Using Nopopups.exe Petzols' app.
This app Sets an app menu.
If you click on a menu item, instead creating a dropdown menu, it should redraw a new menu thanks to a new SetMenu call.
In Windows it works, but in ReactOS seems SetMenu doesn't invalidate the Menu bar, and hence, the new bar is not shown. The bar is there, because if you press a button,it reforce the button repaint, and it shows the new button.
To replicate the issue:
1)Open the Nopopups.exe
1a)A menu with the following buttons appears:Main:,File..,Edit...
2)Click on File...
2A)A menu with the following buttons should appear: File:,New, Open..,Save, Save as, (Main)
The Menu from 2A) doesnt appear, but it exists, it's easy to see that the Menu is there, because forcing a full window invalidate(minimizing, covering, etc), or even clicking on a part of the Menu bar, will make the Menu to be shown properly.