Quote Originally Posted by Kapil
But then am not getting enough examples which could tell me dynamic creation of that part of image which would be in display only...
You shouldn't need this, if your whole design can be represented as QCanvasItems which fit in memory.

If you can't fit your design in memory, then you should rather subclass QWidget and implement such functionality yourself. For example using spatial index like UB-tree, to find objects that fit in areas that should be redrawn.