Change to method of window highlighting
The change made in Wimp-5_02 to Wimp-5_03 (to permit 'f' prefixed toolsprites) introduced a set of interesting boundary cases not covered by that scheme. This commit restores the former behaviour, while retaining its simplification of H/V scrollbar plotting (beefed up with a few ASSERTs). Part of fix for ticket #323. Tagged as Wimp-5_30-pre4.
Showing with 78 additions and 208 deletions