[core] RenderSource creates render items

14 files changed, 141 insertions, 107 deletions

diff --git a/src/mbgl/renderer/layers/render_symbol_layer.cpp b/src/mbgl/renderer/layers/render_symbol_layer.cpp
index e254466e0b..60b0c8e2d8 100644
--- a/src/mbgl/renderer/layers/render_symbol_layer.cpp
+++ b/src/mbgl/renderer/layers/render_symbol_layer.cpp
@@ -508,7 +508,7 @@ void RenderSymbolLayer::prepare(const LayerPrepareParameters& params) {
     std::sort(renderTiles.begin(), renderTiles.end(), comp);
 
     placementData.clear();
-    for (RenderTile& renderTile : renderTiles) {
+    for (const RenderTile& renderTile : renderTiles) {
         auto* bucket = static_cast<SymbolBucket*>(renderTile.getBucket(*baseImpl));
         if (bucket && bucket->bucketLeaderID == getID()) {
             // Only place this layer if it's the "group leader" for the bucket
diff --git a/src/mbgl/renderer/paint_parameters.cpp b/src/mbgl/renderer/paint_parameters.cpp
index 5034850264..0bb66972a8 100644
--- a/src/mbgl/renderer/paint_parameters.cpp
+++ b/src/mbgl/renderer/paint_parameters.cpp
@@ -90,7 +90,7 @@ void PaintParameters::clearStencil() {
 namespace {
 
 // Detects a difference in keys of renderTiles and tileClippingMaskIDs
-bool tileIDsIdentical(const std::vector<std::reference_wrapper<RenderTile>>& renderTiles,
+bool tileIDsIdentical(const RenderTiles& renderTiles,
                       const std::map<UnwrappedTileID, int32_t>& tileClippingMaskIDs) {
     assert(std::is_sorted(renderTiles.begin(), renderTiles.end(),
                           [](const RenderTile& a, const RenderTile& b) { return a.id < b.id; }));
@@ -103,7 +103,7 @@ bool tileIDsIdentical(const std::vector<std::reference_wrapper<RenderTile>>& ren
 
 } // namespace
 
-void PaintParameters::renderTileClippingMasks(const std::vector<std::reference_wrapper<RenderTile>>& renderTiles) {
+void PaintParameters::renderTileClippingMasks(const RenderTiles& renderTiles) {
     if (renderTiles.empty() || tileIDsIdentical(renderTiles, tileClippingMaskIDs)) {
         // The current stencil mask is for this source already; no need to draw another one.
         return;
diff --git a/src/mbgl/renderer/paint_parameters.hpp b/src/mbgl/renderer/paint_parameters.hpp
index d78125da54..a0d26df7c5 100644
--- a/src/mbgl/renderer/paint_parameters.hpp
+++ b/src/mbgl/renderer/paint_parameters.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/renderer/render_pass.hpp>
 #include <mbgl/renderer/render_light.hpp>
+#include <mbgl/renderer/render_source.hpp>
 #include <mbgl/map/mode.hpp>
 #include <mbgl/map/transform_state.hpp>
 #include <mbgl/gfx/depth_mode.hpp>
@@ -23,8 +24,6 @@ class ImageManager;
 class LineAtlas;
 class PatternAtlas;
 class UnwrappedTileID;
-class RenderSource;
-class RenderTile;
 
 namespace gfx {
 class Context;
@@ -89,7 +88,7 @@ public:
 
     // Stencil handling
 public:
-    void renderTileClippingMasks(const std::vector<std::reference_wrapper<RenderTile>>&);
+    void renderTileClippingMasks(const RenderTiles&);
     gfx::StencilMode stencilModeForClipping(const UnwrappedTileID&) const;
     gfx::StencilMode stencilModeFor3D();
 
diff --git a/src/mbgl/renderer/render_layer.cpp b/src/mbgl/renderer/render_layer.cpp
index 2f57d9ed9c..821b10050f 100644
--- a/src/mbgl/renderer/render_layer.cpp
+++ b/src/mbgl/renderer/render_layer.cpp
@@ -54,10 +54,10 @@ optional<Color> RenderLayer::getSolidBackground() const {
     return nullopt;
 }
 
-RenderLayer::RenderTiles RenderLayer::filterRenderTiles(RenderTiles tiles) const {
+RenderTiles RenderLayer::filterRenderTiles(RenderTiles tiles) const {
     RenderTiles filtered;
 
