Turn on D3D9 layers, and open the options dialog. You will get an assertion that mFramesWithLayers is out of sync, and the options dialog will not draw (it'll either be white or transparent).

This also happens with d2d disabled.

This looks like it is caused by us getting confused about whether we should be using an accelerated layer manager or not. The following fixes the problem but may not be correct: diff --git a/widget/src/windows/nsWindow.cpp b/widget/src/windows/nsWindow.cpp --- a/widget/src/windows/nsWindow.cpp +++ b/widget/src/windows/nsWindow.cpp @@ -3164,17 +3164,17 @@ nsWindow::GetLayerManager() { nsWindow *topWindow = GetNSWindowPtr(GetTopLevelHWND(mWnd, PR_TRUE)); if (!topWindow) { return nsBaseWidget::GetLayerManager(); } if (topWindow->GetAcceleratedRendering() != mUseAcceleratedRendering) { - mLayerManager = NULL; + //mLayerManager = NULL; mUseAcceleratedRendering = topWindow->GetAcceleratedRendering(); } #ifndef WINCE if (!mLayerManager) { nsCOMPtr<nsIPrefBranch2> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID); PRBool accelerateByDefault = PR_TRUE;

It doesn't make a ton of sense to make child widgets have the same acceleration status as their parent now that we have (mostly - see bug 593440) only one widget per window. (It might never have made sense.)