with unigine 2.7.1 qt frame
after set the D3d11AppQt as sub widget of other widget (the crash bug will not occure in center widget),and start the engine , unigine will get crash over here.
after debuging ,find that there was called QApplication::processevent when in setVideoMode function in AppQt when an engine object initialization, the processevent will call the timerEvent.
however ,in that time, engine object just do not finish it's initialization, then do the update will cause crash.
below is my resolution to fix that.