Markers update on terrain change

debug/markers.html

@@ -100,7 +100,7 @@
 });
 
 document.getElementById('terrain-checkbox').onclick = function() {
-    map.setTerrain(this.checked ? {"source": "mapbox-dem"} : null);
+    map.setTerrain(this.checked ? {"source": "mapbox-dem", "exaggeration": 10} : null);
 };
 
 </script>

src/ui/map.js

@@ -2764,6 +2764,8 @@ class Map extends Camera {
             this.painter._updateFog(this.style);
             this._updateTerrain(); // Terrain DEM source updates here and skips update in style._updateSources.
             this.style._updateSources(this.transform);
+            // Update positions of markers on enabling/disabling terrain
+            this._forceMarkerUpdate();
         }
 
         this._placementDirty = this.style && this.style._updatePlacement(this.painter.transform, this.showCollisionBoxes, fadeDuration, this._crossSourceCollisions);
@@ -2875,6 +2877,12 @@ class Map extends Camera {
         return this;
     }
 
+    _forceMarkerUpdate() {
+        for (const marker of this._markers) {
+            marker._update();
+        }
+    }
+
     /**
      * Update the average visible elevation by sampling terrain
      *

test/unit/terrain/terrain.test.js

@@ -1380,10 +1380,28 @@ test('Marker interaction and raycast', (t) => {
                 const bottomLngLat = tr.pointLocation3D(new Point(terrainTop.x, tr.height));
                 // Raycast returns distance to closer point evaluates to occluded marker.
                 t.stub(tr, 'pointLocation3D').returns(bottomLngLat);
-                setTimeout(() => {
+                map.once('render', () => {
                     t.deepEqual(marker.getElement().style.opacity, 0.2);
                     t.end();
-                }, 100);
+                });
+            });
+
+            t.test(`Marker updates position on removing terrain (#10982)`, (t) => {
+                const update = t.spy(marker, "_update");
+                map.setTerrain(null);
+                map.once('render', () => {
+                    t.same(update.callCount, 1);
+                    t.end();
+                });
+            });
+
+            t.test(`Marker updates position on adding terrain (#10982)`, (t) => {
+                const update = t.spy(marker, "_update");
+                map.setTerrain({"source": "mapbox-dem"});
+                map.once('render', () => {
+                    t.same(update.callCount, 1);
+                    t.end();
+                });
             });
 
             t.end();