gnome-shell/js/ui/altTab.js

// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-

const Clutter = imports.gi.Clutter;
const Gdk = imports.gi.Gdk;
const Gtk = imports.gi.Gtk;
const Lang = imports.lang;
const Mainloop = imports.mainloop;
const Meta = imports.gi.Meta;
const Shell = imports.gi.Shell;
const Signals = imports.signals;
const St = imports.gi.St;

const Main = imports.ui.main;
const Tweener = imports.ui.tweener;

const POPUP_APPICON_SIZE = 96;
const POPUP_SCROLL_TIME = 0.10; // seconds
const POPUP_DELAY_TIMEOUT = 150; // milliseconds
const POPUP_FADE_OUT_TIME = 0.1; // seconds

const APP_ICON_HOVER_TIMEOUT = 200; // milliseconds

const DISABLE_HOVER_TIMEOUT = 500; // milliseconds

const THUMBNAIL_DEFAULT_SIZE = 256;
const THUMBNAIL_POPUP_TIME = 500; // milliseconds
const THUMBNAIL_FADE_TIME = 0.1; // seconds

const iconSizes = [96, 64, 48, 32, 22];

function mod(a, b) {
    return (a + b) % b;
}

function primaryModifier(mask) {
    if (mask == 0)
        return 0;

    let primary = 1;
    while (mask > 1) {
        mask >>= 1;
        primary <<= 1;
    }
    return primary;
}

const AltTabPopup = new Lang.Class({
    Name: 'AltTabPopup',

    _init : function() {
        this.actor = new Shell.GenericContainer({ name: 'altTabPopup',
                                                  reactive: true,
                                                  visible: false });

        this.actor.connect('get-preferred-width', Lang.bind(this, this._getPreferredWidth));
        this.actor.connect('get-preferred-height', Lang.bind(this, this._getPreferredHeight));
        this.actor.connect('allocate', Lang.bind(this, this._allocate));

        this.actor.connect('destroy', Lang.bind(this, this._onDestroy));

        this._haveModal = false;
        this._modifierMask = 0;

        this._currentApp = 0;
        this._currentWindow = -1;
        this._thumbnailTimeoutId = 0;
        this._motionTimeoutId = 0;
        this._initialDelayTimeoutId = 0;

        this.thumbnailsVisible = false;

        // Initially disable hover so we ignore the enter-event if
        // the switcher appears underneath the current pointer location
        this._disableHover();

        Main.uiGroup.add_actor(this.actor);
    },

    _getPreferredWidth: function (actor, forHeight, alloc) {
        alloc.min_size = global.screen_width;
        alloc.natural_size = global.screen_width;
    },

    _getPreferredHeight: function (actor, forWidth, alloc) {
        alloc.min_size = global.screen_height;
        alloc.natural_size = global.screen_height;
    },

    _allocate: function (actor, box, flags) {
        let childBox = new Clutter.ActorBox();
        let primary = Main.layoutManager.primaryMonitor;

        let leftPadding = this.actor.get_theme_node().get_padding(St.Side.LEFT);
        let rightPadding = this.actor.get_theme_node().get_padding(St.Side.RIGHT);
        let bottomPadding = this.actor.get_theme_node().get_padding(St.Side.BOTTOM);
        let vPadding = this.actor.get_theme_node().get_vertical_padding();
        let hPadding = leftPadding + rightPadding;

        // Allocate the appSwitcher
        // We select a size based on an icon size that does not overflow the screen
        let [childMinHeight, childNaturalHeight] = this._appSwitcher.actor.get_preferred_height(primary.width - hPadding);
        let [childMinWidth, childNaturalWidth] = this._appSwitcher.actor.get_preferred_width(childNaturalHeight);
        childBox.x1 = Math.max(primary.x + leftPadding, primary.x + Math.floor((primary.width - childNaturalWidth) / 2));
        childBox.x2 = Math.min(primary.x + primary.width - rightPadding, childBox.x1 + childNaturalWidth);
        childBox.y1 = primary.y + Math.floor((primary.height - childNaturalHeight) / 2);
        childBox.y2 = childBox.y1 + childNaturalHeight;
        this._appSwitcher.actor.allocate(childBox, flags);

        // Allocate the thumbnails
        // We try to avoid overflowing the screen so we base the resulting size on
        // those calculations
        if (this._thumbnails) {
            let icon = this._appIcons[this._currentApp].actor;
            let [posX, posY] = icon.get_transformed_position();
            let thumbnailCenter = posX + icon.width / 2;
            let [childMinWidth, childNaturalWidth] = this._thumbnails.actor.get_preferred_width(-1);
            childBox.x1 = Math.max(primary.x + leftPadding, Math.floor(thumbnailCenter - childNaturalWidth / 2));
            if (childBox.x1 + childNaturalWidth > primary.x + primary.width - hPadding) {
                let offset = childBox.x1 + childNaturalWidth - primary.width + hPadding;
                childBox.x1 = Math.max(primary.x + leftPadding, childBox.x1 - offset - hPadding);
            }

            let spacing = this.actor.get_theme_node().get_length('spacing');

            childBox.x2 = childBox.x1 +  childNaturalWidth;
            if (childBox.x2 > primary.x + primary.width - rightPadding)
                childBox.x2 = primary.x + primary.width - rightPadding;
            childBox.y1 = this._appSwitcher.actor.allocation.y2 + spacing;
            this._thumbnails.addClones(primary.y + primary.height - bottomPadding - childBox.y1);
            let [childMinHeight, childNaturalHeight] = this._thumbnails.actor.get_preferred_height(-1);
            childBox.y2 = childBox.y1 + childNaturalHeight;
            this._thumbnails.actor.allocate(childBox, flags);
        }
    },

