bug#12876: 24.3.50; DocView problem with cached files

[Stephen Berman]

When I revisit a PDF file that DocView has cached (also when starting
with -Q, with the cache /tmp/docview1000), trying to scroll past the
bottom or top of the page fails with the error
"doc-view-scroll-up-or-next-page: Wrong type argument:
number-or-marker-p, nil" or "doc-view-scroll-down-or-previous-page:
Wrong type argument: number-or-marker-p, nil" and in either case also
with "Error during redisplay: (eval (number-to-string
(doc-view-current-page))) signaled (wrong-type-argument numberp nil)".
In addition, the page number indication in the mode line looks odd:
e.g. for a one page document it shows "P/1", for a five page document it
shows "P/5" (only the first page is displayed).

This problem vanishes if I type `C-c C-c' to view the PDF source and
then type it again to redisplay the image: now scrolling works and the
mode line displays "P1/1" or "P1/5".  If I kill the buffer and revisit
the cached file, the problem reoccurs.  Instead of `C-c C-c', typing `W'
or `H' also redisplays the image, and now scrolling works but the size
is unaltered; repeating `W' or `H' correctly displays the changed size.
Finally, if I delete the cache and then revisit the file, there is no
problem (but there is as soon as I revisit a cached file).

The problem does not seem to happen with large PDF that have many pages;
maybe these are not cached.  It also does not happen with PS files, but
those are initially visited in ps-mode and I have to type `C-c C-c' to
view the image, so this may circumvent the problem I see with PDF files
(I currently cannot view ODF or DOCX files with DocView).

I think this problem started some time between trunk revisions 110689
and 110748 (it happened with my build from the latter but not with my
build from the former revision); I haven't had time to bisect.  It also
happens with the emacs-24 branch, revno 110854; it does not happen with
the openSUSE build of 24.2 from 2012-10-10.


In GNU Emacs 24.3.50.1 (x86_64-suse-linux-gnu, GTK+ Version 3.4.4)
 of 2012-11-12 on rosalinde
Bzr revision: 110874 monnier@iro.umontreal.ca-20121112204343-9y1tr86dl71iztk7
Windowing system distributor `The X.Org Foundation', version 11.0.11203000
System Description:     openSUSE 12.2 (x86_64)

Configured using:
 `configure '--without-toolkit-scroll-bars' 'CFLAGS=-g3 -O0''

Recent messages:
Error during redisplay: (eval (number-to-string (doc-view-current-page))) 
signaled (wrong-type-argument numberp nil) [7 times]
DocView: using cached files!
Type C-c C-c to toggle between editing or viewing the document.
Error during redisplay: (eval (number-to-string (doc-view-current-page))) 
signaled (wrong-type-argument numberp nil)
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