Drawable Renderer (#1570), Improve handling of multiple drawables per tile

include/mbgl/renderer/layer_group.hpp

@@ -77,9 +77,10 @@ public:
     ~TileLayerGroup() override;
 
     void updateLayerIndex(int32_t newLayerIndex);
+    
     std::size_t getDrawableCount() const;
+    std::size_t getDrawableCount(mbgl::RenderPass, const OverscaledTileID&) const;
 
-    const gfx::UniqueDrawable& getDrawable(mbgl::RenderPass, const OverscaledTileID&) const;
     std::vector<gfx::UniqueDrawable> removeDrawables(mbgl::RenderPass, const OverscaledTileID&);
     void addDrawable(mbgl::RenderPass, const OverscaledTileID&, gfx::UniqueDrawable&&);
 
@@ -87,7 +88,11 @@ public:
     void observeDrawables(std::function<void(const gfx::Drawable&)>) const override;
     void observeDrawables(std::function<void(gfx::UniqueDrawable&)>) override;
 
-    void clearDrawables();
+    /// Call the provided function for each drawable for the given tile
+    void observeDrawables(mbgl::RenderPass, const OverscaledTileID&,
+                          std::function<void(const gfx::Drawable&)>) const;
+
+    std::size_t clearDrawables();
 
 protected:
     struct Impl;

src/mbgl/renderer/layer_group.cpp

@@ -48,9 +48,9 @@ std::size_t TileLayerGroup::getDrawableCount() const {
 
 static const gfx::UniqueDrawable no_tile;
 
-const gfx::UniqueDrawable& TileLayerGroup::getDrawable(mbgl::RenderPass pass, const OverscaledTileID& id) const {
-    const auto hit = impl->tileDrawables.find({pass, id});
-    return (hit == impl->tileDrawables.end()) ? no_tile : hit->second;
+std::size_t TileLayerGroup::getDrawableCount(mbgl::RenderPass pass, const OverscaledTileID& id) const {
+    const auto range = impl->tileDrawables.equal_range({pass, id});
+    return std::distance(range.first, range.second);
 }
 
 std::vector<gfx::UniqueDrawable> TileLayerGroup::removeDrawables(mbgl::RenderPass pass, const OverscaledTileID& id) {
@@ -100,8 +100,16 @@ void TileLayerGroup::observeDrawables(std::function<void(gfx::UniqueDrawable&)>
     }
 }
 
-void TileLayerGroup::clearDrawables() {
+void TileLayerGroup::observeDrawables(mbgl::RenderPass pass, const OverscaledTileID& tileID,
+                                      std::function<void(const gfx::Drawable&)> f) const {
+    const auto range = impl->tileDrawables.equal_range({pass, tileID});
+    std::for_each(range.first, range.second, [&f](const auto& pair){ f(*pair.second); });
+}
+
+std::size_t TileLayerGroup::clearDrawables() {
+    const auto count = impl->tileDrawables.size();
     impl->tileDrawables.clear();
+    return count;
 }
 
 } // namespace mbgl

src/mbgl/renderer/layers/render_background_layer.cpp

@@ -286,19 +286,9 @@ void RenderBackgroundLayer::update(gfx::ShaderRegistry& shaders,
         // For each tile in the cover set, add a tile drawable if one doesn't already exist.
         // We currently assume only one drawable per tile.
         for (const auto& tileID : tileCover) {
-            auto& tileDrawable = tileLayerGroup->getDrawable(renderPass, tileID);
-
-            if (!(renderPass & drawPasses)) {
-                // Not in this pass
-                if (tileDrawable) {
-                    tileLayerGroup->removeDrawables(renderPass, tileID);
-                    ++stats.tileDrawablesRemoved;
-                }
-                continue;
-            }
-
-            if (tileDrawable) {
-                // Already created, update it.
+            // If we already have drawables for this tile, skip.
+            // If a drawable needs to be updated, that's handled in the layer tweaker.
+            if (tileLayerGroup->getDrawableCount(renderPass, tileID) > 0) {
                 continue;
             }
 

src/mbgl/renderer/layers/render_circle_layer.cpp

@@ -311,8 +311,7 @@ void RenderCircleLayer::update(gfx::ShaderRegistry& shaders,
     for (const RenderTile& tile : *renderTiles) {
         const auto& tileID = tile.getOverscaledTileID();
 
-        auto& tileDrawable = tileLayerGroup->getDrawable(renderPass, tileID);
-        if (tileDrawable) {
+        if (tileLayerGroup->getDrawableCount(renderPass, tileID) > 0) {
             continue;
         }
 

src/mbgl/renderer/layers/render_fill_layer.cpp

@@ -20,6 +20,7 @@
 #include <mbgl/tile/tile.hpp>
 #include <mbgl/util/convert.hpp>
 #include <mbgl/util/intersection_tests.hpp>
+#include <mbgl/util/logging.hpp>
 #include <mbgl/util/math.hpp>
 
 namespace mbgl {
@@ -287,8 +288,7 @@ void RenderFillLayer::update(gfx::ShaderRegistry& shaders,
 
     if (!renderTiles || renderTiles->empty()) {
         if (tileLayerGroup) {
-            stats.tileDrawablesRemoved += tileLayerGroup->getDrawableCount();
-            tileLayerGroup->clearDrawables();
+            stats.tileDrawablesRemoved += tileLayerGroup->clearDrawables();
         }
         return;
     }
@@ -359,7 +359,11 @@ void RenderFillLayer::update(gfx::ShaderRegistry& shaders,
         for (const RenderTile& tile : *renderTiles) {
             const auto& tileID = tile.getOverscaledTileID();
 
-            auto& tileDrawable = tileLayerGroup->getDrawable(renderPass, tileID);
+            // If we already have drawables for this tile, skip.
+            // If a drawable needs to be updated, that's handled in the layer tweaker.
+            if (tileLayerGroup->getDrawableCount(renderPass, tileID) > 0) {
+                continue;
+            }
 
             const LayerRenderData* renderData = getRenderDataForPass(tile, renderPass);
             if (!renderData) {
@@ -449,10 +453,6 @@ void RenderFillLayer::update(gfx::ShaderRegistry& shaders,
                     }
                 }
 
-                if (tileDrawable) {
-                    continue;
-                }
-
                 if (doFill && !fillBuilder && fillShader) {
                     fillBuilder = context.createDrawableBuilder("fill");
                     fillBuilder->setShader(fillShader);