Enabling including secondary windows causes dirty region to be entire frame

[amirrosi]

On Windows 26100, rendering an app window, enabling the "include secondary windows" toggle causes the dirty region visualizer to show a red rectangle on the entire captured frame.
This suggest that the reporting only the changed regions doesn't work when enabling capturing of secondary windows.

[robmikh]

This is a known issue with the secondary window feature. It should still only provide a frame if something changes, but the dirty region right now is the entire frame. I'm working on a fix for tighter dirty regions when secondary windows are enabled.