The TApplicationEvents component does not receive mouse wheel messages after a user presses the mouse button over a toolbar button, moves the mouse pointer outside a toolbar, and then releases the mouse button

We've got an application where the main form repaints an image when MouseWheel events occur. It's a simple zoom in/out thing. We also have done some work to get a behavior where the control under the mouse gets the MouseWheel event. This is partially accomplished through a handler for the OnMessage event of the TApplicationEvents object.

A special click in the dxBars area will stop the TApplicationEvents object from receiving MouseWheel events.

I've created a small test app to reproduce.

1. In a new project, add a TdxBarManager and use it to add a toolbar and a dxBarButton.
2. Customize the toolbar and drag in the bar button.
3. Add a TApplicationEvents object to the form.
4. Add the following OnMessages event handler

Delphi
 case Msg.message of  
  WM_MOUSEWHEEL: begin  
    Caption := 'MouseWheel: ' + DateTimeToStr(Now);  
  end;  
end;  

That's it. Normal start-up operation of this app will update the form's caption for every mousewheel rotation.

Click the toolbar button (mine was still named "New Item"). Rotate the mouse wheel and the form's caption continues to update.

Now, perform a MouseDown on the toolbar button, but a MouseUp somewhere else. This effectively cancels the button click. Now when you rotate the mouse wheel, nothing happens to the form's caption. The MouseWheel event is not getting to the ApplicationEvents object anymore.