Canvas.DrawFocusRect

[backprop]

I think I used Canvas.DrawFocusRect on Paintbox in Delphi to select part of image inside MouseMoveEvent, but on linux that do not draw anything.

For instance, plain PaintBox1.Canvas.DrawFocusRect (rect(0,0,100,100)) draw nothing, while Canvas.Rectangle draws rectangle...

Can anyone provide working example?

[zeljko]

You should do all paintings in PaintBox.OnPaint event, otherwise nothing will be painted with cocoa or qt widgetsets. Even on windows or using gtk2 it is wise to use paint events to draw stuff.

[wp]

Try this (just a form with a paintbox and events attached):

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, ExtCtrls,Grids,SysUtils, Forms, Controls, Graphics, Dialogs;
9.  
10. type
11.   TForm1 = class(TForm)
12.     Paintbox1: TPaintbox;
13.     procedure FormCreate(Sender:TObject);
14.     procedure PaintBox1MouseDown(Sender:TObject;Button:TMouseButton;Shift:
15.       TShiftState;X,Y:Integer);
16.     procedure PaintBox1MouseMove(Sender:TObject;Shift:TShiftState;X,Y:Integer);
17.     procedure PaintBox1Paint(Sender:TObject);
18.   private
19.     FStartPt, FMousePt: TPoint;
20.  
21.   public
22.  
23.   end;
24.  
25. var
26.   Form1: TForm1;
27.  
28. implementation
29.  
30. {$R *.lfm}
31.  
32. procedure TForm1.PaintBox1MouseDown(Sender:TObject;Button:TMouseButton;Shift:
33.   TShiftState;X,Y:Integer);
34. begin
35.   FStartPt := Point(X, Y);
36.   FMousePt := FStartPt;
37. end;
38.  
39. procedure TForm1.FormCreate(Sender:TObject);
40. begin
41.   FMousePt := Point(-9999, -9999);
42. end;
43.  
44. procedure TForm1.PaintBox1MouseMove(Sender:TObject;Shift:TShiftState;
45.   X,Y:Integer);
46. begin
47.   if (ssLeft in Shift) then
48.   begin
49.     FMousePt := Point(X, Y);
50.     Paintbox1.Invalidate;
51.   end;
52. end;
53.  
54. procedure TForm1.PaintBox1Paint(Sender:TObject);
55. var
56.   R: TRect;
57. begin
58.   Paintbox1.Canvas.Brush.Color := clWhite;
59.   Paintbox1.Canvas.FillRect(0, 0, Paintbox1.Width, Paintbox1.Height);
60.   if (FMousePt.X > -9999) and (FMousePt.Y > -9999) then
61.   begin
62.     R := Rect(FStartPt.X, FStartPt.Y, FMousePt.X, FMousePt.Y);
63.     R.NormalizeRect;
64.     Paintbox1.Canvas.DrawFocusRect(R);
65.   end;
66. end;
67.  
68. end.

A simple Paintbox.Canvas.DrawRect in the Paintbox.OnPaint did not show the focus rect, too. I don't know whether this is specific to my Linux system (Manjaro XFCE in dark mode), but the FocusRect appeared when I filled the background with white color.

[backprop]

Code: Pascal  [Select][+][-]

1. procedure TForm1.PaintBox1Paint(Sender: TObject);
2. begin
3.   PaintBox1.Canvas.Draw(0, 0, bmp);
4.  
5.   PaintBox1.Canvas.Pen.Width := 1;
6.   PaintBox1.Canvas.Brush.Style := bsClear;
7.   PaintBox1.Canvas.Pen.Mode := pmNot;
8.   PaintBox1.Canvas.Pen.Style := psDot;
9.   PaintBox1.Canvas.Pen.Color := clWhite;
10.  
11.   //Paintbox1.Canvas.DrawFocusRect(Selection);
12.   PaintBox1.Canvas.Rectangle(Selection);
13. end;

This works as intended, but DrawFocusRect do nothing.

Linux Neon, X11, defailt theme.