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Dashed lines

Posted on 1997-09-01
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Last Modified: 2010-04-04
How can I set the color of the 'gaps' in a dashed line?

I have a component ('chart') which draws lines on its canvas, it is over a form ('desktop') with a black panel on it. The dashed lines show silver gaps (from the silver form?) instead of transparent or black gaps to match the black panel that forms the background for the lines.
      Chart := TChartPlot.create(DeskTop);
      Chart.parent := DeskTop.BlackPanel;
If I can't get it to work correctly, then if I can just set the color of the gaps to black I'll be happy!

Thanks,
Frog.
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Question by:frog
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2 Comments
 
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Accepted Solution

by:
arh earned 100 total points
ID: 1343335
Use windows API calls: SetBkMode or SetBkColor.
Here is an example (i tested it on a simple form with one
button):

procedure TForm1.Button1Click(Sender: TObject);
begin
  canvas.pen.style:=psDash;
  canvas.pen.color:=clYellow;
  canvas.pen.width:=1;
{ sets 'gap' color to red }
  setbkcolor(canvas.handle, clRed );
  canvas.moveto( 0, height );
  canvas.lineto( width, 0 );
{ sets 'gap' color to transparent }
  setbkmode( canvas.handle, transparent );
  canvas.moveto( 0, 0 );
  canvas.lineto( width, height );
end;

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Author Comment

by:frog
ID: 1343336
As usual it's all in the help, just a matter of finding it.

Thanks for your help.
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