itowns/lib/Layer/ImageryLayers.js

A JS/WebGL framework for 3D geospatial data visualization

// move this to new index
// After the modification :
//      * the minimum sequence will always be 0
//      * the maximum sequence will always be layers.lenght - 1
// the ordering of all layers (Except that specified) doesn't change
export function moveLayerToIndex(layer, newIndex, imageryLayers) {
  newIndex = Math.min(newIndex, imageryLayers.length - 1);
  newIndex = Math.max(newIndex, 0);
  const oldIndex = layer.sequence;
  for (const imagery of imageryLayers) {
    if (imagery.id === layer.id) {
      // change index of specified layer
      imagery.sequence = newIndex;
    } else if (imagery.sequence > oldIndex && imagery.sequence <= newIndex) {
      // down all layers between the old index and new index (to compensate the deletion of the old index)
      imagery.sequence--;
    } else if (imagery.sequence >= newIndex && imagery.sequence < oldIndex) {
      // up all layers between the new index and old index (to compensate the insertion of the new index)
      imagery.sequence++;
    }
  }
}
export function moveLayerDown(layer, imageryLayers) {
  if (layer.sequence > 0) {
    moveLayerToIndex(layer, layer.sequence - 1, imageryLayers);
  }
}
export function moveLayerUp(layer, imageryLayers) {
  const m = imageryLayers.length - 1;
  if (layer.sequence < m) {
    moveLayerToIndex(layer, layer.sequence + 1, imageryLayers);
  }
}
export function getColorLayersIdOrderedBySequence(imageryLayers) {
  const copy = Array.from(imageryLayers);
  copy.sort((a, b) => a.sequence - b.sequence);
  return copy.map(l => l.id);
}