Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/contextual/js/toolbar/models/StateModel.js

@@ -0,0 +1,121 @@
+/**
+ * @file
+ * A Backbone Model for the state of Contextual module's edit toolbar tab.
+ */
+
+(function (Drupal, Backbone) {
+
+  "use strict";
+
+  Drupal.contextualToolbar.StateModel = Backbone.Model.extend(/** @lends Drupal.contextualToolbar.StateModel# */{
+
+    /**
+     * @type {object}
+     *
+     * @prop {bool} isViewing
+     * @prop {bool} isVisible
+     * @prop {number} contextualCount
+     * @prop {Drupal~TabbingContext} tabbingContext
+     */
+    defaults: /** @lends Drupal.contextualToolbar.StateModel# */{
+
+      /**
+       * Indicates whether the toggle is currently in "view" or "edit" mode.
+       *
+       * @type {bool}
+       */
+      isViewing: true,
+
+      /**
+       * Indicates whether the toggle should be visible or hidden. Automatically
+       * calculated, depends on contextualCount.
+       *
+       * @type {bool}
+       */
+      isVisible: false,
+
+      /**
+       * Tracks how many contextual links exist on the page.
+       *
+       * @type {number}
+       */
+      contextualCount: 0,
+
+      /**
+       * A TabbingContext object as returned by {@link Drupal~TabbingManager}:
+       * the set of tabbable elements when edit mode is enabled.
+       *
+       * @type {?Drupal~TabbingContext}
+       */
+      tabbingContext: null
+    },
+
+    /**
+     * Models the state of the edit mode toggle.
+     *
+     * @constructs
+     *
+     * @augments Backbone.Model
+     *
+     * @param {object} attrs
+     * @param {object} options
+     *   An object with the following option:
+     * @param {Backbone.collection} options.contextualCollection
+     *   The collection of {@link Drupal.contextual.StateModel} models that
+     *   represent the contextual links on the page.
+     */
+    initialize: function (attrs, options) {
+      // Respond to new/removed contextual links.
+      this.listenTo(options.contextualCollection, {
+        'reset remove add': this.countContextualLinks,
+        'add': this.lockNewContextualLinks
+      });
+
+      this.listenTo(this, {
+        // Automatically determine visibility.
+        'change:contextualCount': this.updateVisibility,
+        // Whenever edit mode is toggled, lock all contextual links.
+        'change:isViewing': function (model, isViewing) {
+          options.contextualCollection.each(function (contextualModel) {
+            contextualModel.set('isLocked', !isViewing);
+          });
+        }
+      });
+    },
+
+    /**
+     * Tracks the number of contextual link models in the collection.
+     *
+     * @param {Drupal.contextual.StateModel} contextualModel
+     *   The contextual links model that was added or removed.
+     * @param {Backbone.Collection} contextualCollection
+     *    The collection of contextual link models.
+     */
+    countContextualLinks: function (contextualModel, contextualCollection) {
+      this.set('contextualCount', contextualCollection.length);
+    },
+
+    /**
+     * Lock newly added contextual links if edit mode is enabled.
+     *
+     * @param {Drupal.contextual.StateModel} contextualModel
+     *   The contextual links model that was added.
+     * @param {Backbone.Collection} [contextualCollection]
+     *    The collection of contextual link models.
+     */
+    lockNewContextualLinks: function (contextualModel, contextualCollection) {
+      if (!this.get('isViewing')) {
+        contextualModel.set('isLocked', true);
+      }
+    },
+
+    /**
+     * Automatically updates visibility of the view/edit mode toggle.
+     */
+    updateVisibility: function () {
+      this.set('isVisible', this.get('contextualCount') > 0);
+    }
+
+  });
+
+})(Drupal, Backbone);