    _getAppLists: function() {
        let tracker = Shell.WindowTracker.get_default();
        let appSys = Shell.AppSystem.get_default();
        let allApps = appSys.get_running ();

        let screen = global.screen;
        let display = screen.get_display();
        let windows = display.get_tab_list(Meta.TabList.NORMAL, screen,
                                           screen.get_active_workspace());

        // windows is only the windows on the current workspace. For
        // each one, if it corresponds to an app we know, move that
        // app from allApps to apps.
        let apps = [];
        for (let i = 0; i < windows.length && allApps.length != 0; i++) {
            let app = tracker.get_window_app(windows[i]);
            let index = allApps.indexOf(app);
            if (index != -1) {
                apps.push(app);
                allApps.splice(index, 1);
            }
        }

        // Now @apps is a list of apps on the current workspace, in
        // standard Alt+Tab order (MRU except for minimized windows),
        // and allApps is a list of apps that only appear on other
        // workspaces, sorted by user_time, which is good enough.
        return [apps, allApps];
    },

    show : function(backward, binding, mask) {
        let [localApps, otherApps] = this._getAppLists();

        if (localApps.length == 0 && otherApps.length == 0)
            return false;

        if (!Main.pushModal(this.actor)) {
            // Probably someone else has a pointer grab, try again with keyboard only
            if (!Main.pushModal(this.actor, global.get_current_time(), Meta.ModalOptions.POINTER_ALREADY_GRABBED)) {
                return false;
            }
        }
        this._haveModal = true;
        this._modifierMask = primaryModifier(mask);

        this.actor.connect('key-press-event', Lang.bind(this, this._keyPressEvent));
        this.actor.connect('key-release-event', Lang.bind(this, this._keyReleaseEvent));

        this.actor.connect('button-press-event', Lang.bind(this, this._clickedOutside));
        this.actor.connect('scroll-event', Lang.bind(this, this._onScroll));

        this._appSwitcher = new AppSwitcher(localApps, otherApps, this);
        this.actor.add_actor(this._appSwitcher.actor);
        this._appSwitcher.connect('item-activated', Lang.bind(this, this._appActivated));
        this._appSwitcher.connect('item-entered', Lang.bind(this, this._appEntered));

        this._appIcons = this._appSwitcher.icons;

        // Need to force an allocation so we can figure out whether we
        // need to scroll when selecting
        this.actor.opacity = 0;
        this.actor.show();
        this.actor.get_allocation_box();

        // Make the initial selection
        if (binding == 'switch-group') {
            if (backward) {
                this._select(0, this._appIcons[0].cachedWindows.length - 1);
            } else {
                if (this._appIcons[0].cachedWindows.length > 1)
                    this._select(0, 1);
                else
                    this._select(0, 0);
            }
        } else if (binding == 'switch-group-backward') {
            this._select(0, this._appIcons[0].cachedWindows.length - 1);
        } else if (binding == 'switch-windows-backward') {
            this._select(this._appIcons.length - 1);
        } else if (this._appIcons.length == 1) {
            this._select(0);
        } else if (backward) {
            this._select(this._appIcons.length - 1);
        } else {
            this._select(1);
        }

        // There's a race condition; if the user released Alt before
        // we got the grab, then we won't be notified. (See
        // https://bugzilla.gnome.org/show_bug.cgi?id=596695 for
        // details.) So we check now. (Have to do this after updating
        // selection.)
        let [x, y, mods] = global.get_pointer();
        if (!(mods & this._modifierMask)) {
            this._finish();
            return false;
        }

        // We delay showing the popup so that fast Alt+Tab users aren't
        // disturbed by the popup briefly flashing.
        this._initialDelayTimeoutId = Mainloop.timeout_add(POPUP_DELAY_TIMEOUT,
                                                           Lang.bind(this, function () {
                                                               this.actor.opacity = 255;
                                                               this._initialDelayTimeoutId = 0;
                                                           }));

        return true;
    },

    _nextApp : function() {
        return mod(this._currentApp + 1, this._appIcons.length);
    },
    _previousApp : function() {
        return mod(this._currentApp - 1, this._appIcons.length);
    },

    _nextWindow : function() {
        // We actually want the second window if we're in the unset state
        if (this._currentWindow == -1)
            this._currentWindow = 0;
        return mod(this._currentWindow + 1,
                   this._appIcons[this._currentApp].cachedWindows.length);
    },
    _previousWindow : function() {
        // Also assume second window here
        if (this._currentWindow == -1)
            this._currentWindow = 1;
        return mod(this._currentWindow - 1,
                   this._appIcons[this._currentApp].cachedWindows.length);
    },

