There's a potential problem at the awt_Canvas.cpp file. There's a flag named windowSizing declared at the awt_Component.cpp. The flag is shared among all the toplevel windows. Upon receiving the WM_SIZING message, the flag is set to true, and upon the WM_EXITSIZEMOVE message it's set back to false. It was explored that we cannot rely on the WM_EXITSIZEMOVE message (see the evaluation of the 6355340). The flag is used in the awt_Canvas.cpp to determine whether it's necessary to erase the background of a window, and as such fixing the problem could eliminate (or identify new :) ) some flickering issues.