Fix race condition in fog terrain sampling

mapbox · May 3, 2021 · e818766 · e818766
1 parent 8e4214f
commit e818766
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/src/geo/transform.js b/src/geo/transform.js
@@ -347,7 +347,7 @@ class Transform {
             weightSum += weight;
         }
 
-        if (weightSum === 0) return 0;
+        if (weightSum === 0) return NaN;
         return elevationSum / weightSum;
     }
 

diff --git a/src/ui/map.js b/src/ui/map.js
@@ -2806,10 +2806,16 @@ class Map extends Camera {
         const timeoutElapsed = ignoreTimeout || timeStamp - this._averageElevationLastSampledAt > AVERAGE_ELEVATION_SAMPLING_INTERVAL;
 
         if (timeoutElapsed && !this._averageElevation.isEasing(timeStamp)) {
-            this._averageElevationLastSampledAt = timeStamp;
-
             const currentElevation = this.transform.averageElevation;
-            const newElevation = this.transform.sampleAverageElevation();
+            let newElevation = this.transform.sampleAverageElevation();
+
+            // New elevation is NaN if no terrain tiles were available
+            if (isNaN(newElevation)) {
+                newElevation = 0;
+            } else {
+                // Don't activate the timeout if no data was available
+                this._averageElevationLastSampledAt = timeStamp;
+            }
             const elevationChange = Math.abs(currentElevation - newElevation);
 
             if (elevationChange > AVERAGE_ELEVATION_EASE_THRESHOLD) {