    _keyPressEvent : function(actor, event) {
        let keysym = event.get_key_symbol();
        let event_state = event.get_state();
        let backwards = event_state & Clutter.ModifierType.SHIFT_MASK;
        let action = global.display.get_keybinding_action(event.get_key_code(), event_state);

        this._disableHover();

        if (keysym == Clutter.Escape) {
            this.destroy();
        } else if (action == Meta.KeyBindingAction.SWITCH_GROUP) {
            this._select(this._currentApp, backwards ? this._previousWindow() : this._nextWindow());
        } else if (action == Meta.KeyBindingAction.SWITCH_GROUP_BACKWARD) {
            this._select(this._currentApp, this._previousWindow());
        } else if (action == Meta.KeyBindingAction.SWITCH_WINDOWS) {
            this._select(backwards ? this._previousApp() : this._nextApp());
        } else if (action == Meta.KeyBindingAction.SWITCH_WINDOWS_BACKWARD) {
            this._select(this._previousApp());
        } else if (this._thumbnailsFocused) {
            if (keysym == Clutter.Left)
                this._select(this._currentApp, this._previousWindow());
            else if (keysym == Clutter.Right)
                this._select(this._currentApp, this._nextWindow());
            else if (keysym == Clutter.Up)
                this._select(this._currentApp, null, true);
        } else {
            if (keysym == Clutter.Left)
                this._select(this._previousApp());
            else if (keysym == Clutter.Right)
                this._select(this._nextApp());
            else if (keysym == Clutter.Down)
                this._select(this._currentApp, 0);
        }

        return true;
    },

    _keyReleaseEvent : function(actor, event) {
        let [x, y, mods] = global.get_pointer();
        let state = mods & this._modifierMask;

        if (state == 0)
            this._finish();

        return true;
    },

    _onScroll : function(actor, event) {
        let direction = event.get_scroll_direction();
        if (direction == Clutter.ScrollDirection.UP) {
            if (this._thumbnailsFocused) {
                if (this._currentWindow == 0 || this._currentWindow == -1)
                    this._select(this._previousApp());
                else
                    this._select(this._currentApp, this._previousWindow());
            } else {
                let nwindows = this._appIcons[this._currentApp].cachedWindows.length;
                if (nwindows > 1)
                    this._select(this._currentApp, nwindows - 1);
                else
                    this._select(this._previousApp());
            }
        } else if (direction == Clutter.ScrollDirection.DOWN) {
            if (this._thumbnailsFocused) {
                if (this._currentWindow == this._appIcons[this._currentApp].cachedWindows.length - 1)
                    this._select(this._nextApp());
                else
                    this._select(this._currentApp, this._nextWindow());
            } else {
                let nwindows = this._appIcons[this._currentApp].cachedWindows.length;
                if (nwindows > 1)
                    this._select(this._currentApp, 0);
                else
                    this._select(this._nextApp());
            }
        }
    },

    _clickedOutside : function(actor, event) {
        this.destroy();
    },

    _appActivated : function(appSwitcher, n) {
        // If the user clicks on the selected app, activate the
        // selected window; otherwise (eg, they click on an app while
        // !mouseActive) activate the the clicked-on app.
        if (n == this._currentApp) {
            let window;
            if (this._currentWindow >= 0)
                window = this._appIcons[this._currentApp].cachedWindows[this._currentWindow];
            else
                window = null;
            this._appIcons[this._currentApp].app.activate_window(window, global.get_current_time());
        } else {
            this._appIcons[n].app.activate_window(null, global.get_current_time());
        }
        this.destroy();
    },

    _appEntered : function(appSwitcher, n) {
        if (!this._mouseActive)
            return;

        this._select(n);
    },

    _windowActivated : function(thumbnailList, n) {
        let appIcon = this._appIcons[this._currentApp];
        Main.activateWindow(appIcon.cachedWindows[n]);
        this.destroy();
    },

    _windowEntered : function(thumbnailList, n) {
        if (!this._mouseActive)
            return;

        this._select(this._currentApp, n);
    },

    _disableHover : function() {
        this._mouseActive = false;

        if (this._motionTimeoutId != 0)
            Mainloop.source_remove(this._motionTimeoutId);

        this._motionTimeoutId = Mainloop.timeout_add(DISABLE_HOVER_TIMEOUT, Lang.bind(this, this._mouseTimedOut));
    },

    _mouseTimedOut : function() {
        this._motionTimeoutId = 0;
        this._mouseActive = true;
    },

    _finish : function() {
        let app = this._appIcons[this._currentApp];
        if (this._currentWindow >= 0) {
            Main.activateWindow(app.cachedWindows[this._currentWindow]);
        } else {
            app.app.activate_window(null, global.get_current_time());
        }
        this.destroy();
    },

    _popModal: function() {
        if (this._haveModal) {
            Main.popModal(this.actor);
            this._haveModal = false;
        }
    },

    destroy : function() {
        this._popModal();
        if (this.actor.visible) {
            Tweener.addTween(this.actor,
                             { opacity: 0,
                               time: POPUP_FADE_OUT_TIME,
                               transition: 'easeOutQuad',
                               onComplete: Lang.bind(this,
                                   function() {
                                       this.actor.destroy();
                                   })
                             });
        } else
            this.actor.destroy();
    },

    _onDestroy : function() {
        this._popModal();

        if (this._thumbnails)
            this._destroyThumbnails();

        if (this._motionTimeoutId != 0)
            Mainloop.source_remove(this._motionTimeoutId);
        if (this._thumbnailTimeoutId != 0)
            Mainloop.source_remove(this._thumbnailTimeoutId);
        if (this._initialDelayTimeoutId != 0)
            Mainloop.source_remove(this._initialDelayTimeoutId);
    },

