vg/vgsvg: add switch to embed fonts to SVG plot

[sbinet]

Fixes #703.

[codecov-commenter]

Codecov Report

Merging #705 (e774a24) into master (bd0e370) will increase coverage by 0.04%.
The diff coverage is 75.19%.

@@            Coverage Diff             @@
##           master     #705      +/-   ##
==========================================
+ Coverage   71.91%   71.96%   +0.04%     
==========================================
  Files          56       58       +2     
  Lines        4957     5272     +315     
==========================================
+ Hits         3565     3794     +229     
- Misses       1206     1281      +75     
- Partials      186      197      +11     

Impacted Files	Coverage Δ
vg/vgsvg/vgsvg.go	65.59% <75.19%> (+5.01%)	⬆️
vg/vggio/context.go	100.00% <0.00%> (ø)
vg/vggio/vggio.go	67.37% <0.00%> (ø)

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[sbinet]

PTAL.

[kortschak]

We still need docs for the case when the fonts aren't embedded, otherwise we are bound to see issues from people complaining about the effect that I show in this comment.

[kortschak]

Sorry, I missed these, but the golden files need regeneration anyway.

[sbinet]

PTAL.

I've added a simple mechanism that should preserve the old behaviour when relying on the Liberation <==> Times/Helvetica/Courier association map.
could you confirm?

[kortschak]

No, that doesn't fix the issue.

[sbinet]

(sorry, comments/PRs crossed each others... PS4 should address your latest comments)

[sbinet]

ok. I'll remove the mechanism and add a comment linking to the example, then.

where should I hang it?
on vgsvg.Canvas, vgsvg.New or at the package level?

[kortschak]

I would suggest that there also be documentation for installation of the liberation fonts, both in the package-level docs and in a README for the package.

[sbinet]

installing fonts is widely OS (flavour) dependent... (and I actually don't know how to install fonts on darwin nor Windows nor *BSDs...)
I've just redirected to the wikipedia page for now.

(alternatively, we could switch to "embed-fonts=true", like for PDFs: this would make vgsvg do the "right thing" by default.)

[kortschak]

Yeah, I think just embedding it probably the right thing to do. I just checked my install and I do have them installed, so even then we can't guaranteed the correct behaviour.

[sbinet]

PTAL

[kortschak]

The fonts in the originally incorrectly rendering fonts are still incorrectly rendering, but this has gone on long enough, so I'll approve.

[sbinet]

ok. thanks.

out of curiosity, what's your setup? (browser, OS)

[sbinet]

(the force-push is just to lump the PSxxx commits together)

[kortschak]

ff89.0.1 on ubuntu 18.04.4.

[sbinet]

aha!
I can reproduce with ff89 on my archlinux system.

it seems that the culprit is specifying

• font-family: Liberation, serif; or
• font-family: Liberation, serif, Times;

instead of, say: font-family: Liberation, Times;

let me see if there isn't some deeper flaw at work...

[sbinet]

aha!
for firefox (but it also works on my Chromium browser), it should read:
font-family: Liberation Serif;
(or all lower case: font-family: liberation serif;)
it would otherwise switch to its default font "DejaVu" which obviously doesn't metrically match with Liberation/Times.

I'll fix that.
but perhaps we could then switch back the default to "embed=false" ?

[kortschak]

but perhaps we could then switch back the default to "embed=false" ?

If it works with that, then SGTM

[sbinet]

PTAL.

now svgFontDescr will generate the correct font-family name directly from the underlying raw SFNT data (using sfnt.NameIDFamily) and handle the mismatch of meaning for font-variant between SVG and gonum/plot/font.

[sbinet]

PTAL (just rebased off the new master)

[kortschak]

🎉