Subject: Re: bug#7464: 24.0.50; mouse highlighting vanishes upon unsplitting window

From: "Jan D." <[email-masked]>
Date: Fri, 30 Mar 2012 09:43:52 +0200

Hello.

Eli Zaretskii skrev 2012-03-29 20:47:
>> From: Stephen Berman<[email-masked]>
>> Cc: [email-masked],  [email-masked]
>> Date: Thu, 29 Mar 2012 09:57:53 +0200
>>
>> openSUSE's 23.3 has GTK scroll bars, while I built 23.4 like I build 24,
>> i.e., without toolkit scroll bars.  So I rebuilt 23.4 with GTK scroll
>> bars, did the bug recipe and sure enough, now the mouse highlighting
>> remained, i.e., no bug.  Then I disabled the scroll bars in that build,
>> tested again, and got the bug again.  Then I rebuilt Emacs 24 with GTK
>> scroll bars, and now did not see the bug with them enabled but did see
>> it with them disabled.  So the answers to my questions above appear to
>> involve the presence vs. absence of GTK scroll bars.  (I guess Chong
>> Yidong also builds Emacs 24 with GTK scroll bars and tested the recipe
>> with them enabled, so that's why he did not observe the bug.)
>
> Unfortunately, I know almost nothing about how GTK in general and GTK
> scroll bars in particular are integrated into Emacs, and what, if
> anything, they change in how the Emacs display engine works.
>

It probably has something to do with the fact that Gtk+ scrollbars 
aren't handeled by the display engine and we therefore have to force a 
redraw of the scroll bars at certain points so the scrollbars look ok. 
Presumably one of these redraws does something that triggers a redraw of 
mouse highlight?  It might be that a redraw of the scroll bar generates 
some X expose/configuration event that in turn invokes the display 
engine.  I'm just speculating.

	Jan D.