Re: No NEWS entry for doc-view-mupdf-use-svg (Emacs 30.0.91 feedback)

[Tassilo Horn <tsdh@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> When testing the Emacs 30 pre-release I found that all of the PDF
>> files which I tried to view were not readable because the text
>> appeared to be missing.
>> 
>> Eventually I found the variable doc-view-mupdf-use-svg, and setting
>> it to nil reverted the rendering to the old method where the text was
>> visible.
>
> Why is that?  If your system supports display of SVG images, why
> wasn't the text readable?  Tassilo, any ideas?

I suspect it's some sort of background-equals-foreground issue.  I think
by default, the SVGs have transparent background.  So when you use a
dark theme (I tested with the built-in modus-vivendi theme which is very
dark), you might get black foreground on black background.

Visuwesh already cited the cure: in emacs 29 you might want to set
doc-view-svg-foreground/background to white/black or vice versa (and
then re-convert your PDF).

In emacs 30, that has been replaced with the face doc-view-svg-face
where you can customize foreground and background such that the contrast
works for you and your theme.

Hm, but doc-view-svg-face inherits from the default face and that is
white-on-black with modus-vivendi, so actually it should all be good,
i.e., the PDF display should match your theme.  However, depending on
PDF I tested, I sometimes get white-on-black display (good!) and
sometimes darkish-on-black (bad!).  It seems like it works as intended
for "standard black-on-white PDFs" but doesn't really work when the PDF
is "fancy", e.g., gray foreground or colorized borders or what not...

Bye,
  Tassilo