* DictQuickLookup: Preserve alpha when switching dict, and scrolling
inside a dict.
* Start moving the NumberPicker alpha hack to Button itself
This makes handling flash_ui easier and saner, avoiding flickering.
* Handle the transparency hack entirely from within Button
* Murder the now unnecessary NumberPicker update_callback hack
* Tweak comments
* And the Button handling made that redundant, too
* Squish debug print
* More comment tweaks
* Reset transparency on scrolling instead of rpeserving it
* Reset alpha when switching dictionaries
* Simplify the pre/post callbakc transparency state handling
And explain why we need to care.
* Give a named reference to ButtonDialog's MovableContainer, so the Button
alpha hack behaves with it
* Document the "self.movable" convention
* Amend that comment a bit
e.g., we don't care much about MultiConfirmBox'w MpvableContainer, as
any button action will close it.
* And make SkimTo's MovableContainer accessible so that Button can grok
that it's translucent
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