再学 GDI+[74]: 区域(3) - IsVisible

本例效果图:

---

代码文件:

---

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:

---

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