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

[Visuwesh <visuweshm@gmail.com>]

[வெள்ளி செப்டம்பர் 20, 2024] Eli Zaretskii wrote:

>> From: Morgan Willcock <morgan@ice9.digital>
>> Date: Fri, 20 Sep 2024 18:53:44 +0100
>> 
>> 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 am also not sure that having it default to t (enabling SVG rendering
>> by default) is a good idea.  It probably works well for certain types of
>> document but it wasn't usable for the ones which I was viewing (which
>> were all automated invoices sent by e-mail from multiple organisations).
>
> It is only non-nil if your Emacs supports display of SVG images, and
> in that case I don't see why not do it.  I think we should investigate
> your problem in more detail to understand why it didn't work for you.
> I hope Tassilo will have some ideas for looking into this.

I believe the problem might be the one alluded to in NEWS.29:

    *** doc-view can now generate SVG images when viewing PDF files.
    If Emacs is built with SVG support, doc-view can generate SVG files
    when using MuPDF as the converter for PDF files, which generally leads
    to sharper images (especially when zooming), and allows customization
    of background and foreground color of the page via the new user
    options 'doc-view-svg-background' and 'doc-view-svg-foreground'.  To
    activate this behavior, set 'doc-view-mupdf-use-svg' to non-nil if
    your Emacs has SVG support.  Note that, with some versions of MuPDF,
    SVG generation is known to sometimes produce SVG files that are buggy
    or can take a long time to render.

Stefan reported such a case earlier:
https://yhetil.org/emacs-bugs/jwvbkn722qj.fsf-monnier+emacs@gnu.org/