再学 GDI+[35]: TGPPen 虚线画笔位移 SetDashOffset

本例效果图:

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls;

type
  TForm1 = class(TForm)
    Timer1: TTimer;
    procedure FormPaint(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
  n: Integer;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Interval := 100;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclChocolate, 8);
  p.SetDashStyle(DashStyleDashDotDot);

  p.SetDashOffset(n);

  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, 0, 0);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, ClientWidth div 2, 0);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, ClientWidth, 0);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, ClientWidth, ClientHeight div 2);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, ClientWidth, ClientHeight);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, ClientWidth div 2, ClientHeight);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, 0, ClientHeight);
  g.DrawLine(p, ClientWidth div 2, ClientHeight div 2, 0, ClientHeight div 2);

  Dec(n);
  if n > Sqrt(Sqr(ClientWidth) + Sqr(ClientWidth)) then n := 0;

  p.Free;
  g.Free;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 167
  ClientWidth = 242
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnCreate = FormCreate
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 112
    Top = 88
  end
end