Flickering TImage component when drawing on it

[valmierietis]

Hi!
I want to draw rectangles on TImage component imgMain, this is it's `onMouseMove` even:

procedure TfrmMain.imgMainMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
imgMain.Canvas.Pen.Color:=clWhite;
imgMain.canvas.Rectangle(X-10,Y-10,X+10,Y+10);
end;

I wrote in at home, everything was perfect. Then I brought it to my work's computer and I changed nothing, just re-compiled it. And now it flickers when moving mouse over that component (as if it tried to redraw everything or something like that). Why is it so? What to do? Can it be so because at home there is Delphi 7, but at work - Delphi 6? How can I make it normal?

Thank you!

 

[jbpelletier]

hi,
usualy i use

in the form create add :
DoubleBuffered:=true; //this help a lot

also, recently i found that this proc should help (but i havent tryies that much). as is, this should prevent form flicker.. maybe it can be implemented for Ttimage, maybe not.. anyhow its good to know

procedure Tform1.WMEraseBkgnd(var m : TWMEraseBkgnd);
begin
m.Result := LRESULT(False);
end;

but.. in any case, its better to draw on an invisible component and once everything is draw.. copy it to the visible component.. thats the real way to avoid flicker

hope this help
jb

 

[valmierietis]

Wow, thanks, this `DoubleBuffered:=true;` helped instantly, I had to do nothing else! Thanks a lot!