[core] Prepare style observer interfaces for source reloading

* Renamed {Source,Tile}Observer::onNeedsRepaint to onTileUpdated. Messages should be in terms of what happened to the observed object, not in terms of what the observer needs to do. This also removes a confusing overlap of virtual methods on StyleObserver.
* Added style::Observer::onUpdate(Update). This is also a violation of the above rule, but I'm hopeful that it will disappear when update batching is implemented.

src/mbgl/map/map.cpp

@@ -37,7 +37,7 @@ class Map::Impl : public style::Observer {
 public:
     Impl(View&, FileSource&, MapMode, GLContextMode, ConstrainMode, ViewportMode);
 
-    void onNeedsRepaint() override;
+    void onUpdate(Update) override;
     void onStyleError() override;
     void onResourceError(std::exception_ptr) override;
 
@@ -149,12 +149,7 @@ void Map::renderStill(StillImageCallback callback) {
 }
 
 void Map::update(Update flags) {
-    if (flags & Update::Dimensions) {
-        impl->transform.resize(impl->view.getSize());
-    }
-
-    impl->updateFlags |= flags;
-    impl->asyncUpdate.send();
+    impl->onUpdate(flags);
 }
 
 void Map::render() {
@@ -905,8 +900,12 @@ void Map::onLowMemory() {
     impl->view.invalidate();
 }
 
-void Map::Impl::onNeedsRepaint() {
-    updateFlags |= Update::Repaint;
+void Map::Impl::onUpdate(Update flags) {
+    if (flags & Update::Dimensions) {
+        transform.resize(view.getSize());
+    }
+
+    updateFlags |= flags;
     asyncUpdate.send();
 }
 

src/mbgl/style/observer.hpp

@@ -3,6 +3,7 @@
 #include <mbgl/text/glyph_store_observer.hpp>
 #include <mbgl/sprite/sprite_store_observer.hpp>
 #include <mbgl/style/source_observer.hpp>
+#include <mbgl/map/update.hpp>
 
 namespace mbgl {
 namespace style {
@@ -11,13 +12,7 @@ class Observer : public GlyphStoreObserver,
                  public SpriteStoreObserver,
                  public SourceObserver {
 public:
-    /**
-     * In addition to the individual glyph, sprite, and source events, the
-     * following "rollup" events are provided for convenience. They are
-     * strictly additive; e.g. when a source is loaded, both `onSourceLoaded`
-     * and `onNeedsRepaint` will be called.
-     */
-    void onNeedsRepaint() override {}
+    virtual void onUpdate(Update) {}
     virtual void onStyleError() {}
     virtual void onResourceError(std::exception_ptr) {}
 };

src/mbgl/style/source_impl.cpp

@@ -266,8 +266,8 @@ void Source::Impl::onTileError(Tile& tile, std::exception_ptr error) {
     observer->onTileError(base, tile.id, error);
 }
 
-void Source::Impl::onNeedsRepaint() {
-    observer->onNeedsRepaint();
+void Source::Impl::onTileUpdated(Tile& tile) {
+    observer->onTileUpdated(base, tile.id);
 }
 
 void Source::Impl::dumpDebugLogs() const {

src/mbgl/style/source_impl.hpp

@@ -86,7 +86,7 @@ private:
     // TileObserver implementation.
     void onTileLoaded(Tile&, bool isNewTile) override;
     void onTileError(Tile&, std::exception_ptr) override;
-    void onNeedsRepaint() override;
+    void onTileUpdated(Tile&) override;
 
     virtual uint16_t getTileSize() const = 0;
     virtual Range<uint8_t> getZoomRange() = 0;

src/mbgl/style/source_observer.hpp

@@ -16,9 +16,10 @@ public:
 
     virtual void onSourceLoaded(Source&) {}
     virtual void onSourceError(Source&, std::exception_ptr) {}
+
     virtual void onTileLoaded(Source&, const OverscaledTileID&, bool /* isNewTile */) {}
     virtual void onTileError(Source&, const OverscaledTileID&, std::exception_ptr) {}
-    virtual void onNeedsRepaint() {}
+    virtual void onTileUpdated(Source&, const OverscaledTileID&) {}
 };
 
