Merge pull request #12284 from MoonE/layer-group-inherit-zindex

Layers should inherit group z-index

src/ol/layer/Base.js

@@ -111,8 +111,7 @@ class BaseLayer extends BaseObject {
     state.sourceState = this.getSourceState();
     state.visible = this.getVisible();
     state.extent = this.getExtent();
-    state.zIndex =
-      zIndex !== undefined ? zIndex : state.managed === false ? Infinity : 0;
+    state.zIndex = zIndex === undefined && !state.managed ? Infinity : zIndex;
     state.maxResolution = this.getMaxResolution();
     state.minResolution = Math.max(this.getMinResolution(), 0);
     state.minZoom = this.getMinZoom();

src/ol/layer/Group.js

@@ -205,12 +205,16 @@ class LayerGroup extends BaseLayer {
   }
 
   /**
-   * @param {Array<import("./Layer.js").State>} [opt_states] Optional list of layer states (to be modified in place).
+   * Get the layer states list and use this groups z-index as the default
+   * for all layers in this and nested groups, if it is unset at this point.
+   * If opt_states is not provided and this group's z-index is undefined
+   * 0 is used a the default z-index.
+   * @param {Array<import("./Layer.js").State>} [opt_states] Optional list
+   * of layer states (to be modified in place).
    * @return {Array<import("./Layer.js").State>} List of layer states.
    */
   getLayerStatesArray(opt_states) {
     const states = opt_states !== undefined ? opt_states : [];
-
     const pos = states.length;
 
     this.getLayers().forEach(function (layer) {
@@ -218,6 +222,10 @@ class LayerGroup extends BaseLayer {
     });
 
     const ownLayerState = this.getLayerState();
+    let defaultZIndex = ownLayerState.zIndex;
+    if (!opt_states && ownLayerState.zIndex === undefined) {
+      defaultZIndex = 0;
+    }
     for (let i = pos, ii = states.length; i < ii; i++) {
       const layerState = states[i];
       layerState.opacity *= ownLayerState.opacity;
@@ -242,6 +250,9 @@ class LayerGroup extends BaseLayer {
           layerState.extent = ownLayerState.extent;
         }
       }
+      if (layerState.zIndex === undefined) {
+        layerState.zIndex = defaultZIndex;
+      }
     }
 
     return states;