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  • WinAPI: PtInRegion、OffsetRgn

    本例效果图:


    unit Unit1;
    
    interface
    
    uses
      Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
      Dialogs;
    
    type
      TForm1 = class(TForm)
        procedure FormCreate(Sender: TObject);
        procedure FormDestroy(Sender: TObject);
        procedure FormPaint(Sender: TObject);
        procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
          Shift: TShiftState; X, Y: Integer);
        procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
        procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
          Shift: TShiftState; X, Y: Integer);
      end;
    
    var
      Form1: TForm1;
    
    implementation
    
    {$R *.dfm}
    
    var
      Rgn: HRGN;
      f: Boolean;
      x1,y1: Integer;
    
    procedure TForm1.FormCreate(Sender: TObject);
    begin
      Rgn := CreateEllipticRgn(11, 11, 111, 66);
      DoubleBuffered := True; {可以使用双倍缓存来禁止闪烁}
    end;
    
    procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      if PtInRegion(Rgn, X, Y) then {判断鼠标当前点是否在区域内}
      begin
        f := True;
        x1 := X;
        y1 := y;
      end;
    end;
    
    procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    begin
      if not f then Exit;
      OffsetRgn(Rgn, X-x1, Y-y1); {移动区域}
      Repaint;
      x1 := X;
      y1 := y;
    end;
    
    procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      f := False;
    end;
    
    procedure TForm1.FormPaint(Sender: TObject);
    begin
      Canvas.Brush.Color := clSilver;
      Canvas.Brush.Style := bsCross;
      FillRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle);
    
      Canvas.Brush.Color := clRed;
      Canvas.Brush.Style := bsSolid;
      FrameRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle, 2, 2);
    end;
    
    procedure TForm1.FormDestroy(Sender: TObject);
    begin
      DeleteObject(Rgn);
    end;
    
    end.
    
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  • 原文地址:https://www.cnblogs.com/del/p/1208252.html
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