOM,                          // Form bottom border
   CANV_ELEMENT_PROP_ACT_SHIFT_LEFT,                  // Active area offset from the left edge of the form
   CANV_ELEMENT_PROP_ACT_SHIFT_TOP,                   // Active area offset from the top edge of the form
   CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT,                 // Active area offset from the right edge of the form
   CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM,                // Active area offset from the bottom edge of the form
   CANV_ELEMENT_PROP_OPACITY,                         // Form opacity
   CANV_ELEMENT_PROP_COLOR_BG,                        // Form background color
   CANV_ELEMENT_PROP_MOVABLE,                         // Form moveability flag
   CANV_ELEMENT_PROP_ACTIVE,                          // Form activity flag
   CANV_ELEMENT_PROP_COORD_ACT_X,                     // X coordinate of the form's active area
   CANV_ELEMENT_PROP_COORD_ACT_Y,                     // Y coordinate of the form's active area
   CANV_ELEMENT_PROP_ACT_RIGHT,                       // Right border of the form's active area
   CANV_ELEMENT_PROP_ACT_BOTTOM,                      // Bottom border of the form's active area
  };
#define CANV_ELEMENT_PROP_INTEGER_TOTAL (23)          // Total number of integer properties
#define CANV_ELEMENT_PROP_INTEGER_SKIP  (0)           // Number of integer properties not used in sorting
//+------------------------------------------------------------------+
//| Real properties of the graphical element on the canvas           |
//+------------------------------------------------------------------+
enum ENUM_CANV_ELEMENT_PROP_DOUBLE
  {
   CANV_ELEMENT_PROP_DUMMY = CANV_ELEMENT_PROP_INTEGER_TOTAL, // DBL stub
  };
#define CANV_ELEMENT_PROP_DOUBLE_TOTAL  (1)           // Total number of real properties
#define CANV_ELEMENT_PROP_DOUBLE_SKIP   (1)           // Number of real properties not used in sorting
//+------------------------------------------------------------------+
//| String properties of the graphical element on the canvas         |
//+------------------------------------------------------------------+
enum ENUM_CANV_ELEMENT_PROP_STRING
  {
   CANV_ELEMENT_PROP_NAME_OBJ = (CANV_ELEMENT_PROP_INTEGER_TOTAL+CANV_ELEMENT_PROP_DOUBLE_TOTAL), // Form object name
   CANV_ELEMENT_PROP_NAME_RES,                        // Graphical resource name
  };
#define CANV_ELEMENT_PROP_STRING_TOTAL  (2)           // Total number of string properties
//+------------------------------------------------------------------+

由于基于画布的对象还没有实数型属性，而构造函数库对象的概念需要它们的存在，故此我添加了实数型属性 stub，作为唯一的实数型属性。

为了能够按属性对图形元素对象进行排序，添加可能的排序标准枚举：

//+------------------------------------------------------------------+
//| Possible sorting criteria of graphical elements on the canvas    |
//+------------------------------------------------------------------+
#define FIRST_CANV_ELEMENT_DBL_PROP  (CANV_ELEMENT_PROP_INTEGER_TOTAL-CANV_ELEMENT_PROP_INTEGER_SKIP)
#define FIRST_CANV_ELEMENT_STR_PROP  (CANV_ELEMENT_PROP_INTEGER_TOTAL-CANV_ELEMENT_PROP_INTEGER_SKIP+CANV_ELEMENT_PROP_DOUBLE_TOTAL-CANV_ELEMENT_PROP_DOUBLE_SKIP)
enum ENUM_SORT_CANV_ELEMENT_MODE
  {
//--- Sort by integer properties
   SORT_BY_CANV_ELEMENT_ID = 0,                       // Sort by form ID
   SORT_BY_CANV_ELEMENT_TYPE,                         // Sort by graphical element type
   SORT_BY_CANV_ELEMENT_NUM,                          // Sort by form index in the list
   SORT_BY_CANV_ELEMENT_CHART_ID,                     // Sort by chart ID
   SORT_BY_CANV_ELEMENT_WND_NUM,                      // Sort by chart window index
   SORT_BY_CANV_ELEMENT_COORD_X,                      // Sort by the form X coordinate on the chart
   SORT_BY_CANV_ELEMENT_COORD_Y,                      // Sort by the form Y coordinate on the chart
   SORT_BY_CANV_ELEMENT_WIDTH,                        // Sort by the form width
   SORT_BY_CANV_ELEMENT_HEIGHT,                       // Sort by the form height
   SORT_BY_CANV_ELEMENT_RIGHT,                        // Sort by the form right border
   SORT_BY_CANV_ELEMENT_BOTTOM,                       // Sort by the form bottom border
   SORT_BY_CANV_ELEMENT_ACT_SHIFT_LEFT,               // Sort by the active area offset from the left edge of the form
   SORT_BY_CANV_ELEMENT_ACT_SHIFT_TOP,                // Sort by the active area offset from the top edge of the form
   SORT_BY_CANV_ELEMENT_ACT_SHIFT_RIGHT,              // Sort by the active area offset from the right edge of the form
   SORT_BY_CANV_ELEMENT_ACT_SHIFT_BOTTOM,             // Sort by the active area offset from the bottom edge of the form
   SORT_BY_CANV_ELEMENT_OPACITY,                      // Sort by the form opacity
   SORT_BY_CANV_ELEMENT_COLOR_BG,                     // Sort by the form background color
   SORT_BY_CANV_ELEMENT_MOVABLE,                      // Sort by the form moveability flag
   SORT_BY_CANV_ELEMENT_ACTIVE,                       // Sort by the form activity flag
   SORT_BY_CANV_ELEMENT_COORD_ACT_X,                  // Sort by X coordinate of the form active area
   SORT_BY_CANV_ELEMENT_COORD_ACT_Y,                  // Sort by Y coordinate of the form active area
   SORT_BY_CANV_ELEMENT_ACT_RIGHT,                    // Sort by the right border of the form active area
   SORT_BY_CANV_ELEMENT_ACT_BOTTOM,                   // Sort by the bottom border of the form active area
//--- Sort by real properties

