Drawing on TImage.Canvas flickers in Delphi6

Dimitri Solomatine

Delphi Developer

Fri, 19 Nov 2004 20:23:23 GMT

Drawing on TImage.Canvas flickers in Delphi6

I had a smooth plot refresh by redrawing Image.Canvas.Polyline using
pmXOR.

FormPlot.Image1.Canvas.FillRect(ClientRect); //uses Brush color
(white)
FormPlot.Image1.Canvas.Pen.Mode := pmXOR;
make new Array of points
FormPlot.Image1.Canvas.PolyLine (Arr) //draw
for loop:
FormPlot.Image1.Canvas.PolyLine (Arr) //erase
make new Array
FormPlot.Image1.Canvas.PolyLine (Arr) //draw new Array
end loop;

But that was in Delphi 5, and the code compiled under D5 still runs
without flicker. Now I recompiled for D6 and a have flicker with the
gray horizontal line jumping around.
Anybody knows the reason?.. could help please?...
I would really appreciate this.

Regards
Dimitri Solomatine

Mauro Pati?

Delphi Developer

Fri, 19 Nov 2004 21:39:13 GMT

Re:Drawing on TImage.Canvas flickers in Delphi6

Quote

Dimitri Solomatine wrote:
> I had a smooth plot refresh by redrawing Image.Canvas.Polyline using
> pmXOR.

> FormPlot.Image1.Canvas.FillRect(ClientRect); //uses Brush color
> (white)
> FormPlot.Image1.Canvas.Pen.Mode := pmXOR;
> make new Array of points
> FormPlot.Image1.Canvas.PolyLine (Arr) //draw
> for loop:
> FormPlot.Image1.Canvas.PolyLine (Arr) //erase
> make new Array
> FormPlot.Image1.Canvas.PolyLine (Arr) //draw new Array
> end loop;

> But that was in Delphi 5, and the code compiled under D5 still runs
> without flicker. Now I recompiled for D6 and a have flicker with the
> gray horizontal line jumping around.
> Anybody knows the reason?.. could help please?...
> I would really appreciate this.

It's a bug with TImage. Try setting the Stretch property to true.

Kluf

Delphi Developer

Fri, 19 Nov 2004 21:58:08 GMT

Re:Drawing on TImage.Canvas flickers in Delphi6

Just in time :) XXX

Quote

"Mauro Pati?o" <M-Pat...@govst.edu> wrote in message

news:3CFB7181.29ACA46F@govst.edu...

Quote

> Dimitri Solomatine wrote:

> > I had a smooth plot refresh by redrawing Image.Canvas.Polyline using
> > pmXOR.

> > FormPlot.Image1.Canvas.FillRect(ClientRect); file://uses Brush color
> > (white)
> > FormPlot.Image1.Canvas.Pen.Mode := pmXOR;
> > make new Array of points
> > FormPlot.Image1.Canvas.PolyLine (Arr) file://draw
> > for loop:
> > FormPlot.Image1.Canvas.PolyLine (Arr) file://erase
> > make new Array
> > FormPlot.Image1.Canvas.PolyLine (Arr) file://draw new Array
> > end loop;

> > But that was in Delphi 5, and the code compiled under D5 still runs
> > without flicker. Now I recompiled for D6 and a have flicker with the
> > gray horizontal line jumping around.
> > Anybody knows the reason?.. could help please?...
> > I would really appreciate this.

> It's a bug with TImage. Try setting the Stretch property to true.

AzreA

Delphi Developer

Mon, 22 Nov 2004 16:24:59 GMT

Re:Drawing on TImage.Canvas flickers in Delphi6

What you have to do, is to tell your Form, that it does not erease its
background.
Try following code:

{ ... }
public
{ Public declarations }
procedure WMEraseBkgnd(var Message: TWmEraseBkgnd); message
WM_ERASEBKGND;
end;
{ ... }

{ ... }
procedure TForm1.WMEraseBkgnd(var Message: TWmEraseBkgnd);
begin
Message.Result := 1;
end;
{ ... }

I think this should work.

azr...@pfucrew.de

"Dimitri Solomatine" <s...@ihe.nl> schrieb im Newsbeitrag
news:3CFB5FBB.9D77AC4E@ihe.nl...

Quote

> I had a smooth plot refresh by redrawing Image.Canvas.Polyline using
> pmXOR.

> FormPlot.Image1.Canvas.FillRect(ClientRect); //uses Brush color
> (white)
> FormPlot.Image1.Canvas.Pen.Mode := pmXOR;
> make new Array of points
> FormPlot.Image1.Canvas.PolyLine (Arr) //draw
> for loop:
> FormPlot.Image1.Canvas.PolyLine (Arr) //erase
> make new Array
> FormPlot.Image1.Canvas.PolyLine (Arr) //draw new Array
> end loop;

> But that was in Delphi 5, and the code compiled under D5 still runs
> without flicker. Now I recompiled for D6 and a have flicker with the
> gray horizontal line jumping around.
> Anybody knows the reason?.. could help please?...
> I would really appreciate this.

> Regards
> Dimitri Solomatine

Other Threads

1. Drawing on canvas without flickering?

2. how to canvas.draw without flickering

3. Illiminate Flicker with function Line To (Timage.canvas)

4. D6: TImage flickering at canvas operations

5. Timage.canvas.ellipse..................flickering screen

6. How to Avoid Flicker when drawing into a bitmap canvas

7. Flickering unsynced image on drawing canvas in BCB6

8. TImage->Canvas , Threads & Flickering

9. Drawing on a TImage canvas

10. How to get to TImage Canvas drawing bitmap