-    for (RenderTile& tile : tiles) {
+    for (const RenderTile& tile : tiles) {
         if (tile.holdForFade()) {
             continue;
         }
diff --git a/src/mbgl/renderer/render_layer.hpp b/src/mbgl/renderer/render_layer.hpp
index 7f73826c34..11c7587893 100644
--- a/src/mbgl/renderer/render_layer.hpp
+++ b/src/mbgl/renderer/render_layer.hpp
@@ -30,7 +30,7 @@ public:
 class LayerPlacementData {
 public:
     std::reference_wrapper<Bucket> bucket;
-    std::reference_wrapper<RenderTile> tile;
+    std::reference_wrapper<const RenderTile> tile;
     std::shared_ptr<FeatureIndex> featureIndex;
 };
 
@@ -43,6 +43,8 @@ public:
     const TransformState& state;
 };
 
+using RenderTiles = std::vector<std::reference_wrapper<const RenderTile>>;
+
 class RenderLayer {
 protected:
     RenderLayer(Immutable<style::LayerProperties>);
@@ -115,7 +117,6 @@ protected:
     void checkRenderability(const PaintParameters&, uint32_t activeBindingCount);
 
 protected:
-    using RenderTiles = std::vector<std::reference_wrapper<RenderTile>>;
     // Stores current set of tiles to be rendered for this layer.
     RenderTiles renderTiles;
 
diff --git a/src/mbgl/renderer/render_orchestrator.cpp b/src/mbgl/renderer/render_orchestrator.cpp
index b980efcff8..fafbc8b635 100644
--- a/src/mbgl/renderer/render_orchestrator.cpp
+++ b/src/mbgl/renderer/render_orchestrator.cpp
@@ -55,25 +55,11 @@ private:
     uint32_t index;
 };
 
-class SourceRenderItem final : public RenderItem { 
-public:
-    explicit SourceRenderItem(RenderSource& source_) 
-        : source(source_) {}
-
-private:
-    bool hasRenderPass(RenderPass) const override { return false; }
-    void upload(gfx::UploadPass& pass) const override { source.get().upload(pass); }
-    void render(PaintParameters& parameters) const override { source.get().finishRender(parameters); }
-    const std::string& getName() const override { return source.get().baseImpl->id; } 
-
-    std::reference_wrapper<RenderSource> source;
-};
-
 class RenderTreeImpl final : public RenderTree {
 public:
     RenderTreeImpl(std::unique_ptr<RenderTreeParameters> parameters_,
                    std::set<LayerRenderItem> layerRenderItems_,
-                   std::vector<SourceRenderItem> sourceRenderItems_,
+                   std::vector<std::unique_ptr<RenderItem>> sourceRenderItems_,
                    LineAtlas& lineAtlas_,
                    PatternAtlas& patternAtlas_)
         : RenderTree(std::move(parameters_)),
@@ -87,13 +73,16 @@ public:
         return { layerRenderItems.begin(), layerRenderItems.end() };
     }
     RenderItems getSourceRenderItems() const override {
-        return { sourceRenderItems.begin(), sourceRenderItems.end() };
+        RenderItems result;
+        result.reserve(sourceRenderItems.size());
+        for (const auto& item : sourceRenderItems) result.emplace_back(*item);
+        return result;
     }
     LineAtlas& getLineAtlas() const override { return lineAtlas; }
     PatternAtlas& getPatternAtlas() const override { return patternAtlas; }
 
     std::set<LayerRenderItem> layerRenderItems;
-    std::vector<SourceRenderItem> sourceRenderItems;
+    std::vector<std::unique_ptr<RenderItem>> sourceRenderItems;
     std::reference_wrapper<LineAtlas> lineAtlas;
     std::reference_wrapper<PatternAtlas> patternAtlas;
 };
@@ -339,12 +328,10 @@ std::unique_ptr<RenderTree> RenderOrchestrator::createRenderTree(const UpdatePar
         return nullptr;
     }
 
-    std::vector<SourceRenderItem> sourceRenderItems;
-    // Update all matrices and generate data that we should upload to the GPU.
+    // Prepare. Update all matrices and generate data that we should upload to the GPU.
     for (const auto& entry : renderSources) {
         if (entry.second->isEnabled()) {
             entry.second->prepare({renderTreeParameters->transformParams, updateParameters.debugOptions, *imageManager});
-            sourceRenderItems.emplace_back(*entry.second);
         }
     }
 