    /**
     * _select:
     * @app: index of the app to select
     * @window: (optional) index of which of @app's windows to select
     * @forceAppFocus: optional flag, see below
     *
     * Selects the indicated @app, and optional @window, and sets
     * this._thumbnailsFocused appropriately to indicate whether the
     * arrow keys should act on the app list or the thumbnail list.
     *
     * If @app is specified and @window is unspecified or %null, then
     * the app is highlighted (ie, given a light background), and the
     * current thumbnail list, if any, is destroyed. If @app has
     * multiple windows, and @forceAppFocus is not %true, then a
     * timeout is started to open a thumbnail list.
     *
     * If @app and @window are specified (and @forceAppFocus is not),
     * then @app will be outlined, a thumbnail list will be created
     * and focused (if it hasn't been already), and the @window'th
     * window in it will be highlighted.
     *
     * If @app and @window are specified and @forceAppFocus is %true,
     * then @app will be highlighted, and @window outlined, and the
     * app list will have the keyboard focus.
     */
    _select : function(app, window, forceAppFocus) {
        if (app != this._currentApp || window == null) {
            if (this._thumbnails)
                this._destroyThumbnails();
        }

        if (this._thumbnailTimeoutId != 0) {
            Mainloop.source_remove(this._thumbnailTimeoutId);
            this._thumbnailTimeoutId = 0;
        }

        this._thumbnailsFocused = (window != null) && !forceAppFocus;

        this._currentApp = app;
        this._currentWindow = window ? window : -1;
        this._appSwitcher.highlight(app, this._thumbnailsFocused);

        if (window != null) {
            if (!this._thumbnails)
                this._createThumbnails();
            this._currentWindow = window;
            this._thumbnails.highlight(window, forceAppFocus);
        } else if (this._appIcons[this._currentApp].cachedWindows.length > 1 &&
                   !forceAppFocus) {
            this._thumbnailTimeoutId = Mainloop.timeout_add (
                THUMBNAIL_POPUP_TIME,
                Lang.bind(this, this._timeoutPopupThumbnails));
        }
    },

    _timeoutPopupThumbnails: function() {
        if (!this._thumbnails)
            this._createThumbnails();
        this._thumbnailTimeoutId = 0;
        this._thumbnailsFocused = false;
        return false;
    },

    _destroyThumbnails : function() {
        let thumbnailsActor = this._thumbnails.actor;
        Tweener.addTween(thumbnailsActor,
                         { opacity: 0,
                           time: THUMBNAIL_FADE_TIME,
                           transition: 'easeOutQuad',
                           onComplete: Lang.bind(this, function() {
                                                            thumbnailsActor.destroy();
                                                            this.thumbnailsVisible = false;
                                                        })
                         });
        this._thumbnails = null;
    },

    _createThumbnails : function() {
        this._thumbnails = new ThumbnailList (this._appIcons[this._currentApp].cachedWindows);
        this._thumbnails.connect('item-activated', Lang.bind(this, this._windowActivated));
        this._thumbnails.connect('item-entered', Lang.bind(this, this._windowEntered));

        this.actor.add_actor(this._thumbnails.actor);

        // Need to force an allocation so we can figure out whether we
        // need to scroll when selecting
        this._thumbnails.actor.get_allocation_box();

        this._thumbnails.actor.opacity = 0;
        Tweener.addTween(this._thumbnails.actor,
                         { opacity: 255,
                           time: THUMBNAIL_FADE_TIME,
                           transition: 'easeOutQuad',
                           onComplete: Lang.bind(this, function () { this.thumbnailsVisible = true; })
                         });
    }
});

const SwitcherList = new Lang.Class({
    Name: 'SwitcherList',

    _init : function(squareItems) {
        this.actor = new Shell.GenericContainer({ style_class: 'switcher-list' });
        this.actor.connect('get-preferred-width', Lang.bind(this, this._getPreferredWidth));
        this.actor.connect('get-preferred-height', Lang.bind(this, this._getPreferredHeight));
        this.actor.connect('allocate', Lang.bind(this, this._allocateTop));

        // Here we use a GenericContainer so that we can force all the
        // children except the separator to have the same width.
        this._list = new Shell.GenericContainer({ style_class: 'switcher-list-item-container' });
        this._list.spacing = 0;
        this._list.connect('style-changed', Lang.bind(this, function() {
                                                        this._list.spacing = this._list.get_theme_node().get_length('spacing');
                                                     }));

        this._list.connect('get-preferred-width', Lang.bind(this, this._getPreferredWidth));
        this._list.connect('get-preferred-height', Lang.bind(this, this._getPreferredHeight));
        this._list.connect('allocate', Lang.bind(this, this._allocate));

        this._scrollView = new St.ScrollView({ style_class: 'hfade',
                                               enable_mouse_scrolling: false });
        this._scrollView.set_policy(Gtk.PolicyType.NEVER, Gtk.PolicyType.NEVER);

        let scrollBox = new St.BoxLayout();
        scrollBox.add_actor(this._list);
        this._scrollView.add_actor(scrollBox);
        this.actor.add_actor(this._scrollView);

