Use font-provided metadata to determine glyph baseline position

[ansis]

@kkaefer, is this something harfbuzz can produce?

Otherwise, the median bottom edge would probably be a good approximation.

[kkaefer]

Why did you close this?

[ansis]

Not sure, reopening

[mourner]

Should this move to fontserver?

[mikemorris]

@ansis Not sure if this ticket is still relevant, but Harfbuzz is not necessary (FreeType is sufficient) for getting ascender (distance from top to baseline) for a font face. I have an open PR at mapbox/node-fontnik#50 for #154 that implements this and adds it to the glyph PBF (note that all glyphs in a face have the same ascender, so the PBF structure could be optimized a bit here)

[ansis]

re-opening because this is still hardcoded in -js:

mapbox-gl-js/js/symbol/shaping.js

Line 33 in ec62ab8

var yOffset = -17;

[ansis]

@mikemorris https://github.com/mapbox/node-fontnik/pull/50/files got merged into master but master doesn't have the ascender version?