@@ -355,7 +342,7 @@ std::unique_ptr<RenderTree> RenderOrchestrator::createRenderTree(const UpdatePar
             layersNeedPlacement.emplace_back(renderLayer);
         }
     }
-
+    // Symbol placement.
     {
         if (!isMapModeContinuous) {
             // TODO: Think about right way for symbol index to handle still rendering
@@ -406,6 +393,13 @@ std::unique_ptr<RenderTree> RenderOrchestrator::createRenderTree(const UpdatePar
         imageManager->reduceMemoryUseIfCacheSizeExceedsLimit();
     }
 
+    std::vector<std::unique_ptr<RenderItem>> sourceRenderItems;
+    for (const auto& entry : renderSources) {
+        if (entry.second->isEnabled()) {
+            sourceRenderItems.emplace_back(entry.second->createRenderItem());
+        }
+    }
+
     return std::make_unique<RenderTreeImpl>(
         std::move(renderTreeParameters),
         std::move(layerRenderItems),
diff --git a/src/mbgl/renderer/render_source.hpp b/src/mbgl/renderer/render_source.hpp
index d9af901664..fc770f83cf 100644
--- a/src/mbgl/renderer/render_source.hpp
+++ b/src/mbgl/renderer/render_source.hpp
@@ -30,6 +30,7 @@ class CollisionIndex;
 class TransformParameters;
 class ImageManager;
 class ImageSourceRenderData;
+class RenderItem;
 
 namespace gfx {
 class UploadPass;
@@ -42,6 +43,8 @@ public:
     const ImageManager& imageManager;
 };
 
+using RenderTiles = std::vector<std::reference_wrapper<const RenderTile>>;
+
 class RenderSource : protected TileObserver {
 public:
     static std::unique_ptr<RenderSource> create(Immutable<style::Source::Impl>);
@@ -55,14 +58,14 @@ public:
                         bool needsRendering,
                         bool needsRelayout,
                         const TileParameters&) = 0;
-
-    virtual void upload(gfx::UploadPass&) = 0;
+    // Note: calling of this method might reset the contained render data.
+    virtual std::unique_ptr<RenderItem> createRenderItem() = 0;
+    // Creates the render data to be passed to the render item.
     virtual void prepare(const SourcePrepareParameters&) = 0;
-    virtual void finishRender(PaintParameters&) = 0;
     virtual void updateFadingTiles() = 0;
     virtual bool hasFadingTiles() const = 0;
     // Returns a list of RenderTiles, sorted by tile id.
-    virtual std::vector<std::reference_wrapper<RenderTile>> getRenderTiles() = 0;
+    virtual RenderTiles getRenderTiles() = 0;
     virtual const ImageSourceRenderData* getImageRenderData() const { return nullptr; }
     virtual const Tile* getRenderedTile(const UnwrappedTileID&) const { return nullptr; }
 
diff --git a/src/mbgl/renderer/render_tile.cpp b/src/mbgl/renderer/render_tile.cpp
index 3c61e7d7a3..fbb2ae81de 100644
--- a/src/mbgl/renderer/render_tile.cpp
+++ b/src/mbgl/renderer/render_tile.cpp
@@ -91,7 +91,7 @@ const gfx::Texture& RenderTile::getIconAtlasTexture() const {
     return renderData->getIconAtlasTexture();
 }
 
-void RenderTile::upload(gfx::UploadPass& uploadPass) {
+void RenderTile::upload(gfx::UploadPass& uploadPass) const {
     assert(renderData);
     renderData->upload(uploadPass);
 
@@ -129,7 +129,7 @@ void RenderTile::prepare(const SourcePrepareParameters& parameters) {
     matrix::multiply(nearClippedMatrix, transform.nearClippedProjMatrix, nearClippedMatrix);
 }
 
-void RenderTile::finishRender(PaintParameters& parameters) {
+void RenderTile::finishRender(PaintParameters& parameters) const {
     if (!needsRendering || parameters.debugOptions == MapDebugOptions::NoDebug)
         return;
 
diff --git a/src/mbgl/renderer/render_tile.hpp b/src/mbgl/renderer/render_tile.hpp
index a532bf8dd8..34d027cae5 100644
--- a/src/mbgl/renderer/render_tile.hpp
+++ b/src/mbgl/renderer/render_tile.hpp
@@ -59,9 +59,9 @@ public:
     const gfx::Texture& getGlyphAtlasTexture() const;
     const gfx::Texture& getIconAtlasTexture() const;
 
