Unify time point for Mapcontext::update

- Let style classes cascade use the same time point as the one used to
  recalculate style.
- Cleaned up MapContext::update to return early whenever possible.
- Cleaned up MapContext::loadStyleJSON to avoid redundant calls to style
  classes cascade.

4 files changed, 25 insertions, 32 deletions

diff --git a/src/mbgl/map/map_context.cpp b/src/mbgl/map/map_context.cpp
index 4447ecc4f0..fc700581d9 100644
--- a/src/mbgl/map/map_context.cpp
+++ b/src/mbgl/map/map_context.cpp
@@ -131,10 +131,10 @@ void MapContext::loadStyleJSON(const std::string& json, const std::string& base)
     assert(util::ThreadContext::currentlyOn(util::ThreadType::Map));
 
     style->setJSON(json, base);
-    style->cascade(data.getClasses());
-    style->setDefaultTransitionDuration(data.getDefaultTransitionDuration());
     style->setObserver(this);
 
+    updated |= static_cast<UpdateType>(Update::DefaultTransitionDuration);
+    updated |= static_cast<UpdateType>(Update::Classes);
     updated |= static_cast<UpdateType>(Update::Zoom);
     asyncUpdate->send();
 
@@ -240,45 +240,43 @@ void MapContext::updateAnnotationTiles(const std::unordered_set<TileID, TileID::
         }
     }
 
-    cascadeClasses();
-
     updated |= static_cast<UpdateType>(Update::Classes);
     asyncUpdate->send();
 
     annotationManager->resetStaleTiles();
 }
 
-void MapContext::cascadeClasses() {
-    style->cascade(data.getClasses());
-}
-
 void MapContext::update() {
     assert(util::ThreadContext::currentlyOn(util::ThreadType::Map));
 
-    const auto now = Clock::now();
+    if (!style) {
+        updated = static_cast<UpdateType>(Update::Nothing);
+        return;
+    }
+
+    TimePoint now = Clock::now();
+
     data.setAnimationTime(now);
 
-    if (style) {
-        if (updated & static_cast<UpdateType>(Update::DefaultTransitionDuration)) {
-            style->setDefaultTransitionDuration(data.getDefaultTransitionDuration());
-        }
+    if (updated & static_cast<UpdateType>(Update::DefaultTransitionDuration)) {
+        style->setDefaultTransitionDuration(data.getDefaultTransitionDuration());
+    }
 
-        if (updated & static_cast<UpdateType>(Update::Classes)) {
-            cascadeClasses();
-        }
+    if (updated & static_cast<UpdateType>(Update::Classes)) {
+        style->cascade(data.getClasses(), now);
+    }
 
-        if (updated & static_cast<UpdateType>(Update::Classes) ||
+    if (updated & static_cast<UpdateType>(Update::Classes) ||
             updated & static_cast<UpdateType>(Update::Zoom)) {
-            style->recalculate(transformState.getNormalizedZoom(), now);
-        }
+        style->recalculate(transformState.getNormalizedZoom(), now);
+    }
 
-        style->update(transformState, *texturePool);
+    style->update(transformState, *texturePool);
 
-        if (data.mode == MapMode::Continuous) {
-            view.invalidate();
-        } else if (callback && style->isLoaded()) {
-            renderSync(transformState, frameData);
-        }
+    if (data.mode == MapMode::Continuous) {
+        view.invalidate();
+    } else if (callback && style->isLoaded()) {
+        renderSync(transformState, frameData);
     }
 
     updated = static_cast<UpdateType>(Update::Nothing);
diff --git a/src/mbgl/map/map_context.hpp b/src/mbgl/map/map_context.hpp
index 2e60d8eae0..8c8c90ff8b 100644
--- a/src/mbgl/map/map_context.hpp
+++ b/src/mbgl/map/map_context.hpp
@@ -72,9 +72,6 @@ public:
     void onResourceLoadingFailed(std::exception_ptr error) override;
 
 private:
-    // Style-related updates.
-    void cascadeClasses();
-
     // Update the state indicated by the accumulated Update flags, then render.
     void update();
 
diff --git a/src/mbgl/style/style.cpp b/src/mbgl/style/style.cpp
index e091c92f53..4e0c41185a 100644
--- a/src/mbgl/style/style.cpp
+++ b/src/mbgl/style/style.cpp
@@ -86,9 +86,7 @@ void Style::update(const TransformState& transform,
     }
 }
 
-void Style::cascade(const std::vector<std::string>& classes) {
-    TimePoint now = Clock::now();
-
+void Style::cascade(const std::vector<std::string>& classes, TimePoint now) {
     for (const auto& layer : layers) {
         layer->setClasses(classes, now, defaultTransition);
     }
diff --git a/src/mbgl/style/style.hpp b/src/mbgl/style/style.hpp
index d6b762a830..850c066592 100644
--- a/src/mbgl/style/style.hpp
+++ b/src/mbgl/style/style.hpp
@@ -54,7 +54,7 @@ public:
     // a tile is ready so observers can render the tile.
     void update(const TransformState&, TexturePool&);
 
-    void cascade(const std::vector<std::string>&);
+    void cascade(const std::vector<std::string>&, TimePoint now);
     void recalculate(float z, TimePoint now);
 
     void setDefaultTransitionDuration(Duration);