//--- Sort by string properties
   SORT_BY_CANV_ELEMENT_NAME_OBJ = FIRST_CANV_ELEMENT_STR_PROP,// Sort by the form object name
   SORT_BY_CANV_ELEMENT_NAME_RES,                     // Sort by the graphical resource name
  };
//+------------------------------------------------------------------+

所有这些列举在首发文章中都有讲述，且研究过多次，故我不会在此赘述。

在创建“图形元素”对象之前，修改 MQL5\Include\DoEasy\Objects\Graph\GBaseObj.mqh 中所有函数库图形对象的基准对象类。

该对象是为了存储任意图形对象的所有公共属性，例如所创建对象类型、图表 ID、和子窗口索引，子窗口内已设置了图形对象、及其名称和名称前缀。 函数库的任意图形对象都将从该类继承。

全新创建这个类比修补现有的类更方便。 因此，简单地从文件中删除所有内容，并加入必要的内容：

//+------------------------------------------------------------------+
//|                                                     GBaseObj.mqh |
//|                                  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"
#property strict    // Necessary for mql4
//+------------------------------------------------------------------+
//| Include files                                                    |
//+------------------------------------------------------------------+
#include "..\..\Services\DELib.mqh"
#include <Graphics\Graphic.mqh>
//+------------------------------------------------------------------+
//| Class of the base object of the library graphical objects        |
//+------------------------------------------------------------------+
class CGBaseObj : public CObject
  {
private:
   int               m_type;                             // Object type
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
   
public:
//--- Return the values of class variables
   string            Name(void)                          const { return this.m_name;      }
   long              ChartID(void)                       const { return this.m_chart_id;  }
   int               SubWindow(void)                     const { return this.m_subwindow; }
//--- The virtual method returning the object type
   virtual int       Type(void)                          const { return this.m_type;      }

//--- Constructor/destructor
                     CGBaseObj();
                    ~CGBaseObj();
  };
//+------------------------------------------------------------------+
//| Constructor                                                      |
//+------------------------------------------------------------------+
CGBaseObj::CGBaseObj() : m_shift_y(0), m_type(0), m_name_prefix(::MQLInfoString(MQL_PROGRAM_NAME)+"_")
  {
  }
//+------------------------------------------------------------------+
//| Destructor                                                       |
//+------------------------------------------------------------------+
CGBaseObj::~CGBaseObj()
  {
  }
//+------------------------------------------------------------------+

函数库服务函数文件和标准库 CGraphic 类文件即刻包含在文件当中。 CCanvas 类文件已经包含在 CGraphic 之中。 与此同时，CGraphic 类拥有广泛的绘制各种图形的方法。 我们将来也需要这个。

该类继承自标准库的基类，允许我们将图形元素创建为 CObject 类对象，并遵照相同的方式把所有对象存储在相应图形对象的列表集合中。

m_type 私有变量存储我上面讨论的 ENUM_GRAPH_ELEMENT_TYPE 枚举中的对象类型。
默认情况下，对象类型为零，并由标准库基类的 Type() 虚方法返回：

   //--- method of identifying the object
   virtual int       Type(void)                                    const { return(0);      }

在此，我已重新定义了该方法，从而它可根据所创建图形对象的时间返回 m_type 变量。

受保护的类变量：

• m_name_prefix — 在此，我将存储对象的名称前缀，依据它们识别图形对象与程序的从属关系。 相应地，在此我将存储基于函数库的程序名称。
  
• m_name 存储图形对象名称。 完整的对象名称是由前缀和名称相加而创建的。 因此，在创建对象时，我们只需为新创建的对象指定唯一的一个名称，而“图形元素”对象类则会自行为名称添加前缀。 前缀允许用创建它的程序标识对象。
  
• m_chart_id — 在此，我设置要在其上创建图形对象的图表 ID。
• m_subwindow — 构建图形对象所在的图表子窗口。
  
• m_shift_y — 在图表子窗口中创建对象的 Y 坐标偏移。

公开方法简单地返回相应类的变量值：

public:
//--- Return the values of class variables
   string            Name(void)                          const { return this.m_name;      }
   long              ChartID(void)                       const { return this.m_chart_id;  }
   int               SubWindow(void)                     const { return this.m_subwindow; }
//--- The virtual method returning the object type
   virtual int       Type(void)                          const { return this.m_type;      }

