[Ohrrpgce] SVN: teeemcee/11506 Fix plank_menu_scroll_page to keep going up/down even if window is very

[subversion at HamsterRepublic.com]

teeemcee
2019-12-26 18:38:57 -0800 (Thu, 26 Dec 2019)
312
Fix plank_menu_scroll_page to keep going up/down even if window is very wide

It now does distance checking against the horizontal extent of a slice instead
of just the center point. Previously in a wide window, page down wouldn't be
able to select the Add New Thing thingbrowser button from the leftmost column.
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U   wip/plankmenu.bas