-    void upload(gfx::UploadPass&);
+    void upload(gfx::UploadPass&) const;
     void prepare(const SourcePrepareParameters&);
-    void finishRender(PaintParameters&);
+    void finishRender(PaintParameters&) const;
 
     mat4 translateVtxMatrix(const mat4& tileMatrix,
                             const std::array<float, 2>& translation,
diff --git a/src/mbgl/renderer/sources/render_image_source.cpp b/src/mbgl/renderer/sources/render_image_source.cpp
index 04edced011..7e793c6a4a 100644
--- a/src/mbgl/renderer/sources/render_image_source.cpp
+++ b/src/mbgl/renderer/sources/render_image_source.cpp
@@ -17,55 +17,25 @@ namespace mbgl {
 
 using namespace style;
 
-RenderImageSource::RenderImageSource(Immutable<style::ImageSource::Impl> impl_)
-    : RenderSource(impl_) {
-}
-
-RenderImageSource::~RenderImageSource() = default;
-
-const style::ImageSource::Impl& RenderImageSource::impl() const {
-    return static_cast<const style::ImageSource::Impl&>(*baseImpl);
-}
+ImageSourceRenderData::~ImageSourceRenderData() = default;
 
-bool RenderImageSource::isLoaded() const {
-    return !!bucket;
-}
-
-void RenderImageSource::upload(gfx::UploadPass& uploadPass) {
-    if (bucket->needsUpload()) {
+void ImageSourceRenderData::upload(gfx::UploadPass& uploadPass) const {
+    if (bucket && bucket->needsUpload()) {
         bucket->upload(uploadPass);
     }
 }
 
-void RenderImageSource::prepare(const SourcePrepareParameters& parameters) {
-    if (!isLoaded()) {
-        return;
-    }
-
-    std::vector<mat4> matrices{tileIds.size(), mat4()};
-    const auto& transformParams = parameters.transform;
-    for (size_t i = 0u; i < tileIds.size(); ++i) {
-        mat4& matrix = matrices[i];
-        matrix::identity(matrix);
-        transformParams.state.matrixFor(matrix, tileIds[i]);
-        matrix::multiply(matrix, transformParams.alignedProjMatrix, matrix);
-    }
-
-    renderData = std::make_unique<ImageSourceRenderData>(bucket, std::move(matrices));
-}
-
-void RenderImageSource::finishRender(PaintParameters& parameters) {
-    if (!isLoaded() || !(parameters.debugOptions & MapDebugOptions::TileBorders)) {
+void ImageSourceRenderData::render(PaintParameters& parameters) const {
+    if (!bucket || !(parameters.debugOptions & MapDebugOptions::TileBorders)) {
         return;
     }
-    assert(renderData);
 
     static const style::Properties<>::PossiblyEvaluated properties {};
     static const DebugProgram::Binders paintAttributeData(properties, 0);
 
     auto& programInstance = parameters.programs.debug;
 
-    for (auto matrix : renderData->matrices) {
+    for (auto matrix : matrices) {
         programInstance.draw(
             parameters.context,
             *parameters.renderPass,
@@ -96,6 +66,43 @@ void RenderImageSource::finishRender(PaintParameters& parameters) {
     }
 }
 
+RenderImageSource::RenderImageSource(Immutable<style::ImageSource::Impl> impl_)
+    : RenderSource(std::move(impl_)) {
+}
+
+RenderImageSource::~RenderImageSource() = default;
+
+const style::ImageSource::Impl& RenderImageSource::impl() const {
+    return static_cast<const style::ImageSource::Impl&>(*baseImpl);
+}
+
+bool RenderImageSource::isLoaded() const {
+    return !!bucket;
+}
+
+std::unique_ptr<RenderItem> RenderImageSource::createRenderItem() {
+    assert(renderData);
+    return std::move(renderData);
+}
+
+void RenderImageSource::prepare(const SourcePrepareParameters& parameters) {
+    assert(!renderData);
+    if (!isLoaded()) {
+        renderData = std::make_unique<ImageSourceRenderData>(bucket, std::vector<mat4>{}, baseImpl->id);
+        return;
+    }
+
+    std::vector<mat4> matrices{tileIds.size(), mat4()};
+    const auto& transformParams = parameters.transform;
+    for (size_t i = 0u; i < tileIds.size(); ++i) {
+        mat4& matrix = matrices[i];
+        matrix::identity(matrix);
+        transformParams.state.matrixFor(matrix, tileIds[i]);
+        matrix::multiply(matrix, transformParams.alignedProjMatrix, matrix);
+    }
+    renderData = std::make_unique<ImageSourceRenderData>(bucket, std::move(matrices), baseImpl->id);
+}
+
 std::unordered_map<std::string, std::vector<Feature>>
 RenderImageSource::queryRenderedFeatures(const ScreenLineString&,
                                          const TransformState&,
diff --git a/src/mbgl/renderer/sources/render_image_source.hpp b/src/mbgl/renderer/sources/render_image_source.hpp
index 804daeef87..d21f4fae10 100644
--- a/src/mbgl/renderer/sources/render_image_source.hpp
+++ b/src/mbgl/renderer/sources/render_image_source.hpp
@@ -9,14 +9,25 @@ namespace mbgl {
 
