appDisplay: Add additional view showing frequently used apps

According to the design mockups, the app picker should follow the
recent view pattern as used by applications, where the user is first
offered a subset of applications he/she is likely to start, and only
then allow switching to the full set of installed applications.
So implement the ability to manage several views in AppDisplay and add
FrequentView as additional view, which uses the existing ShellAppUsage
to display a list of frequently used applications.

https://bugzilla.gnome.org/show_bug.cgi?id=694192

data/theme/gnome-shell.css

@@ -848,13 +848,44 @@ StScrollBar StButton#vhandle:active {
 }
 
 .app-display {
-    padding: 0px 16px 32px 32px;
+    padding: 8px;
     spacing: 20px;
 }
 
-.app-display:rtl {
+.app-view-controls {
-    padding-left: 16px;
+    border-radius: 8px;
-    padding-right: 32px;
+    border: 1px solid rgba(245,245,245,0.6);
+    width: 250px;
+}
+
+.app-view-controls-bin {
+    padding-right: 10px;
+}
+
+.app-view-control {
+    padding: 4px 16px;
+    background-gradient-start: rgba(254,254,254,0.1);
+    background-gradient-end: rgba(5,5,6,0.1);
+    background-gradient-direction: vertical;
+}
+
+.app-view-control:first-child {
+    border-radius: 8px 0px 0px 8px;
+}
+
+.app-view-control:last-child {
+    border-radius: 0px 8px 8px 0px;
+}
+
+.app-view-control:checked {
+    background-gradient-start: rgba(0,0,0,0.8);
+    background-gradient-end: rgba(5,5,6,0.1);
+    background-gradient-direction: vertical;
+}
+
+StScrollView.frequent-apps StScrollBar {
+    min-width: 0px;
+    width: 0px;
 }
 
 .app-folder-icon {

js/ui/appDisplay.js

@@ -20,6 +20,7 @@ const DND = imports.ui.dnd;
 const IconGrid = imports.ui.iconGrid;
 const Main = imports.ui.main;
 const Overview = imports.ui.overview;
+const OverviewControls = imports.ui.overviewControls;
 const PopupMenu = imports.ui.popupMenu;
 const Tweener = imports.ui.tweener;
 const Workspace = imports.ui.workspace;
@@ -288,61 +289,174 @@ const AllView = new Lang.Class({
     }
 });
 
+const FrequentView = new Lang.Class({
+    Name: 'FrequentView',
+
+    _init: function() {
+        this._grid = new IconGrid.IconGrid({ xAlign: St.Align.MIDDLE,
+                                             columnLimit: MAX_COLUMNS });
+        let box = new St.BoxLayout({ vertical: true });
+        box.add(this._grid.actor);
+
+        // HACK: IconGrid currently lacks API to only display items that match
+        // the allocation, so rather than clipping away eventual overflow, we
+        // use an unscrollable ScrollView with hidden scrollbars to nicely
+        // fade out cut off items
+        this.actor = new St.ScrollView({ x_fill: true,
+                                         y_fill: false,
+                                         y_align: St.Align.START,
+                                         x_expand: true,
+                                         reactive: false,
+                                         style_class: 'frequent-apps vfade' });
+        this.actor.add_actor(box);
+        this.actor.set_policy(Gtk.PolicyType.NEVER, Gtk.PolicyType.AUTOMATIC);
+
+        this._usage = Shell.AppUsage.get_default();
+    },
+
+    removeAll: function() {
+        this._grid.removeAll();
+    },
+
+    loadApps: function() {
+        let mostUsed = this._usage.get_most_used ("");
+        for (let i = 0; i < mostUsed.length; i++) {
+            let appIcon = new AppIcon(mostUsed[i]);
+            this._grid.addItem(appIcon.actor, -1);
+        }
+    }
+});
+
+const Views = {
+    FREQUENT: 0,
+    ALL: 1
+};
+
 const AppDisplay = new Lang.Class({
     Name: 'AppDisplay',
 
     _init: function() {
         this._appSystem = Shell.AppSystem.get_default();
         this._appSystem.connect('installed-changed', Lang.bind(this, function() {
-            Main.queueDeferredWork(this._workId);
+            Main.queueDeferredWork(this._allAppsWorkId);
+        }));
+        Main.overview.connect('showing', Lang.bind(this, function() {
+            Main.queueDeferredWork(this._frequentAppsWorkId);
         }));
         global.settings.connect('changed::app-folder-categories', Lang.bind(this, function() {
             Main.queueDeferredWork(this._workId);
         }));
 
-        let box = new St.BoxLayout();
+        this._views = [];
-        this.actor = new St.Bin({ child: box,
-                                  style_class: 'app-display',
-                                  x_fill: true, y_fill: true });
 
