[Bug 51553] Purple bitmap should be transparent in scrollbar theming

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51553

Zhiyi Zhang  changed:

What    |Removed                     |Added
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             Status|NEEDINFO                    |NEW

--- Comment #5 from Zhiyi Zhang  ---
Confirmed. The scrollbar gripper parts of the Win8RTM theme use a 32bit bitmap,
which makes uxtheme think it has an alpha channel but doesn't, specifically,
uxtheme/msstyles.c prepare_alpha() should return FALSE has_alpha value. Further
investigation is needed because XP seems to handle such bitmaps well.