 } // namespace style

src/mbgl/style/style.cpp

@@ -423,7 +423,7 @@ void Style::setObserver(style::Observer* observer_) {
 void Style::onGlyphsLoaded(const FontStack& fontStack, const GlyphRange& glyphRange) {
     shouldReparsePartialTiles = true;
     observer->onGlyphsLoaded(fontStack, glyphRange);
-    observer->onNeedsRepaint();
+    observer->onUpdate(Update::Repaint);
 }
 
 void Style::onGlyphsError(const FontStack& fontStack, const GlyphRange& glyphRange, std::exception_ptr error) {
@@ -436,7 +436,7 @@ void Style::onGlyphsError(const FontStack& fontStack, const GlyphRange& glyphRan
 
 void Style::onSourceLoaded(Source& source) {
     observer->onSourceLoaded(source);
-    observer->onNeedsRepaint();
+    observer->onUpdate(Update::Repaint);
 }
 
 void Style::onSourceError(Source& source, std::exception_ptr error) {
@@ -453,7 +453,7 @@ void Style::onTileLoaded(Source& source, const OverscaledTileID& tileID, bool is
     }
 
     observer->onTileLoaded(source, tileID, isNewTile);
-    observer->onNeedsRepaint();
+    observer->onUpdate(Update::Repaint);
 }
 
 void Style::onTileError(Source& source, const OverscaledTileID& tileID, std::exception_ptr error) {
@@ -464,14 +464,14 @@ void Style::onTileError(Source& source, const OverscaledTileID& tileID, std::exc
     observer->onResourceError(error);
 }
 
-void Style::onNeedsRepaint() {
-    observer->onNeedsRepaint();
+void Style::onTileUpdated(Source&, const OverscaledTileID&) {
+    observer->onUpdate(Update::Repaint);
 }
 
 void Style::onSpriteLoaded() {
     shouldReparsePartialTiles = true;
     observer->onSpriteLoaded();
-    observer->onNeedsRepaint();
+    observer->onUpdate(Update::Repaint);
 }
 
 void Style::onSpriteError(std::exception_ptr error) {

src/mbgl/style/style.hpp

@@ -127,7 +127,7 @@ private:
     void onSourceError(Source&, std::exception_ptr) override;
     void onTileLoaded(Source&, const OverscaledTileID&, bool isNewTile) override;
     void onTileError(Source&, const OverscaledTileID&, std::exception_ptr) override;
-    void onNeedsRepaint() override;
+    void onTileUpdated(Source&, const OverscaledTileID&) override;
 
     Observer nullObserver;
     Observer* observer = &nullObserver;

src/mbgl/tile/geometry_tile.cpp

@@ -213,7 +213,7 @@ void GeometryTile::redoPlacement() {
         if (placedConfig != targetConfig) {
             redoPlacement();
         } else {
-            observer->onNeedsRepaint();
+            observer->onTileUpdated(*this);
         }
     });
 }

src/mbgl/tile/tile.cpp

@@ -18,7 +18,7 @@ void Tile::setObserver(TileObserver* observer_) {
 
 void Tile::setTriedOptional() {
     triedOptional = true;
-    observer->onNeedsRepaint();
+    observer->onTileUpdated(*this);
 }
 
 void Tile::dumpDebugLogs() const {

src/mbgl/tile/tile_observer.hpp

@@ -12,7 +12,7 @@ public:
 
     virtual void onTileLoaded(Tile&, bool /*isNewTile*/) {}
     virtual void onTileError(Tile&, std::exception_ptr) {}
-    virtual void onNeedsRepaint() {}
+    virtual void onTileUpdated(Tile&) {}
 };
 
 } // namespace mbgl

test/src/mbgl/test/stub_style_observer.hpp

@@ -43,8 +43,8 @@ public:
         if (tileError) tileError(source, tileID, error);
     }
 
-    void onNeedsRepaint() override {
-        if (needsRepaint) needsRepaint();
+    void onTileUpdated(Source& source, const OverscaledTileID& tileID) override {
+        if (tileUpdated) tileUpdated(source, tileID);
     };
 
     void onResourceError(std::exception_ptr error) override {
@@ -59,6 +59,6 @@ public:
     std::function<void (Source&, std::exception_ptr)> sourceError;
     std::function<void (Source&, const OverscaledTileID&, bool isNewTile)> tileLoaded;
     std::function<void (Source&, const OverscaledTileID&, std::exception_ptr)> tileError;
-    std::function<void ()> needsRepaint;
+    std::function<void (Source&, const OverscaledTileID&)> tileUpdated;
     std::function<void (std::exception_ptr)> resourceError;
 };