Question

I am writing a little component which i derive from speed button. All i need to do is actually override the paint method because i would like to change the appearance.
Now i’ve reached to the point where i would like to give different background color when button is clicked. However, i can’t find a way to catch left mouse button click message in my component.

What i’ve used so far:

procedure KeyboardButton.WndProc(var Message: TMessage);
begin
  if Message.LParam = VK_LBUTTON then
  begin
    //Some code
  end
  else
    inherited;
end;

Which doesn’t work as when i click on the button Message.LParam is not 1.

Also i tried…

procedure CMMouseLeave(var Message: TMessage); message CM_MOUSELEAVE;

Well, i know that CM_MOUSELEAVE is not a message that represents mouse click. But maybe there’s a message like CM_MOUSECLICK??? I couldn’t find it though. At all, can anyone please tell me what is CM_XXXX as i can’t find anything from msdn? Seems like Delphi specific messages.

Thanks in advance!

Answer 1

You’re not correctly testing for a mouse event. Try this:

if Message.Msg = WM_LBUTTONDOWN then
  // Some code
else
  inherited;

BTW, TMessage.LParam and TMessage.WParam are parameters passed with a specific message type (like WM_LBUTTONDOWN), and have different meanings depending on what TMessage.Msg actually is. There should never be a case where you get a generic message like TMessage and check only the WParam or LParam.