Fonts missing arrow glyphs

[quincylvania]

The up-down arrow glyph (↕︎) is used in OpenTrailMap to specify waterfall and dam heights. Unless I'm doing something wrong, it seems that this and other arrow characters are missing from the fonts hosted in the tileservice.

[1ec5]

Does MapLibre GL JS at least fall back to the arrow glyphs in a system font or Web font if you use v5.11 or above?

[quincylvania]

It doesn't seem to, no.

[jake-low]

From what I can tell by looking at fonts.google.com, at least some of the fonts we host don't include ↕︎ (U+2195) at all. I checked Noto Sans, Open Sans, and Roboto, and none of them have it for example. It looks like it might be included in the Noto Sans Math supplemental font, but we don't currently serve that one.

I've thought about maybe merging multiple fonts (e.g. all of the Noto fonts) together into a super-font that covers more glyphs, although I think this creates problems with CJK glyphs that have different forms in different languages. Another option is to use a list of fonts in MapLibre and have the server return the first one that supports the requested glyphs; a rudimentary version of this is already supported.

Open to suggestions on what the right approach is.

[1ec5]

Font substitution in MapLibre should already handle any missing glyphs. If this is not the case for the arrow characters when using a different fontstack, such as Americana’s, it would be a good bug report to MapLibre. Something I ran into with OpenHistoricalMap is that the glyph PBFs there do include some glyphs as tofu where they should’ve just omitting the glyphs.