Re: Why buffer_shared is a mistake

[Eli Zaretskii]

> Date: Thu, 06 Dec 2012 20:02:30 +0400
> From: Dmitry Antipov <address@hidden>
> CC: Eli Zaretskii <address@hidden>
> 
> 1) Redisplay is invoked with "xaxa" as current_buffer, and buffer_shared is 
> recalculated
>     to 2 because "xaxa" is displayed in 2 windows. On leaving 
> redisplay_internal, buffer_shared
>     is 2.
> 
> 2) modify_overlay is called for "*scratch*", and this function still sees 
> buffer_shared as 2
>     (unchanged since last redisplay invocation), although *scratch* is 
> displayed in the only
>     window.
> 
> 3) ???
> 
> IIUC, as the minimum minorum, buffer_shared should be reset to 0 after 
> leaving redisplay_internal.
> Or it should be a per-buffer field.

buffer_shared is used only by xdisp.c, with the single exception of
modify_overlay.  How about changing modify_overlay to compute this
value by itself?

IOW, I think modify_overlay shouldn't have used that variable to
begin with.  It's an internal variable used by the display engine.