再學 GDI+[74]: 區域(3) - IsVisible

本例效果圖:

　　代碼文件: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);
　{建立區域}
　rgn := TGPRegion.Create(MakeRect(rt));
　{建立路徑}
　InflateRect(rt, -2, -2);
　path := TGPGraphicsPath.Create;
　path.AddEllipse(MakeRect(rt));
　{從區域中減去路徑}
　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 := '在區域中';
end;
end.窗體文件: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