Render Window images need to be cached
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
I have noticed that when one of the render windows needs to be updated but none of the view parameters changed, a full rerender is performed. This occurs, for example, when one of the docable windows or a window from another application is dragged over the display. This can cause the whole window system to slow down.
Rather than redraw the image, the last rendered image should be cached and redrawn over the window. The QVTKWidget already has this ability. We just need to enable it.