use callbacks for onStyleImageMissing

We need some asynchronous way of telling the renderer when the listener
has been called. This is important on Android when the renderer and map
exist on separate threads.

9 files changed, 54 insertions, 19 deletions

diff --git a/include/mbgl/map/map_observer.hpp b/include/mbgl/map/map_observer.hpp
index 39fe516ff3..e405c5dd0e 100644
--- a/include/mbgl/map/map_observer.hpp
+++ b/include/mbgl/map/map_observer.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <mbgl/style/source.hpp>
+#include <mbgl/style/image.hpp>
 
 #include <cstdint>
 #include <string>
@@ -46,7 +47,7 @@ public:
     virtual void onDidFinishLoadingStyle() {}
     virtual void onSourceChanged(style::Source&) {}
     virtual void onDidBecomeIdle() {}
-    virtual void onStyleImageMissing(const std::string&) {}
+    virtual void onStyleImageMissing(const std::string&, std::function<void(optional<std::unique_ptr<mbgl::style::Image>>)> callback) { callback({}); }
 };
 
 } // namespace mbgl
diff --git a/include/mbgl/renderer/renderer_observer.hpp b/include/mbgl/renderer/renderer_observer.hpp
index 71620355e8..e2b3441e37 100644
--- a/include/mbgl/renderer/renderer_observer.hpp
+++ b/include/mbgl/renderer/renderer_observer.hpp
@@ -33,7 +33,7 @@ public:
     virtual void onDidFinishRenderingMap() {}
 
     // Style is missing an image
-    virtual void onStyleImageMissing(const std::string&) {}
+    virtual void onStyleImageMissing(const std::string&, std::function<void()> done) { done(); }
 };
 
 } // namespace mbgl
diff --git a/src/mbgl/map/map_impl.cpp b/src/mbgl/map/map_impl.cpp
index ecb9238362..0edf26e262 100644
--- a/src/mbgl/map/map_impl.cpp
+++ b/src/mbgl/map/map_impl.cpp
@@ -172,8 +172,19 @@ void Map::Impl::jumpTo(const CameraOptions& camera) {
     onUpdate();
 }
 
-void Map::Impl::onStyleImageMissing(const std::string& id) {
-    observer.onStyleImageMissing(id);
+void Map::Impl::onStyleImageMissing(const std::string& id, std::function<void()> done) {
+
+    if (style->getImage(id) != nullptr) {
+        done();
+        return;
+    }
+
+    observer.onStyleImageMissing(id, [this, done](optional<std::unique_ptr<mbgl::style::Image>> image = {}) {
+        if (image) {
+            style->addImage(std::move(*image));
+        }
+        done();
+    });
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/map/map_impl.hpp b/src/mbgl/map/map_impl.hpp
index 425e136b66..0e0b47e8a9 100644
--- a/src/mbgl/map/map_impl.hpp
+++ b/src/mbgl/map/map_impl.hpp
@@ -47,7 +47,7 @@ public:
     void onDidFinishRenderingFrame(RenderMode, bool) final;
     void onWillStartRenderingMap() final;
     void onDidFinishRenderingMap() final;
-    void onStyleImageMissing(const std::string&) final;
+    void onStyleImageMissing(const std::string&, std::function<void()>) final;
 
     // Map
     void jumpTo(const CameraOptions&);
diff --git a/src/mbgl/renderer/image_manager.cpp b/src/mbgl/renderer/image_manager.cpp
index f756e201cb..cdcf83210a 100644
--- a/src/mbgl/renderer/image_manager.cpp
+++ b/src/mbgl/renderer/image_manager.cpp
@@ -92,23 +92,42 @@ void ImageManager::removeRequestor(ImageRequestor& requestor) {
 }
 
 void ImageManager::imagesAdded() {
-    for (const auto& entry : missingImageRequestors) {
-        notify(*entry.first, entry.second);
+    for (auto it = missingImageRequestors.begin(); it != missingImageRequestors.end();) {
+        if (it->second.callbacksRemaining == 0) {
+            notify(*it->first, it->second.pair);
+            missingImageRequestors.erase(it++);
+        } else {
+            it++;
+        }
     }
-    requestors.clear();
 }
 
