var Extension = imports.misc.extensionUtils.extensions['paperwm@hedning:matrix.org'];
var GLib = imports.gi.GLib;
var Tweener = imports.ui.tweener;
var Lang = imports.lang;
var Meta = imports.gi.Meta;
var Clutter = imports.gi.Clutter;
var St = imports.gi.St;
var Main = imports.ui.main;
var Shell = imports.gi.Shell;
var Gio = imports.gi.Gio;
var Signals = imports.signals;
var utils = Extension.imports.utils;
var debug = utils.debug;

var Gdk = imports.gi.Gdk;

var workspaceManager = global.workspace_manager;
var display = global.display;

var spaces;

var Minimap = Extension.imports.minimap;
var Scratch = Extension.imports.scratch;
var TopBar = Extension.imports.topbar;
var Navigator = Extension.imports.navigator;
var ClickOverlay = Extension.imports.stackoverlay.ClickOverlay;
var Settings = Extension.imports.settings;
var Me = Extension.imports.tiling;

var prefs = Settings.prefs;

// Mutter prevints windows from being placed further off the screen than 75 pixels.
var stack_margin = 75;
// Minimum margin
var minimumMargin = 15;

var panelBox = Main.layoutManager.panelBox;

var inPreview = false;

var signals, oldSpaces, backgroundGroup, oldMonitors, WindowCloneLayout;
function init() {
    // Symbol to retrieve the focus handler id
    signals = new utils.Signals();
    oldSpaces = new Map();
    oldMonitors = new Map();

    backgroundGroup = global.window_group.first_child;

    // LayoutManagers can't be re-evaluated so we wrap this in `init`
    /**
       A simple layout for our window clones that aligns the coordinates and
       size of our clone with the window's frame
     */
    WindowCloneLayout = new imports.lang.Class ({
        Name: 'TiledCloneLayout',
        Extends: Clutter.LayoutManager,

        vfunc_get_preferred_height(container, forWidth) {
            let frame = container.get_first_child().meta_window.get_frame_rect();
            return [frame.height, frame.height];
        },

        vfunc_get_preferred_width(container, forHeight) {
            let frame = container.get_first_child().meta_window.get_frame_rect();
            return [frame.width, frame.width];
        },

        vfunc_allocate(container, box, flags) {
            let child = container.first_child;
            let actor = child.source;
            if (!actor)
                return;

            let metaWindow = actor.meta_window;
            let frame = metaWindow.get_frame_rect();
            // Adjust the clone's origin to the north-west, so it will line up
            // with the frame.
            box.set_origin(actor.x - frame.x,
                           actor.y - frame.y);
            box.set_size(actor.width, actor.height);
            child.allocate(box, flags);
        }
    });
}

/**
   Scrolled and tiled per monitor workspace.

   The tiling is composed of an array of columns. A column being an array of
   MetaWindows. Ie. the type being [[MetaWindow]].

   A Space also contains a visual representation of the tiling. The structure is
   currently like this:

   A @clip actor which spans the monitor and clips all its contents to the
   monitor. The clip lives along side all other space's clips in an actor
   spanning the whole global.workspaceManager

   An @actor to hold everything that's visible, it contains a @background,
   a @label and a @cloneContainer.

   The @background is sized somewhat larger than the monitor, with the top left
   and right corners rounded. It's positioned slightly above the monitor so the
   corners aren't visible when the space is active.

   The @cloneContainer holds all the WindowActor clones, it's clipped
   by @cloneClip to avoid protruding into neighbouringing monitors.

   Clones are necessary due to restrictions mutter places on MetaWindowActors
   MetaWindowActors can only live in the `global.window_group` and can't be
   moved reliably off workspaceManager. We create a Clutter.Clone for every window which
   live in its @cloneContainer to avoid these problems. Scrolling to a window in
   the tiling can then be done by simply moving the @cloneContainer.

   The clones are also useful when constructing the workspace stack as it's
   easier to scale and move the whole @actor in one go.
 */
class Space extends Array {
    constructor (workspace, container) {
        super(0);
        this.workspace = workspace;

        this.signals = new utils.Signals();
        this.signals.connect(workspace, "window-added", utils.dynamic_function_ref("add_handler", Me));
        this.signals.connect(workspace, "window-removed",
                             utils.dynamic_function_ref("remove_handler", Me));
        this.signals.connect(Main.overview, 'showing', this.startAnimate.bind(this));
        this.signals.connect(Main.overview, 'hidden', this.moveDone.bind(this));

