throttle placementupstream/start-collision-throttle

3 files changed, 22 insertions, 7 deletions

diff --git a/src/mbgl/renderer/renderer_impl.cpp b/src/mbgl/renderer/renderer_impl.cpp
index d96215a550..57135fb1fb 100644
--- a/src/mbgl/renderer/renderer_impl.cpp
+++ b/src/mbgl/renderer/renderer_impl.cpp
@@ -373,15 +373,26 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
         }
     }
 
-    auto newPlacement = std::make_unique<Placement>(parameters.state, parameters.mapMode);
-    for (auto it = order.rbegin(); it != order.rend(); ++it) {
-        if (it->layer.is<RenderSymbolLayer>()) {
-            newPlacement->placeLayer(*it->layer.as<RenderSymbolLayer>(), parameters.projMatrix, parameters.debugOptions & MapDebugOptions::Collision);
+    bool placementChanged = false;
+    if (placement->recentUntil <= parameters.timePoint || updateParameters.mode == MapMode::Still) {
+        auto newPlacement = std::make_unique<Placement>(parameters.state, parameters.mapMode);
+        for (auto it = order.rbegin(); it != order.rend(); ++it) {
+            if (it->layer.is<RenderSymbolLayer>()) {
+                newPlacement->placeLayer(*it->layer.as<RenderSymbolLayer>(), parameters.projMatrix, parameters.debugOptions & MapDebugOptions::Collision);
+            }
         }
+
+        placementChanged = newPlacement->commit(*placement, parameters.timePoint);
+        if (placementChanged) {
+            placement = std::move(newPlacement);
+        }
+
+        placement->stale = false;
+        placement->recentUntil = parameters.timePoint + Duration(std::chrono::milliseconds(300));
+    } else {
+        placement->stale = true;
     }
 
-    const bool placementChanged = newPlacement->commit(*placement, parameters.timePoint);
-    if (placementChanged) placement = std::move(newPlacement);
     parameters.symbolFadeChange = placement->symbolFadeChange(parameters.timePoint);
 
     if (placementChanged || symbolBucketsChanged) {
diff --git a/src/mbgl/text/placement.cpp b/src/mbgl/text/placement.cpp
index 9a9456db2f..b7de01623f 100644
--- a/src/mbgl/text/placement.cpp
+++ b/src/mbgl/text/placement.cpp
@@ -32,6 +32,7 @@ bool JointOpacityState::isHidden() const {
 
 Placement::Placement(const TransformState& state_, MapMode mapMode_)
     : collisionIndex(state_)
+    , recentUntil(TimePoint::min())
     , state(state_)
     , mapMode(mapMode_)
 {}
@@ -290,7 +291,7 @@ float Placement::symbolFadeChange(TimePoint now) const {
 }
 
 bool Placement::hasTransitions(TimePoint now) const {
-    return symbolFadeChange(now) < 1.0;
+    return symbolFadeChange(now) < 1.0 || stale;
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/text/placement.hpp b/src/mbgl/text/placement.hpp
index 2902192b52..8d51d86ce7 100644
--- a/src/mbgl/text/placement.hpp
+++ b/src/mbgl/text/placement.hpp
@@ -50,6 +50,9 @@ namespace mbgl {
             // TODO: public for queryRenderedFeatures
             CollisionIndex collisionIndex;
 
+            TimePoint recentUntil;
+            bool stale = false;
+
         private:
 
             void placeLayerBucket(