Webengine parent transparency cause other widgets to disappear or stretch

Run attached sample application.

There's transparent widget that contains child widgets. One is webengineview. When webengine loads URL in widget constructor it makes other widgets disappear (bad.png). If URL is loaded from the slot it works correctly (good.png).

There's other issue that if parent is transparent and it's resized it makes other than webview content to stretch (resize_stretch). Without transparent parent it works correctly (resize_good.png). Stretched widget focus area is not stretched.