An empty/stubbed style with no glyphs URL declaration causes a SymbolLayer's icons to disappear when a textField is added

[TobiasDettmers-MW]

Hi, I'm using MapLibre in a semi-offline use-case to render GeoJsons which is a relatively fringe one but this is an issue nonetheless.

I'm developing for Android with MapLibre 9.5.1.

Repro

1. Have a map without an explicit style (should be empty/stubbed; just Style.Builder() for instance)
2. Add a symbolLayer with some markers
3. Give those markers an icon (works)
4. Also give the markers a textField (no markers or text! No warning emitted to logcat either)
5. Change the style to

   Style.Builder().fromJson("""{
            "glyphs": "https://orangemug.github.io/font-glyphs/glyphs/{fontstack}/{range}.pbf"
        }""".trimIndent())
   

   and set a supported font on the textField like textFont(arrayOf("Roboto Black")).
   Now the text and icons show up again.

Expected behaviour

MapLibre should use a local font as fallback (i.e. "sans-serif") and at least show the icon without text.

Context

Supposedly that functionality already exists for symbolic/CJK characters:

mapbox/mapbox-gl-native#10522

and there's the localIdeographFontFamily mapboxOption which (at least to me) sounds like it should prevent this issue and is enabled by default.

[TobiasDettmers-MW]

localIdeographFontFamily is for fixed-width CJK characters only because TinySDF can't handle (highly) variably-sized characters: mapbox/tiny-sdf#6

Here's the check whether a character can be handled:

https://github.com/maplibre/maplibre-gl-native/blob/004a849d8c53a22279a4901f5a44d5ac83d9425d/src/mbgl/util/i18n.cpp#L416-L420

Hacking the function to allow regular western characters makes it work technically but the result is bad spacing and correcting that with textLetterSpacing makes the text appear off-center and kerning is still non-existent.