only update the render order array when there are changes to tiles

src/mbgl/map/map_context.cpp

@@ -334,6 +334,7 @@ bool MapContext::renderSync(const TransformState& state, const FrameData& frame)
     if (!painter) {
         painter = std::make_unique<Painter>(data);
         painter->setup();
+        painter->updateRenderOrder(*style);
     }
 
     painter->setDebug(data.getDebug());
@@ -400,6 +401,10 @@ void MapContext::setSprite(const std::string& name, std::shared_ptr<const Sprite
 void MapContext::onTileDataChanged() {
     assert(util::ThreadContext::currentlyOn(util::ThreadType::Map));
 
+    if (painter) {
+        painter->updateRenderOrder(*style);
+    }
+
     updateFlags |= Update::Repaint;
     asyncUpdate->send();
 }

src/mbgl/map/source.cpp

@@ -529,9 +529,14 @@ void Source::invalidateTiles(const std::unordered_set<TileID, TileID::Hash>& ids
 }
 
 void Source::updateTilePtrs() {
-    tilePtrs.clear();
+    std::vector<Tile*> newPtrs;
     for (const auto& pair : tiles) {
-        tilePtrs.push_back(pair.second.get());
+        newPtrs.push_back(pair.second.get());
+    }
+
+    if (tilePtrs != newPtrs) {
+        tilePtrs = newPtrs;
+        emitTileLoaded(true);
     }
 }
 

src/mbgl/renderer/painter.cpp

@@ -181,9 +181,6 @@ void Painter::render(const Style& style, TransformState state_, const FrameData&
     resize();
     changeMatrix();
 
-    // Figure out what buckets we have to draw and what order we have to draw them in.
-    const auto order = determineRenderOrder(style);
-
     // - UPLOAD PASS -------------------------------------------------------------------------------
     // Uploads all required buffers and images before we do any actual rendering.
     {
@@ -202,7 +199,6 @@ void Painter::render(const Style& style, TransformState state_, const FrameData&
         }
     }
 
-
     // - CLIPPING MASKS ----------------------------------------------------------------------------
     // Draws the clipping masks to the stencil buffer.
     {
@@ -273,6 +269,8 @@ void Painter::renderPass(RenderPass pass_,
                          const float strataThickness) {
     pass = pass_;
 
+    const double zoom = state.getZoom();
+
     MBGL_DEBUG_GROUP(pass == RenderPass::Opaque ? "opaque" : "translucent");
 
     if (debug::renderTree) {
@@ -285,6 +283,13 @@ void Painter::renderPass(RenderPass pass_,
     for (; it != end; ++it, i += increment) {
         const auto& item = *it;
         if (item.bucket && item.tile) {
+            // Skip this layer if it's outside the range of min/maxzoom.
+            // This may occur when there /is/ a bucket created for this layer, but the min/max-zoom
+            // is set to a fractional value, or value that is larger than the source maxzoom.
+            if (item.layer.bucket->min_zoom > zoom ||
+                item.layer.bucket->max_zoom <= zoom) {
+                continue;
+            }
             if (item.layer.hasRenderPass(pass)) {
                 MBGL_DEBUG_GROUP(item.layer.id + " - " + std::string(item.tile->id));
                 setStrata(i * strataThickness);
@@ -303,8 +308,8 @@ void Painter::renderPass(RenderPass pass_,
     }
 }
 
-std::vector<RenderItem> Painter::determineRenderOrder(const Style& style) {
-    std::vector<RenderItem> order;
+void Painter::updateRenderOrder(const Style& style) {
+    order.clear();
 
     for (const auto& layerPtr : style.layers) {
         const auto& layer = *layerPtr;
@@ -341,15 +346,6 @@ std::vector<RenderItem> Painter::determineRenderOrder(const Style& style) {
             continue;
         }
 
-        // Skip this layer if it's outside the range of min/maxzoom.
-        // This may occur when there /is/ a bucket created for this layer, but the min/max-zoom
-        // is set to a fractional value, or value that is larger than the source maxzoom.
-        const double zoom = state.getZoom();
-        if (layer.bucket->min_zoom > zoom ||
-            layer.bucket->max_zoom <= zoom) {
-            continue;
-        }
-
         const auto& tiles = source->getTiles();
         for (auto tile : tiles) {
             assert(tile);
@@ -363,8 +359,6 @@ std::vector<RenderItem> Painter::determineRenderOrder(const Style& style) {
             }
         }
     }
-
-    return order;
 }
 
 void Painter::renderBackground(const StyleLayer &layer_desc) {

src/mbgl/renderer/painter.hpp

@@ -134,12 +134,12 @@ public:
 
     bool needsAnimation() const;
 
+    void updateRenderOrder(const Style& style);
+
 private:
     void setupShaders();
     mat4 translatedMatrix(const mat4& matrix, const std::array<float, 2> &translation, const TileID &id, TranslateAnchorType anchor);
 
-    std::vector<RenderItem> determineRenderOrder(const Style& style);
-
     template <class Iterator>
     void renderPass(RenderPass,
                     Iterator it, Iterator end,
@@ -201,6 +201,8 @@ private:
     const float strata_epsilon = 1.0f / (1 << 16);
     Color background = {{ 0, 0, 0, 0 }};
 
+    std::vector<RenderItem> order;
+
 public:
     FrameHistory frameHistory;