wip fixup

src/mbgl/text/placement.cpp

@@ -113,10 +113,9 @@ void Placement::placeLayers(const RenderLayerReferences& layers) {
 }
 
 void Placement::placeLayer(const RenderLayer& layer) {
-    std::set<uint32_t> seenCrossTileIDs;
     for (const BucketPlacementData& data : layer.getPlacementData()) {
         Bucket& bucket = data.bucket;
-        bucket.place(*this, data, seenCrossTileIDs);
+        bucket.place(*this, data, seenLayerCrossTileIDs[layer.getID()]);
     }
 }
 
@@ -1159,7 +1158,7 @@ class StaticPlacement : public Placement {
     StaticPlacement(std::shared_ptr<const UpdateParameters> updateParameters_)
         : Placement(std::move(updateParameters_), nullopt) {}
 
-private:
+protected:
     void commit() override;
     float symbolFadeChange(TimePoint) const override { return 1.0f; }
     bool hasTransitions(TimePoint) const override { return false; }
@@ -1306,21 +1305,32 @@ SymbolInstanceReferences TilePlacement::getSortedSymbols(const BucketPlacementDa
 
         return intersects;
     };
-
-    if (onlyLabelsIntersectingTileBorders) {
-        SymbolInstanceReferences filtered;
-        filtered.reserve(symbolInstances.size());
-        for (const SymbolInstance& symbol : symbolInstances) {
-            if (symbolIntersectsTileEdges(symbol)) filtered.push_back(symbol);
-        }
-        // Add more stability, sorting tile border labels by their Y position.
-        std::stable_sort(filtered.begin(), filtered.end(), [](const SymbolInstance& a, const SymbolInstance& b) {
-            return a.anchor.point.y < b.anchor.point.y;
-        });
-        return filtered;
+    if (!onlyLabelsIntersectingTileBorders) {
+        std::stable_sort(
+            symbolInstances.begin(),
+            symbolInstances.end(),
+            [&symbolIntersectsTileEdges](const SymbolInstance& a, const SymbolInstance& b) noexcept {
+                assert(!a.textCollisionFeature.alongLine);
+                assert(!b.textCollisionFeature.alongLine);
+                auto intersectsA = symbolIntersectsTileEdges(a);
+                auto intersectsB = symbolIntersectsTileEdges(b);
+                if (intersectsA) {
+                    if (!intersectsB) return true;
+                    // Both symbols are inrecepting the tile borders, we need a universal cross-tile rule
+                    // to define which of them shall be placed first - use anchor `y` point.
+                    return a.anchor.point.y < b.anchor.point.y; 
+                }
+                return false;
+            });
     }
 
-    return symbolInstances;
+
+    SymbolInstanceReferences filtered;
+    filtered.reserve(symbolInstances.size());
+    for (const SymbolInstance& symbol : symbolInstances) {
+        if (onlyLabelsIntersectingTileBorders == symbolIntersectsTileEdges(symbol)) filtered.push_back(symbol);
+    }
+    return filtered;
 }
 
 bool TilePlacement::stickToFirstVariableAnchor(const CollisionBox& box,

src/mbgl/text/placement.hpp

@@ -185,6 +185,7 @@ class Placement {
     bool showCollisionBoxes = false;
     // Used for debug purposes.
     std::unordered_map<const CollisionFeature*, std::vector<ProjectedCollisionBox>> collisionCircles;
+    std::unordered_map<std::string, std::set<uint32_t>> seenLayerCrossTileIDs;
 };
 
 } // namespace mbgl