[core] fix symbol flickering after data updates

src/mbgl/renderer/buckets/symbol_bucket.hpp

@@ -130,6 +130,7 @@ public:
     } collisionCircle;
 
     uint32_t bucketInstanceId = 0;
+    bool justReloaded = false;
 };
 
 } // namespace mbgl

src/mbgl/text/placement.cpp

@@ -8,8 +8,8 @@
 
 namespace mbgl {
 
-OpacityState::OpacityState(bool placed_, bool offscreen)
-    : opacity((offscreen && placed_) ? 1 : 0)
+OpacityState::OpacityState(bool placed_, bool skipFade)
+    : opacity((skipFade && placed_) ? 1 : 0)
     , placed(placed_)
 {
 }
@@ -22,11 +22,11 @@ bool OpacityState::isHidden() const {
     return opacity == 0 && !placed;
 }
 
-JointOpacityState::JointOpacityState(bool placedIcon, bool placedText, bool offscreen) :
-    icon(OpacityState(placedIcon, offscreen)),
-    text(OpacityState(placedText, offscreen)) {}
+JointOpacityState::JointOpacityState(bool placedText, bool placedIcon, bool skipFade) :
+    icon(OpacityState(placedIcon, skipFade)),
+    text(OpacityState(placedText, skipFade)) {}
 
-JointOpacityState::JointOpacityState(const JointOpacityState& prevOpacityState, float increment, bool placedIcon, bool placedText) :
+JointOpacityState::JointOpacityState(const JointOpacityState& prevOpacityState, float increment, bool placedText, bool placedIcon) :
     icon(OpacityState(prevOpacityState.icon, increment, placedIcon)),
     text(OpacityState(prevOpacityState.text, increment, placedText)) {}
 
@@ -165,10 +165,12 @@ void Placement::placeLayerBucket(
                 placements.erase(symbolInstance.crossTileID);
             }
             
-            placements.emplace(symbolInstance.crossTileID, JointPlacement(placeText, placeIcon, offscreen));
+            placements.emplace(symbolInstance.crossTileID, JointPlacement(placeText, placeIcon, offscreen || bucket.justReloaded));
             seenCrossTileIDs.insert(symbolInstance.crossTileID);
         }
     } 
+
+    bucket.justReloaded = false;
 }
 
 bool Placement::commit(const Placement& prevPlacement, TimePoint now) {
@@ -184,12 +186,12 @@ bool Placement::commit(const Placement& prevPlacement, TimePoint now) {
     for (auto& jointPlacement : placements) {
         auto prevOpacity = prevPlacement.opacities.find(jointPlacement.first);
         if (prevOpacity != prevPlacement.opacities.end()) {
-            opacities.emplace(jointPlacement.first, JointOpacityState(prevOpacity->second, increment, jointPlacement.second.icon, jointPlacement.second.text));
+            opacities.emplace(jointPlacement.first, JointOpacityState(prevOpacity->second, increment, jointPlacement.second.text, jointPlacement.second.icon));
             placementChanged = placementChanged ||
                 jointPlacement.second.icon != prevOpacity->second.icon.placed ||
                 jointPlacement.second.text != prevOpacity->second.text.placed;
         } else {
-            opacities.emplace(jointPlacement.first, JointOpacityState(jointPlacement.second.icon, jointPlacement.second.text, jointPlacement.second.offscreen));
+            opacities.emplace(jointPlacement.first, JointOpacityState(jointPlacement.second.text, jointPlacement.second.icon, jointPlacement.second.skipFade));
             placementChanged = placementChanged || jointPlacement.second.icon || jointPlacement.second.text;
         }
     }
@@ -234,10 +236,17 @@ void Placement::updateBucketOpacities(SymbolBucket& bucket, std::set<uint32_t>&
             true);
 
     for (SymbolInstance& symbolInstance : bucket.symbolInstances) {
-        auto opacityState = seenCrossTileIDs.count(symbolInstance.crossTileID) == 0 ?
-            getOpacity(symbolInstance.crossTileID) :
+        bool isDuplicate = seenCrossTileIDs.count(symbolInstance.crossTileID) > 0;
+
+        auto it = opacities.find(symbolInstance.crossTileID);
+        auto opacityState = it != opacities.end() && !isDuplicate ?
+            it->second :
             defaultOpacityState;
 
