add way for adding/removing classes

include/llmr/style/style_layer.hpp

@@ -5,11 +5,13 @@
 #include <llmr/style/class_properties.hpp>
 #include <llmr/style/style_properties.hpp>
 #include <llmr/style/rasterize_properties.hpp>
+#include <llmr/style/applied_class_properties.hpp>
 
 #include <vector>
 #include <memory>
 #include <string>
 #include <map>
+#include <set>
 
 namespace llmr {
 
@@ -33,6 +35,15 @@ public:
 
     bool isBackground() const;
 
+    // Sets the list of classes and creates transitions to the currently applied values.
+    void setClasses(const std::vector<std::string> &class_names, timestamp now,
+                    const ClassPropertyTransition &defaultTransition);
+
+private:
+    // Applies all properties from a class, if they haven't been applied already.
+    void applyClassProperties(ClassID class_id, std::set<PropertyKey> &already_applied,
+                              timestamp now, const ClassPropertyTransition &defaultTransition);
+
 public:
     // The name of this layer.
     const std::string id;
@@ -44,6 +55,12 @@ public:
     // Contains all style classes that can be applied to this layer.
     const std::map<ClassID, ClassProperties> styles;
 
+private:
+    // For every property, stores a list of applied property values, with
+    // optional transition times.
+    std::map<PropertyKey, AppliedClassProperties> appliedStyle;
+
+public:
     // Stores the evaluated, and cascaded styling information, specific to this
     // layer's type.
     StyleProperties style;

src/style/style_layer.cpp

@@ -1,4 +1,5 @@
 #include <llmr/style/style_layer.hpp>
+#include <llmr/style/property_fallback.hpp>
 
 namespace llmr {
 
@@ -10,4 +11,81 @@ bool StyleLayer::isBackground() const {
     return id == "background";
 }
 
+void StyleLayer::setClasses(const std::vector<std::string> &class_names, const timestamp now,
+                            const ClassPropertyTransition &defaultTransition) {
+    // Stores all keys that we have already added transitions for.
+    std::set<PropertyKey> already_applied;
+
+    // Reverse iterate through all class names and apply them last to first.
+    for (auto it = class_names.rbegin(); it != class_names.rend(); it++) {
+        const std::string &class_name = *it;
+        // From here on, we're only dealing with IDs to avoid comparing strings all the time.
+        const ClassID class_id = ClassDictionary::Lookup(class_name);
+        applyClassProperties(class_id, already_applied, now, defaultTransition);
+    }
+
+    // As the last class, apply the default class.
+    applyClassProperties(ClassID::Default, already_applied, now, defaultTransition);
+
+    // Make sure that we also transition to the fallback value for keys that aren't changed by
+    // any applied classes.
+    for (std::pair<const PropertyKey, AppliedClassProperties> &property_pair : appliedStyle) {
+        const PropertyKey key = property_pair.first;
+        if (already_applied.find(key) != already_applied.end()) {
+            // This property has already been set by a previous class, so we don't need to
+            // transition to the fallback.
+            continue;
+        }
+
+        AppliedClassProperties &appliedProperties = property_pair.second;
+        // Make sure that we don't do double transitions to the fallback value.
+        if (appliedProperties.mostRecent() != ClassID::Fallback) {
+            // This property key hasn't been set by a previous class, so we need to add a transition
+            // to the fallback value for that key.
+            const timestamp begin = now + defaultTransition.delay;
+            const timestamp end = begin + defaultTransition.duration;
+            const PropertyValue &value = PropertyFallbackValue::Get(key);
+            appliedProperties.add(ClassID::Fallback, begin, end, value);
+        }
+    }
+}
+
+// Helper function for applying all properties of a a single class that haven't been applied yet.
+void StyleLayer::applyClassProperties(const ClassID class_id,
+                                      std::set<PropertyKey> &already_applied, timestamp now,
+                                      const ClassPropertyTransition &defaultTransition) {
+    auto style_it = styles.find(class_id);
+    if (style_it == styles.end()) {
+        // There is no class in this layer with this class_name.
+        return;
+    }
+
+    // Loop through all the properties in this style, and add transitions to them, if they're
+    // not already the most recent transition.
+    const ClassProperties &properties = style_it->second;
+    for (const std::pair<PropertyKey, PropertyValue> &property_pair : properties)  {
+        PropertyKey key = property_pair.first;
+        if (already_applied.find(key) != already_applied.end()) {
+            // This property has already been set by a previous class.
+            continue;
+        }
+
+        // Mark this property as written by a previous class, so that subsequent
+        // classes won't override this.
+        already_applied.insert(key);
+
+        // If the most recent transition is not the one with the highest priority, create
+        // a transition.
+        AppliedClassProperties &appliedProperties = appliedStyle[key];
+        if (appliedProperties.mostRecent() != class_id) {
+            const ClassPropertyTransition &transition =
+                properties.getTransition(key, defaultTransition);
+            const timestamp begin = now + transition.delay;
+            const timestamp end = begin + transition.duration;
+            const PropertyValue &value = property_pair.second;
+            appliedProperties.add(class_id, begin, end, value);
+        }
+    }
+}
+
 }