Make GlyphStore observable

GlyphStore will notify observers when a glyph range is loaded. By now
the notification is generic, but could be fine grained, causing the
processing of buckets depending on this particular range.

src/mbgl/map/resource_loader.cpp

@@ -73,6 +73,10 @@ void ResourceLoader::update(MapData& data,
     }
 }
 
+void ResourceLoader::onGlyphRangeLoaded() {
+    emitTileDataChanged();
+}
+
 void ResourceLoader::onSourceLoaded() {
     emitTileDataChanged();
 }

src/mbgl/map/resource_loader.hpp

@@ -3,6 +3,7 @@
 
 #include <mbgl/map/source.hpp>
 #include <mbgl/map/sprite.hpp>
+#include <mbgl/text/glyph_store.hpp>
 #include <mbgl/util/noncopyable.hpp>
 
 #include <string>
@@ -21,7 +22,10 @@ class TransformState;
 // by the Style. The Source object currently owns all the tiles, thus this
 // class will notify its observers of any change on these tiles which will
 // ultimately cause a new rendering to be triggered.
-class ResourceLoader : public Source::Observer, public Sprite::Observer, private util::noncopyable {
+class ResourceLoader : public GlyphStore::Observer,
+                       public Source::Observer,
+                       public Sprite::Observer,
+                       private util::noncopyable {
 public:
     class Observer {
     public:
@@ -52,6 +56,9 @@ public:
         return sprite_;
     }
 
+    // GlyphStore::Observer implementation.
+    void onGlyphRangeLoaded() override;
+
     // Source::Observer implementation.
     void onSourceLoaded() override;
     void onTileLoaded() override;

src/mbgl/text/glyph_store.cpp

@@ -226,7 +226,13 @@ void GlyphPBF::parse(FontStack &stack) {
     data.clear();
 }
 
-GlyphStore::GlyphStore(Environment& env_) : env(env_), mtx(util::make_unique<uv::mutex>()) {}
+GlyphStore::GlyphStore(Environment& env_)
+    : env(env_), mtx(util::make_unique<uv::mutex>()), observer(nullptr) {
+}
+
+GlyphStore::~GlyphStore() {
+    observer = nullptr;
+}
 
 void GlyphStore::setURL(const std::string &url) {
     glyphURL = url;
@@ -289,5 +295,14 @@ uv::exclusive<FontStack> GlyphStore::getFontStack(const std::string &fontStack)
     return stack;
 }
 
+void GlyphStore::setObserver(Observer* observer_) {
+    observer = observer_;
+}
+
+void GlyphStore::emitGlyphRangeLoaded() {
+    if (observer) {
+        observer->onGlyphRangeLoaded();
+    }
+}
 
 }

src/mbgl/text/glyph_store.hpp

@@ -75,7 +75,15 @@ private:
 // Manages Glyphrange PBF loading.
 class GlyphStore {
 public:
+    class Observer {
+    public:
+        virtual ~Observer() = default;
+
+        virtual void onGlyphRangeLoaded() = 0;
+    };
+
     GlyphStore(Environment &);
+    ~GlyphStore();
 
     // Block until all specified GlyphRanges of the specified font stack are loaded.
     void waitForGlyphRanges(const std::string &fontStack, const std::set<GlyphRange> &glyphRanges);
@@ -84,7 +92,11 @@ public:
 
     void setURL(const std::string &url);
 
+    void setObserver(Observer* observer);
+
 private:
+    void emitGlyphRangeLoaded();
+
     // Loads an individual glyph range from the font stack and adds it to rangeSets
     std::shared_future<GlyphPBF &> loadGlyphRange(const std::string &fontStack, std::map<GlyphRange, std::unique_ptr<GlyphPBF>> &rangeSets, GlyphRange range);
 
@@ -95,6 +107,8 @@ private:
     std::unordered_map<std::string, std::map<GlyphRange, std::unique_ptr<GlyphPBF>>> ranges;
     std::unordered_map<std::string, std::unique_ptr<FontStack>> stacks;
     std::unique_ptr<uv::mutex> mtx;
+
+    Observer* observer;
 };