        // Those arrows indicate whether scrolling in one direction is possible
        this._leftArrow = new St.DrawingArea({ style_class: 'switcher-arrow',
                                               pseudo_class: 'highlighted' });
        this._leftArrow.connect('repaint', Lang.bind(this,
            function() { _drawArrow(this._leftArrow, St.Side.LEFT); }));
        this._rightArrow = new St.DrawingArea({ style_class: 'switcher-arrow',
                                                pseudo_class: 'highlighted' });
        this._rightArrow.connect('repaint', Lang.bind(this,
            function() { _drawArrow(this._rightArrow, St.Side.RIGHT); }));

        this.actor.add_actor(this._leftArrow);
        this.actor.add_actor(this._rightArrow);

        this._items = [];
        this._highlighted = -1;
        this._separator = null;
        this._squareItems = squareItems;
        this._minSize = 0;
        this._scrollableRight = true;
        this._scrollableLeft = false;
    },

    _allocateTop: function(actor, box, flags) {
        let leftPadding = this.actor.get_theme_node().get_padding(St.Side.LEFT);
        let rightPadding = this.actor.get_theme_node().get_padding(St.Side.RIGHT);

        let childBox = new Clutter.ActorBox();
        let scrollable = this._minSize > box.x2 - box.x1;

        box.y1 -= this.actor.get_theme_node().get_padding(St.Side.TOP);
        box.y2 += this.actor.get_theme_node().get_padding(St.Side.BOTTOM);
        this._scrollView.allocate(box, flags);

        let arrowWidth = Math.floor(leftPadding / 3);
        let arrowHeight = arrowWidth * 2;
        childBox.x1 = leftPadding / 2;
        childBox.y1 = this.actor.height / 2 - arrowWidth;
        childBox.x2 = childBox.x1 + arrowWidth;
        childBox.y2 = childBox.y1 + arrowHeight;
        this._leftArrow.allocate(childBox, flags);
        this._leftArrow.opacity = (this._scrollableLeft && scrollable) ? 255 : 0;

        arrowWidth = Math.floor(rightPadding / 3);
        arrowHeight = arrowWidth * 2;
        childBox.x1 = this.actor.width - arrowWidth - rightPadding / 2;
        childBox.y1 = this.actor.height / 2 - arrowWidth;
        childBox.x2 = childBox.x1 + arrowWidth;
        childBox.y2 = childBox.y1 + arrowHeight;
        this._rightArrow.allocate(childBox, flags);
        this._rightArrow.opacity = (this._scrollableRight && scrollable) ? 255 : 0;
    },

    addItem : function(item, label) {
        let bbox = new St.Button({ style_class: 'item-box',
                                   reactive: true });

        bbox.set_child(item);
        this._list.add_actor(bbox);

        let n = this._items.length;
        bbox.connect('clicked', Lang.bind(this, function() { this._onItemClicked(n); }));
        bbox.connect('enter-event', Lang.bind(this, function() { this._onItemEnter(n); }));

        bbox.label_actor = label;

        this._items.push(bbox);
    },

    _onItemClicked: function (index) {
        this._itemActivated(index);
    },

    _onItemEnter: function (index) {
        this._itemEntered(index);
    },

    addSeparator: function () {
        let box = new St.Bin({ style_class: 'separator' });
        this._separator = box;
        this._list.add_actor(box);
    },

    highlight: function(index, justOutline) {
        if (this._highlighted != -1) {
            this._items[this._highlighted].remove_style_pseudo_class('outlined');
            this._items[this._highlighted].remove_style_pseudo_class('selected');
        }

        this._highlighted = index;

        if (this._highlighted != -1) {
            if (justOutline)
                this._items[this._highlighted].add_style_pseudo_class('outlined');
            else
                this._items[this._highlighted].add_style_pseudo_class('selected');
        }

        let adjustment = this._scrollView.hscroll.adjustment;
        let [value, lower, upper, stepIncrement, pageIncrement, pageSize] = adjustment.get_values();
        let [absItemX, absItemY] = this._items[index].get_transformed_position();
        let [result, posX, posY] = this.actor.transform_stage_point(absItemX, 0);
        let [containerWidth, containerHeight] = this.actor.get_transformed_size();
        if (posX + this._items[index].get_width() > containerWidth)
            this._scrollToRight();
        else if (this._items[index].allocation.x1 - value < 0)
            this._scrollToLeft();

    },

    _scrollToLeft : function() {
        let adjustment = this._scrollView.hscroll.adjustment;
        let [value, lower, upper, stepIncrement, pageIncrement, pageSize] = adjustment.get_values();

        let item = this._items[this._highlighted];

        if (item.allocation.x1 < value)
            value = Math.min(0, item.allocation.x1);
        else if (item.allocation.x2 > value + pageSize)
            value = Math.max(upper, item.allocation.x2 - pageSize);

        this._scrollableRight = true;
        Tweener.addTween(adjustment,
                         { value: value,
                           time: POPUP_SCROLL_TIME,
                           transition: 'easeOutQuad',
                           onComplete: Lang.bind(this, function () {
                                if (this._highlighted == 0) {
                                    this._scrollableLeft = false;
                                    this.actor.queue_relayout();
                                }
                           })
                          });
    },

