WinAPI: OffsetClipRgn、PtVisible

OffsetClipRgn: 移动剪切区域; PtVisible: 判断点是否在剪切区域中.

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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;



type

  TForm1 = class(TForm)

    procedure FormCreate(Sender: TObject);

    procedure FormDestroy(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);

    procedure FormPaint(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



var

  bit: TBITMAP;

  f: Boolean;

  x1,y1: Integer;

  cvs: TCanvas;



procedure TForm1.FormCreate(Sender: TObject);

var

  Rgn: HRGN;

begin

  bit := TBitmap.Create;

  bit.LoadFromFile('c:\temp\Test.bmp');

  ClientWidth := bit.Width;

  ClientHeight := bit.Height;



  cvs := TCanvas.Create;

  cvs.Handle := GetDC(Handle);



  Rgn := CreateEllipticRgn(30,30,140,140);

  SelectClipRgn(cvs.Handle, Rgn);



  DeleteObject(Rgn);

end;



procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  if PtVisible(cvs.Handle, X, Y) then

  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;

  OffsetClipRgn(cvs.Handle, X-x1, Y-Y1);

  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

  cvs.Draw(0,0,bit);

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  bit.Free;

  cvs.Free;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 402

  Top = 230

  Caption = 'Form1'

  ClientHeight = 206

  ClientWidth = 339

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesigned

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  OnMouseDown = FormMouseDown

  OnMouseMove = FormMouseMove

  OnMouseUp = FormMouseUp

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

end