WMMouseWheel not working in Delphi

I wrote the following code: procedure MouseWheel(var Msg:TWMMouseWheel);message WM_MOUSEHWHEEL; I used it for a component based on TPanel (TMyP=class(TPanel)) (Notice that I don't want to use TCustomPanel due to my own开发者_Python百科 reasons)

But anyway the event is not called when I use mouse wheel on the panel. Please Help me!

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The mouse wheel messages are sent to the control with the focus. And panels usually aren't focusable.

I use this TApplicationEvents.OnMessage handler in my applications to send the mouse wheel message to the window under the mouse cursor instead of the focused control.

procedure TMainDataModule.ApplicationEventsMessage(var Msg: tagMSG; var Handled: Boolean);
var
  Wnd: HWND;
begin
  if Msg.message = WM_MOUSEWHEEL then
  begin
    Wnd := WindowFromPoint(Msg.pt);
    // It must be a VCL control otherwise we could get access violations
    if IsVCLControl(Wnd) then
      Msg.hwnd := Wnd; // change the message receiver to the control under the cursor
  end;
end;

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In addition to Andreas Hausladen's answer you need to know, that some mouse drivers don't send WM_MOUSEWHEEL and instead send several WM_VSCROLL messages. You need to check this as well.

Upd: Note, that there exist also WM_HSCROLL messages which can also be sent by some mice which have two wheels or a tilting wheel. That's why I wrote WM_SCROLL initially.