Redraw issues on window class with CS_OWNDC set

It seems that ReactOS have some issues on window class with CS_OWNDC set.

For example, GreenPad uses CS_OWNDC for its edit view control:

(it doesn't set wndclass.hbrBackground on outer control and main window, only the inner view control is responsible to paint the text and background)

and clicking on taskbar item to hide and unhide GreenPad sometimes will make inner view control becomes completely invisible:

in such case, even GreenPad loads a file and scrollbar becoming usable, scrolling it can not make control to redraw its context correctly:

test binary is attached.