Split out DiffMap functionality into new widget
The DiffMap widget (the bars showing a coloured summary of changes at the left and right of the main file comparison window) has always been a purely custom creation based on gtk.DrawingArea. This commit breaks it out into a separate file and makes it a DrawingArea subclass. This also changes the drawing done, syncing the colours used with the LinkMap and TextView, and allowing thinner lines for insert chunks. In addition, our style-dependent calculations should now be more robust for unusual themes.
Showing with 161 additions and 57 deletions