        // The windows that should be represented by their WindowActor
        this.visible = [];
        this._populated = false;

        let clip = new Clutter.Actor();
        this.clip = clip;
        let actor = new Clutter.Actor();
        this.actor = actor;
        let cloneClip = new Clutter.Actor();
        this.cloneClip = cloneClip;
        let cloneContainer = new St.Widget();
        this.cloneContainer = cloneContainer;

        let meta_display = global.screen ?
            { meta_screen: global.screen } :
            { meta_display: display };

        const GDesktopEnums = imports.gi.GDesktopEnums;
        let metaBackground = new Meta.Background(meta_display);
        let background = new Meta.BackgroundActor(
            Object.assign({
                monitor: 0, background: metaBackground,
                reactive: true // Disable the background menu
            }, meta_display)
        );
        background.space = this;

        // This kills all input on X11, but works on wayland...
        if (Meta.is_wayland_compositor()) {
            Main.layoutManager.trackChrome(background);
            this.signals.connect(background, 'button-press-event', () => {
                if (!inPreview)
                    return;
                let nav = Navigator.getNavigator();
                spaces.selectedSpace = this;
                nav.finish();
            });

            this.signals.connect(background, 'captured-event',
                                 (actor, event) => {
                                     Extension.imports.gestures.horizontalScroll(actor, event);
                                 });
        }
        this.background = background;
        this.shadow = new St.Widget();;
        this.shadow.set_style(
            `background: black;
             box-shadow: 0px -4px 8px 0 rgba(0, 0, 0, .5);`);

        let label = new St.Label();
        this.label = label;
        label.set_style('font-weight: bold; height: 1.86em;');
        label.hide();

        let selection = new St.Widget({style_class: 'tile-preview'});
        this.selection = selection;
        selection.width = 0;

        clip.space = this;
        cloneContainer.space = this;

        container.add_actor(clip);
        clip.add_actor(actor);
        actor.add_actor(this.shadow);
        this.shadow.add_actor(background);
        actor.add_actor(label);
        actor.add_actor(cloneClip);
        cloneClip.add_actor(cloneContainer);
        cloneContainer.add_actor(selection);

        container.set_child_below_sibling(clip,
                                          container.first_child);

        let monitor = Main.layoutManager.primaryMonitor;
        let oldSpace = oldSpaces.get(workspace);
        this.targetX = 0;
        if (oldSpace) {
            monitor = Main.layoutManager.monitors[oldSpace.monitor.index];
        }
        this.setMonitor(monitor, false);

        this.setSettings(Settings.getWorkspaceSettings(this.workspace.index()));

        actor.set_pivot_point(0.5, 0);

        this.shadow.set_position(-8 - Math.round(prefs.window_gap/2), -4);

        this.selectedWindow = null;
        this.moving = false;
        this.leftStack = 0; // not implemented
        this.rightStack = 0; // not implemented
    }

    layout(animate = true) {
        // Guard against recursively calling layout
        if (this._inLayout)
            return;
        this._inLayout = true;

        let time = animate ? 0.25 : 0;
        let gap = prefs.window_gap;
        let x = 0;
        this.startAnimate();

        for (let i=0; i<this.length; i++) {
            let column = this[i];
            let widthChanged = false;

            let y = panelBox.height + prefs.vertical_margin;

            let targetWidth = Math.max(...column.map(w => w.get_frame_rect().width));
            if (column.includes(this.selectedWindow))
                targetWidth = this.selectedWindow.get_frame_rect().width;

            targetWidth = Math.min(targetWidth, this.width - 2*minimumMargin);
            let height = Math.round(
                (this.height - panelBox.height - prefs.vertical_margin
                 - prefs.window_gap*(column.length - 1))/column.length) ;

            for (let w of column) {
                if (!w.get_compositor_private())
                    continue;
                let f = w.get_frame_rect();
                let b = w.get_buffer_rect();

                let resizable = !w.fullscreen &&
                    w.get_maximized() !== Meta.MaximizeFlags.BOTH;
                if (resizable) {
                    w.move_resize_frame(true, f.x, f.y, targetWidth, height);
                } else {
                    targetWidth = f.width;
                }
                // When resize is synchronous, ie. for X11 windows
                let newWidth = w.get_frame_rect().width;
                if (newWidth !== targetWidth && newWidth !== f.width) {
                    widthChanged = true;
                }

                let c = w.clone;
                c.targetX = x;
                c.targetY = y;
                Tweener.addTween(c, {
                    x, y,
                    time,
                    transition: 'easeInOutQuad',
                });

                y += height + gap;
            }

            if (widthChanged) {
                // Redo current column
                i--;
            } else {
                x += targetWidth + gap;
            }
        }
        this._inLayout = false;
        this.cloneContainer.width = x - gap;

        let width = x - gap;
        this.cloneContainer.width = width;
        if (width < this.width) {
            this.targetX = Math.round((this.width - width)/2);
        }
        if (animate) {
            Tweener.addTween(this.cloneContainer,
                             { x: this.targetX,
                               time: 0.25,
                               transition: 'easeInOutQuad',
                               onComplete: this.moveDone.bind(this)
                             });
            updateSelection(this);
        }
    }

