[core] shader program must always match bucket in render symbol layer

Before this change, `RenderSymbolLayer` with updated style was trying to render
symbols using the previous bucket (with paint property binders that matched a previous program).

Now, symbol bucket caches the latest corresponding paint properties (caching is happening on
complete tiles only). As a result, `RenderSymbolLayer` always picks the shader program and
its parameters in sync with the obtained bucket.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/mbgl/renderer/render_layer.hpp b/src/mbgl/renderer/render_layer.hpp
index 485e5551c6..758412f932 100644
--- a/src/mbgl/renderer/render_layer.hpp
+++ b/src/mbgl/renderer/render_layer.hpp
@@ -96,6 +96,10 @@ protected:
     // Code specific to RenderTiles sorting / filtering
     virtual RenderTiles filterRenderTiles(RenderTiles) const;
     virtual void sortRenderTiles(const TransformState&);
+    // For some layers, we want Buckets to cache their corresponding paint properties, so that outdated buckets (and
+    // the cached paint properties) can be still in use while the tile is loading new buckets (which will
+    // correpond to the current paint properties of the layer).
+    virtual void updateBucketPaintProperties(Bucket*) const;
     using FilterFunctionPtr = bool (*)(RenderTile&);
     RenderTiles filterRenderTiles(RenderTiles, FilterFunctionPtr) const;