[core] Load sources only if there is at least one visible layer

src/mbgl/map/source.cpp

@@ -39,9 +39,7 @@ Source::Source() {}
 Source::~Source() = default;
 
 bool Source::isLoaded() const {
-    if (!loaded) {
-        return false;
-    }
+    if (!loaded) return false;
 
     for (const auto& tile : tiles) {
         if (tile.second->data->getState() != TileData::State::parsed) {
@@ -52,6 +50,10 @@ bool Source::isLoaded() const {
     return true;
 }
 
+bool Source::isLoading() const {
+    return !loaded && req.operator bool();
+}
+
 // Note: This is a separate function that must be called exactly once after creation
 // The reason this isn't part of the constructor is that calling shared_from_this() in
 // the constructor fails.

src/mbgl/map/source.hpp

@@ -35,7 +35,9 @@ public:
     Source();
     ~Source();
 
+    bool loaded = false;
     void load();
+    bool isLoading() const;
     bool isLoaded() const;
 
     // Request or parse all the tiles relevant for the "TransformState". This method
@@ -58,7 +60,7 @@ public:
     void dumpDebugLogs() const;
 
     SourceInfo info;
-    bool enabled;
+    bool enabled = false;
 
 private:
     void tileLoadingCompleteCallback(const TileID&, const TransformState&, bool collisionDebug);
@@ -80,7 +82,6 @@ private:
 
     double getZoom(const TransformState &state) const;
 
-    bool loaded = false;
 
     // Stores the time when this source was most recently updated.
     TimePoint updated = TimePoint::min();

src/mbgl/style/style.cpp

@@ -77,7 +77,6 @@ Style::~Style() {
 
 void Style::addSource(std::unique_ptr<Source> source) {
     source->setObserver(this);
-    source->load();
     sources.emplace_back(std::move(source));
 }
 
@@ -184,11 +183,10 @@ void Style::recalculate(float z) {
         hasPendingTransitions |= layer->recalculate(parameters);
 
         Source* source = getSource(layer->source);
-        if (!source) {
-            continue;
+        if (source && layer->needsRendering()) {
+            source->enabled = true;
+            if (!source->loaded && !source->isLoading()) source->load();
         }
-
-        source->enabled = true;
     }
 }
 
@@ -209,10 +207,8 @@ bool Style::isLoaded() const {
         return false;
     }
 
-    for (const auto& source : sources) {
-        if (!source->isLoaded()) {
-            return false;
-        }
+    for (const auto& source: sources) {
+        if (source->enabled && !source->isLoaded()) return false;
     }
 
     if (!spriteStore->isLoaded()) {

src/mbgl/style/style_layer.cpp

@@ -10,4 +10,8 @@ bool StyleLayer::hasRenderPass(RenderPass pass) const {
     return bool(passes & pass);
 }
 
+bool StyleLayer::needsRendering() const {
+    return passes != RenderPass::None && visibility != VisibilityType::None;
+}
+
 } // namespace mbgl

src/mbgl/style/style_layer.hpp

@@ -50,6 +50,9 @@ public:
     // Checks whether this layer needs to be rendered in the given render pass.
     bool hasRenderPass(RenderPass) const;
 
+    // Checks whether this layer can be rendered.
+    bool needsRendering() const;
+
 public:
     std::string id;
     std::string ref;

test/fixtures/resources/style.json

@@ -32,5 +32,9 @@
       "text-font": ["Open Sans Regular", "Arial Unicode MS Regular"],
       "icon-image": "{maki}_icon"
     }
+  }, {
+    "id":  "rasterlayer",
+    "type": "fill",
+    "source": "rastersource"
   }]
 }

test/style/pending_resources.cpp

@@ -39,7 +39,7 @@ TEST_P(PendingResources, DeleteMapObjectWithPendingRequest) {
     const std::string style = util::read_file("test/fixtures/resources/style.json");
     map->setStyleJSON(style, ".");
 
-    map->renderStill([&endTest](std::exception_ptr, PremultipliedImage&&) {
+    map->renderStill([](std::exception_ptr, PremultipliedImage&&) {
         EXPECT_TRUE(false) << "Should never happen.";
     });
 

test/style/resource_loading.cpp

@@ -51,6 +51,8 @@ public:
         data_.setAnimationTime(now);
         transform_.updateTransitions(now);
 
+        style_->cascade();
+        style_->recalculate(16);
         style_->update(transform_.getState(), texturePool_);
     }