Make window thumbnails in overview more distinct from real windows
In usability testing we found that some people have a hard time telling the difference between window thumbnails in the overview and "real" windows in the session. This happens especially when there are only one or two small, non-overlapping windows on the workspace, so that they are shown at 100% size in the overview.
In order to make this distinction clearer, a relatively easy thing we could try is:
- Always scale down window thumbnails in the overview a little bit (e.g. by a minimum of 2%), even if they would fit unscaled
- Have a more prominent window thumbnail hover state than the current border, e.g. scaling the whole thumbnail up by a few percent
cc @feaneron