# Technical Documentation: microg/GmsCore

> ℹ️ **Provenance:** Multi-Tier Ingestion · [CodeWiki Reference](https://codewiki.google/github.com/microg/GmsCore)

### Overview (`README.md`)

# microG Services

[](https://github.com/microg/GmsCore/actions/workflows/build.yml)
<a href=TRANSLATION.md>
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microG Services is a FLOSS (Free/Libre Open Source Software) framework to allow applications designed for Google Play Services to run on systems, where Play Services is not available.

### Please refer to the [wiki](https://github.com/microg/GmsCore/wiki) for downloads and instructions

## Translations

If you'd like to help translate microG, take a look at [TRANSLATION](TRANSLATION.md).


License
-------
    Copyright 2013-2025 microG Project Team

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

---

### Overview (`artwork/styles/README.md`)

## The files

* `style-microg-normal-openmaptiles.json` is a pure OpenMapTiles schema version of microG's custom style. The sources are set to Stadia but could be modified to be used with another schema-compliant vendor, e.g. MapTiler.
* `style-microg-normal-stadia.json` is a variant with Stadia custom layers.
* `style-microg-normal-mapbox.json` is a historic, unmaintained variant for use with Mapbox.
* `style-microg-satellite-*.json` is the same, but with a satellite layer (the stadia variant is almost pure openmaptiles, but openmaptiles does not specify a satellite layer).
* `style-stadia-outdoors.json` is identical to Stadia's Outdoors style, but with added microG metadata.

* `sprite_sources` files can be generated to a single sprite file as found in the app's assets using `spreet` (see below).
* PBF files for fonts can be generated using `build_pbf_glyphs` from the `fonts` folder.

## Resources

### For creating styles

* Tool: https://maputnik.github.io/
* Style spec: https://maplibre.org/maplibre-style-spec/
	* https://maplibre.org/maplibre-style-spec/expressions/
* Style schema: **https://openmaptiles.org/schema/**
* Schema tileset explorer (requires maptiler login): https://cloud.maptiler.com/tiles/v3-openmaptiles/

#### Vendor-specific
* Mapbox
    * https://docs.mapbox.com/data/tilesets/reference/mapbox-streets-v8/
* Stadia
    * https://docs.stadiamaps.com/custom-styles/
    * https://docs.stadiamaps.com/tilesets/
    
### For converting assets

* https://github.com/flother/spreet
* https://github.com/stadiamaps/sdf_font_tools/tree/main/build_pbf_glyphs


Commands:

```
$ cp style-microg-{satellite,normal}-{mapbox,stadia}.json style-stadia-outdoors.json style-mapbox-outdoors-v12.json ../../play-services-maps-core-mapbox/src/main/assets/
$ spreet sprite_sources/ ../../play-services-maps-core-mapbox/src/main/assets/sprites
$ spreet --retina sprite_sources/ ../../play-services-maps-core-mapbox/src/main/assets/sprites@2x
$ build_pbf_glyphs --overwrite -c fonts/combinations.json fonts/ ../../play-services-maps-core-mapbox/src/main/assets
$ rm -r ../../play-services-maps-core-mapbox/src/main/assets/OpenSans\ Regular # remove temporary files
```

* We combine Open Sans Regular with Roboto Regular so that no glyphs are missing.
* A symbolic link in the assets folder points from the font stack specification "Open Sans Regular,Arial Unicode MS Regular" to "Roboto Regular". It is unclear why MapLibre sometimes tries to access this font and fails rendering entire tiles if it is not present.

The assets are referenced using `asset://` in the style. For using Maputnik, it may be convenient to set the glyphs and sprites source to these Mapbox-hosted sources:

```
    "sprite": "mapbox://sprites/microg/cjui4020201oo1fmca7yuwbor/8fkcj5fgn4mftlzuak3guz1f9",
    "glyphs": "mapbox://fonts/microg/{fontstack}/{range}.pbf",
```

## Legal

* normal and satellite microG styles based on Mapbox Basic, part of the Mapbox Open Styles, licensed under
    * Style code: BSD license
    * Style virtual features / design: CC BY 3.0
    * Reference: https://github.com/mapbox/mapbox-gl-styles/blob/master/LICENSE.md
* derivation created by larma
* derivation created by /e/ foundation
* makes use of snippets from [Stadia's variant of OSM Bright](https://docs.stadiamaps.com/map-styles/osm-bright/), also a derivation of Mapbox Open Styles
	* Style code: BSD 3-Clause License
	* Style design: CC-BY 4.0
	* Reference: https://stadiamaps.com/attribution/
* fonts: Roboto family, licensed Apache 2.0, https://fonts.google.com/specimen/Roboto/about

* outdoor style based on https://docs.stadiamaps.com/map-styles/outdoors/#__tabbed_1_2
    * Style code: BSD 3-Clause License
	* Style design: CC-BY 4.0
	* Reference: https://stadiamaps.com

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- Canonical Reference: https://codewiki.google/github.com/microg/GmsCore