23.0.60; doc-view: occasionally stuck at welcome screen

23.0.60; doc-view: occasionally stuck at welcome screen

[Markus Triska]

When I do M-x doc-view-clear-cache, and then:

   $ emacs -Q file.pdf

doc-view correctly displays the file (for example, with:
http://www.logic.at/prolog/testqueens.pdf ). If I quit, and again

   $ emacs -Q file.pdf

then doc-view is stuck at the welcome screen. (When I press "C-c" four
times, it displays the document.) When I do M-x doc-view-clear-cache,
I can again view the document with "emacs -Q file.pdf", but it fails
on every later attempt ("emacs -Q..."), until I clear the cache again.


In GNU Emacs 23.0.60.2 (i386-apple-darwin8.11.1, GTK+ Version 2.12.9)
 of 2008-04-15 on mt-computer.local
Windowing system distributor `The XFree86 Project, Inc', version 11.0.40400000
configured using `configure  '--disable-font-backend''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Re: 23.0.60; doc-view: occasionally stuck at welcome screen

[Tassilo Horn]

Markus Triska <markus.triska@gmx.at> writes:

> When I do M-x doc-view-clear-cache, and then:
>
>    $ emacs -Q file.pdf
>
> doc-view correctly displays the file (for example, with:
> http://www.logic.at/prolog/testqueens.pdf ). If I quit, and again
>
>    $ emacs -Q file.pdf
>
> then doc-view is stuck at the welcome screen. (When I press "C-c" four
> times, it displays the document.)

I can reproduce that.  Hitting PageDown on the welcome screen is a
woraround, too.

> When I do M-x doc-view-clear-cache, I can again view the document with
> "emacs -Q file.pdf", but it fails on every later attempt ("emacs
> -Q..."), until I clear the cache again.

I've located the source of the problem.  In doc-view-display the

  (dolist (win (get-buffer-window-list buffer nil t)) ...)

doesn't iterate over any windows, e.g. get-buffer-window-list returns
nil.  I don't know why.  Maybe the with-current-buffer form shadows the
buffer-window association?

The caller is doc-view-initiate-display and the problem occurs when a
doc is already converted and thus the cached png files are used.  Then
the call is

  (doc-view-display (current-buffer) 'force)

Since the current buffer (which shows the welcome screen) in visible,
get-buffer-window-list should return that window...

Bye,
Tassilo

Re: 23.0.60; doc-view: occasionally stuck at welcome screen

[Stefan Monnier]

>> When I do M-x doc-view-clear-cache, and then:
>> 
>> $ emacs -Q file.pdf
>> 
>> doc-view correctly displays the file (for example, with:
>> http://www.logic.at/prolog/testqueens.pdf ). If I quit, and again
>> 
>> $ emacs -Q file.pdf
>> 
>> then doc-view is stuck at the welcome screen. (When I press "C-c" four
>> times, it displays the document.)

> I can reproduce that.  Hitting PageDown on the welcome screen is a
> woraround, too.

>> When I do M-x doc-view-clear-cache, I can again view the document with
>> "emacs -Q file.pdf", but it fails on every later attempt ("emacs
>> -Q..."), until I clear the cache again.

> I've located the source of the problem.  In doc-view-display the
>   (dolist (win (get-buffer-window-list buffer nil t)) ...)
> doesn't iterate over any windows, e.g. get-buffer-window-list returns nil.

Is it run before `buffer' is shown in a window, maybe?

> I don't know why.  Maybe the with-current-buffer form shadows the
> buffer-window association?

No, with-current-buffer (i.e. set-buffer) should never affect the output
of get-buffer-window-list.

> The caller is doc-view-initiate-display and the problem occurs when a
> doc is already converted and thus the cached png files are used.  Then
> the call is

>   (doc-view-display (current-buffer) 'force)

> Since the current buffer (which shows the welcome screen) in visible,
> get-buffer-window-list should return that window...

Hmmm....


        Stefan

Re: 23.0.60; doc-view: occasionally stuck at welcome screen

[Chong Yidong]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I've located the source of the problem.  In doc-view-display the
>>   (dolist (win (get-buffer-window-list buffer nil t)) ...)
>> doesn't iterate over any windows, e.g. get-buffer-window-list returns nil.
>
> Is it run before `buffer' is shown in a window, maybe?

I think what's happening is that doc-view-mode is being run during file
autodetection, before the selected window switches to the doc-view
buffer.  Thus, (window-buffer (selected-window)) is not equal to
(current-buffer).

Maybe you could fix this by reinstating the variable
doc-view-current-page, which was removed in your 2008-02-21 change.
That would provide a "default" current-page, applicable when the buffer
isn't shown in any windows.  Then modify doc-view-display accordingly.

Re: 23.0.60; doc-view: occasionally stuck at welcome screen

[Chong Yidong]

Chong Yidong <cyd@stupidchicken.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> I've located the source of the problem.  In doc-view-display the
>>>   (dolist (win (get-buffer-window-list buffer nil t)) ...)
>>> doesn't iterate over any windows, e.g. get-buffer-window-list returns nil.
>>
>> Is it run before `buffer' is shown in a window, maybe?
>
> I think what's happening is that doc-view-mode is being run during file
> autodetection, before the selected window switches to the doc-view
> buffer.  Thus, (window-buffer (selected-window)) is not equal to
> (current-buffer).

I've checked in a fix for this particular problem.

Taking a step back, though, I think the "window memory" feature you
introduced to image-mode and doc-view may be a misfeature.

Currently, if a window has previously been used to view a pdf file at a
particular page, then switching back to the pdf file jumps back to that
page automatically.  But this is not the way Emacs behaves for ordinary
buffers.  There, you jump to the value of point determined roughly as
follows:

(i) if there is at least one existing window displaying that buffer, use
the first such window found.

(ii) otherwise, use the last value of point set in that buffer (in any
window).

I think image-mode and doc-view should mirror the behavior of ordinary
buffers.  So instead of a buffer-local alist variable
((WIN . PROPS)...), we should have a buffer-local variable PROPS, and
update PROPS every time you scroll the image.

WDYT?