Draw currently displayed page area in DiffMap (closes bgo#470729)
While ideally the scrollbar thumb should give a decent indication of the location and size of the current viewing pane in terms of the whole file, it doesn't always correspond very well. For example, in long files, the scroll thumb will not shrink below a certain size for usability purposes, which damages its use as an indicator. This commit introduces a relatively subtle overlay on our DiffMaps to show which part of the file is currently being displayed.
Showing with 20 additions and 3 deletions