removing empty AppliedClassProperties objects

include/llmr/style/applied_class_properties.hpp

@@ -31,6 +31,7 @@ public:
     void add(ClassID class_id, timestamp begin, timestamp end, const PropertyValue &value);
     bool hasTransitions() const;
     void cleanup(timestamp now);
+    bool empty() const;
 };
 
 }

src/style/applied_class_properties.cpp

@@ -24,13 +24,29 @@ bool AppliedClassProperties::hasTransitions() const {
 // Erase all items in the property list that are before a completed transition.
 // Then, if the only remaining property is a Fallback value, remove it too.
 void AppliedClassProperties::cleanup(timestamp now) {
+    // Iterate backwards, but without using the rbegin/rend interface since we need forward
+    // iterators to use .erase().
     for (auto it = properties.end(), begin = properties.begin(); it != begin;) {
         // If the property is finished, break iteration and delete all remaining items.
         if ((--it)->end <= now) {
+            // Removes all items that precede the current iterator, but *not* the element currently
+            // pointed to by the iterator. This preserves the last completed transition as the
+            // first element in the property list.
             properties.erase(begin, it);
+
+            // Also erase the pivot element if it's a fallback value. This means we can remove the
+            // entire applied properties object as well, because we already have the fallback
+            // value set as the default.
+            if (it->name == ClassID::Fallback) {
+                properties.erase(it);
+            }
             break;
         }
     }
 }
 
+bool AppliedClassProperties::empty() const {
+    return properties.empty();
+}
+
 }

src/style/class_properties.cpp

@@ -5,7 +5,6 @@ namespace llmr {
 const PropertyTransition &ClassProperties::getTransition(PropertyKey key, const PropertyTransition &defaultTransition) const {
     auto it = transitions.find(key);
     if (it == transitions.end()) {
-        fprintf(stderr, "using default transition: %d/%d\n", defaultTransition.duration, defaultTransition.delay);
         return defaultTransition;
     } else {
         return it->second;

src/style/style_layer.cpp

@@ -290,8 +290,18 @@ bool StyleLayer::hasTransitions() const {
 
 
 void StyleLayer::cleanupAppliedStyleProperties(timestamp now) {
-    for (std::pair<const PropertyKey, AppliedClassProperties> &pair : appliedStyle) {
-        pair.second.cleanup(now);
+    auto it = appliedStyle.begin();
+    const auto end = appliedStyle.end();
+    while (it != end) {
+        AppliedClassProperties &properties = it->second;
+        properties.cleanup(now);
+
+        // If the current properties object is empty, remove it from the map entirely.
+        if (properties.empty()) {
+            appliedStyle.erase(it++);
+        } else {
+            ++it;
+        }
     }
 }