    isPlaceable(metaWindow) {
        let clone = metaWindow.clone;
        let x = clone.targetX + this.targetX;

        if (x + clone.width < stack_margin
            || x > this.width - stack_margin) {
            return false;
        } else {
            // Fullscreen windows are only placeable on the monitor origin
            if ((metaWindow.get_maximized() === Meta.MaximizeFlags.BOTH ||
                 metaWindow.fullscreen) && x !== 0) {
                return false;
            }
            return true;
        }
    }

    getWindows() {
        return this.reduce((ws, column) => ws.concat(column), []);
    }

    getWindow(index, row) {
        if (row < 0 || index < 0 || index >= this.length)
            return false;

        let column = this[index];
        if (row >= column.length)
            return false;
        return column[row];
    }

    addWindow(metaWindow, index, row) {
        if (!this.selectedWindow)
            this.selectedWindow = metaWindow;
        if (this.indexOf(metaWindow) !== -1)
            return false;
        if (row !== undefined && this[index]) {
            let column = this[index];
            column.splice(row, 0, metaWindow);
        } else {
            this.splice(index, 0, [metaWindow]);
        }
        metaWindow.clone.reparent(this.cloneContainer);
        this._populated && this.layout();
        this.emit('window-added', metaWindow, index, row);
        return true;
    }

    removeWindow(metaWindow) {
        let index = this.indexOf(metaWindow);
        if (index === -1)
            return false;

        let selected = this.selectedWindow;
        if (selected === metaWindow) {
            // Select a new window using the stack ordering;
            let windows = this.getWindows();
            let i = windows.indexOf(metaWindow);
            let neighbours = [windows[i - 1], windows[i + 1]].filter(w => w);
            let stack = display.sort_windows_by_stacking(neighbours);
            selected = stack[stack.length - 1];
        }

        let column = this[index];
        let row = column.indexOf(metaWindow);
        column.splice(row, 1);
        if (column.length === 0)
            this.splice(index, 1);


        this.cloneContainer.remove_actor(metaWindow.clone);

        this.layout();
        this.emit('window-removed', metaWindow, index, row);
        if (selected) {
            ensureViewport(selected, this, true);
        } else {
            this.selectedWindow = null;
            Tweener.removeTweens(this.selection);
            this.selection.width = 0;
        }
        return true;
    }

    swap(direction, metaWindow) {
        metaWindow = metaWindow || this.selectedWindow;

        let [index, row] = this.positionOf(metaWindow);
        let targetIndex = index;
        let targetRow = row;
        switch (direction) {
        case Meta.MotionDirection.LEFT:
            targetIndex--;
            break;
        case Meta.MotionDirection.RIGHT:
            targetIndex++;
            break;
        case Meta.MotionDirection.DOWN:
            targetRow++;
            break;
        case Meta.MotionDirection.UP:
            targetRow--;
            break;
        }
        let column = this[index];
        if (targetIndex < 0 || targetIndex >= this.length
            || targetRow < 0 || targetRow >= column.length)
            return;

        utils.swap(this[index], row, targetRow);
        utils.swap(this, index, targetIndex);
        metaWindow.clone.raise_top();

        this.layout();
        this.emit('swapped', index, targetIndex, row, targetRow);
        ensureViewport(this.selectedWindow, this, true);
    }

    switchLinear(dir) {
        let index = this.selectedIndex();
        let column = this[index];
        if (!column)
            return false;
        let row = column.indexOf(this.selectedWindow);
        if (utils.in_bounds(column, row + dir) == false) {
            index += dir;
            if (dir === 1) {
                if (index < this.length) row = 0;
            } else {
                if (index >= 0)
                    row = this[index].length - 1
            }
        } else {
            row += dir;
        }

        let metaWindow = this.getWindow(index, row);
        ensureViewport(metaWindow, this);
        return true;
    }

    switchLeft() { this.switch(Meta.MotionDirection.LEFT) }
    switchRight() { this.switch(Meta.MotionDirection.RIGHT) }
    switchUp() { this.switch(Meta.MotionDirection.UP) }
    switchDown() { this.switch(Meta.MotionDirection.DOWN) }
    switch(direction) {
        let space = this;
        let index = space.selectedIndex();
        let row = space[index].indexOf(space.selectedWindow);
        switch (direction) {
        case Meta.MotionDirection.RIGHT:
            index++;
            row = -1;
            break;;
        case Meta.MotionDirection.LEFT:
            index--;
            row = -1;
        }
        if (index < 0 || index >= space.length)
            return;

        let column = space[index];

        if (row === -1) {
            let selected =
                display.sort_windows_by_stacking(column)[column.length - 1];
            row = column.indexOf(selected);
        }