在类构造函数的初始化清单中，设置 Y 坐标偏移量、对象类型（默认为0），以及由程序名称和下划线组成的名称前缀：

//+------------------------------------------------------------------+
//| Constructor                                                      |
//+------------------------------------------------------------------+
CGBaseObj::CGBaseObj() : m_shift_y(0), m_type(0), m_name_prefix(::MQLInfoString(MQL_PROGRAM_NAME)+"_")
  {
  }
//+------------------------------------------------------------------+

基于画布的所有函数库图形对象的基准对象

我们开始基于 CCanvas 类开发“图形元素”对象类。
在 \MQL5\Include\DoEasy\Objects\Graph\ 里，创建含 CGCnvElement 类的新文件 GCnvElement.mqh。

包含函数库基准图形对象文件，该类需继承自基类：

//+------------------------------------------------------------------+
//|                                                  GCnvElement.mqh |
//|                                  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"
#property strict    // Necessary for mql4
//+------------------------------------------------------------------+
//| Include files                                                    |
//+------------------------------------------------------------------+
#include "GBaseObj.mqh"
//+------------------------------------------------------------------+
//| Class of the base object of the library graphical objects        |
//+------------------------------------------------------------------+
class CGCnvElement : public CGBaseObj
  {
  }

在类的受保护部分，声明 CCanvas 和 CPause 类的对象，以及返回指定坐标相对于元素和其活动区域位置的两个方法：

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's active area
   bool              CursorInsideElement(const int x,const int y);
   bool              CursorInsideActiveArea(const int x,const int y);

private:

在类的私密部分，声明存储对象属性的数组，并编写两个方法，在相应的数组中返回指定属性的实际索引：

private:
   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

//--- Return the index of the array the order's (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;  }

public:

该类的公开部分提供了函数库类对象的标准方法，可将属性设置到数组，并从数组中返回属性值，返回对象支持指定属性标志的方法，以及比较两个对象的方法：

public:
//--- Set object's (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’s (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 true; }
   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;
//--- Creates the control

所有这些方法对于函数库对象都是标准化的。 我在第一篇文章中已研究过它们。

类的公开部分提供了在画布上创建“图形元素”对象的方法、返回指向所创建画布对象指针的方法、设置画布更新频率的方法、在图表上移动画布的方法、以及简化访问对象属性的方法：

//--- Creates the control
   bool              Create(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 redraw=false);
                                
//--- Return the pointer to a canvas object
   CCanvas          *CanvasObj(void)                                                   { return &this.m_canvas;               }
//--- Set the canvas update frequency
   void              SetFrequency(const ulong value)                                   { this.m_pause.SetWaitingMSC(value);   }
//--- Update the coordinates (shift the canvas)
   bool              Move(const int x,const int y,const bool redraw=false);
   
//--- Constructors/Destructor
                     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);
                     CGCnvElement(){;}
                    ~CGCnvElement();
     
//+------------------------------------------------------------------+
//| Methods of simplified access to object properties                |
//+------------------------------------------------------------------+
//--- Set the (1) X, (2) Y coordinates, (3) element width and (4) height,
   bool              SetCoordX(const int coord_x);
   bool              SetCoordY(const int coord_y);
   bool              SetWidth(const int width);
   bool              SetHeight(const int height);
//--- 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 and (6) 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              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 opacity, coordinate (2) of the right and (3) bottom element edge
   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);           }
                    
  };
//+------------------------------------------------------------------+

我们来详研所声明方法的实现。

参数型类构造函数：

//+------------------------------------------------------------------+
//| 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;
   if(this.Create(chart_id,wnd_num,this.m_name,x,y,w,h,colour,opacity,redraw))
     {
      this.SetProperty(CANV_ELEMENT_PROP_NAME_RES,this.m_canvas.ResourceName()); // Graphical resource name
      this.SetProperty(CANV_ELEMENT_PROP_CHART_ID,CGBaseObj::ChartID());         // Chart ID
      this.SetProperty(CANV_ELEMENT_PROP_WND_NUM,CGBaseObj::SubWindow());        // Chart subwindow index
      this.SetProperty(CANV_ELEMENT_PROP_NAME_OBJ,CGBaseObj::Name());            // Element object name
      this.SetProperty(CANV_ELEMENT_PROP_TYPE,element_type);                     // Graphical element type
      this.SetProperty(CANV_ELEMENT_PROP_ID,element_id);                         // Element ID
      this.SetProperty(CANV_ELEMENT_PROP_NUM,element_num);                       // Element index in the list
      this.SetProperty(CANV_ELEMENT_PROP_COORD_X,x);                             // Element's X coordinate on the chart
      this.SetProperty(CANV_ELEMENT_PROP_COORD_Y,y);                             // Element's Y coordinate on the chart
      this.SetProperty(CANV_ELEMENT_PROP_WIDTH,w);                               // Element width
      this.SetProperty(CANV_ELEMENT_PROP_HEIGHT,h);                              // Element height
      this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_LEFT,0);                      // Active area offset from the left edge of the element
      this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_TOP,0);                       // Active area offset from the upper edge of the element
      this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_RIGHT,0);                     // Active area offset from the right edge of the element
      this.SetProperty(CANV_ELEMENT_PROP_ACT_SHIFT_BOTTOM,0);                    // Active area offset from the bottom edge of the element
      this.SetProperty(CANV_ELEMENT_PROP_OPACITY,opacity);                       // Element opacity
      this.SetProperty(CANV_ELEMENT_PROP_COLOR_BG,colour);                       // Element color
      this.SetProperty(CANV_ELEMENT_PROP_MOVABLE,movable);                       // Element moveability flag
      this.SetProperty(CANV_ELEMENT_PROP_ACTIVE,activity);                       // Element activity flag
      this.SetProperty(CANV_ELEMENT_PROP_RIGHT,this.RightEdge());                // Element right border
      this.SetProperty(CANV_ELEMENT_PROP_BOTTOM,this.BottomEdge());              // Element bottom border
      this.SetProperty(CANV_ELEMENT_PROP_COORD_ACT_X,this.ActiveAreaLeft());     // X coordinate of the element active area
      this.SetProperty(CANV_ELEMENT_PROP_COORD_ACT_Y,this.ActiveAreaTop());      // Y coordinate of the element active area
      this.SetProperty(CANV_ELEMENT_PROP_ACT_RIGHT,this.ActiveAreaRight());      // Right border of the element active area
      this.SetProperty(CANV_ELEMENT_PROP_ACT_BOTTOM,this.ActiveAreaBottom());    // Bottom border of the element active area
     }
   else
     {
      ::Print(CMessage::Text(MSG_LIB_SYS_FAILED_CREATE_ELM_OBJ),this.m_name);
     }
  }
//+------------------------------------------------------------------+