 void ImageManager::checkMissingAndNotify(ImageRequestor& requestor, const ImageRequestPair& pair) {
-    bool missing = false;
+    int missing = 0;
     for (const auto& dependency : pair.first) {
         auto it = images.find(dependency.first);
         if (it == images.end()) {
-            missing = true;
-            observer->onStyleImageMissing(dependency.first);
+            missing++;
         }
     }
-    if (missing) {
-        missingImageRequestors.emplace(&requestor, std::move(pair));
+
+
+    if (missing > 0) {
+        ImageRequestor* requestorPtr = &requestor;
+        missingImageRequestors.emplace(requestorPtr, MissingImageRequestPair { std::move(pair), missing });
+
+        for (const auto& dependency : pair.first) {
+            auto it = images.find(dependency.first);
+            if (it == images.end()) {
+                observer->onStyleImageMissing(dependency.first, [this, requestorPtr]() {
+                    auto it = missingImageRequestors.find(requestorPtr);
+                    if (it != missingImageRequestors.end()) {
+                        it->second.callbacksRemaining--;
+                    }
+                });
+            }
+        }
+
     } else {
         notify(requestor, pair);
     }
diff --git a/src/mbgl/renderer/image_manager.hpp b/src/mbgl/renderer/image_manager.hpp
index 9adb0fa113..789183dd1f 100644
--- a/src/mbgl/renderer/image_manager.hpp
+++ b/src/mbgl/renderer/image_manager.hpp
@@ -64,7 +64,11 @@ private:
     bool loaded = false;
 
     std::unordered_map<ImageRequestor*, ImageRequestPair> requestors;
-    std::unordered_map<ImageRequestor*, ImageRequestPair> missingImageRequestors;
+    struct MissingImageRequestPair {
+        ImageRequestPair pair;
+        int callbacksRemaining;
+    };
+    std::unordered_map<ImageRequestor*, MissingImageRequestPair> missingImageRequestors;
     ImageMap images;
 
     ImageManagerObserver* observer = nullptr;
diff --git a/src/mbgl/renderer/image_manager_observer.hpp b/src/mbgl/renderer/image_manager_observer.hpp
index e483c5b8f6..ff4ed1f48e 100644
--- a/src/mbgl/renderer/image_manager_observer.hpp
+++ b/src/mbgl/renderer/image_manager_observer.hpp
@@ -6,7 +6,7 @@ class ImageManagerObserver {
 public:
     virtual ~ImageManagerObserver() = default;
 
-    virtual void onStyleImageMissing(const std::string&) {}
+    virtual void onStyleImageMissing(const std::string&, std::function<void()>) {}
 };
 
 } // namespace mbgl
diff --git a/src/mbgl/renderer/renderer_impl.cpp b/src/mbgl/renderer/renderer_impl.cpp
index adef3890bf..e6ce6a63bd 100644
--- a/src/mbgl/renderer/renderer_impl.cpp
+++ b/src/mbgl/renderer/renderer_impl.cpp
@@ -159,8 +159,8 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
         imageManager->updateImage(entry.second.after);
     }
 
-    imageManager->imagesAdded();
     imageManager->setLoaded(updateParameters.spriteLoaded);
+    imageManager->imagesAdded();
 
 
     const LayerDifference layerDiff = diffLayers(layerImpls, updateParameters.layers);
@@ -836,8 +836,8 @@ void Renderer::Impl::onTileChanged(RenderSource&, const OverscaledTileID&) {
     observer->onInvalidate();
 }
 
-void Renderer::Impl::onStyleImageMissing(const std::string& id) {
-    observer->onStyleImageMissing(id);
+void Renderer::Impl::onStyleImageMissing(const std::string& id, std::function<void()> done) {
+    observer->onStyleImageMissing(id, done);
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/renderer/renderer_impl.hpp b/src/mbgl/renderer/renderer_impl.hpp
index 8ec7d26988..624b4c273c 100644
--- a/src/mbgl/renderer/renderer_impl.hpp
+++ b/src/mbgl/renderer/renderer_impl.hpp
@@ -89,7 +89,7 @@ private:
     void onTileError(RenderSource&, const OverscaledTileID&, std::exception_ptr) override;
 
     // ImageManagerObserver implementation
-    void onStyleImageMissing(const std::string&) override;
+    void onStyleImageMissing(const std::string&, std::function<void()>) override;
 
     void updateFadingTiles();