-        this._view = new AllView();
+        let view, button;
-        box.add(this._view.actor, { expand: true });
+        view = new FrequentView();
+        button = new St.Button({ label: _("Frequent"),
+                                 style_class: 'app-view-control',
+                                 can_focus: true,
+                                 x_expand: true });
+        this._views[Views.FREQUENT] = { 'view': view, 'control': button };
+
+        view = new AllView();
+        button = new St.Button({ label: _("All"),
+                                 style_class: 'app-view-control',
+                                 can_focus: true,
+                                 x_expand: true });
+        this._views[Views.ALL] = { 'view': view, 'control': button };
+
+        this.actor = new St.BoxLayout({ style_class: 'app-display',
+                                        vertical: true,
+                                        x_expand: true, y_expand: true });
+
+        this._viewStack = new St.Widget({ layout_manager: new Clutter.BinLayout(),
+                                          x_expand: true, y_expand: true });
+        let bin = new St.Bin({ child: this._viewStack,
+                               clip_to_allocation: true,
+                               x_fill: true, y_fill: true });
+        this.actor.add(bin, { expand: true });
+
+        let layout = new Clutter.BoxLayout({ homogeneous: true });
+        this._controls = new St.Widget({ style_class: 'app-view-controls',
+                                         layout_manager: layout });
+        this.actor.add(new St.Bin({ child: this._controls }));
+
+
+        for (let i = 0; i < this._views.length; i++) {
+            this._viewStack.add_actor(this._views[i].view.actor);
+            this._controls.add_actor(this._views[i].control);
+
+            let viewIndex = i;
+            this._views[i].control.connect('clicked', Lang.bind(this,
+                function(actor) {
+                    this._showView(viewIndex);
+                }));
+        }
+        this._showView(Views.FREQUENT);
 
         // We need a dummy actor to catch the keyboard focus if the
         // user Ctrl-Alt-Tabs here before the deferred work creates
         // our real contents
         this._focusDummy = new St.Bin({ can_focus: true });
-        box.add(this._focusDummy);
+        this._viewStack.add_actor(this._focusDummy);
 
-        this._workId = Main.initializeDeferredWork(this.actor, Lang.bind(this, this._redisplay));
+        this._allAppsWorkId = Main.initializeDeferredWork(this.actor, Lang.bind(this, this._redisplayAllApps));
+        this._frequentAppsWorkId = Main.initializeDeferredWork(this.actor, Lang.bind(this, this._redisplayFrequentApps));
     },
 
-    _removeAll: function() {
+    _showView: function(activeIndex) {
-        this._view.removeAll();
+        for (let i = 0; i < this._views.length; i++) {
+            let actor = this._views[i].view.actor;
+            let params = { time: OverviewControls.SIDE_CONTROLS_ANIMATION_TIME,
+                           opacity: (i == activeIndex) ? 255 : 0 };
+            if (i == activeIndex)
+                actor.visible = true;
+            else
+                params.onComplete = function() { actor.hide(); };
+            Tweener.addTween(actor, params);
+
+            if (i == activeIndex)
+                this._views[i].control.add_style_pseudo_class('checked');
+            else
+                this._views[i].control.remove_style_pseudo_class('checked');
+        }
     },
 
     _redisplay: function() {
-        this._removeAll();
+        this._redisplayFrequentApps();
+        this._redisplayAllApps();
+    },
 
-        var tree = this._appSystem.get_tree();
+    _redisplayFrequentApps: function() {
-        var root = tree.get_root_directory();
+        let view = this._views[Views.FREQUENT].view;
 
-        var iter = root.iter();
+        view.removeAll();
-        var nextType;
+        view.loadApps();
+    },
+
+    _redisplayAllApps: function() {
+        let view = this._views[Views.ALL].view;
+
+        view.removeAll();
+
+        let tree = this._appSystem.get_tree();
+        let root = tree.get_root_directory();
+
+        let iter = root.iter();
+        let nextType;
         let folderCategories = global.settings.get_strv('app-folder-categories');
         while ((nextType = iter.next()) != GMenu.TreeItemType.INVALID) {
             if (nextType == GMenu.TreeItemType.DIRECTORY) {
-                var dir = iter.get_directory();
+                let dir = iter.get_directory();
                 if (dir.get_is_nodisplay())
                     continue;
 
                 if (folderCategories.indexOf(dir.get_menu_id()) != -1)
-                    this._view.addFolder(dir);
+                    view.addFolder(dir);
                 else
-                    _loadCategory(dir, this._view);
+                    _loadCategory(dir, view);
             }
         }
-        this._view.loadGrid();
+        view.loadGrid();
 
         if (this._focusDummy) {
             let focused = this._focusDummy.has_key_focus();