unit Unit1;



interface



uses

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

  Dialogs, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    Timer1: TTimer;

    Memo1: TMemo;

    procedure FormCreate(Sender: TObject);

    procedure Timer1Timer(Sender: TObject);

  private

    { Private declarations }

    FAnchors: TAnchors;

    procedure WMMOVING(var Msg: TMessage); message WM_MOVING;

  public

    { Public declarations }

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses Math;



procedure TForm1.WMMOVING(var Msg: TMessage);

begin

  inherited;

  with PRect(Msg.LParam)^ do begin

    Left := Min(Max(0, Left), Screen.Width - Width);

    Top := Min(Max(0, Top), Screen.Height - Height);

    Right := Min(Max(Width, Right), Screen.Width);

    Bottom := Min(Max(Height, Bottom), Screen.Height);

    FAnchors := [];

    if Left = 0 then Include(FAnchors, akLeft);

    if Right = Screen.Width then Include(FAnchors, akRight);

    if Top = 0 then Include(FAnchors, akTop);

    if Bottom = Screen.Height then Include(FAnchors, akBottom);

    Timer1.Enabled := FAnchors <> [];

  end;

end;



procedure TForm1.FormCreate(Sender: TObject);

begin

  Timer1.Enabled := False;

  Timer1.Interval := 200;

  FormStyle := fsStayOnTop;

end;



procedure TForm1.Timer1Timer(Sender: TObject);

const

  cOffset = 2;

var

  vHandle: THandle;

begin

  vHandle := WindowFromPoint(Mouse.CursorPos);

  while (vHandle <> 0) and (vHandle <> Handle) do

    vHandle := GetParent(vHandle);

  if vHandle = Handle then begin

    if akLeft in FAnchors then Left := 0;

    if akTop in FAnchors then Top := 0;

    if akRight in FAnchors then Left := Screen.Width - Width;

    if akBottom in FAnchors then Top := Screen.Height - Height;

  end else begin

    if akLeft in FAnchors then Left := -Width + cOffset;

    if akTop in FAnchors then Top := -Height + cOffset;

    if akRight in FAnchors then Left := Screen.Width - cOffset;

    if akBottom in FAnchors then Top := Screen.Height - cOffset;

  end;

end;



end.