        switch (direction) {
        case Meta.MotionDirection.UP:
            row--;
            break;;
        case Meta.MotionDirection.DOWN:
            row++;
        }
        if (row < 0 || row >= column.length)
            return;

        let metaWindow = space.getWindow(index, row);
        ensureViewport(metaWindow, space);
    }

    positionOf(metaWindow) {
        metaWindow = metaWindow || this.selectedWindow;
        let index, row;
        for (let i=0; i < this.length; i++) {
            if (this[i].includes(metaWindow))
                return [i, this[i].indexOf(metaWindow)];
        }
        return false;
    }

    indexOf(metaWindow) {
        for (let i=0; i < this.length; i++) {
            if (this[i].includes(metaWindow))
                return i;
        }
        return -1;
    }

    rowOf(metaWindow) {
        let column = this[this.indexOf(metaWindow)];
        return column.indexOf(metaWindow);
    }

    moveDone() {
        if (this.cloneContainer.x !== this.targetX
            || Navigator.navigating || inPreview || noAnimate
            || Main.overview.visible) {
            return;
        }
        this.visible = [];
        this.getWindows().forEach(w => {
            if (!w.get_compositor_private())
                return;

            if (this.isPlaceable(w)) {
                this.visible.push(w);
            }

            let unMovable = w.fullscreen ||
                w.get_maximized() === Meta.MaximizeFlags.BOTH;
            if (unMovable)
                return;

            let clone = w.clone;
            let x = this.monitor.x + Math.round(clone.x) + this.targetX;
            let y = this.monitor.y + Math.round(clone.y);
            w.move_frame(true, x, y);
        });

        this.visible.forEach(w => {
            w.clone.hide();
            let actor = w.get_compositor_private();
            clipWindowActor(actor, this.monitor);
            actor.show();
        });

        this.emit('move-done');
    }

    startAnimate(grabWindow) {
        this.visible.forEach(w => {
            let actor = w.get_compositor_private();
            if (!actor)
                return;
            actor.remove_clip();
            if (w === grabWindow) {
                w.clone.hide();
                actor.show();
                return;
            }
            actor.hide();
            w.clone.show();
        });
    }

    setSettings([uuid, settings]) {
        this.signals.disconnect(this.settings);

        this.settings = settings;
        this.uuid = uuid;
        this.updateColor();
        this.updateBackground();
        this.updateName();
        this.signals.connect(this.settings, 'changed::name',
                             this.updateName.bind(this));
        this.signals.connect(this.settings, 'changed::color',
                             this.updateColor.bind(this));
        this.signals.connect(this.settings, 'changed::background',
                             this.updateBackground.bind(this));
    }

    updateColor() {
        let color = this.settings.get_string('color');
        if (color === '') {
            let colors = prefs.workspace_colors;
            let index = this.workspace.index() % prefs.workspace_colors.length;
            color = colors[index];
        }
        this.color = color;
        this.background.background.set_color(Clutter.color_from_string(color)[1]);
    }

    updateBackground() {
        let path = this.settings.get_string('background');
        let file = Gio.File.new_for_path(path);
        if (path === '' || !file.query_exists(null)) {
            file = Gio.File.new_for_uri('resource:///org/gnome/shell/theme/noise-texture.png');
        }
        const GDesktopEnums = imports.gi.GDesktopEnums;
        this.background.background.set_file(file, GDesktopEnums.BackgroundStyle.WALLPAPER);
    }

    updateName() {
        let name = this.settings.get_string('name');
        if (name === '')
            name = Meta.prefs_get_workspace_name(this.workspace.index());
        Meta.prefs_change_workspace_name(this.workspace.index(), name);
        this.label.text = name;
        this.name = name;

        if (this.workspace === workspaceManager.get_active_workspace()) {
            TopBar.setWorkspaceName(this.name);
        }
    }

    setMonitor(monitor, animate) {
        let cloneContainer = this.cloneContainer;
        let background = this.background;
        let clip = this.clip;

        this.monitor = monitor;
        this.width = monitor.width;
        this.height = monitor.height;

        let time = animate ? 0.25 : 0;

        let transition = 'easeInOutQuad';
        Tweener.addTween(this.actor,
                        {x: 0, y: 0, scale_x: 1, scale_y: 1,
                         time, transition});
        Tweener.addTween(clip,
                         {scale_x: 1, scale_y: 1, time});

        clip.set_position(monitor.x, monitor.y);
        clip.set_size(monitor.width, monitor.height);
        clip.set_clip(0, 0,
                      monitor.width,
                      monitor.height);

        this.shadow.set_size(monitor.width + 8*2 + prefs.window_gap,
                             monitor.height + 4 + prefs.window_gap);
        background.set_size(this.shadow.width, this.shadow.height);

        this.cloneClip.set_size(monitor.width, monitor.height);
        this.cloneClip.set_clip(-Math.round(prefs.window_gap/2), 0,
                                monitor.width + prefs.window_gap, this.shadow.height);

        this.emit('monitor-changed');
    }

    /**
       Add existing windows on workspace to the space. Restore the
       layout of oldSpace if present.
    */
    addAll(oldSpace) {

