unit1.pas

屏幕自由画笔

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure cmerasebkgnd(var message:twmerasebkgnd);message wm_erasebkgnd;
    procedure FormResize(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }

  end;

var
  Form1: TForm1;
    Down: Boolean;
  prePt: TPoint;


implementation

{$R *.dfm}
procedure Tform1.cmerasebkgnd(var message:twmerasebkgnd);
begin
   brush.style:=bsclear;
   inherited;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := True;
  Canvas.MoveTo(X, Y);
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := False;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if Down then
  begin
    canvas.pen.color:=clred;
    canvas.Pen.Width:=5;
    Canvas.LineTo(X, Y);
    prePt := Point(X, Y);
  end;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
   form1.Repaint;
   form1.Refresh;
end;

end.