flickering images

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The point here is to suppress the flickering. Fast reloading images tend
to flicker, as Windows erases the background before painting the image.
This happens when images are reloaded in a loop into a TImage, or when
updating scenes in OpenGL. There are several possibilities :

handle the EraseBackground message

The TWinControl message handler is overridden.
insert a procedure into the form :

 type 
  TForm1=class(TForm)
   ..
   procedure WMEraseBkgnd(var message:TWMEraseBkgnd); message  WM_ERASEBKGND;
  private
   ..
  public
   ..
 end;

 
procedure TForm1.WMEraseBkgnd(var message:TWMEraseBkgnd);
begin
 message.result:=1;
end;

this means all background erase of this form are cancelled.

Change the controlstyle of the form

Change the ControlStyle in the formpaint.

procedure TForm1.FormPaint(Sender:TObject);
begin
 ControlStyle:=ControlStyle+ [csOpaque];
 .. 
end;

Use doublebuffering

This does not help with OpenGL, as the rendering context is different.
But it was recommended when the refresh method flickers on some components.

Form1.Doublebuffered:=true;

Feedback is welcome

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last updated: 4.june.99

Copyright (99,2000) Ing.Büro R.Tschaggelar