    _scrollToRight : function() {
        let adjustment = this._scrollView.hscroll.adjustment;
        let [value, lower, upper, stepIncrement, pageIncrement, pageSize] = adjustment.get_values();

        let item = this._items[this._highlighted];

        if (item.allocation.x1 < value)
            value = Math.max(0, item.allocation.x1);
        else if (item.allocation.x2 > value + pageSize)
            value = Math.min(upper, item.allocation.x2 - pageSize);

        this._scrollableLeft = true;
        Tweener.addTween(adjustment,
                         { value: value,
                           time: POPUP_SCROLL_TIME,
                           transition: 'easeOutQuad',
                           onComplete: Lang.bind(this, function () {
                                if (this._highlighted == this._items.length - 1) {
                                    this._scrollableRight = false;
                                    this.actor.queue_relayout();
                                }
                            })
                          });
    },

    _itemActivated: function(n) {
        this.emit('item-activated', n);
    },

    _itemEntered: function(n) {
        this.emit('item-entered', n);
    },

    _maxChildWidth: function (forHeight) {
        let maxChildMin = 0;
        let maxChildNat = 0;

        for (let i = 0; i < this._items.length; i++) {
            let [childMin, childNat] = this._items[i].get_preferred_width(forHeight);
            maxChildMin = Math.max(childMin, maxChildMin);
            maxChildNat = Math.max(childNat, maxChildNat);

            if (this._squareItems) {
                let [childMin, childNat] = this._items[i].get_preferred_height(-1);
                maxChildMin = Math.max(childMin, maxChildMin);
                maxChildNat = Math.max(childNat, maxChildNat);
            }
        }

        return [maxChildMin, maxChildNat];
    },

    _getPreferredWidth: function (actor, forHeight, alloc) {
        let [maxChildMin, maxChildNat] = this._maxChildWidth(forHeight);

        let separatorWidth = 0;
        if (this._separator) {
            let [sepMin, sepNat] = this._separator.get_preferred_width(forHeight);
            separatorWidth = sepNat + this._list.spacing;
        }

        let totalSpacing = this._list.spacing * (this._items.length - 1);
        alloc.min_size = this._items.length * maxChildMin + separatorWidth + totalSpacing;
        alloc.natural_size = alloc.min_size;
        this._minSize = alloc.min_size;
    },

    _getPreferredHeight: function (actor, forWidth, alloc) {
        let maxChildMin = 0;
        let maxChildNat = 0;

        for (let i = 0; i < this._items.length; i++) {
            let [childMin, childNat] = this._items[i].get_preferred_height(-1);
            maxChildMin = Math.max(childMin, maxChildMin);
            maxChildNat = Math.max(childNat, maxChildNat);
        }

        if (this._squareItems) {
            let [childMin, childNat] = this._maxChildWidth(-1);
            maxChildMin = Math.max(childMin, maxChildMin);
            maxChildNat = maxChildMin;
        }

        alloc.min_size = maxChildMin;
        alloc.natural_size = maxChildNat;
    },

    _allocate: function (actor, box, flags) {
        let childHeight = box.y2 - box.y1;

        let [maxChildMin, maxChildNat] = this._maxChildWidth(childHeight);
        let totalSpacing = this._list.spacing * (this._items.length - 1);

        let separatorWidth = 0;
        if (this._separator) {
            let [sepMin, sepNat] = this._separator.get_preferred_width(childHeight);
            separatorWidth = sepNat;
            totalSpacing += this._list.spacing;
        }

        let childWidth = Math.floor(Math.max(0, box.x2 - box.x1 - totalSpacing - separatorWidth) / this._items.length);

        let x = 0;
        let children = this._list.get_children();
        let childBox = new Clutter.ActorBox();

        let primary = Main.layoutManager.primaryMonitor;
        let parentRightPadding = this.actor.get_parent().get_theme_node().get_padding(St.Side.RIGHT);

        for (let i = 0; i < children.length; i++) {
            if (this._items.indexOf(children[i]) != -1) {
                let [childMin, childNat] = children[i].get_preferred_height(childWidth);
                let vSpacing = (childHeight - childNat) / 2;
                childBox.x1 = x;
                childBox.y1 = vSpacing;
                childBox.x2 = x + childWidth;
                childBox.y2 = childBox.y1 + childNat;
                children[i].allocate(childBox, flags);

                x += this._list.spacing + childWidth;
            } else if (children[i] == this._separator) {
                // We want the separator to be more compact than the rest.
                childBox.x1 = x;
                childBox.y1 = 0;
                childBox.x2 = x + separatorWidth;
                childBox.y2 = childHeight;
                children[i].allocate(childBox, flags);
                x += this._list.spacing + separatorWidth;
            } else {
                // Something else, eg, AppSwitcher's arrows;
                // we don't allocate it.
            }
        }
    }
});

Signals.addSignalMethods(SwitcherList.prototype);

const AppIcon = new Lang.Class({
    Name: 'AppIcon',

    _init: function(app) {
        this.app = app;
        this.actor = new St.BoxLayout({ style_class: 'alt-tab-app',
                                         vertical: true });
        this.icon = null;
        this._iconBin = new St.Bin({ x_fill: true, y_fill: true });

        this.actor.add(this._iconBin, { x_fill: false, y_fill: false } );
        this.label = new St.Label({ text: this.app.get_name() });
        this.actor.add(this.label, { x_fill: false });
    },

    set_size: function(size) {
        this.icon = this.app.create_icon_texture(size);
        this._iconBin.set_size(size, size);
        this._iconBin.child = this.icon;
    }
});

const AppSwitcher = new Lang.Class({
    Name: 'AppSwitcher',
    Extends: SwitcherList,

