WinAPI: RectInRegion - 判断矩形是否位于区域中

本例效果图:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  BoolStr: array[Boolean] of string = ('矩形不在区域中', '矩形在区域中');

var
  Rgn: HRGN;
  Rect: TRect;

procedure TForm1.FormCreate(Sender: TObject);
const
  n = 50;
var
  x1,y1,x2,y2: Integer;
begin
  x1 := n;
  y1 := n div 2;
  x2 := ClientWidth - n;
  y2 := ClientHeight - n;
  Rgn := CreateEllipticRgn(x1, y1, x2, y2);

  Rect := Bounds(10,10,10,10);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  OffsetRect(Rect, 10, 6);
  Repaint;
  Text := BoolStr[RectInRegion(Rgn, Rect)];
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  OffsetRect(Rect, -10, -6);
  Repaint;
  Text := BoolStr[RectInRegion(Rgn, Rect)];
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);

  FillRect(Canvas.Handle, Rect, Canvas.Brush.Handle);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  DeleteObject(Rgn);
end;

end.