detecting open overlapping windows

[shbonita]

If a Ctrl+F is pressed, we need to detect what part of the code editor is occluded. These events should be written out to the gaze output so that we can use this information during post processing. We also need to know what part of the screen is occluded.

The above is one example of an overlapping window. There could be other windows that overlap the code editor such as the larger search window.

This issue does not deal with tracking contents of what is on the window.