再学 GDI+[74]: 区域(3) - IsVisible

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, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    procedure FormPaint(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure FormDestroy(Sender: TObject);

    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



var rgn: TGPRegion;



procedure TForm1.FormCreate(Sender: TObject);

var

  rt: TRect;

  path: TGPGraphicsPath;

begin

  rt := ClientRect;

  InflateRect(rt, -20, -20);



  {建立区域}

  rgn := TGPRegion.Create(MakeRect(rt));



  {建立路径}

  InflateRect(rt, -2, -2);

  path := TGPGraphicsPath.Create;

  path.AddEllipse(MakeRect(rt));



  {从区域中减去路径}

  rgn.Exclude(path);



  path.Free;

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  rgn.Free;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  b: TGPBrush;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  b := TGPHatchBrush.Create(HatchStyleMin, aclSilver, aclRed);

  g.FillRegion(b, rgn);

  b.Free;

  g.Free;

end;



procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

begin

  Text := 'Form1';

  if rgn.IsVisible(X, Y) then Text := '在区域中';

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 129

  ClientWidth = 177

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  OnMouseMove = FormMouseMove

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

end