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[SOLVED] How to Draw a TCanvas on a GTK2 Window

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aydın:
Hi everyone!

For one of my projects, I'm not using the TForm in Lazarus LCL. Instead, I'm writing my own widgetset using pure API.

On Windows, I capture and draw the painting (WM_PAINT) event as follows:

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---Procedure Form_Paint(hwnd: THandle);Var  Context: HDC;  BufCanvas: TCanvas;Begin  Context := GetDC(hwnd);   BufCanvas := TCanvas.Create;  BufCanvas.Handle := Context;   {I make my drawings}   //FIA(BufCanvas);  BufCanvas.Free;   ReleaseDC(hwnd, Context);End;
To achieve the same in GTK2, you need to set up a drawing trigger as follows:

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---gtk_signal_connect(GTK_OBJECT(window), 'expose-event', G_CALLBACK(@Form_Paint), nil);
My question is, how can I draw the TCanvas I created on the GTK2 window?

Thank you in advance.

aydın:
Hello again.

I've examined Lcl a bit, and although I don't fully understand its logic, I managed to create a working system.

After creating my window, I set up the trigger as follows:

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---gtk_signal_connect(GTK_OBJECT(PGtkWidget(Result)), 'expose-event', G_CALLBACK(@onDrawEvent),
And here is my drawing code:

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---function onDrawEvent(widget: PGtkWidget; event: PGdkEvent; user_data: gpointer): gboolean; cdecl;var  Bmp: TCanvas;  Context: HDC;begin  Context:= InterfaceBase.WidgetSet.GetDC(THandle(widget));    Bmp:= TCanvas.Create;  Bmp.Handle:= Context;    // Sample drawings  Bmp.Pen.Color:= clBlue;  Bmp.Pen.Width:= 2;  Bmp.Line(10, 10, 100, 100);    // FIA(Bmp);  Bmp.Free;    InterfaceBase.WidgetSet.ReleaseDC(THandle(widget), Context);    Result:= True;end;
In fact, it's almost identical; I hadn't thought of converting PGtkWidget to THandle.

I hope it's useful to someone.

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