bug#12463: 24.2; pos-visible-in-window-p gets slower over time

[Jörg Walter]

Op den Dingsdag, de 18. September 2012 Klock 19:19:15 hett Eli Zaretskii 
schreven:
> Can you see what happened in revision 104105?  That was before the
> previous image-handling code was modified into its present form, which
> originally made pbm images unavailable (that was fixed in 104186).
> The question is, was the recipe in this bug slow or fast then.
> Knowing that will probably give a hint in the right direction.

Look at 104108. In a way, it is the reverse of my suggested patch. That at 
least explains something.

-- 
CU
        Jörg