 class RasterBucket;
 
-class ImageSourceRenderData {
+class ImageSourceRenderData final : public RenderItem {
 public:
     ImageSourceRenderData(std::shared_ptr<RasterBucket> bucket_,
-                          std::vector<mat4> matrices_)
+                          std::vector<mat4> matrices_,
+                          std::string name_)
         : bucket(std::move(bucket_)),
-          matrices(std::move(matrices_)) {}
-    std::shared_ptr<RasterBucket> bucket;
-    std::vector<mat4> matrices;
+          matrices(std::move(matrices_)),
+          name(std::move(name_)) {}
+    ~ImageSourceRenderData() override;
+    const std::shared_ptr<RasterBucket> bucket;
+    const std::vector<mat4> matrices;
+
+private:
+    void upload(gfx::UploadPass&) const override;
+    void render(PaintParameters&) const override;
+    bool hasRenderPass(RenderPass) const override { return false; }
+    const std::string& getName() const override { return name; }
+
+    std::string name;
 };
 
 class RenderImageSource final : public RenderSource {
@@ -26,9 +37,8 @@ public:
 
     bool isLoaded() const final;
 
-    void upload(gfx::UploadPass&) final;
+    std::unique_ptr<RenderItem> createRenderItem() override;
     void prepare(const SourcePrepareParameters&) final;
-    void finishRender(PaintParameters&) final;
     void updateFadingTiles() final {}
     bool hasFadingTiles() const final { return false; }
 
@@ -38,9 +48,7 @@ public:
                 bool needsRelayout,
                 const TileParameters&) final;
 
-    std::vector<std::reference_wrapper<RenderTile>> getRenderTiles() final {
-        return {};
-    }
+    RenderTiles getRenderTiles() override { return {}; }
 
     const ImageSourceRenderData* getImageRenderData() const override { 
         return renderData.get();
diff --git a/src/mbgl/renderer/sources/render_tile_source.cpp b/src/mbgl/renderer/sources/render_tile_source.cpp
index 3af3b92e77..99bdfde485 100644
--- a/src/mbgl/renderer/sources/render_tile_source.cpp
+++ b/src/mbgl/renderer/sources/render_tile_source.cpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/renderer/buckets/debug_bucket.hpp>
 #include <mbgl/renderer/render_tile.hpp>
+#include <mbgl/renderer/render_tree.hpp>
 #include <mbgl/renderer/paint_parameters.hpp>
 #include <mbgl/renderer/tile_render_data.hpp>
 #include <mbgl/tile/vector_tile.hpp>
@@ -10,8 +11,37 @@ namespace mbgl {
 
 using namespace style;
 
+class TileSourceRenderItem : public RenderItem {
+public:
+    TileSourceRenderItem(Immutable<std::vector<RenderTile>> renderTiles_, std::string name_)
+        : renderTiles(std::move(renderTiles_))
+        , name(std::move(name_)) {}
+
+private:
+    void upload(gfx::UploadPass&) const override;
+    void render(PaintParameters&) const override;
+    bool hasRenderPass(RenderPass) const override { return false; }
+    const std::string& getName() const override { return name; }
+
+    Immutable<std::vector<RenderTile>> renderTiles;
+    std::string name;
+};
+
+void TileSourceRenderItem::upload(gfx::UploadPass& parameters) const {
+    for (auto& tile : *renderTiles) {
+        tile.upload(parameters);
+    }
+}
+
+void TileSourceRenderItem::render(PaintParameters& parameters) const {
+    for (auto& tile : *renderTiles) {
+        tile.finishRender(parameters);
+    }
+}
+
 RenderTileSource::RenderTileSource(Immutable<style::Source::Impl> impl_)
-    : RenderSource(std::move(impl_)) {
+    : RenderSource(std::move(impl_))
+    , renderTiles(makeMutable<std::vector<RenderTile>>()) {
     tilePyramid.setObserver(this);
 }
 
