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

[Visuwesh <visuweshm@gmail.com>]

[சனி செப்டம்பர் 21, 2024] Morgan Willcock wrote:

> Tassilo Horn <tsdh@gnu.org> writes:
>
>> 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.
>
> I use modus-vivendi and sometimes toggle it to modus-operandi to use the
> light version.  It does seem to be the currently active theme which
> makes the text invisible, with the dark theme making the text
> unreadable.
>
> If I load no theme then the documents are rendered normally (as far as I
> can tell).
>
>> 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).
>
> If I use image-save to save a copy of the SVG file, the conversion
> always appears to be usable and a good representation of the original
> document, even when what is displayed in the buffer is not.
>
> Toggling the theme between the light and dark theme while viewing the
> image in the buffer toggles it between readable and unreadable.
>
>> 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!).
>
> Is there any way to opt-out from the theme having any effect on how the
> result is presented while still giving a usable result?

You can customise the face doc-view-svg-face to have :background "white"
and :foreground "black".

>> 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...
>
> This does describe the documents I am testing with.  They all have some
> kind of coloured border.  Azure invoices use a light gray foreground
> colour with black text on it, while also using a darker gray background
> with white text on it.