onLayerVisible

onLayerVisible refers to a callback or event in mapping applications that fires when a layer transitions to a visible state on the map. It is commonly used in conjunction with layer toggles in layer switchers, or when programmatic visibility changes occur.

Implementation and naming vary by library. In some frameworks, the event is named change:visible or layervisible; in others it may use a visibilitychange-like name. The handler typically receives an event object or a reference to the affected layer, and may expose the layer’s current visibility status via methods such as getVisible() or isVisible().

Common uses include updating user interface elements (for example, highlighting the active layer in a legend), initiating data loading or tile fetching for the layer, or adjusting rendering order and styling to optimize performance when the layer becomes visible.

Best practices include adding the listener when the map or layer is created and removing it when no longer needed to prevent memory leaks. Consider debouncing rapid visibility changes and ensuring the handler gracefully handles cases where the layer is removed. Because the exact API differs among libraries, consult the specific documentation for the correct event name and payload to implement onLayerVisible correctly.