Hello!
I was having this problem with CEF + GTK on Windows some time ago, and apparently this was due to GTK using WS_EX_LAYERED for borderless windows. Now I'm facing the same problem, because the same thing happens with any windows on Windows 8 and newer.
My current workaround is just to use off-screen rendering, which is not optimal for obvious reasons.
Could you confirm if CEF is even supposed to work on a layered window, and maybe hint on what is needed to make it work?
I wonder if I am just missing some WINAPI thing that I'm unaware of, after dealing with only cross-platform frameworks all this time...