bug#37159: 26.1; svg images in eww

[Lars Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> All the equations on this page are SVG images:
>> 
>> https://en.wikipedia.org/wiki/Banach_fixed-point_theorem
>
> For those I see empty rectangles on my display.  I have no idea what
> that means, it could be that the image is displayed with white on
> white, or it could be some other issue with SVG images specific to
> MS-Windows.

The SVG images wikipedia uses for the math are kinda special: They
specify neither the foreground colour nor the background colour.  So
perhaps the svg libraries just choose a random colour for either, and
that's black-on-background in Linux and white-on-background in Windows.

The colours are instead set via CSS, which is why they're legible in
most browsers.

I'm not quite sure what a solution here would be.  shr could parse the
SVG data (it's just XML, after all) and insert a stroke (i.e.,
foreground) colour if none is specified, and one that's sufficiently
different from the background colour that the image would be kinda-sorta
readable.

But is it worth it just to display these unusually degenerate SVG
images?

> Btw, why does EWW break the text line when it encounters an image?

When doing the layout, in general the dimensions of the images isn't
known -- the images are fetched asynchronously after displaying the
text.

There's also a historical reason -- the code was written before shr did
pixel-based layouts, so even if it knew the dimensions, it couldn't do
anything about it.  That could be fixed now (so that if the <img> has a
width attribute, the layout engine could use it and insert the
placeholder there).

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no