        // On gnome-shell-restarts the windows are moved into the viewport, but
        // they're moved minimally and the stacking is not changed, so the tiling
        // order is preserved (sans full-width windows..)
        let xz_comparator = (windows) => {
            // Seems to be the only documented way to get stacking order?
            // Could also rely on the MetaWindowActor's index in it's parent
            // children array: That seem to correspond to clutters z-index (note:
            // z_position is something else)
            let z_sorted = display.sort_windows_by_stacking(windows);
            let xkey = (mw) => {
                let frame = mw.get_frame_rect();
                if(frame.x <= 0)
                    return 0;
                if(frame.x+frame.width == this.width) {
                    return this.width;
                }
                return frame.x;
            }
            // xorder: a|b c|d
            // zorder: a d b c
            return (a,b) => {
                let ax = xkey(a);
                let bx = xkey(b);
                // Yes, this is not efficient
                let az = z_sorted.indexOf(a);
                let bz = z_sorted.indexOf(b);
                let xcmp = ax - bx;
                if (xcmp !== 0)
                    return xcmp;

                if (ax === 0) {
                    // Left side: lower stacking first
                    return az - bz;
                } else {
                    // Right side: higher stacking first
                    return bz - az;
                }
            };
        }

        if (oldSpace) {
            this.targetX = oldSpace.targetX;
            for (let i=0; i < oldSpace.length; i++) {
                let column = oldSpace[i];
                for(let j=0; j < column.length; j++) {
                    let metaWindow = column[j];
                    this.addWindow(metaWindow, i, j);
                }
            }
        }

        let workspace = this.workspace;
        let windows = workspace.list_windows()
            .sort(xz_comparator(workspace.list_windows()));

        windows.forEach((meta_window, i) => {
            if (meta_window.above || meta_window.minimized) {
                // Rough heuristic to figure out if a window should float
                Scratch.makeScratch(meta_window);
                return;
            }
            if(this.indexOf(meta_window) < 0 && add_filter(meta_window)) {
                this.addWindow(meta_window, this.length);
            }
        })

        let tabList = display.get_tab_list(Meta.TabList.NORMAL, workspace)
            .filter(metaWindow => { return this.indexOf(metaWindow) !== -1; });
        if (tabList[0]) {
            this.selectedWindow = tabList[0]
            // ensureViewport(space.selectedWindow, space);
        }

        this._populated = true;
        this.cloneContainer.x = this.targetX;
        this.getWindows().forEach(w => {
            w.get_compositor_private().hide();
            w.clone.show();
        });
        this.layout(false);
        let selected = this.selectedWindow;
        if (selected) {
            ensureViewport(selected, this, true);
        }
        oldSpaces.delete(this.workspace);
    }

    // Fix for eg. space.map, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes#Species
    static get [Symbol.species]() { return Array; }

    selectedIndex () {
        if (this.selectedWindow) {
            return this.indexOf(this.selectedWindow);
        } else {
            return -1;
        }
    }

    destroy() {
        this.background.destroy();
        this.cloneContainer.destroy();
        this.clip.destroy();
        let workspace = this.workspace;
        this.signals.destroy();
    }
}
Signals.addSignalMethods(Space.prototype);

/**
   A `Map` to store all `Spaces`'s, indexed by the corresponding workspace.

   TODO: Move initialization to enable
*/
class Spaces extends Map {
    // Fix for eg. space.map, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes#Species
    static get [Symbol.species]() { return Map; }

    constructor() {
        super();

        this.clickOverlays = [];

        let signals = new utils.Signals();
        this.signals = signals;
        this._moving = [];
        this._yPositions = [0.95, 0.10, 0.035, 0.01];


        signals.connect(workspaceManager, 'notify::n-workspaces',
                        utils.dynamic_function_ref('workspacesChanged', this).bind(this));
        signals.connect(workspaceManager, 'workspace-removed',
                        utils.dynamic_function_ref('workspaceRemoved', this));
        signals.connect(global.screen || display,
                        'window-left-monitor',
                        this.windowLeftMonitor.bind(this));
        signals.connect(global.screen || display,
                        "window-entered-monitor",
                        this.windowEnteredMonitor.bind(this));

        signals.connect(display, 'window-created',
                        this.window_created.bind(this));
        signals.connect(display, 'grab-op-begin',
                        global.screen ?
                        (display, screen, mw, type) => grabBegin(mw, type) :
                        (display, mw, type) => grabBegin(mw, type));
        signals.connect(display, 'grab-op-end',
                        global.screen ?
                        (display, screen, mw, type) => grabEnd(mw, type) :
                        (display, mw, type) => grabEnd(mw, type));

        signals.connect(Main.layoutManager, 'monitors-changed', this.monitorsChanged.bind(this));

        signals.connect(global.window_manager, 'switch-workspace',
                        this.switchWorkspace.bind(this));

        const OVERRIDE_SCHEMA = 'org.gnome.shell.overrides';
        this.overrideSettings = new Gio.Settings({ schema_id: OVERRIDE_SCHEMA });
        signals.connect(this.overrideSettings, 'changed::workspaces-only-on-primary',
                        this.monitorsChanged.bind(this));

