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Frequently Asked Questions

Creating temporary canvas

Question:

I need a temporary canvas to draw to, but when I attempt to create one, I get several application errors. How do I do this?

Answer:

Create a Bitmap, and use the TBitmap's canvas property to
draw on. The following example creates a Bitmap, draw on its'
canvas, draws the canvas to the form's backgound, and then
free the bitmap.

Example:

procedure TForm1.Button1Click(Sender: TObject);
var
  bm : TBitmap;
begin
  bm := TBitmap.Create;
  bm.Width := 100;
  bm.Height := 100;
  bm.Canvas.Brush.Color := clRed;
  bm.Canvas.FillRect(Rect(0, 0, 100, 100));
  bm.Canvas.MoveTo(0, 0);
  bm.Canvas.LineTo(100, 100);
  Form1.Canvas.StretchDraw(Form1.ClientRect,
                           Bm);
  bm.Free;
end;

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