Question

If a mouse button is pressed and a window is shown that window will receive the MouseUp event when the mouse button is released.

Is it possible to detect, once the window is shown, whether or not a mouse button is already pressed?

Answer 1

I would try this:

procedure TForm1.FormShow(Sender: TObject);
begin
  if GetKeyState(VK_LBUTTON) and $8000 <> 0 then
    ShowMessage('Left mouse button is pressed...')
  else
    ShowMessage('Left mouse button is not pressed...')
end;