此处，我们首先创建一个对象名称，它是由父类中所创建对象名称前缀，和构造函数参数中传入的名称组成。 因此，唯一的对象名称看起来像 "Prefix_Object_Name"。
接下来，设置需在参数中传递至父类的图表 ID 和子窗口索引变量。 之后调用在画布上创建图形对象的方法。 如果对象创建成功，则将所有数据写入元素对象属性。 如果创建 CCanvas 类的图形对象失败，则在日志中通知。 带有前缀的名称已被创建，图表 ID 将与其子窗口一起随同设置。 因此，我们可以尝试调用 Create() 方法再次创建 CCanvas 类对象。 默认情况下，创建对象时，距活动区域每个边侧的偏移量设置为零，即对象活动区域与创建的图形元素的大小相匹配。 创建之后，活动区域的大小和位置始终可用以下研究的相应方法进行更改。

在类的析构函数里，销毁所创建的 CCanvas 类对象:

//+------------------------------------------------------------------+
//| Destructor                                                       |
//+------------------------------------------------------------------+
CGCnvElement::~CGCnvElement()
  {
   this.m_canvas.Destroy();
  }
//+------------------------------------------------------------------+

该方法依据指定属性比较图形元素对象：

//+----------------------------------------------------------------------+
//|Compare CGCnvElement objects with each other by the specified property|
//+----------------------------------------------------------------------+
int CGCnvElement::Compare(const CObject *node,const int mode=0) const
  {
   const CGCnvElement *obj_compared=node;
//--- compare integer properties of two objects
   if(mode<CANV_ELEMENT_PROP_INTEGER_TOTAL)
     {
      long value_compared=obj_compared.GetProperty((ENUM_CANV_ELEMENT_PROP_INTEGER)mode);
      long value_current=this.GetProperty((ENUM_CANV_ELEMENT_PROP_INTEGER)mode);
      return(value_current>value_compared ? 1 : value_current<value_compared ? -1 : 0);
     }
//--- compare real properties of two objects
   else if(mode<CANV_ELEMENT_PROP_DOUBLE_TOTAL+CANV_ELEMENT_PROP_INTEGER_TOTAL)
     {
      double value_compared=obj_compared.GetProperty((ENUM_CANV_ELEMENT_PROP_DOUBLE)mode);
      double value_current=this.GetProperty((ENUM_CANV_ELEMENT_PROP_DOUBLE)mode);
      return(value_current>value_compared ? 1 : value_current<value_compared ? -1 : 0);
     }
//--- compare string properties of two objects
   else if(mode<ORDER_PROP_DOUBLE_TOTAL+ORDER_PROP_INTEGER_TOTAL+ORDER_PROP_STRING_TOTAL)
     {
      string value_compared=obj_compared.GetProperty((ENUM_CANV_ELEMENT_PROP_STRING)mode);
      string value_current=this.GetProperty((ENUM_CANV_ELEMENT_PROP_STRING)mode);
      return(value_current>value_compared ? 1 : value_current<value_compared ? -1 : 0);
     }
   return 0;
  }
//+------------------------------------------------------------------+

该方法是所有函数库对象的标准方法。 之前也曾研究过。 简而言之，该方法接收指定对象参数，并与当前对象的相应参数进行比较。 根据传递的参数，获取一个相似的参数，并返回两个对象参数的比较结果（1、-1 和 0 分别表示“更多”、“更少”和“相等”）。

