Background information

We will enhance the tile server without the intention to change styles in a way that affects user-facing. We should be able to render the same style with the current vector-tile schema, but if there is any change necessary to the current vector-tile schema, it should be reflected in the osm-bright.tm2 style.

What

Adapt current WMF map style to mapbox-gl-style renderer specification.

How

• The new style should use the current vector-tile schema as a baseline, which can be accessed from https://maps.wikimedia.org/osm-pbf/4/1/7.pbf, this endpoint will be later replaced with the output in Tegola.
• The current style is in CartoCSS and should be migrated to mapbox-gl-style spec https://github.com/kartotherian/osm-bright.tm2
• Work will concentrate on including as much pre-processing as possible in the schema rather than the mapbox gl-js code so as to maximize rendering efficiency on the client. A spriteset and a fontset will be created.
• It’s worth mentioning that the legacy code using mapnik and the current style will still be available for backward compatibility until we have a plan to phase it down without affecting the static image endpoint.
  • Example
  • Static snapshot diagram
    

• Code versioning will be concentrated in the Kartographer extension, see the WIP patch for the future work https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Kartographer/+/663867/3/mvt-style.json

Open questions

• Does Tangram suffer from the same problems as mapbox-gl regarding Brahmic scripts not being supported? see T270189#6764054
• Is the original artwork for the water waves available?
  • https://github.com/kartotherian/osm-bright.tm2/blob/master/pattern/wave.png
• Are there any other sprites we need to be aware of other than maki?
  • AFAIK maki and osm-bright.tm2 SVGs are the only ones used
  • It’s worth mentioning that we’re stuck in old versions of maki while we need to keep mapnik around, see T145475

Acceptance criteria

• Documentation is updated
• Tiles can be rendered client-side with mapbox-gl-style specification without user-facing changes
• Code versioning is hosted in the Kartographer extension
• Changes to the vector-tile schema are applied to the CartoCSS style osm-bright.tm2
• The new WebGL style will be compared with the current production style, like this
  • The percentage of difference pixels should be minimal and if it happens should be justifiable, e. g. labels placing, font-size slightly changing, etc