Setting the Line End Styles for Canvas.LineTo

问题

Is there any way to set the style for the lineends for the TCanvas.LineTo method? It seems to default to rounded ends, which looks very bad for several lines in a row of different colours when Pen.Width is set to a large value (e.g. 9).

It looks like this (rounded ends):

 ********........******
**********........******
**********........******
 ********........******

(where * is e.g. blue and . is yellow)

It is even worse if the two outer lines are drawn after the middle line:

 ********........******
**********......********
**********......********
 ********........******

I'd like it to look like this (streight ends):

 ********........******
 ********........******
 ********........******
 ********........******

Pen does not seem to offer any setting for this and neither does the LineTo method. Is there maybe a windows API function I could call?

回答1:

Maybe ExtCreatePen helps. Check the PS_ENDCAP_* and PS_JOIN_* flags.

回答2:

Sample code from DelphiPraxis forum (German language)

procedure TForm1.FormCreate(Sender: TObject);
   var LogBrush:TLOGBRUSH;
begin
   ZeroMemory(@LogBrush, SizeOf(LogBrush));
   LogBrush.lbColor:=ColorToRGB(Canvas.Pen.Color);
   LogBrush.lbHatch:=0;

   DeleteObject(Canvas.Pen.Handle);
   Canvas.Pen.Handle:=ExtCreatePen(PS_Geometric or PS_Solid or PS_EndCap_Square or PS_Join_Miter, 10, LogBrush, 0, nil);
end;

procedure TForm1.FormPaint(Sender: TObject);
begin
   Canvas.MoveTo(0, 0);
   Canvas.LineTo(50, 50);
end;

来源：https://stackoverflow.com/questions/368432/setting-the-line-end-styles-for-canvas-lineto

标签

Delphi

winapi

gdi

tcanvas