该方法依据所有属性比较图形元素对象：

//+------------------------------------------------------------------+
//| Compare CGCnvElement objects with each other by all properties   |
//+------------------------------------------------------------------+
bool CGCnvElement::IsEqual(CGCnvElement *compared_obj) const
  {
   int beg=0, end=CANV_ELEMENT_PROP_INTEGER_TOTAL;
   for(int i=beg; i<end; i++)
     {
      ENUM_CANV_ELEMENT_PROP_INTEGER prop=(ENUM_CANV_ELEMENT_PROP_INTEGER)i;
      if(this.GetProperty(prop)!=compared_obj.GetProperty(prop)) return false; 
     }
   beg=end; end+=CANV_ELEMENT_PROP_DOUBLE_TOTAL;
   for(int i=beg; i<end; i++)
     {
      ENUM_CANV_ELEMENT_PROP_DOUBLE prop=(ENUM_CANV_ELEMENT_PROP_DOUBLE)i;
      if(this.GetProperty(prop)!=compared_obj.GetProperty(prop)) return false; 
     }
   beg=end; end+=CANV_ELEMENT_PROP_STRING_TOTAL;
   for(int i=beg; i<end; i++)
     {
      ENUM_CANV_ELEMENT_PROP_STRING prop=(ENUM_CANV_ELEMENT_PROP_STRING)i;
      if(this.GetProperty(prop)!=compared_obj.GetProperty(prop)) return false; 
     }
   return true;
  }
//+------------------------------------------------------------------+

该方法也是所有函数库对象的标准方法。 简而言之，该方法接收对象参数，并与当前对象进行比较。 在所有对象属性的三重循环中，比较两个对象的每个新属性。 如果存在不相等的属性，则该方法返回 false — 比较的对象不相等。 直至三个循环完成后，返回 true — 所比较的两个对象所有属性都相等。

该方法创建图形元素对象：

//+------------------------------------------------------------------+
//| Create the graphical element object                              |
//+------------------------------------------------------------------+
bool CGCnvElement::Create(const long chart_id,     // Chart ID
                          const int wnd_num,       // Chart subwindow
                          const string name,       // Element name
                          const int x,             // X coordinate
                          const int y,             // Y coordinate
                          const int w,             // Width
                          const int h,             // Height
                          const color colour,      // Background color
                          const uchar opacity,     // Opacity
                          const bool redraw=false) // Flag indicating the need to redraw
                         
  {
   if(this.m_canvas.CreateBitmapLabel(chart_id,wnd_num,name,x,y,w,h,COLOR_FORMAT_ARGB_NORMALIZE))
     {
      this.m_canvas.Erase(::ColorToARGB(colour,opacity));
      this.m_canvas.Update(redraw);
      this.m_shift_y=(int)::ChartGetInteger(chart_id,CHART_WINDOW_YDISTANCE,wnd_num);
      return true;
     }
   return false;
  }
//+------------------------------------------------------------------+

该方法接收构造所需的所有参数，调用 CCanvas 类中 CreateBitmapLabel() 方法的第二种形式。 如果与图表对象绑定的图形资源创建成功，则图形元素填充颜色，并调用 Update() 方法在屏幕上显示已实现的变更。 该方法接收屏幕重绘标志。 如果我们更新一个由若干个图形元素组成的复合对象，那么应该在所有复合对象元素都进行更改之后再重新绘制图表，如此可避免单个元素变更后即刷新图表。 接下来，m_shift 父类变量接收子窗口的 Y 坐标偏移量，并返回 true。 如果没有创建 CCanvas 类对象，则返回 false。

该方法返回光标相对于元素的位置：

//+------------------------------------------------------------------+
//| Return the cursor position relative to the element               |
//+------------------------------------------------------------------+
bool CGCnvElement::CursorInsideElement(const int x,const int y)
  {
   return(x>=this.CoordX() && x<=this.RightEdge() && y>=this.CoordY() && y<=this.BottomEdge());
  }
//+------------------------------------------------------------------+

该方法接收光标的 X 和 Y 坐标整数值，以及所传递的相对于元素维度的坐标位置 — 仅当光标位于元素内部时才返回 true。

该方法返回光标相对于元素活动区域的位置：

//+------------------------------------------------------------------+
//| Return the cursor position relative to the element active area   |
//+------------------------------------------------------------------+
bool CGCnvElement::CursorInsideActiveArea(const int x,const int y)
  {
   return(x>=this.ActiveAreaLeft() && x<=this.ActiveAreaRight() && y>=this.ActiveAreaTop() && y<=this.ActiveAreaBottom());
  }
//+------------------------------------------------------------------+

方法逻辑与前面的那个方法类似。 但返回的光标坐标位置是相对于元素活动区域的边界 — 只有当光标在活动区域之​​内时才返回 true 。

该方法更新元素坐标：

//+------------------------------------------------------------------+
//| Update the coordinate elements                                   |
//+------------------------------------------------------------------+
bool CGCnvElement::Move(const int x,const int y,const bool redraw=false)
  {
//--- Leave if the element is not movable or inactive
   if(!this.Movable())
      return false;
//--- If failed to set new values into graphical object properties, return 'false'
   if(!this.SetCoordX(x) || !this.SetCoordY(y))
      return false;
   //--- If the update flag is activated, redraw the chart.
   if(redraw)
      ::ChartRedraw(this.ChartID());
   //--- Return 'true'
   return true;
  }
//+------------------------------------------------------------------+

