Move still image callback to MapContext

include/mbgl/map/map.hpp

@@ -46,6 +46,8 @@ public:
     // Resumes a paused render thread
     void resume();
 
+    // Register a callback that will get called (on the render thread) when all resources have
+    // been loaded and a complete render occurs.
     using StillImageCallback = std::function<void(std::unique_ptr<const StillImage>)>;
     void renderStill(StillImageCallback callback);
 

src/mbgl/map/map.cpp

@@ -64,19 +64,8 @@ void Map::resume() {
     data->condResume.notify_all();
 }
 
-void Map::renderStill(StillImageCallback fn) {
-    assert(Environment::currentlyOn(ThreadType::Main));
-
-    if (data->mode != MapMode::Still) {
-        throw util::Exception("Map is not in still image render mode");
-    }
-
-    if (data->callback) {
-        throw util::Exception("Map is currently rendering an image");
-    }
-
-    data->callback = std::move(fn);
-    update(Update::RenderStill);
+void Map::renderStill(StillImageCallback callback) {
+    context->invoke(&MapContext::renderStill, callback);
 }
 
 void Map::renderSync() {

src/mbgl/map/map_context.cpp

@@ -26,6 +26,7 @@
 #include <mbgl/util/worker.hpp>
 #include <mbgl/util/texture_pool.hpp>
 #include <mbgl/util/mapbox.hpp>
+#include <mbgl/util/exception.hpp>
 
 namespace mbgl {
 
@@ -226,6 +227,19 @@ void MapContext::update() {
     }
 }
 
+void MapContext::renderStill(StillImageCallback fn) {
+    if (data.mode != MapMode::Still) {
+        throw util::Exception("Map is not in still image render mode");
+    }
+
+    if (callback) {
+        throw util::Exception("Map is currently rendering an image");
+    }
+
+    callback = fn;
+    triggerUpdate(Update::RenderStill);
+}
+
 void MapContext::render() {
     assert(Environment::currentlyOn(ThreadType::Map));
 
@@ -237,16 +251,9 @@ void MapContext::render() {
 
     painter->render(*style, transformState, data.getAnimationTime());
 
-    if (data.mode == MapMode::Still && data.callback && style->isLoaded() && getSprite()->isLoaded()) {
-        auto image = view.readStillImage();
-
-        // We are moving the callback out of the way and empty it in case the callback function
-        // starts the next map image render.
-        MapData::StillImageCallback cb;
-        std::swap(cb, data.callback);
-
-        // Now we can finally invoke the callback function with the map image we rendered.
-        cb(std::move(image));
+    if (data.mode == MapMode::Still && callback && style->isLoaded() && getSprite()->isLoaded()) {
+        callback(view.readStillImage());
+        callback = nullptr;
     }
 
     // Schedule another rerender when we definitely need a next frame.

src/mbgl/map/map_context.hpp

@@ -32,6 +32,7 @@ class Painter;
 class Sprite;
 class Style;
 class Worker;
+class StillImage;
 struct LatLng;
 struct LatLngBounds;
 
@@ -45,7 +46,9 @@ public:
 
     void resize(uint16_t width, uint16_t height, float ratio);
 
-    // Notifies the Map thread that the state has changed and an update might be necessary.
+    using StillImageCallback = std::function<void(std::unique_ptr<const StillImage>)>;
+    void renderStill(StillImageCallback callback);
+
     void triggerUpdate(Update = Update::Nothing);
 
     void setStyleURL(const std::string&);
@@ -93,6 +96,7 @@ private:
     std::string styleURL;
     std::string styleJSON;
 
+    StillImageCallback callback;
     size_t sourceCacheSize;
     TransformState transformState;
 };

src/mbgl/map/map_data.hpp

@@ -18,8 +18,6 @@
 
 namespace mbgl {
 
-class StillImage;
-
 class MapData {
     using Lock = std::lock_guard<std::mutex>;
 
@@ -101,9 +99,6 @@ public:
     std::mutex mutexPause;
     std::condition_variable condPaused;
     std::condition_variable condResume;
-
-    using StillImageCallback = std::function<void(std::unique_ptr<const StillImage>)>;
-    StillImageCallback callback;
 };
 
 }