    _init : function(localApps, otherApps, altTabPopup) {
        this.parent(true);

        // Construct the AppIcons, add to the popup
        let activeWorkspace = global.screen.get_active_workspace();
        let workspaceIcons = [];
        let otherIcons = [];
        for (let i = 0; i < localApps.length; i++) {
            let appIcon = new AppIcon(localApps[i]);
            // Cache the window list now; we don't handle dynamic changes here,
            // and we don't want to be continually retrieving it
            appIcon.cachedWindows = appIcon.app.get_windows();
            workspaceIcons.push(appIcon);
        }
        for (let i = 0; i < otherApps.length; i++) {
            let appIcon = new AppIcon(otherApps[i]);
            appIcon.cachedWindows = appIcon.app.get_windows();
            otherIcons.push(appIcon);
        }

        this.icons = [];
        this._arrows = [];
        for (let i = 0; i < workspaceIcons.length; i++)
            this._addIcon(workspaceIcons[i]);
        if (workspaceIcons.length > 0 && otherIcons.length > 0)
            this.addSeparator();
        for (let i = 0; i < otherIcons.length; i++)
            this._addIcon(otherIcons[i]);

        this._curApp = -1;
        this._iconSize = 0;
        this._altTabPopup = altTabPopup;
        this._mouseTimeOutId = 0;
    },

    _getPreferredHeight: function (actor, forWidth, alloc) {
        let j = 0;
        while(this._items.length > 1 && this._items[j].style_class != 'item-box') {
                j++;
        }
        let themeNode = this._items[j].get_theme_node();
        let iconPadding = themeNode.get_horizontal_padding();
        let iconBorder = themeNode.get_border_width(St.Side.LEFT) + themeNode.get_border_width(St.Side.RIGHT);
        let [iconMinHeight, iconNaturalHeight] = this.icons[j].label.get_preferred_height(-1);
        let iconSpacing = iconNaturalHeight + iconPadding + iconBorder;
        let totalSpacing = this._list.spacing * (this._items.length - 1);
        if (this._separator)
           totalSpacing += this._separator.width + this._list.spacing;

        // We just assume the whole screen here due to weirdness happing with the passed width
        let primary = Main.layoutManager.primaryMonitor;
        let parentPadding = this.actor.get_parent().get_theme_node().get_horizontal_padding();
        let availWidth = primary.width - parentPadding - this.actor.get_theme_node().get_horizontal_padding();
        let height = 0;

        for(let i =  0; i < iconSizes.length; i++) {
                this._iconSize = iconSizes[i];
                height = iconSizes[i] + iconSpacing;
                let w = height * this._items.length + totalSpacing;
                if (w <= availWidth)
                        break;
        }

        if (this._items.length == 1) {
            this._iconSize = iconSizes[0];
            height = iconSizes[0] + iconSpacing;
        }

        for(let i = 0; i < this.icons.length; i++) {
            if (this.icons[i].icon != null)
                break;
            this.icons[i].set_size(this._iconSize);
        }

        alloc.min_size = height;
        alloc.natural_size = height;
    },

    _allocate: function (actor, box, flags) {
        // Allocate the main list items
        this.parent(actor, box, flags);

        let arrowHeight = Math.floor(this.actor.get_theme_node().get_padding(St.Side.BOTTOM) / 3);
        let arrowWidth = arrowHeight * 2;

        // Now allocate each arrow underneath its item
        let childBox = new Clutter.ActorBox();
        for (let i = 0; i < this._items.length; i++) {
            let itemBox = this._items[i].allocation;
            childBox.x1 = Math.floor(itemBox.x1 + (itemBox.x2 - itemBox.x1 - arrowWidth) / 2);
            childBox.x2 = childBox.x1 + arrowWidth;
            childBox.y1 = itemBox.y2 + arrowHeight;
            childBox.y2 = childBox.y1 + arrowHeight;
            this._arrows[i].allocate(childBox, flags);
        }
    },

    // We override SwitcherList's _onItemEnter method to delay
    // activation when the thumbnail list is open
    _onItemEnter: function (index) {
        if (this._mouseTimeOutId != 0)
            Mainloop.source_remove(this._mouseTimeOutId);
        if (this._altTabPopup.thumbnailsVisible) {
            this._mouseTimeOutId = Mainloop.timeout_add(APP_ICON_HOVER_TIMEOUT,
                                                        Lang.bind(this, function () {
                                                                            this._enterItem(index);
                                                                            this._mouseTimeOutId = 0;
                                                                            return false;
                                                        }));
        } else
           this._itemEntered(index);
    },

    _enterItem: function(index) {
        let [x, y, mask] = global.get_pointer();
        let pickedActor = global.stage.get_actor_at_pos(Clutter.PickMode.ALL, x, y);
        if (this._items[index].contains(pickedActor))
            this._itemEntered(index);
    },