该方法接收需放置图形元素的左上角位置新坐标，以及图表重绘标志。 接下来，检查对象可移动标志，如果对象不可移动则离开。 如果调用下面研究的方法为对象设置新坐标失败，则返回 false。 接下来，如果设置了图表重绘标志，则更新图表.。 作为结果，返回 true。

该方法设置新的 X 坐标：

//+------------------------------------------------------------------+
//| Set the new  X coordinate                                        |
//+------------------------------------------------------------------+
bool CGCnvElement::SetCoordX(const int coord_x)
  {
   int x=(int)::ObjectGetInteger(this.ChartID(),this.NameObj(),OBJPROP_XDISTANCE);
   if(coord_x==x)
     {
      if(coord_x==GetProperty(CANV_ELEMENT_PROP_COORD_X))
         return true;
      this.SetProperty(CANV_ELEMENT_PROP_COORD_X,coord_x);
      return true;
     }
   if(::ObjectSetInteger(this.ChartID(),this.NameObj(),OBJPROP_XDISTANCE,coord_x))
     {
      this.SetProperty(CANV_ELEMENT_PROP_COORD_X,coord_x);
      return true;
     }
   return false;
  }
//+------------------------------------------------------------------+

该方法接收所需的 X 坐标值。 接着，从对象中获取此坐标。 如果传递的坐标与那个对象等于，则不应移动该对象。 但是我们需要检查对象属性中是否设置了相同的值。 如果值匹配，则返回 true，否则为对象属性设置所传递的新坐标值，并返回 true。
如果传递的坐标与对象坐标不匹配，则为对象设置新坐标。 如果设置成功，则将值写入对象属性，并返回 true。 在所有其他情况下，返回 false。

该方法设置新的 Y 坐标：

//+------------------------------------------------------------------+
//| Set the new Y coordinate                                         |
//+------------------------------------------------------------------+
bool CGCnvElement::SetCoordY(const int coord_y)
  {
   int y=(int)::ObjectGetInteger(this.ChartID(),this.NameObj(),OBJPROP_YDISTANCE);
   if(coord_y==y)
     {
      if(coord_y==GetProperty(CANV_ELEMENT_PROP_COORD_Y))
         return true;
      this.SetProperty(CANV_ELEMENT_PROP_COORD_Y,coord_y);
      return true;
     }
   if(::ObjectSetInteger(this.ChartID(),this.NameObj(),OBJPROP_YDISTANCE,coord_y))
     {
      this.SetProperty(CANV_ELEMENT_PROP_COORD_Y,coord_y);
      return true;
     }
   return false;
  }
//+------------------------------------------------------------------+

方法逻辑与上面研究过的设置 X 坐标类似。

该方法设置新对象的宽度：

//+------------------------------------------------------------------+
//| Set the new width                                                |
//+------------------------------------------------------------------+
bool CGCnvElement::SetWidth(const int width)
  {
   return this.m_canvas.Resize(width,this.m_canvas.Height());
  }
//+------------------------------------------------------------------+

该方法接收对象的新宽度 ，和调用 Resize() 方法调整图形资源大小的结果。
Resize() 方法传递对象的新宽度和当前高度。

该方法设置对象新高度：

//+------------------------------------------------------------------+
//| Set the new height                                               |
//+------------------------------------------------------------------+
bool CGCnvElement::SetHeight(const int height)
  {
   return this.m_canvas.Resize(this.m_canvas.Width(),height);
  }
//+------------------------------------------------------------------+

该方法接收对象的新高度 ，和调用 Resize() 方法调整图形资源大小的结果。
Resize() 方法传递对象的当前高度和新宽度。

请注意，在调整资源大小时，会覆盖画布上先前已绘制的图像。
因此，这些方法会在稍后细化。

该方法设置活动区域相对于元素的所有偏移：

//+------------------------------------------------------------------+
//| Set all shifts of the active area relative to the element        |
//+------------------------------------------------------------------+
void CGCnvElement::SetActiveAreaShift(const int left_shift,const int bottom_shift,const int right_shift,const int top_shift)
  {
   this.SetActiveAreaLeftShift(left_shift);
   this.SetActiveAreaBottomShift(bottom_shift);
   this.SetActiveAreaRightShift(right_shift);
   this.SetActiveAreaTopShift(top_shift);
  }
//+------------------------------------------------------------------+

该方法接收距“图形元素”对象边缘的所有必要的向内偏移值。 所有四个偏移值都是通过调用相应方法逐一设置的。

的方法该置元素不透明度：

//+------------------------------------------------------------------+
//| Set the element opacity                                          |
//+------------------------------------------------------------------+
void CGCnvElement::SetOpacity(const uchar value,const bool redraw=false)
  {
   this.m_canvas.TransparentLevelSet(value);
   this.SetProperty(CANV_ELEMENT_PROP_OPACITY,value);
   this.m_canvas.Update(redraw);
  }
//+------------------------------------------------------------------+

该方法接收所需的对象不透明度值（0 — 完全透明，255 — 完全不透明），和图表重绘标志。
接下来，调用 CCanvas 类的 TransparentLevelSet() 方法，将新的属性值写入对象属性，并依据所传递重绘标志刷新对象。

“图形元素”对象已准备就绪。 现在，我们需要在存储它们的列表中针对这些对象进行排序。 为达此目的，我们需要 CSelect 类，在该类中我们设置针对所有函数库对象进行排序和搜索的方法。

