[gnome-maps/gnome-3-12] Add MapSource module with Mapbox URIs

[Jonas Danielsson <jonasdn src gnome org>]

commit 386d3e94000fe3c85940bbe25d420571028887dc
Author: Jonas Danielsson <jonas threetimestwo org>
Date:   Sat Jul 30 11:01:48 2016 +0200

    Add MapSource module with Mapbox URIs
    
    Add mapSource.js which contains functions for creating
    cached Champlain MapSources using Mapbox URI.

 src/mapSource.js |   95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 95 insertions(+), 0 deletions(-)
---
diff --git a/src/mapSource.js b/src/mapSource.js
new file mode 100644
index 0000000..7ab24fa
--- /dev/null
+++ b/src/mapSource.js
@@ -0,0 +1,95 @@
+/* -*- Mode: JS2; indent-tabs-mode: nil; js2-basic-offset: 4 -*- */
+/* vim: set et ts=4 sw=4: */
+/*
+ * GNOME Maps is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * GNOME Maps is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with GNOME Maps; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Jonas Danielsson <jonas threetimestwo org>
+ */
+
+const Champlain = imports.gi.Champlain;
+const Lang = imports.lang;
+
+const Utils = imports.utils;
+
+/*
+ * These URIs are used by the libchamplain network tile source.
+ * The #X#, #Y#, #Z# coords will get replaced with actual tile numbers.
+ */
+const _AERIAL_URI = "https://gis.gnome.org/tiles/satellite/v1/#Z#/#X#/#Y#";;
+const _STREET_URI = "https://gis.gnome.org/tiles/street/v1/#Z#/#X#/#Y#";;
+
+/* unique names are needed for file caching */
+const _AERIAL_NAME = "mapbox-satellite-v1";
+const _STREET_NAME = "mapbox-street-v1";
+
+const _TILE_SIZE = 256;
+const _MIN_ZOOM = 0;
+const _MAX_ZOOM = 19;
+
+const _FILE_CACHE_SIZE_LIMIT = (10 * 1024 * 1024); /* 10Mb */
+const _MEMORY_CACHE_SIZE_LIMIT = 100; /* number of tiles */
+
+function _createTileSource(uri, name) {
+    return new Champlain.NetworkTileSource(
+        { id: name,
+          name: name,
+          license: null,
+          license_uri: null,
+          min_zoom_level: _MIN_ZOOM,
+          max_zoom_level: _MAX_ZOOM,
+          tile_size: _TILE_SIZE,
+          projection: Champlain.MapProjection.MERCATOR,
+          renderer: new Champlain.ImageRenderer(),
+          uri_format: uri
+        });
+}
+
+function _createCachedSource(uri, name) {
+    let tileSource = _createTileSource(uri, name);
+
+    let fileCache = new Champlain.FileCache({
+        size_limit: _FILE_CACHE_SIZE_LIMIT,
+        renderer: new Champlain.ImageRenderer()
+    });
+
+    let memoryCache = new Champlain.MemoryCache({
+        size_limit: _MEMORY_CACHE_SIZE_LIMIT,
+        renderer: new Champlain.ImageRenderer()
+    });
+
+    let errorSource = new Champlain.NullTileSource({
+        renderer: new Champlain.ImageRenderer()
+    });
+
+    /*
+     * When the a source in the chain fails to load a given tile
+     * the next one in the chain tries instead. Until we get to the error
+     * source.
+     */
+    let sourceChain = new Champlain.MapSourceChain();
+    sourceChain.push(errorSource);
+    sourceChain.push(tileSource);
+    sourceChain.push(fileCache);
+    sourceChain.push(memoryCache);
+
+    return sourceChain;
+}
+
+function createAerialSource() {
+    return _createCachedSource(_AERIAL_URI, _AERIAL_NAME);
+};
+
+function createStreetSource() {
+    return _createCachedSource(_STREET_URI, _STREET_NAME);
+};