Event listeners

Add and remove

Listener listener = await map.OnClick("my-layer", e => { ... });
await listener.Remove(); // calls map.off() in JavaScript

Listener implements IAsyncDisposable — use await using or DisposeAsync() on the component.

APIs

• AddListener<T>(eventName, handler, layer?, throttleMs?) — generic subscription
• AddListener<T>(eventName, handler, params string[] layerIds) — multiple layers
• AddOnceListener<T> / AddOnceAsyncListener<T> — single fire (map.once), including multi-layer overloads
• RemoveAllListeners(eventName?) — detach all listeners on this map
• OnClick, OnMoveEnd, OnIdle, OnMouseMove (with optional throttleMs), OnData, OnSourceData, OnError
• OnTouchStart, OnTouchEnd, OnTouchMove, OnTouchCancel — use MapTouchEvent
• OnWheel, OnRender, OnStyleImageMissing, OnDragStart, OnDrag, OnDragEnd
• OnStyleDataLoading, OnSourceDataLoading — loading-phase data events
• OnCooperativeGesturePrevented, OnProjectionTransition, OnTerrain, OnSourceDataAbort

Event model reference

Event	Model	Convenience API	Layer filter
click, mousemove, mouse events	MapMouseEvent	OnClick, OnMouseMove	Yes
touchstart, touchmove, touchend, touchcancel	MapTouchEvent	OnTouch*	Yes
wheel	MapWheelEvent	OnWheel	No
moveend, camera/drag	MapMoveEvent / MapEvent	OnMoveEnd, OnDrag*	No
data, sourcedata, sourcedataabort, styledataloading, sourcedataloading	MapDataEvent	OnData, OnSourceData, OnSourceDataAbort, OnStyleDataLoading, OnSourceDataLoading	No
error	MapErrorEvent	OnError	No
styleimagemissing	MapStyleImageMissingEvent	OnStyleImageMissing (observe only in MapLibre 6+; use SetMissingStyleImageResolver to supply images)	No
render, idle	MapEvent	OnRender, OnIdle	No
cooperativegestureprevented	MapCooperativeGestureEvent	OnCooperativeGesturePrevented	No
projectiontransition	MapProjectionEvent	OnProjectionTransition	No
terrain	MapTerrainEvent	OnTerrain	No

Aliases (MapLibre 6 naming): MapSourceDataEvent / MapStyleDataEvent (data events), MapMovementEvent (camera), MapBoxZoomEvent (boxzoom).

Compact interop DTO includes dataType, sourceId, sourceDataType, isSourceLoaded, tile, newProjection, and missing-image id in addition to type / point / lngLat / features.

Pitfalls

• Always remove listeners when re-subscribing (e.g. before adding a duplicate handler).
• MapMouseEvent.Features is LayerFeatureFeature[] — use the same shape as QueryRenderedLayerFeatures.
• Layer-scoped events require the layer to exist before subscribing.
• preventDefault() is not available from C#. MapLibre requires calling preventDefault() synchronously in the JavaScript event handler. Because Blazor invokes .NET callbacks asynchronously after JSON.stringify, you cannot block default map gestures from C#. Use MapOptions instead (CooperativeGestures, DragPan, ScrollZoom, etc.) or handle gestures in custom JavaScript.

Marker and Popup handles

• AddMarker returns MapMarker — SetLngLat, SetRotation, SetDraggable, SetPopup, TogglePopup, OnClick, OnDrag*
• AddPopup returns MapPopup — SetHtml, SetText, TrackPointer, IsOpen, OnOpen, OnClose
• CreatePopup remains as a legacy wrapper around AddPopup