@@ -21,25 +51,18 @@ bool RenderTileSource::isLoaded() const {
     return tilePyramid.isLoaded();
 }
 
-void RenderTileSource::upload(gfx::UploadPass& parameters) {
-    for (auto& tile : renderTiles) {
-        tile.upload(parameters);
-    }
+std::unique_ptr<RenderItem> RenderTileSource::createRenderItem() {
+    return std::make_unique<TileSourceRenderItem>(renderTiles, baseImpl->id);
 }
 
 void RenderTileSource::prepare(const SourcePrepareParameters& parameters) {
-    renderTiles.clear();
-    renderTiles.reserve(tilePyramid.getRenderedTiles().size());
+    auto tiles = makeMutable<std::vector<RenderTile>>();
+    tiles->reserve(tilePyramid.getRenderedTiles().size());
     for (auto& entry : tilePyramid.getRenderedTiles()) {
-        renderTiles.emplace_back(entry.first, entry.second);
-        renderTiles.back().prepare(parameters);
-    }
-}
-
-void RenderTileSource::finishRender(PaintParameters& parameters) {
-    for (auto& tile : renderTiles) {
-        tile.finishRender(parameters);
+        tiles->emplace_back(entry.first, entry.second);
+        tiles->back().prepare(parameters);
     }
+    renderTiles = std::move(tiles);
 }
 
 void RenderTileSource::updateFadingTiles() {
@@ -50,8 +73,8 @@ bool RenderTileSource::hasFadingTiles() const {
     return tilePyramid.hasFadingTiles();
 }
 
-std::vector<std::reference_wrapper<RenderTile>> RenderTileSource::getRenderTiles() {
-    return { renderTiles.begin(), renderTiles.end() };
+RenderTiles RenderTileSource::getRenderTiles() {
+    return { renderTiles->begin(), renderTiles->end() };
 }
 
 const Tile* RenderTileSource::getRenderedTile(const UnwrappedTileID& tileID) const {
diff --git a/src/mbgl/renderer/sources/render_tile_source.hpp b/src/mbgl/renderer/sources/render_tile_source.hpp
index 91b453968d..e3148b45b9 100644
--- a/src/mbgl/renderer/sources/render_tile_source.hpp
+++ b/src/mbgl/renderer/sources/render_tile_source.hpp
@@ -16,13 +16,12 @@ public:
 
     bool isLoaded() const override;
 
-    void upload(gfx::UploadPass&) override;
+    std::unique_ptr<RenderItem> createRenderItem() override;
     void prepare(const SourcePrepareParameters&) override;
-    void finishRender(PaintParameters&) override;
     void updateFadingTiles() override;
     bool hasFadingTiles() const override;
 
-    std::vector<std::reference_wrapper<RenderTile>> getRenderTiles() override;
+    RenderTiles getRenderTiles() override;
     const Tile* getRenderedTile(const UnwrappedTileID&) const override;
 
     std::unordered_map<std::string, std::vector<Feature>>
@@ -40,7 +39,7 @@ public:
 
 protected:
     TilePyramid tilePyramid;
-    std::vector<RenderTile> renderTiles;
+    Immutable<std::vector<RenderTile>> renderTiles;
 };
 
 } // namespace mbgl
diff --git a/src/mbgl/text/cross_tile_symbol_index.cpp b/src/mbgl/text/cross_tile_symbol_index.cpp
index b92bab861f..43ed85d957 100644
--- a/src/mbgl/text/cross_tile_symbol_index.cpp
+++ b/src/mbgl/text/cross_tile_symbol_index.cpp
@@ -172,7 +172,7 @@ bool CrossTileSymbolIndex::addLayer(const RenderLayer& layer, float lng) {
     layerIndex.handleWrapJump(lng);
 
     for (const auto& item : layer.getPlacementData()) {
-        RenderTile& renderTile = item.tile;
+        const RenderTile& renderTile = item.tile;
         Bucket& bucket = item.bucket;
         auto result = bucket.registerAtCrossTileIndex(layerIndex, renderTile.getOverscaledTileID(), maxCrossTileID);
         assert(result.first != 0u);