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votes: 16
2018.10.25 18:37
iCanvas.mqh (31.88 KB)view
The library and iCanvas class simplify writing programs using Canvas.

Here is an example of a simple indicator using this library.

In this example, the indicator body features no function for processing OnChartEvent events. But it may also be present.

#property indicator_chart_window
#include <Canvas\iCanvas.mqh>

int OnInit()
   ChartSetInteger(0,CHART_CROSSHAIR_TOOL,false);  // turn off the crosshair

void OnDeinit(const int reason) {if(reason<2) {ChartSetInteger(0,CHART_CROSSHAIR_TOOL,true); ChartRedraw();}}

void  OnTimer()
   static int X=0;
   static int Y=0;
   if(X!=W.MouseX || Y!=W.MouseY)
      // Draw a blurry spot
      for(int ix=-20;ix<=20;ix++) for(int iy=-20;iy<=20;iy++)
         double p=sqrt(ix*ix+iy*iy)/20.0;
         if(p>1) p=1;
         uchar P=(uchar)Round((1.0-p)*255.0);
      //  Display the information block
      int Y1=(int)Canvas.Y(Canvas.Close(W.MouseX));
      Canvas.TextOut(W.MouseX+5,Y1+2,"Close = "+DoubleToString(Canvas.Close(W.MouseX),_Digits),0xFFFFFFFF);
      Canvas.TextOut(W.MouseX+5,Y1+18,"Bar = "+DoubleToString(W.MouseBar,2),0xFFFFFFFF);
      Canvas.TextOut(W.MouseX+5,Y1+50,"SubWindow = "+string(W.MouseSubWin),0xFFFFFFFF);
      //  Crosshairs
      int Ym=(W.MouseY>16)?(W.MouseY-16):(W.MouseY+2);
      int Xm=(W.MouseX<(W.Width-140))?(W.MouseX+4):(W.MouseX-125);

      X=W.MouseX; Y=W.MouseY;

int OnCalculate(const int rates_total,
                const int prev_calculated,
                const int begin,
                const double &price[])

Library features:

  • when connecting the library, one instance with the name Canvas of the iCanvas class derived from the CCanvas class is created immediately.
  • the size of this instance matches the entire window. Further, when the window is resized, the canvas is automatically resized (except for scripts).
  • using the OnChartEvent event handler function is optional.
  • inside the library, there is also an instance of the Window structure named W. The window parameters (except for scripts) are located and automatically updated inside this structure.

Window structure:

struct Window
   uint              Color;       // window background color
   int               Width;       // window width
   int               Height;      // window height
   int               Left_bar;    // number of the leftmost bar in the window
   double            Right_bar;   // number of the rightmost bar in the window
   double            Total_bars;  // the maximum number of bars in the window
   int               BarsInWind;  // number of visible bars in the window
   double            Y_min;       // The minimum value of the price in the window
   double            Y_max;       // The maximum value of the price in the window
   double            dy_pix;      // price change for one pixel
   int               dx_pix;      // changing the number of bars per pixel
   int               MouseX;      // coordinate X of the current position of the mouse pointer
   int               MouseY;      // coordinate Y of the current position of the mouse pointer
   double            MouseBar;    // the current bar position of the mouse pointer 
   double            MousePrice;  // the current price of the mouse pointer
   datetime          MouseTime;   // the current time of the mouse pointer
   int               MouseSubWin; // number of the subwindow in which the mouse pointer is located
   int               WindowsTotal;// total subwindows, including the main window
   int               SubWin;      // current subwindow
   datetime          time[];      // array of opening time of all visible bars in the window

iCanvas class:

class iCanvas : public CCanvas
   datetime          T[1];
   double            Pr[1];
   bool              FullWinCanvW; // using full window canvas by width
   bool              FullWinCanvH; // using full window canvas by height
                     iCanvas(int Xpos=0,int Ypos=0,string Name="iCanvas",int width=0,int height=0,ENUM_COLOR_FORMAT formatCF=COLOR_FORMAT_ARGB_NORMALIZE,int subwin=-1);
                    ~iCanvas() { Destroy();};
   double            X(double bar);
   double            X(datetime Time) {return X((double)Ceil(W.Right_bar)+iBarShift(NULL,0,Time));};
   double            Y(double Price)  {return((W.Y_max-Price)/W.dy_pix); };
   double            Bar(int x)       {return((double)W.Left_bar+1-(double)x/(double)W.dx_pix);};
   datetime          TimePos(int x)   {double B=Bar(x); CopyTime(_Symbol,_Period,Floor(B),1,T); return T[0]+int((double)PeriodSeconds()*(1-B+(int)B));};
   double            Close(int x)     {CopyClose(_Symbol,_Period,int(Bar(x)),1,Pr); return Pr[0];};
   double            Open(int x)      {CopyOpen(_Symbol,_Period,int(Bar(x)),1,Pr); return Pr[0];};
   double            High(int x)      {CopyHigh(_Symbol,_Period,int(Bar(x)),1,Pr); return Pr[0];};
   double            Low(int x)       {CopyLow(_Symbol,_Period,int(Bar(x)),1,Pr); return Pr[0];};
   bool              FullWinCanvWidth()  {return FullWinCanvW;}; // using full window canvas by width  
   bool              FullWinCanvHeight() {return FullWinCanvH;}; // using full window canvas by height             

Translated from Russian by MetaQuotes Software Corp.
Original code:

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