        // Clone and hook up existing windows
        display.get_tab_list(Meta.TabList.NORMAL_ALL, null)
            .forEach(w => {
                registerWindow(w);
                signals.connect(w, 'size-changed', resizeHandler);
            });

        let spaceContainer = new Clutter.Actor({name: 'spaceContainer'});
        spaceContainer.hide();
        this.spaceContainer = spaceContainer;

        backgroundGroup.add_actor(spaceContainer);
        backgroundGroup.set_child_above_sibling(
            spaceContainer,
            backgroundGroup.last_child);

        // Hook up existing workspaces
        for (let i=0; i < workspaceManager.n_workspaces; i++) {
            let workspace = workspaceManager.get_workspace_by_index(i);
            this.addSpace(workspace);
            debug("workspace", workspace)
        }

        this.monitorsChanged();
    }

    /**
       The monitors-changed signal can trigger _many_ times when
       connection/disconnecting monitors.

       Monitors also doesn't seem to have a stable identity, which means we're
       left with heuristics.
     */
    monitorsChanged() {
        if (this.monitors)
            oldMonitors = this.monitors;

        this.monitors = new Map();
        this.get(workspaceManager.get_active_workspace()).getWindows().forEach(w => {
            w.get_compositor_private().hide();
            w.clone.show();
        });

        this.spaceContainer.set_size(global.screen_width, global.screen_height);

        for (let overlay of this.clickOverlays) {
            overlay.destroy();
        }
        this.clickOverlays = [];
        let mru = this.mru();
        let primary = Main.layoutManager.primaryMonitor;
        let monitors = Main.layoutManager.monitors;

        let finish = () => {
            let activeSpace = this.get(workspaceManager.get_active_workspace());
            let visible = monitors.map(m => this.monitors.get(m));
            let mru = this.mru();
            this.stack = mru.filter(s => !visible.includes(s));
            this.selectedSpace = mru[0];
            this.monitors.set(activeSpace.monitor, activeSpace);
            for (let [monitor, space] of this.monitors) {
                space.clip.raise_top();
            }
            this.forEach(space => {
                space.layout(false);
                let selected = space.selectedWindow;
                if (selected) {
                    ensureViewport(selected, space, true);
                }
            });
            this.spaceContainer.show();
        };

        if (this.overrideSettings.get_boolean('workspaces-only-on-primary')) {
            this.forEach(space => {
                space.setMonitor(primary, false);
            });
            this.monitors.set(primary, mru[0]);
            let overlay = new ClickOverlay(primary);
            primary.clickOverlay = overlay;
            this.clickOverlays.push(overlay);
            finish();
            return;
        }

        for (let monitor of Main.layoutManager.monitors) {
            let overlay = new ClickOverlay(monitor);
            monitor.clickOverlay = overlay;
            overlay.activate();
            this.clickOverlays.push(overlay);
        }


        // Persist as many monitors as possible
        for (let [oldMonitor, oldSpace] of oldMonitors) {
            let monitor = monitors[oldMonitor.index];
            if (monitor &&
                oldMonitor.width === monitor.width &&
                oldMonitor.height === monitor.height &&
                oldMonitor.x === monitor.x &&
                oldMonitor.y === monitor.y) {
                let space = this.get(oldSpace.workspace);
                this.monitors.set(monitor, space);
                space.setMonitor(monitor, false);
                mru = mru.filter(s => s !== space);
            }
            oldMonitors.delete(oldMonitor);
        }

        // Populate any remaining monitors
        for (let monitor of monitors) {
            if (this.monitors.get(monitor) === undefined) {
                let space = mru[0];
                this.monitors.set(monitor, space);
                space.setMonitor(monitor, false);
                mru = mru.slice(1);
            }
        }

        // Reset any removed monitors
        mru.forEach(space => {
            if (!monitors.includes(space.monitor)) {
                let monitor = monitors[space.monitor.index];
                if (!monitor)
                    monitor = primary;
                space.setMonitor(monitor, false);
            }
        });

        finish();
    }

    destroy() {
        for (let overlay of this.clickOverlays) {
            overlay.destroy();
        }
        for (let monitor of Main.layoutManager.monitors) {
            delete monitor.clickOverlay;
        }

        display.get_tab_list(Meta.TabList.NORMAL_ALL, null)
            .forEach(metaWindow => {
                let actor = metaWindow.get_compositor_private();
                actor.remove_clip();

                if (metaWindow.get_workspace() === workspaceManager.get_active_workspace()
                   && !metaWindow.minimized)
                    actor.show();
                else
                    actor.hide();
            });

        this.signals.destroy();

