[core] Share render tiles lists between layers

This helps to avoid unneeded allocations.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/mbgl/renderer/render_source.hpp b/src/mbgl/renderer/render_source.hpp
index 2a4983e799..cd471223a8 100644
--- a/src/mbgl/renderer/render_source.hpp
+++ b/src/mbgl/renderer/render_source.hpp
@@ -43,7 +43,7 @@ public:
     const ImageManager& imageManager;
 };
 
-using RenderTiles = std::vector<std::reference_wrapper<const RenderTile>>;
+using RenderTiles = std::shared_ptr<const std::vector<std::reference_wrapper<const RenderTile>>>;
 
 class RenderSource : protected TileObserver {
 public:
@@ -64,8 +64,14 @@ public:
     virtual void prepare(const SourcePrepareParameters&) = 0;
     virtual void updateFadingTiles() = 0;
     virtual bool hasFadingTiles() const = 0;
-    // Returns a list of RenderTiles, sorted by tile id.
-    virtual RenderTiles getRenderTiles() = 0;
+    // If supported, returns a shared list of RenderTiles, sorted by tile id and excluding tiles hold for fade;
+    // returns nullptr otherwise.
+    virtual RenderTiles getRenderTiles() const { return nullptr; }
+    // If supported, returns a shared list of RenderTiles, sorted in opposite y position, so tiles with overlapping
+    // symbols are drawn on top of each other, with lower symbols being drawn on top of higher symbols;
+    // returns nullptr otherwise.
+    virtual RenderTiles getRenderTilesSortedByYPosition() const { return nullptr; }
+    // If supported, returns pointer to image data; returns nullptr otherwise.
     virtual const ImageSourceRenderData* getImageRenderData() const { return nullptr; }
     virtual const Tile* getRenderedTile(const UnwrappedTileID&) const { return nullptr; }