Mega Code Archive
Dashed and Dotted Lines
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Title: Dashed and Dotted Lines
Question: How do you draw dashed and dotted lines with a pen width greater than 1 ?
Answer:
The Pen styles psDash and psDot don't work
for a Pen width greater than 1. With the API function
ExtCreatePen you can draw dotted and dashed lines
of any width and style, but only for Win2K or NT.
Specify a geometric pen with a certain userstyle,
defined by an array. The values you put in this
userstyle array correspond to the size of the dash,
then the size of the first gap, then the next dash,
and so on.
See also
How to draw custom dashed/dotted lines on a canvas. -
by Borland Developer Support Staff
http://community.borland.com/article/0,1410,26475,00.html
The following examples demonstrates this. It draws
a custom line of width w, which can for example
be specified by a TrackBar.
procedure TForm1.FormPaint(Sender: TObject);
var LogBrush : tLogBrush;
Userstyle : array[0..3] of integer;
begin
UserStyle[0]:=w*4;
UserStyle[1]:=w*2;
UserStyle[2]:=w*4;
UserStyle[3]:=w*2;
LogBrush.lbStyle := BS_Solid;
LogBrush.lbColor := $ff;
LogBrush.lbHatch := 0;
Canvas.Pen.Handle:=ExtCreatePen(PS_GEOMETRIC or PS_USERSTYLE, w, LogBrush, 4, @Userstyle);
canvas.MoveTo(20,20);
canvas.LineTo(20+200,220);
end;
Use the following UserStyle Arrays for
dotted, dashed and mixed lines:
psDot
UserStyle[0]:=w div 2;
UserStyle[1]:=w*2;
UserStyle[2]:=w div 2;
UserStyle[3]:=w*2;
psDash
UserStyle[0]:=w*4;
UserStyle[1]:=w*2;
UserStyle[2]:=w*4;
UserStyle[3]:=w*2;
psDashDot
UserStyle[0]:=w div 2;
UserStyle[1]:=w*2;
UserStyle[2]:=w*4;
UserStyle[3]:=w*2;
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