        // Hold onto a copy of the old monitors and spaces to support reload.
        oldMonitors = this.monitors;
        oldSpaces = new Map(spaces);
        for (let [workspace, space] of this) {
            this.removeSpace(space);
        }

        this.spaceContainer.destroy();
    }

    workspacesChanged() {
        let nWorkspaces = workspaceManager.n_workspaces;

        // Identifying destroyed workspaces is rather bothersome,
        // as it will for example report having windows,
        // but will crash when looking at the workspace index

        // Gather all indexed workspaces for easy comparison
        let workspaces = {};
        for (let i=0; i < nWorkspaces; i++) {
            let workspace = workspaceManager.get_workspace_by_index(i);
            workspaces[workspace] = true;
            if (this.spaceOf(workspace) === undefined) {
                debug('workspace added', workspace);
                this.addSpace(workspace);
            }
        }

        for (let [workspace, space] of this) {
            if (workspaces[space.workspace] !== true) {
                debug('workspace removed', space.workspace);
                this.removeSpace(space);
            }
        }
    };

    workspaceRemoved(workspaceManager, index) {
        let settings = new Gio.Settings({ schema_id:
                                          'org.gnome.desktop.wm.preferences'});
        let names = settings.get_strv('workspace-names');

        // Move removed workspace name to the end. Could've simply removed it
        // too, but this way it's not lost. In the future we want a UI to select
        // old names when selecting a new workspace.
        names = names.slice(0, index).concat(names.slice(index+1), [names[index]]);
        settings.set_strv('workspace-names', names);
    };

    switchWorkspace(wm, fromIndex, toIndex) {
        let to = workspaceManager.get_workspace_by_index(toIndex);
        let from = workspaceManager.get_workspace_by_index(fromIndex);
        let toSpace = this.spaceOf(to);

        this.stack = this.stack.filter(s => s !== toSpace);
        let monitor = toSpace.monitor;
        this.monitors.set(monitor, toSpace);

        let fromSpace = this.spaceOf(from);

        this.animateToSpace(toSpace, fromSpace);

        if (toSpace.monitor === fromSpace.monitor) {
            this.stack.splice(0, 0, fromSpace);
            return;
        }

        TopBar.setMonitor(toSpace.monitor);
        toSpace.monitor.clickOverlay.deactivate();

        let display = Gdk.Display.get_default();
        let deviceManager = display.get_device_manager();
        let pointer = deviceManager.get_client_pointer();
        let [gdkscreen, pointerX, pointerY] = pointer.get_position();

        pointerX -= monitor.x;
        pointerY -= monitor.y;
        if (pointerX < 0 ||
            pointerX > monitor.width ||
            pointerY < 0 ||
            pointerY > monitor.height)
            pointer.warp(gdkscreen,
                         monitor.x + Math.floor(monitor.width/2),
                         monitor.y + Math.floor(monitor.height/2));

        for (let monitor of Main.layoutManager.monitors) {
            if (monitor === toSpace.monitor)
                continue;
            monitor.clickOverlay.activate();
        }
    }

    _initWorkspaceStack() {
        if (inPreview)
            return;
        const scale = 0.9;
        let space = this.spaceOf(workspaceManager.get_active_workspace());
        let mru = [space, ...this.stack];

        if (Main.panel.statusArea.appMenu)
            Main.panel.statusArea.appMenu.container.hide();
        let monitor = space.monitor;
        this.selectedSpace = space;
        inPreview = true;

        let heights = [0].concat(this._yPositions.slice(2));

        let cloneParent = space.clip.get_parent();
        mru.forEach((space, i) => {
            TopBar.updateIndicatorPosition(space.workspace);
            space.clip.set_position(monitor.x, monitor.y);
            space.startAnimate();

            let scaleX = monitor.width/space.width;
            let scaleY = monitor.height/space.height;
            space.clip.set_scale(scaleX, scaleY);

            let h = heights[i];
            if (h === undefined)
                h = heights[heights.length-1];
            space.actor.set_position(0, space.height*h);

            space.actor.scale_y = scale - i*0.01;
            space.actor.scale_x = scale - i*0.01;
            if (mru[i - 1] === undefined)
                return;
            cloneParent.set_child_below_sibling(
                space.clip,
                mru[i - 1].clip
            );
            Tweener.removeTweens(space.actor);
            space.actor.show();

            let selected = space.selectedWindow;
            if (selected && selected.fullscreen) {
                selected.clone.y = Main.panel.actor.height + prefs.vertical_margin;
            }
        });