打开 \MQL5\Include\DoEasy\Services\Select.mqh，并包含“图形元素”对象类文件，以及在类主体末尾声明依据其属性对“图形元素”对象进行排序和搜索的方法：

//+------------------------------------------------------------------+
//|                                                       Select.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 version   "1.00"
//+------------------------------------------------------------------+
//| Include files                                                    |
//+------------------------------------------------------------------+
#include <Arrays\ArrayObj.mqh>
#include "..\Objects\Orders\Order.mqh"
#include "..\Objects\Events\Event.mqh"
#include "..\Objects\Accounts\Account.mqh"
#include "..\Objects\Symbols\Symbol.mqh"
#include "..\Objects\PendRequest\PendRequest.mqh"
#include "..\Objects\Series\SeriesDE.mqh"
#include "..\Objects\Indicators\Buffer.mqh"
#include "..\Objects\Indicators\IndicatorDE.mqh"
#include "..\Objects\Indicators\DataInd.mqh"
#include "..\Objects\Ticks\DataTick.mqh"
#include "..\Objects\Book\MarketBookOrd.mqh"
#include "..\Objects\MQLSignalBase\MQLSignal.mqh"
#include "..\Objects\Chart\ChartObj.mqh"
#include "..\Objects\Graph\GCnvElement.mqh"
//+------------------------------------------------------------------+

...

//+--------------------------------------------------------------------------+
//| The methods of working with data of the graphical elements on the canvas |
//+--------------------------------------------------------------------------+
   //--- Return the list of objects with one of (1) integer, (2) real and (3) string properties meeting a specified criterion
   static CArrayObj *ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property,long value,ENUM_COMPARER_TYPE mode);
   static CArrayObj *ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property,double value,ENUM_COMPARER_TYPE mode);
   static CArrayObj *ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_STRING property,string value,ENUM_COMPARER_TYPE mode);
   //--- Return the chart index with the maximum value of the (1) integer, (2) real and (3) string properties
   static int        FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property);
   static int        FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property);
   static int        FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_STRING property);
   //--- Return the chart index with the minimum value of the (1) integer, (2) real and (3) string properties
   static int        FindGraphCanvElementMin(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property);
   static int        FindGraphCanvElementMin(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property);
   static int        FindGraphCanvElementMin(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_STRING property);
//---
  };
//+------------------------------------------------------------------+

在文件清单的末尾，添加新声明方法的实现：

//+------------------------------------------------------------------+
//+---------------------------------------------------------------------------+
//| The methods of working with data of the graphical elements on the canvas  |
//+---------------------------------------------------------------------------+
//+------------------------------------------------------------------+
//| Return the list of objects with one integer                      |
//| property meeting the specified criterion                         |
//+------------------------------------------------------------------+
CArrayObj *CSelect::ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property,long value,ENUM_COMPARER_TYPE mode)
  {
   if(list_source==NULL) return NULL;
   CArrayObj *list=new CArrayObj();
   if(list==NULL) return NULL;
   list.FreeMode(false);
   ListStorage.Add(list);
   int total=list_source.Total();
   for(int i=0; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      if(!obj.SupportProperty(property)) continue;
      long obj_prop=obj.GetProperty(property);
      if(CompareValues(obj_prop,value,mode)) list.Add(obj);
     }
   return list;
  }
//+------------------------------------------------------------------+
//| Return the list of objects with one real                         |
//| property meeting the specified criterion                         |
//+------------------------------------------------------------------+
CArrayObj *CSelect::ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property,double value,ENUM_COMPARER_TYPE mode)
  {
   if(list_source==NULL) return NULL;
   CArrayObj *list=new CArrayObj();
   if(list==NULL) return NULL;
   list.FreeMode(false);
   ListStorage.Add(list);
   for(int i=0; i<list_source.Total(); i++)
     {
      CGCnvElement *obj=list_source.At(i);
      if(!obj.SupportProperty(property)) continue;
      double obj_prop=obj.GetProperty(property);
      if(CompareValues(obj_prop,value,mode)) list.Add(obj);
     }
   return list;
  }
//+------------------------------------------------------------------+
//| Return the list of objects with one string                       |
//| property meeting the specified criterion                         |
//+------------------------------------------------------------------+
CArrayObj *CSelect::ByGraphCanvElementProperty(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_STRING property,string value,ENUM_COMPARER_TYPE mode)
  {
   if(list_source==NULL) return NULL;
   CArrayObj *list=new CArrayObj();
   if(list==NULL) return NULL;
   list.FreeMode(false);
   ListStorage.Add(list);
   for(int i=0; i<list_source.Total(); i++)
     {
      CGCnvElement *obj=list_source.At(i);
      if(!obj.SupportProperty(property)) continue;
      string obj_prop=obj.GetProperty(property);
      if(CompareValues(obj_prop,value,mode)) list.Add(obj);
     }
   return list;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the maximum integer property value                          |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property)
  {
   if(list_source==NULL) return WRONG_VALUE;
   int index=0;
   CGCnvElement *max_obj=NULL;
   int total=list_source.Total();
   if(total==0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      long obj1_prop=obj.GetProperty(property);
      max_obj=list_source.At(index);
      long obj2_prop=max_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,MORE)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the maximum real property value                             |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property)
  {
   if(list_source==NULL) return WRONG_VALUE;
   int index=0;
   CGCnvElement *max_obj=NULL;
   int total=list_source.Total();
   if(total==0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      double obj1_prop=obj.GetProperty(property);
      max_obj=list_source.At(index);
      double obj2_prop=max_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,MORE)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the maximum string property value                           |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMax(CArrayObj *list_source,ENUM_CANV_ELEMENT_PROP_STRING property)
  {
   if(list_source==NULL) return WRONG_VALUE;
   int index=0;
   CGCnvElement *max_obj=NULL;
   int total=list_source.Total();
   if(total==0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      string obj1_prop=obj.GetProperty(property);
      max_obj=list_source.At(index);
      string obj2_prop=max_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,MORE)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the minimum integer property value                          |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMin(CArrayObj* list_source,ENUM_CANV_ELEMENT_PROP_INTEGER property)
  {
   int index=0;
   CGCnvElement *min_obj=NULL;
   int total=list_source.Total();
   if(total==0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      long obj1_prop=obj.GetProperty(property);
      min_obj=list_source.At(index);
      long obj2_prop=min_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,LESS)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the minimum real property value                             |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMin(CArrayObj* list_source,ENUM_CANV_ELEMENT_PROP_DOUBLE property)
  {
   int index=0;
   CGCnvElement *min_obj=NULL;
   int total=list_source.Total();
   if(total== 0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      double obj1_prop=obj.GetProperty(property);
      min_obj=list_source.At(index);
      double obj2_prop=min_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,LESS)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+
//| Return the object index in the list                              |
//| with the minimum string property value                           |
//+------------------------------------------------------------------+
int CSelect::FindGraphCanvElementMin(CArrayObj* list_source,ENUM_CANV_ELEMENT_PROP_STRING property)
  {
   int index=0;
   CGCnvElement *min_obj=NULL;
   int total=list_source.Total();
   if(total==0) return WRONG_VALUE;
   for(int i=1; i<total; i++)
     {
      CGCnvElement *obj=list_source.At(i);
      string obj1_prop=obj.GetProperty(property);
      min_obj=list_source.At(index);
      string obj2_prop=min_obj.GetProperty(property);
      if(CompareValues(obj1_prop,obj2_prop,LESS)) index=i;
     }
   return index;
  }
//+------------------------------------------------------------------+

