[google_maps_flutter_android] Reindex clustered markers in spatial index on position change by EverCamilo · Pull Request #11749 · flutter/packages

EverCamilo · 2026-05-21T02:00:59Z

Description

When a clustered marker's position is updated in-place via MarkersController.changeMarkers(), the ClusterManager's NonHierarchicalDistanceBasedAlgorithm retains stale QuadTree entries at the old coordinates. This causes ghost clusters to appear at positions where no marker currently exists.

Root cause

MarkersController.changeMarkers() has two code paths when updating a marker:

Cluster ID changed — correctly calls removeItem + addItem on the ClusterManager, refreshing the spatial index.
Same cluster ID (in-place update) — calls interpretMarkerOptions() to update the MarkerBuilder properties (including position), but does not reindex the item in the ClusterManager. The QuadTree inside NonHierarchicalDistanceBasedAlgorithm stores a QuadItem wrapper that captures the position at insertion time. Without reindexing, the spatial index retains the stale position.

Fix

Capture the marker's LatLng position before interpretMarkerOptions() updates the builder.
After the update, compare old vs. new position.
If changed and the marker belongs to a ClusterManager, call removeItem + addItem to refresh the QuadTree.
Batch variant (reindexItems) added for the public changeMarkers() path — calls cluster() only once per ClusterManager for efficiency.

Files changed

ClusterManagersController.java: added reindexItem() and reindexItems() methods.
MarkersController.java: added position-change detection and reindex call in both the changeMarkers() (batch) and changeMarker() (single) paths.

Reproduction

Create a GoogleMap with a ClusterManager and several markers.
Programmatically update the position of a clustered marker (keeping the same MarkerId and ClusterManagerId).
Observe that ghost clusters appear at the old positions and persist until the ClusterManager is fully rebuilt.

Issues

No associated issue yet — I will file one in flutter/flutter describing the ghost-cluster behavior and link it here before requesting review.

Pre-Review Checklist

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…dex on position change When a clustered marker position is updated in-place via MarkersController.changeMarkers(), the ClusterManager NonHierarchicalDistanceBasedAlgorithm retains stale QuadTree entries at the old coordinates. This causes ghost clusters to appear at positions where no marker currently exists. Fix: capture the marker position before interpretMarkerOptions(), compare after, and if changed call removeItem + addItem on the ClusterManager to refresh the QuadTree. Batch variant added for the public changeMarkers() path for efficiency. Co-authored-by: Cursor <cursoragent@cursor.com>

flutter-dashboard · 2026-05-21T02:01:03Z

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

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google-cla · 2026-05-21T02:01:15Z

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gemini-code-assist

Code Review

This pull request introduces reindexing logic to handle in-place position updates for clustered markers by adding reindexItem and reindexItems methods to ClusterManagersController. However, the review feedback indicates a logic error where marker positions are updated before the removal from the spatial index is triggered. This prevents the ClusterManager from correctly locating and removing markers from their old coordinates in the QuadTree, which would result in the failure to clear stale data.

gemini-code-assist · 2026-05-21T02:02:37Z

+  public void reindexItem(@NonNull String clusterManagerId, @NonNull MarkerBuilder item) {
+    ClusterManager<MarkerBuilder> clusterManager = clusterManagerIdToManager.get(clusterManagerId);
+    if (clusterManager != null) {
+      clusterManager.removeItem(item);


The reindexItem method (and reindexItems below) will fail to remove the item from the spatial index if its position has already been updated. The ClusterManager.removeItem method relies on the item's current getPosition() to locate it in the underlying QuadTree. If the position was mutated before calling this method, the removal will look at the new coordinates, while the item is still indexed at the old coordinates, leading to the "ghost clusters" this PR intends to fix.

gemini-code-assist · 2026-05-21T02:02:37Z

+        if (clusterManagerId != null && !markerBuilder.getPosition().equals(oldPosition)) {
+          markersToReindexByCluster
+              .computeIfAbsent(clusterManagerId, k -> new ArrayList<>())
+              .add(markerBuilder);
+        }


In changeMarkers, interpretMarkerOptions is called at line 140, which updates the markerBuilder's position. The subsequent call to reindexItems (line 168) will attempt to remove the markers using their new positions. This will fail to clear the old entries from the ClusterManager's spatial index. To fix this, markers whose positions are changing should be removed from the ClusterManager before their state is mutated, or the reindexing logic must be provided with the old coordinates to perform the removal.

gemini-code-assist · 2026-05-21T02:02:37Z

+    if (clusterManagerId != null && !markerBuilder.getPosition().equals(oldPosition)) {
+      clusterManagersController.reindexItem(clusterManagerId, markerBuilder);
+    }


Similar to the batch update path, in changeMarker, the markerBuilder is updated at line 397 before reindexItem is called. This prevents the ClusterManager from correctly identifying and removing the marker from its old position in the spatial index because removeItem will be searching at the new coordinates.

The QuadTree locates entries by getPosition(). The previous reindexItem approach called removeItem after the position was already mutated, so the spatial lookup searched at the new coordinates and missed the stale entry at the old position. Fix: call removeItemSilently (without recluster) BEFORE interpretMarkerOptions mutates the builder, then batch re-add after mutation. This ensures the QuadTree removal finds the item at its original coordinates. Co-authored-by: Cursor <cursoragent@cursor.com>

The previous commit removed and re-added ALL clustered markers unconditionally, causing excessive cluster() calls that could interfere with tap detection. Now we only reindex markers whose position actually changed. To correctly remove the stale QuadTree entry (which requires the old position), the builder is temporarily set back to the old coordinates for removal, then restored to the new coordinates for re-addition. Co-authored-by: Cursor <cursoragent@cursor.com>

stuartmorgan-g · 2026-05-26T18:19:07Z

Thanks for the contribution!

Please do not replace our PR checklist with an AI-created alternative; the things on our checklist are all there for a reason. This PR is missing required elements described in the checklist, which need to be addressed before it moves forward with review.

I am marking the PR as a Draft. Please add and complete the correct checklist, updating the PR as appropriate, and when that’s complete please feel free to mark the PR as ready for review.

github-actions Bot added p: google_maps_flutter platform-android labels May 21, 2026

gemini-code-assist Bot reviewed May 21, 2026

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EverCamilo and others added 2 commits May 20, 2026 23:09

stuartmorgan-g marked this pull request as draft May 26, 2026 18:19

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[google_maps_flutter_android] Reindex clustered markers in spatial index on position change#11749

[google_maps_flutter_android] Reindex clustered markers in spatial index on position change#11749
EverCamilo wants to merge 3 commits into
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EverCamilo:fix/cluster-position-reindex

EverCamilo commented May 21, 2026 •

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Description

Root cause

Fix

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Reproduction

Issues

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EverCamilo commented May 21, 2026 •

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