Add preliminary tile loading

data/maps.gresource.xml

@@ -9,4 +9,12 @@
     <file compressed="true" preprocess="xml-stripblanks" alias="map-tile-explore.svg">icons/48/explore.svg</file>
     <file compressed="true" preprocess="xml-stripblanks" alias="map-tile-transit.svg">icons/48/transit.svg</file>
   </gresource>
+
+  <gresource prefix="/io/elementary/maps/tiles">
+    <file preprocess="json-stripblanks" alias="style.json">tiles/style.json</file>
+    <file preprocess="json-stripblanks" alias="sprites.json">tiles/sprites.json</file>
+    <file preprocess="json-stripblanks" alias="sprites@2x.json">tiles/sprites@2x.json</file>
+    <file alias="sprites.png">tiles/sprites.png</file>
+    <file alias="sprites@2x.png">tiles/sprites@2x.png</file>
+  </gresource>
 </gresources>

data/maps.gschema.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <schemalist>
   <enum id="map-sources">
-    <value value="0" nick="mapnik"/>
+    <value value="0" nick="explore"/>
     <value value="1" nick="transport"/>
   </enum>
 
@@ -37,7 +37,7 @@
       <description>Zoom level of the map last used</description>
     </key>
     <key enum="map-sources" name="map-source">
-      <default>'mapnik'</default>
+      <default>'explore'</default>
       <summary>Active map source</summary>
       <description>The type of the map last used</description>
     </key>

data/tiles/LICENSE.md

@@ -0,0 +1,39 @@
+## Code License
+
+The Mapbox GL Style JSON file is originally derived from [OSM Bright from Mapbox Open Styles](https://github.com/mapbox/mapbox-gl-styles/blob/master/LICENSE.md). The modified Mapbox GL Style JSON retains the same BSD license.
+
+> Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+> * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+* Neither the name of Mapbox nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+
+> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+## Design License
+
+The look and feel of the OSM liberty map design is also derived (although heavily altered) from [OSM Bright from Mapbox Open Styles](https://github.com/mapbox/mapbox-gl-styles/blob/master/LICENSE.md) which is licensed under the Creative Commons Attribution 3.0 license.
+
+The map is displaying and styling the data from [OpenMapTiles](https://openmaptiles.org/) with [CC-BY 4.0 design license](https://github.com/openmaptiles/openmaptiles/blob/master/LICENSE.md).
+
+The products or services using this map style need to visibly credit "OpenMapTiles.org" or reference "OpenMapTiles" with a link to http://openmaptiles.org/. For a browsable electronic map based on OpenMapTiles and OpenStreetMap data, the credit should appear in the corner of the map. For example:
+
+[© OpenMapTiles](https://openmaptiles.org/)
+[© OpenStreetMap contributors](https://www.openstreetmap.org/copyright)
+
+For printed and static maps a similar attribution should be made in a textual description near the image, in the same fashion as if you cite a photograph.
+
+## Icons
+
+OSM Liberty is using the [Maki POI icon set](https://github.com/mapbox/maki/blob/master/LICENSE.txt) which is licensed under CC0 1.0 Universal.
+
+The right arrow was derived from [Wikipedia][wiki_arrow] which is in the public domain.
+
+[wiki_arrow]: https://commons.wikimedia.org/wiki/File:Arrowright.svg
+
+## Fonts
+
+OSM Liberty is using the Roboto font family (Copyright 2011 Google).
+Roboto is licensed under the [Apache License, Version 2.0](https://github.com/google/roboto/blob/master/LICENSE).
+

data/tiles/README.md

@@ -0,0 +1,14 @@
+# OSM Liberty style
+
+This is the vector style used in the demo. It is taken from
+<https://github.com/maputnik/osm-liberty> at commit [539d0525](https://github.com/maputnik/osm-liberty/commit/539d0525421eb5be901ede630c49947dfe5a343f),
+with a few modifications:
+
+- Removed the Natural Earth raster layer, since libshumate doesn't support that
+  yet
+- Removed the 3D buildings layer, since libshumate doesn't support fill-extrusion
+  layers yet
+- Changed the tile source URL
+
+OSM Liberty is covered by several licenses. See LICENSE.md, which is copied
+from the upstream repository.