--- /dev/null
+/**
+ * @file
+ * A Backbone Model for the state of Contextual module's edit toolbar tab.
+ */
+
+(function (Drupal, Backbone) {
+ 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
+ * Attributes for the backbone model.
+ * @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(attrs, options) {
+ // Respond to new/removed contextual links.
+ this.listenTo(options.contextualCollection, 'reset remove add', this.countContextualLinks);
+ this.listenTo(options.contextualCollection, 'add', this.lockNewContextualLinks);
+
+ // Automatically determine visibility.
+ this.listenTo(this, 'change:contextualCount', this.updateVisibility);
+
+ // Whenever edit mode is toggled, lock all contextual links.
+ this.listenTo(this, 'change:isViewing', (model, isViewing) => {
+ options.contextualCollection.each((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(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(contextualModel, contextualCollection) {
+ if (!this.get('isViewing')) {
+ contextualModel.set('isLocked', true);
+ }
+ },
+
+ /**
+ * Automatically updates visibility of the view/edit mode toggle.
+ */
+ updateVisibility() {
+ this.set('isVisible', this.get('contextualCount') > 0);
+ },
+
+ });
+}(Drupal, Backbone));