make the debug flag atomic and move to MapData

include/mbgl/map/map.hpp

@@ -80,6 +80,7 @@ public:
     enum class Update : UpdateType {
         Nothing   = 0,
         StyleInfo = 1 << 0,
+        Debug     = 1 << 1,
     };
     void triggerUpdate(Update = Update::Nothing);
 
@@ -254,7 +255,6 @@ private:
 
     std::chrono::steady_clock::duration defaultTransitionDuration;
 
-    bool debug = false;
     std::chrono::steady_clock::time_point animationTime = std::chrono::steady_clock::time_point::min();
 
     std::set<util::ptr<StyleSource>> activeSources;

src/mbgl/map/map.cpp

@@ -591,18 +591,17 @@ void Map::updateAnnotationTiles(std::vector<Tile::ID>& ids) {
 #pragma mark - Toggles
 
 void Map::setDebug(bool value) {
-    debug = value;
-    assert(painter);
-    painter->setDebug(debug);
-    triggerUpdate();
+    data->setDebug(value);
+    triggerUpdate(Update::Debug);
 }
 
 void Map::toggleDebug() {
-    setDebug(!debug);
+    data->toggleDebug();
+    triggerUpdate(Update::Debug);
 }
 
 bool Map::getDebug() const {
-    return debug;
+    return data->getDebug();
 }
 
 void Map::addClass(const std::string& klass) {
@@ -765,6 +764,10 @@ void Map::prepare() {
     if (u & static_cast<UpdateType>(Update::StyleInfo)) {
         reloadStyle();
     }
+    if (u & static_cast<UpdateType>(Update::Debug)) {
+        assert(painter);
+        painter->setDebug(data->getDebug());
+    }
 
     // Update transform transitions.
     animationTime = std::chrono::steady_clock::now();

src/mbgl/map/map_data.hpp

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <mutex>
+#include <atomic>
 
 namespace mbgl {
 
@@ -25,10 +26,15 @@ public:
         styleInfo = info;
     }
 
+    inline bool getDebug() const { return debug; }
+    inline bool toggleDebug() { return debug ^= 1u; }
+    inline void setDebug(bool value) { debug = value; }
+
 private:
     mutable std::mutex mtx;
 
     StyleInfo styleInfo;
+    std::atomic<uint8_t> debug;
 };
 
 }