这些方法在第三篇文章中我们讨论创建 CSelect 类时已进行了讲述。

我们测试一下结果。

测试

为了执行测试，我们借用上一篇文章中的 EA 并将其保存在 \MQL5\Experts\TestDoEasy\Part74\ 里，命名为 TestDoEasyPart74.mq5。

包含指向 CObject 类及其后代实例的动态指针数组的类的文件、标准库、 CSelect 和 CGCnvElement 库类文件，指定创建的“图形元素”对象的数量，并声明存储所创建图形元素的列表：

//+------------------------------------------------------------------+
//|                                             TestDoEasyPart74.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        FORMS_TOTAL (2)
//--- input parameters
sinput   bool  InpMovable  = true;  // Movable flag
//--- global variables
CArrayObj      list_elements;
//+------------------------------------------------------------------+

在 EA 的 OnInit() 处理程序中，把所有必要的参数传递给类构造函数来创建新的图形元素对象：

//+------------------------------------------------------------------+
//| 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
   int total=FORMS_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);
  }
//+------------------------------------------------------------------+

在 OnDeinit() 处理程序中，删除图表中的所有注释：

//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
//--- destroy timer
   EventKillTimer();
   Comment("");
  }
//+------------------------------------------------------------------+

在 OnChartEvent() 处理程序中，捕获对象单击事件，获取名称与处理程序 sparam 参数中设置的对象名称对应的元素对象，并将其不透明度级别加 5。 在图表注释中显示含有已处理的对象名称和不透明度级别的消息：

//+------------------------------------------------------------------+
//| 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(obj_list!=NULL && obj_list.Total()>0)
        {
         //--- Get the pointer to the object in the list
         CGCnvElement *obj=obj_list.At(0);
         //--- and set the new opacity level for it
         uchar opasity=obj.Opacity();
         if((opasity+5)>255)
            opasity=0;
         else 
            opasity+=5;
         //--- Set the new opacity to the object and display the object name and opacity level in the journal
         obj.SetOpacity(opasity);
         Comment(DFUN,"Object name: ",obj.NameObj(),", opasity=",opasity);
        }
     }
  }
//+------------------------------------------------------------------+

编译 EA，并在品种图表上启动它。 单击任何“图形元素”对象时，其不透明度增加到 255，然后在达到最大值 (255) 时，它轮回从 0 增加到 255，同时在图表注释中显示单击对象的名称，及其不透明度：

下一步是什么？

在下一篇文章中，我将继续开发“图形元素”对象，并开始在其上添加显示图形基元和文本的方法。

以下是该函数库当前版本的所有文件，以及 MQL5 的测试 EA 文件，供您测试和下载。
请您在评论中留下问题和建议。

返回内容目录

*该系列的前几篇文章:

DoEasy 函数库中的图形（第七十三部分）：图形元素的交互窗对象