registerOnRenderMapScale method

void registerOnRenderMapScale(
  1. RenderMapScaleCallback? scaleCallback, {
  2. bool onlyOnChange = false,
})

Registers for map scale rendering callbacks.

Requires MapViewPreferences.showMapScale to be true. Adjust scale positioning using MapViewPreferences.mapScalePosition.

The callback is invoked twice per rendered frame, and the scale only changes when the zoom level does, so most of those invocations repeat the previous values. Pass onlyOnChange to receive the changes alone.

Parameters

  • scaleCallback: (RenderMapScaleCallback?) Receives scale width, value, and units. Pass null to unregister.
  • onlyOnChange: (bool) When true, the callback is invoked only when at least one of the three values differs from the last one delivered. The first values after registering always arrive. Defaults to false, which invokes the callback for every rendered frame.

Implementation

void registerOnRenderMapScale(
  RenderMapScaleCallback? scaleCallback, {
  bool onlyOnChange = false,
}) {
  _renderMapScaleCallback = scaleCallback;

  // Set before the event is unblocked so the first delivered frame is already
  // governed, and on every call so registering again starts from a clean
  // comparison rather than waiting for the next scale change.
  objectMethod(
    pointerId,
    'MapView',
    'setRenderMapScaleOnlyOnChange',
    args: onlyOnChange,
  );

  GemKitPlatform.instance.filterEvent(
    pointerId,
    'renderMapScale',
    scaleCallback == null,
  );
}