text-max-size is applied to text-size, not just collision box

[friedbunny]

Per @peterqliu in chat, -native mistakenly applies the text-max-size styling property to the entire text and not just the collision box. Effectively, text-size can never be larger than text-max-size, even if it should be.

You can see this in Emerald's city labels. Set text-max-size: 35 and city labels scale as expected.

GL-JS appears to implement this properly (example, code), to spec.

Here is SymbolBucket::addFeature on -native.

The style spec says:

text-max-size
Optional number. Units in pixels. Defaults to 16. Requires text-field.
The maximum size text will be laid out, to calculate collisions with.

It seems like this property should be renamed to something like text-max-collision-size if it's not meant to constrain text-size.

[friedbunny]

Workaround (and the way that Streets currently does it) is to always set text-max-size to your desired display maximum, which allows text to size properly but presumably also creates a large collision box.

[ansis]

I think this is the guilty line:

mapbox-gl-native/src/mbgl/renderer/painter_symbol.cpp

Line 38 in ec94e03

float fontSize = std::fmin(styleProperties.size, bucketProperties.max_size);

-js uses text-max-size only if text-size is missing, which I'm not sure actually happens ever: https://github.com/mapbox/mapbox-gl-js/blob/91285d64440a055cf4bc5d9e6b2d84baeb26c757/js/render/draw_symbol.js#L56

[friedbunny]

@ansis So this is totally borked. I wonder, does the text of the spec represent an actual/desirable use-case, or should there also/only be a literal text-max-size?

[ansis]

Since text-size has a default, painter_symbol.cpp and draw_symbol.js should only use text-size.

Collision placement code should use text-max-size which it's already doing.

There is also an issue about getting rid of text-max-size.
mapbox/mapbox-gl-style-spec#255

[ansis]

Fixed in 17010bf

-js cleaned up in mapbox/mapbox-gl-js@98af024