    // We override SwitcherList's highlight() method to also deal with
    // the AppSwitcher->ThumbnailList arrows. Apps with only 1 window
    // will hide their arrows by default, but show them when their
    // thumbnails are visible (ie, when the app icon is supposed to be
    // in justOutline mode). Apps with multiple windows will normally
    // show a dim arrow, but show a bright arrow when they are
    // highlighted.
    highlight : function(n, justOutline) {
        if (this._curApp != -1) {
            if (this.icons[this._curApp].cachedWindows.length == 1)
                this._arrows[this._curApp].hide();
            else
                this._arrows[this._curApp].remove_style_pseudo_class('highlighted');
        }

        this.parent(n, justOutline);
        this._curApp = n;

        if (this._curApp != -1) {
            if (justOutline && this.icons[this._curApp].cachedWindows.length == 1)
                this._arrows[this._curApp].show();
            else
                this._arrows[this._curApp].add_style_pseudo_class('highlighted');
        }
    },

    _addIcon : function(appIcon) {
        this.icons.push(appIcon);
        this.addItem(appIcon.actor, appIcon.label);

        let n = this._arrows.length;
        let arrow = new St.DrawingArea({ style_class: 'switcher-arrow' });
        arrow.connect('repaint', function() { _drawArrow(arrow, St.Side.BOTTOM); });
        this._list.add_actor(arrow);
        this._arrows.push(arrow);

        if (appIcon.cachedWindows.length == 1)
            arrow.hide();
    }
});

const ThumbnailList = new Lang.Class({
    Name: 'ThumbnailList',
    Extends: SwitcherList,

    _init : function(windows) {
        this.parent(false);

        let activeWorkspace = global.screen.get_active_workspace();

        // We fake the value of 'separatorAdded' when the app has no window
        // on the current workspace, to avoid displaying a useless separator in
        // that case.
        let separatorAdded = windows.length == 0 || windows[0].get_workspace() != activeWorkspace;

        this._labels = new Array();
        this._thumbnailBins = new Array();
        this._clones = new Array();
        this._windows = windows;

        for (let i = 0; i < windows.length; i++) {
            if (!separatorAdded && windows[i].get_workspace() != activeWorkspace) {
              this.addSeparator();
              separatorAdded = true;
            }

            let box = new St.BoxLayout({ style_class: 'thumbnail-box',
                                         vertical: true });

            let bin = new St.Bin({ style_class: 'thumbnail' });

            box.add_actor(bin);
            this._thumbnailBins.push(bin);

            let title = windows[i].get_title();
            if (title) {
                let name = new St.Label({ text: title });
                // St.Label doesn't support text-align so use a Bin
                let bin = new St.Bin({ x_align: St.Align.MIDDLE });
                this._labels.push(bin);
                bin.add_actor(name);
                box.add_actor(bin);

                this.addItem(box, name);
            } else {
                this.addItem(box, null);
            }

        }
    },

    addClones : function (availHeight) {
        if (!this._thumbnailBins.length)
            return;
        let totalPadding = this._items[0].get_theme_node().get_horizontal_padding() + this._items[0].get_theme_node().get_vertical_padding();
        totalPadding += this.actor.get_theme_node().get_horizontal_padding() + this.actor.get_theme_node().get_vertical_padding();
        let [labelMinHeight, labelNaturalHeight] = this._labels[0].get_preferred_height(-1);
        let spacing = this._items[0].child.get_theme_node().get_length('spacing');

        availHeight = Math.min(availHeight - labelNaturalHeight - totalPadding - spacing, THUMBNAIL_DEFAULT_SIZE);
        let binHeight = availHeight + this._items[0].get_theme_node().get_vertical_padding() + this.actor.get_theme_node().get_vertical_padding() - spacing;
        binHeight = Math.min(THUMBNAIL_DEFAULT_SIZE, binHeight);

        for (let i = 0; i < this._thumbnailBins.length; i++) {
            let mutterWindow = this._windows[i].get_compositor_private();
            if (!mutterWindow)
                continue;

            let windowTexture = mutterWindow.get_texture ();
            let [width, height] = windowTexture.get_size();
            let scale = Math.min(1.0, THUMBNAIL_DEFAULT_SIZE / width, availHeight / height);
            let clone = new Clutter.Clone ({ source: windowTexture,
                                                reactive: true,
                                                width: width * scale,
                                                height: height * scale });

            this._thumbnailBins[i].set_height(binHeight);
            this._thumbnailBins[i].add_actor(clone);
            this._clones.push(clone);
        }

        // Make sure we only do this once
        this._thumbnailBins = new Array();
    }
});

function _drawArrow(area, side) {
    let themeNode = area.get_theme_node();
    let borderColor = themeNode.get_border_color(side);
    let bodyColor = themeNode.get_foreground_color();

    let [width, height] = area.get_surface_size ();
    let cr = area.get_context();

    cr.setLineWidth(1.0);
    Clutter.cairo_set_source_color(cr, borderColor);

    switch (side) {
    case St.Side.TOP:
        cr.moveTo(0, height);
        cr.lineTo(Math.floor(width * 0.5), 0);
        cr.lineTo(width, height);
        break;

    case St.Side.BOTTOM:
        cr.moveTo(width, 0);
        cr.lineTo(Math.floor(width * 0.5), height);
        cr.lineTo(0, 0);
        break;

    case St.Side.LEFT:
        cr.moveTo(width, height);
        cr.lineTo(0, Math.floor(height * 0.5));
        cr.lineTo(width, 0);
        break;

    case St.Side.RIGHT:
        cr.moveTo(0, 0);
        cr.lineTo(width, Math.floor(height * 0.5));
        cr.lineTo(0, height);
        break;
    }

    cr.strokePreserve();

    Clutter.cairo_set_source_color(cr, bodyColor);
    cr.fill();
}