bug#34138: 27.0.50; Delayed display of PDF file images

[Eli Zaretskii]

> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: rudalics@gmx.at,  34138@debbugs.gnu.org,  politza@hochschule-trier.de,  
> tsdh@gnu.org
> Date: Mon, 21 Jan 2019 19:17:53 +0100
> 
> > Can you establish (e.g., by adding 'message' lines to the Lisp source)
> > where in the pdf-view-mode's sources this delay starts?  IOW, what is
> > the last thing pdf-view-mode does before the delay begins?
> 
> I don't know where it makes sense to output messages.  I did step
> through pdf-view-mode and the last function it calls,
> pdf-view-goto-page, but when that function returns it's just the raw PDF
> that's displayed.  I then instrumented all pdf-view defuns and while
> stepping though, the PDF image appeared on calling
> pdf-view-maybe-redisplay-resized-windows, which is added to
> window-configuration-change-hook in pdf-view-mode.  So it appears that
> the delay starts between pdf-view-goto-page returning and
> pdf-view-maybe-redisplay-resized-windows being called, but when stepping
> through the long call chain, I did not see the transition (no raw PDF
> was displayed, just the rendered image at the end).

So you are saying that the image is displayed by a function that is on
window-configuration-change-hook?  If so, what change in the window
configuration is supposed to trigger the hook in your scenario?  (I
think I'm missing something, because I don't see how it would make
sense to display PDF documents from that particular hook.)

In any case, is it certain that once
pdf-view-maybe-redisplay-resized-windows starts running, the image is
displayed immediately without delays?