Hi,
I tryed to run on win32 the exact same code that worked perfectly on
gtk, but it gave me a lot of flickering. I simplified the code to locate
the problem and I have basicaly a timer running at 10Hz and a custom
control. The timer tell the control to repaint. The image is first drawn
to a bitmap and then to the canvas.
First I thought it was a problem on Lazarus, but then I put this code on
Delphi and it also flickers. It also flickers on wine.
I googled for some time without sucess. Tryed some methods, like:
- Set double buffer for the form
- Add opaque to the control states
- Use a different method to draw the bitmap on the canvas
- Use a different method to repaint the image on the timer
- Removing the bitmap and painting directly to the Canvas
And I was about to post asking for help when I found a answer. Simply
set DoubleBuffered for the control ... strange.
I´m just posting because it may help someone else ^^ (and I have already
written the text when I found the solution).
thanks,
With lucky I will have a multi-platform opensource osciloscope written
partially on Lazarus on a month or two.
here is the code:
type
TTela = class(TCustomControl)
public
procedure Paint; override;
end;
TForm1 = class(TForm)
Timer1: TTimer;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
private
Tela: TTela
----
procedure TTela.Paint;
var
x, y: Integer;
Bitmap: TBitmap;
begin
Bitmap := TBitmap.Create;
try
Bitmap.Height := Height;
Bitmap.Width := Width;
Bitmap.Canvas.Pen.Color := clWhite;
Bitmap.Canvas.Rectangle(0, 0, Width, Height);
Canvas.Draw(0, 0, Bitmap);
finally
Bitmap.Free;
end;
inherited Paint;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Tela := TTela.Create(Self);
Tela.Height := 400;
Tela.Width := 500;
Tela.Parent := Self;
Tela.DoubleBuffered := True; // Required to avoid flickering on Windows
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
Tela.Free;
end;
procedure TForm1.Timer1Timer(Sender: TObject);
begin
Tela.Invalidade;
end;
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