+        if (it == opacities.end()) {
+            opacities.emplace(symbolInstance.crossTileID, defaultOpacityState);
+        }
+
         seenCrossTileIDs.insert(symbolInstance.crossTileID);
 
         if (symbolInstance.hasText) {
@@ -293,16 +302,6 @@ void Placement::updateBucketOpacities(SymbolBucket& bucket, std::set<uint32_t>&
     bucket.sortFeatures(state.getAngle());
 }
 
-JointOpacityState Placement::getOpacity(uint32_t crossTileSymbolID) const {
-    auto it = opacities.find(crossTileSymbolID);
-    if (it != opacities.end()) {
-        return it->second;
-    } else {
-        return JointOpacityState(false, false, false);
-    }
-
-}
-
 float Placement::symbolFadeChange(TimePoint now) const {
     if (mapMode == MapMode::Continuous) {
         return std::chrono::duration<float>(now - commitTime) / Duration(std::chrono::milliseconds(300));

src/mbgl/text/placement.hpp

@@ -14,7 +14,7 @@ class SymbolBucket;
 
 class OpacityState {
 public:
-    OpacityState(bool placed, bool offscreen);
+    OpacityState(bool placed, bool skipFade);
     OpacityState(const OpacityState& prevOpacityState, float increment, bool placed);
     bool isHidden() const;
     float opacity;
@@ -23,7 +23,7 @@ public:
 
 class JointOpacityState {
 public:
-    JointOpacityState(bool placedIcon, bool placedText, bool offscreen);
+    JointOpacityState(bool placedIcon, bool placedText, bool skipFade);
     JointOpacityState(const JointOpacityState& prevOpacityState, float increment, bool placedIcon, bool placedText);
     bool isHidden() const;
     OpacityState icon;
@@ -32,17 +32,17 @@ public:
 
 class JointPlacement {
 public:
-    JointPlacement(bool text_, bool icon_, bool offscreen_)
-        : text(text_), icon(icon_), offscreen(offscreen_)
+    JointPlacement(bool text_, bool icon_, bool skipFade_)
+        : text(text_), icon(icon_), skipFade(skipFade_)
     {}
 
     const bool text;
     const bool icon;
-    // offscreen = outside viewport, but within CollisionIndex::viewportPadding px of the edge
+    // skipFade = outside viewport, but within CollisionIndex::viewportPadding px of the edge
     // Because these symbols aren't onscreen yet, we can skip the "fade in" animation,
     // and if a subsequent viewport change brings them into view, they'll be fully
     // visible right away.
-    const bool offscreen;
+    const bool skipFade;
 };
 
 class Placement {
@@ -51,7 +51,6 @@ public:
     void placeLayer(RenderSymbolLayer&, const mat4&, bool showCollisionBoxes);
     bool commit(const Placement& prevPlacement, TimePoint);
     void updateLayerOpacities(RenderSymbolLayer&);
-    JointOpacityState getOpacity(uint32_t crossTileSymbolID) const;
     float symbolFadeChange(TimePoint now) const;
     bool hasTransitions(TimePoint now) const;
 

src/mbgl/tile/geometry_tile_worker.cpp

@@ -425,12 +425,17 @@ void GeometryTileWorker::attemptPlacement() {
             continue;
         }
 
-        std::shared_ptr<Bucket> bucket = symbolLayout->place(showCollisionBoxes);
+        std::shared_ptr<SymbolBucket> bucket = symbolLayout->place(showCollisionBoxes);
         for (const auto& pair : symbolLayout->layerPaintProperties) {
+            if (!firstLoad) {
+                bucket->justReloaded = true;
+            }
             buckets.emplace(pair.first, bucket);
         }
     }
 
+    firstLoad = false;
+
     parent.invoke(&GeometryTile::onPlacement, GeometryTile::PlacementResult {
         std::move(buckets),
         std::move(glyphAtlasImage),

src/mbgl/tile/geometry_tile_worker.hpp

@@ -86,6 +86,7 @@ private:
     ImageMap imageMap;
     
     bool showCollisionBoxes;
+    bool firstLoad = true;
 };
 
 } // namespace mbgl