I am using NT 4.0.
I programmed sort of a plugin-system for my application (PlugIns are dynamically loaded DLLs).
Plugins may draw onto certain areas inside the applications's main window by using HWNDs of controls passed to them:
Main App -> createbutton -> HWND(of button) -> PlugIn
Plugin uses GetDC(HWND) and then draws...
This works fine. Almost always.
But there are situations, were nothing is visible on screen, although the HWND is valid and the DC is valid as well. (I am using DrawIconEx for example)
Sorry for not beeing able to clearify this "Situations" but it is rather hard. Example: Pressing CTRL+ALT+DELETE shows the lock screen under NT. When not returning to the normal screen, the whole app is beeing redrawed. I intercept the WM_PAINT and try to redraw my icon and nothing happens..
I even tried GetDCEx(hDrawWnd, 0, DCX_LOCKWINDOWUPDATE | DCX_PARENTCLIP); but no results.