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

[Morgan Willcock <morgan@ice9.digital>]

Tassilo Horn <tsdh@gnu.org> writes:

> Since doc-view-svg-face inherits from the default theme, in theory the
> SVG should be adjusted acording to your theme.

>> If the SVG rendering is enabled (when available) by default, does this
>> mean that it is the user's responsibility to set usable default
>> colours?  Or should the theme be setting usable default colours?
>
> The latter.  If the theme sets the default face sensibly (which it
> surely does), then your PDFs should look the same.  Well, and that's
> true for "normal" PDF documents (black on white, e.g., academic papers)
> but somehow fails for "fancy" documents.
>
> I don't know how the :foreground/:background SVG image properties work
> but it looks to me as if :background works well every time but
> :foreground doesn't as soon as the text is not black.  I suspect the
> heuristic is something like: if it's transparent, it's the background,
> and if it's either black or white, it's the foreground.

When looking at the SVG files in the location browsed by
doc-view-dired-cache I can see that the Azure invoice has:

- A transparent background with black and grey text on it.
- A dark grey border with white text on it.
- A white border with black text on it.

The transparent background is shown as white or black, depending on
whether the light or dark theme is loaded, but the text is always
readable because the text colour complements the background.

The problem is the text that is not on the transparent area of the
document, presumably because a coloured border cannot be identified as
being part of the background and so the border colours will never follow
the theme.

Based on my usage, setting doc-view-mupdf-use-svg to t seems to make
reading PDF documents significantly more difficult.

Perhaps there should be an option to just assume a white background and
render using the original colours, and turn that on by default.  Would
that be what a regular PDF viewer does?

-- 
Morgan Willcock