[libchamplain] Add python demo demonstrating custom tile source

[Jiří Techet <jiritechet src gnome org>]

commit e60d0fd405a93f517fd7478b862dfae5bfb87d4f
Author: Jiří Techet <techet gmail com>
Date:   Tue Aug 9 23:42:53 2016 +0200

    Add python demo demonstrating custom tile source

 demos/mapbox.py |   72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 72 insertions(+), 0 deletions(-)
---
diff --git a/demos/mapbox.py b/demos/mapbox.py
new file mode 100755
index 0000000..c2d141d
--- /dev/null
+++ b/demos/mapbox.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+
+# To run this example, you need to set the GI_TYPELIB_PATH environment
+# variable to point to the gir directory:
+#
+# export GI_TYPELIB_PATH=$GI_TYPELIB_PATH:/usr/local/lib/girepository-1.0/
+
+from gi.repository import GtkClutter
+from gi.repository import GObject, Gtk, Champlain, GtkChamplain
+
+ACCESS_TOKEN = "PUT YOUR ACCESS TOKEN HERE!!!"
+
+CACHE_SIZE = 100000000  # size of cache stored on disk
+MEMORY_CACHE_SIZE = 100 # in-memory cache size (tiles stored in memory)
+MIN_ZOOM = 0
+MAX_ZOOM = 19
+TILE_SIZE = 256
+LICENSE_TEXT = ""
+LICENSE_URI = "https://www.mapbox.com/tos/";
+
+
+def create_cached_source():
+    factory = Champlain.MapSourceFactory.dup_default()
+
+    tile_source = Champlain.NetworkTileSource.new_full(
+        "mapbox",
+        "mapbox",
+        LICENSE_TEXT,
+        LICENSE_URI,
+        MIN_ZOOM,
+        MAX_ZOOM,
+        TILE_SIZE,
+        Champlain.MapProjection.MAP_PROJECTION_MERCATOR,
+        "https://a.tiles.mapbox.com/v4/mapbox.streets/#Z#/#X#/#Y#.png?access_token="; + ACCESS_TOKEN,
+        Champlain.ImageRenderer())
+
+    tile_size = tile_source.get_tile_size()
+
+    error_source = factory.create_error_source(tile_size)
+    file_cache = Champlain.FileCache.new_full(CACHE_SIZE, None, Champlain.ImageRenderer())
+    memory_cache = Champlain.MemoryCache.new_full(MEMORY_CACHE_SIZE, Champlain.ImageRenderer())
+
+    source_chain = Champlain.MapSourceChain()
+    # tile is retrieved in this order:
+    # memory_cache -> file_cache -> tile_source -> error_source
+    # the first source that contains the tile returns it
+    source_chain.push(error_source)
+    source_chain.push(tile_source)
+    source_chain.push(file_cache)
+    source_chain.push(memory_cache)
+
+    return source_chain
+
+
+GtkClutter.init([])
+
+window = Gtk.Window(type=Gtk.WindowType.TOPLEVEL)
+window.connect("destroy", Gtk.main_quit)
+
+widget = GtkChamplain.Embed()
+widget.set_size_request(640, 480)
+
+view = widget.get_view()
+
+view.set_map_source(create_cached_source())
+
+window.add(widget)
+window.show_all()
+
+Gtk.main()
+
+