RemoteMenu: add support for section labels

According to the GIO docs, sections can have labels too. We support
them by inserting a non reactive menu item at the beginning of the
section. This item is specially flagged to be ignored while processing
changed signals from the model (since it does not correspond to any
model item)

https://bugzilla.gnome.org/show_bug.cgi?id=666681

js/ui/popupMenu.js

@@ -1398,12 +1398,23 @@ const PopupMenuSection = new Lang.Class({
         this.actor = this.box;
         this.actor._delegate = this;
         this.isOpen = true;
+
+        // an array of externally managed separators
+        this.separators = [];
     },
 
     // deliberately ignore any attempt to open() or close(), but emit the
     // corresponding signal so children can still pick it up
     open: function(animate) { this.emit('open-state-changed', true); },
     close: function() { this.emit('open-state-changed', false); },
+
+    destroy: function() {
+        for (let i = 0; i < this.separators.length; i++)
+            this.separators[i].destroy();
+        this.separators = [];
+
+        this.parent();
+    }
 });
 
 const PopupSubMenuMenuItem = new Lang.Class({
@@ -1737,17 +1748,25 @@ const RemoteMenu = new Lang.Class({
     },
 
     _createMenuItem: function(model, index) {
+        let labelValue = model.get_item_attribute_value(index, Gio.MENU_ATTRIBUTE_LABEL, null);
+        let label = labelValue ? labelValue.deep_unpack() : '';
+        // remove all underscores that are not followed by another underscore
+        label = label.replace(/_([^_])/, '$1');
+
         let section_link = model.get_item_link(index, Gio.MENU_LINK_SECTION);
         if (section_link) {
             let item = new PopupMenuSection();
+            if (label) {
+                let title = new PopupMenuItem(label, { reactive: false,
+                                                       style_class: 'popup-subtitle-menu-item' });
+                item._titleMenuItem = title;
+                title._ignored = true;
+                item.addMenuItem(title);
+            }
             this._modelChanged(section_link, 0, 0, section_link.get_n_items(), item);
             return [item, true, ''];
         }
 
-        // labels are not checked for existance, as they're required for all items
-        let label = model.get_item_attribute_value(index, Gio.MENU_ATTRIBUTE_LABEL, null).deep_unpack();
-        // remove all underscores that are not followed by another underscore
-        label = label.replace(/_([^_])/, '$1');
         let submenu_link = model.get_item_link(index, Gio.MENU_LINK_SUBMENU);
 
         if (submenu_link) {
@@ -1831,8 +1850,13 @@ const RemoteMenu = new Lang.Class({
 
         let currentItems = target._getMenuItems();
 
-        for (j0 = 0, k0 = 0; j0 < position; j0++, k0++) {
+        k0 = 0;
-            if (currentItems[k0] instanceof PopupSeparatorMenuItem)
+        // skip ignored items at the beginning
+        while (k0 < currentItems.length && currentItems[k0]._ignored)
+            k0++;
+        // find the right menu item matching the model item
+        for (j0 = 0; j0 < position; j0++, k0++) {
+            if (currentItems[k0]._ignored)
                 k0++;
         }
 
@@ -1844,7 +1868,7 @@ const RemoteMenu = new Lang.Class({
             for (j = j0, k = k0; j < j0 + removed; j++, k++) {
                 currentItems[k].destroy();
 
-                if (currentItems[k] instanceof PopupSeparatorMenuItem)
+                if (currentItems[k]._ignored)
                     j--;
             }
         }
@@ -1855,14 +1879,20 @@ const RemoteMenu = new Lang.Class({
             if (item) {
                 // separators must be added in the parent to make autohiding work
                 if (addSeparator) {
-                    target.addMenuItem(new PopupSeparatorMenuItem(), k+1);
+                    let separator = new PopupSeparatorMenuItem();
+                    item.separators.push(separator);
+                    separator._ignored = true;
+                    target.addMenuItem(separator, k+1);
                     k++;
                 }
 
                 target.addMenuItem(item, k);
 
                 if (addSeparator) {
-                    target.addMenuItem(new PopupSeparatorMenuItem(), k+1);
+                    let separator = new PopupSeparatorMenuItem();
+                    item.separators.push(separator);
+                    separator._ignored = true;
+                    target.addMenuItem(separator, k+1);
                     k++;
                 }
             } else if (changeSignal) {
@@ -1888,6 +1918,9 @@ const RemoteMenu = new Lang.Class({
         }
 
         if (target instanceof PopupMenuSection) {
+            if (target._titleMenuItem)
+                target.actor.visible = target.numMenuItems != 1;
+            else
                 target.actor.visible = target.numMenuItems != 0;
         } else {
             let sourceItem = target.sourceActor._delegate;

src/test-gapplication.js

@@ -68,7 +68,7 @@ function main() {
     section = new Gio.Menu();
     section.append('Checkbox', 'app.toggle');
     section.append('Disabled', 'app.disable');
-    menu.append_section(null, section);
+    menu.append_section('Subsection', section);
 
     // empty sections or submenus should be invisible
     menu.append_section('Empty section', new Gio.Menu());