Title: Create a nonstandard region of hint
First of all, you should create a new class with ActiveHint procedure. When you create form, you should set HintWindowClass to your new class (TMyHint).
Try this:
TMyHint = class(THintWindow)
private
FRegion: THandle;
public
procedure ActivateHint(Rect: TRect; const AHint: string); override;
end;
...
procedure TMyHint.ActivateHint(Rect: TRect; const AHint: string);
begin
SetWindowRgn(Handle, 0, True);
DeleteObject(FRegion);
BoundsRect:=Rect;
FRegion:=CreateEllipticRgn(0,0,Width,Height);
SetWindowRgn(Handle, FRegion, True);
inherited ActivateHint(Rect, AHint);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.ShowHint:=False;
HintWindowClass:=TMyHint;
Application.ShowHint:=True;
end;