Q: What is a snapshot layer?
A: A snapshot layer is a special layer group. All layers in the snapshot layer group are snapshot layers of the map. The snapshot layer is drawn in a special way. It is drawn only when it displays for the first time. Afterwards, when the map is browsed, the snapshot layer will not be redrawn if the display bounds of the map have not changed, that is, the snapshot layer will not be redrawn with the map refresh. However, if the display bounds of the map change, the auto refresh event for the snapshot layer will be automatically triggered. The snapshot layer is one way to improve the performance of the map display.