From feab36a9fbc5162150de8c3e26df8585b1430318 Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <ansis.brammanis@gmail.com>
Date: Mon, 8 Jan 2018 12:57:03 -0500
Subject: [core] port minor collision changes from -js (#10764)

---
 src/mbgl/text/cross_tile_symbol_index.cpp | 66 +++++++++++++------------------
 1 file changed, 27 insertions(+), 39 deletions(-)

(limited to 'src/mbgl/text/cross_tile_symbol_index.cpp')

diff --git a/src/mbgl/text/cross_tile_symbol_index.cpp b/src/mbgl/text/cross_tile_symbol_index.cpp
index 177615857f..6efded8e4a 100644
--- a/src/mbgl/text/cross_tile_symbol_index.cpp
+++ b/src/mbgl/text/cross_tile_symbol_index.cpp
@@ -57,50 +57,35 @@ void TileLayerIndex::findMatches(std::vector<SymbolInstance>& symbolInstances, c
 CrossTileSymbolLayerIndex::CrossTileSymbolLayerIndex() {
 }
 
-void CrossTileSymbolLayerIndex::addBucket(const OverscaledTileID& coord, SymbolBucket& bucket, uint32_t& maxCrossTileID) {
-    if (bucket.bucketInstanceId) return;
-    bucket.bucketInstanceId = ++maxBucketInstanceId;
-
-    uint8_t minZoom = 25;
-    uint8_t maxZoom = 0;
-    for (auto& it : indexes) {
-        auto z = it.first;
-        minZoom = std::min(minZoom, z);
-        maxZoom = std::max(maxZoom, z);
+bool CrossTileSymbolLayerIndex::addBucket(const OverscaledTileID& tileID, SymbolBucket& bucket, uint32_t& maxCrossTileID) {
+    auto thisZoomIndexes = indexes[tileID.overscaledZ];
+    auto previousIndex = thisZoomIndexes.find(tileID);
+    if (previousIndex != thisZoomIndexes.end() && previousIndex->second.bucketInstanceId == bucket.bucketInstanceId) {
+        return false;
     }
 
+    for (auto& symbolInstance: bucket.symbolInstances) {
+        symbolInstance.crossTileID = 0;
+    }
 
-    // make all higher-res child tiles block duplicate labels in this tile
-    for (auto z = maxZoom; z > coord.overscaledZ; z--) {
-        auto zoomIndexes = indexes.find(z);
-        if (zoomIndexes != indexes.end()) {
-            for (auto& childIndex : zoomIndexes->second) {
-                if (!childIndex.second.coord.isChildOf(coord)) {
-                    continue;
+    for (auto& it : indexes) {
+        auto zoom = it.first;
+        auto zoomIndexes = it.second;
+        if (zoom > tileID.overscaledZ) {
+            for (auto& childIndex : zoomIndexes) {
+                if (childIndex.second.coord.isChildOf(tileID)) {
+                    childIndex.second.findMatches(bucket.symbolInstances, tileID);
                 }
-                childIndex.second.findMatches(bucket.symbolInstances, coord);
             }
-        }
-        if (z == 0) {
-            break;
-        }
-    }
-
-    // make this tile block duplicate labels in lower-res parent tiles
-    for (auto z = coord.overscaledZ; z >= minZoom; z--) {
-        auto parentCoord = coord.scaledTo(z);
-        auto zoomIndexes = indexes.find(z);
-        if (zoomIndexes != indexes.end()) {
-            auto parentIndex = zoomIndexes->second.find(parentCoord);
-            if (parentIndex != zoomIndexes->second.end()) {
-                parentIndex->second.findMatches(bucket.symbolInstances, coord);
+        } else {
+            auto parentTileID = tileID.scaledTo(zoom);
+            auto parentIndex = zoomIndexes.find(parentTileID);
+            if (parentIndex != zoomIndexes.end()) {
+                parentIndex->second.findMatches(bucket.symbolInstances, tileID);
             }
         }
-        if (z == 0) {
-            break;
-        }
     }
-    
+
     for (auto& symbolInstance : bucket.symbolInstances) {
         if (!symbolInstance.crossTileID) {
             // symbol did not match any known symbol, assign a new id
@@ -108,7 +93,8 @@ void CrossTileSymbolLayerIndex::addBucket(const OverscaledTileID& coord, SymbolB
         }
     }
 
-    indexes[coord.overscaledZ].emplace(coord, TileLayerIndex(coord, bucket.symbolInstances, bucket.bucketInstanceId));
+    indexes[tileID.overscaledZ].emplace(tileID, TileLayerIndex(tileID, bucket.symbolInstances, bucket.bucketInstanceId));
+    return true;
 }
 
 bool CrossTileSymbolLayerIndex::removeStaleBuckets(const std::unordered_set<uint32_t>& currentIDs) {
@@ -145,9 +131,11 @@ bool CrossTileSymbolIndex::addLayer(RenderSymbolLayer& symbolLayer) {
         SymbolBucket& symbolBucket = *reinterpret_cast<SymbolBucket*>(bucket);
 
         if (!symbolBucket.bucketInstanceId) {
-            symbolBucketsChanged = true;
+            symbolBucket.bucketInstanceId = ++maxBucketInstanceId;
         }
-        layerIndex.addBucket(renderTile.tile.id, symbolBucket, maxCrossTileID);
+
+        const bool bucketAdded = layerIndex.addBucket(renderTile.tile.id, symbolBucket, maxCrossTileID);
+        symbolBucketsChanged = symbolBucketsChanged || bucketAdded;
         currentBucketIDs.insert(symbolBucket.bucketInstanceId);
     }
 
-- 
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