Re-learning gdi+[25]: Tgppen

This example effect chart:

Code files:Unit Unit1;
Interface
Uses
Windows, Messages, sysutils, variants, Classes, Graphics, Controls, Forms,
Dialogs, Stdctrls, Tecanvas, Comctrls;
Type
TForm1 = Class (Tform)
Combobox1:tcombobox;
Combobox2:tcombobox;
Trackbar1:ttrackbar;
Buttoncolor1:tbuttoncolor;
Procedure Formcreate (Sender:tobject);
Procedure Formpaint (Sender:tobject);
Procedure Combobox1change (Sender:tobject);
Procedure Combobox2change (Sender:tobject);
Procedure Trackbar1change (Sender:tobject);
Procedure Buttoncolor1click (Sender:tobject);
End
Var
Form1:tform1;
Implementation
{$R *.DFM}
Uses Gdipobj,gdipapi, Typinfo;
Var
StartCap, Endcap:integer;
Linewidth:single = 2;
Linecolor:tgpcolor = aclred;
Procedure Tform1.formcreate (Sender:tobject);
Begin
With Combobox1.items do
Begin
ADD (' Linecapflat ');
ADD (' Linecapsquare ');
ADD (' Linecapround ');
ADD (' Linecaptriangle ');
ADD (' Linecapnoanchor ');
ADD (' Linecapsquareanchor ');
ADD (' Linecaproundanchor ');
ADD (' Linecapdiamondanchor ');
ADD (' Linecaparrowanchor ');
ADD (' Linecapcustom ');
End
Combobox1.itemindex: = 0;
Combobox2.items: = Combobox1.items;
Combobox2.itemindex: = 0;
Trackbar1.showselrange: = False;
Trackbar1.min: = 1;
Trackbar1.max: = 50;
Trackbar1.position: = 2;
Buttoncolor1.symbolcolor: = clred;
End
Procedure Tform1.formpaint (Sender:tobject);
Var
G:tgpgraphics;
P:tgppen;
X1,y1,x2,y2:integer;
Begin
G: = Tgpgraphics.create (Canvas.handle);
P: = tgppen.create (0);
G.clear (Makecolor (255,255,255));
X1: = 50;
x2: = ClientWidth-50;
Y1: = clientheight Div 2;
y2: = y1;
P.setcolor (LineColor);
P.setwidth (linewidth);
P.setstartcap (STARTCAP);
P.setendcap (ENDCAP);
G.drawline (p, x1, y1, x2, y2);
G.free;
P.free;
End
Procedure Tform1.combobox1change (Sender:tobject);
Var
I:integer;
Begin
I: = 0;
Case Tcombobox (Sender). ItemIndex of
0:I: = Linecapflat;
1:I: = Linecapsquare;
2:I: = Linecapround;
3:I: = Linecaptriangle;
4:I: = Linecapnoanchor;
5:I: = Linecapsquareanchor;
6:I: = Linecaproundanchor;
7:I: = Linecapdiamondanchor;
8:I: = Linecaparrowanchor;
9:I: = Linecapcustom;
10:I: = Linecapanchormask;
End
If Tcombobox (Sender) = ComboBox1 then startcap: = i;
If Tcombobox (Sender) = ComboBox2 then endcap: = i;
Repaint;
End
Procedure Tform1.combobox2change (Sender:tobject);
Begin
Combobox1change (Sender);
End
Procedure Tform1.trackbar1change (Sender:tobject);
Begin
LineWidth: = trackbar1.position;
Repaint;
End
Procedure Tform1.buttoncolor1click (Sender:tobject);
Begin
LineColor: = Colorreftoargb (Buttoncolor1.symbolcolor);
Repaint;
End
End.