Screen goes black for a moment when changing device orientation in Symbian

Steps to reproduce

1. Open the sample application (rc732889.sis)
2. Switch between landscape and portrait views by rotating the device

Actual result

Screen goes black for moment during the switch

Expected result

No black screen during the switch
In the sample application, the top part and the bottom part of the screen won't go black because they're not Qt components. Qt components should behave as those non-Qt components.