        space.actor.scale_y = 1;
        space.actor.scale_x = 1;

        let selected = space.selectedWindow;
        if (selected && selected.fullscreen) {
            Tweener.addTween(selected.clone, {
                y: Main.panel.actor.height + prefs.vertical_margin,
                time: 0.25
            });
        }
    }

    selectSpace(direction, move, transition) {
        transition = transition || 'easeInOutQuad';
        const scale = 0.9;
        let space = this.spaceOf(workspaceManager.get_active_workspace());
        let mru = [space, ...this.stack];

        if (!inPreview) {
            this._initWorkspaceStack();
        }

        let from = mru.indexOf(this.selectedSpace);
        let newSpace = this.selectedSpace;
        let to = from;
        if (move && this.selectedSpace.selectedWindow) {
            let space = this.selectedSpace;
            let moving = this.selectedSpace.selectedWindow;
            this._moving.push(moving);

            this.selectedSpace.removeWindow(moving);
            let actor = moving.get_compositor_private();
            Main.uiGroup.add_actor(moving.clone);
            let point = space.cloneContainer.apply_relative_transform_to_point(
                this.spaceContainer, new Clutter.Vertex({x: moving.clone.x,
                                          y: moving.clone.y}));
            moving.clone.set_position(point.x, point.y);
            moving.move_frame(true, point.x, point.y);
            moving.clone.show();
            actor.hide();
            Tweener.addTween(moving.clone,
                             {y: Math.round(space.monitor.y
                                            + space.monitor.height/2),
                              time: 0.25,
                              transition
                             });
        } else {
            if (direction === Meta.MotionDirection.DOWN)
                to = from + 1;
            else
                to = from - 1;
            if (to < 0 || to >= mru.length) {
                to = from;
            }
            if (to === from && Tweener.getTweenCount(newSpace.actor) > 0)
                return;

            newSpace = mru[to];
            this.selectedSpace = newSpace;
        }


        TopBar.updateWorkspaceIndicator(newSpace.workspace.index());

        let heights = this._yPositions;

        mru.forEach((space, i) => {
            let actor = space.actor;
            let h;
            if (to === i)
                h = heights[1];
            else if (to + 1 === i)
                h = heights[2];
            else if (to - 1 === i)
                h = heights[0];
            else if (i > to)
                h = heights[3];
            else if (i < to)
                h = 1;

            Tweener.addTween(actor,
                             {y: h*space.height,
                              time: 0.25,
                              scale_x: scale + (to - i)*0.01,
                              scale_y: scale + (to - i)*0.01,
                              transition
                             });

        });
    }

    animateToSpace(to, from, callback) {
        inPreview = false;
        TopBar.updateWorkspaceIndicator(to.workspace.index());

        this._moving.forEach(w => {
            w.change_workspace(to.workspace);
            if (w.get_workspace() === to.workspace) {
                insertWindow(w, {existing: true});
            }
        });
        this._moving = [];

        let xDest = 0, yDest = global.screen_height;

        this.selectedSpace = to;

        to.actor.show();
        let selected = to.selectedWindow;
        if (selected)
            ensureViewport(selected, to, true);

        if (from) {
            from.startAnimate();
        }

        Tweener.addTween(to.actor,
                         { x: 0,
                           y: 0,
                           scale_x: 1,
                           scale_y: 1,
                           time: 0.25,
                           transition: 'easeInOutQuad',
                           onComplete: () => {
                               // Meta.enable_unredirect_for_screen(screen);

                               to.clip.raise_top();
                               callback && callback();
                           }
                         });

        let next = to.clip.get_next_sibling();

        let visible = new Map();
        for (let [monitor, space] of this.monitors) {
            visible.set(space, true);
        }
        let scale = 0.9;
        while (next !== null) {
            if (!visible.get(next.space))
                Tweener.addTween(
                    next.first_child,
                    { x: xDest,
                      y: yDest,
                      scale_x: scale,
                      scale_y: scale,
                      time: 0.25,
                      transition: 'easeInOutQuad',
                      onComplete() {
                          this.set_position(0, global.screen_height*0.1);
                          this.hide();
                      },
                      onCompleteScope: next.first_child
                    });

            next = next.get_next_sibling();
        }
    }

    addSpace(workspace) {
        this.set(workspace, new Space(workspace, this.spaceContainer));
    };

    removeSpace(space) {
        this.delete(space.workspace);
        space.destroy();
    };

    spaceOfWindow(meta_window) {
        return this.get(meta_window.get_workspace());
    };

    spaceOf(workspace) {
        return this.get(workspace);
    };

    /**
       Return an array of Space's ordered in most recently used order.
     */
    mru() {
        let seen = new Map(), out = [];
        let active = workspaceManager.get_active_workspace();
        out.push(this.get(active));
        seen.set(active, true);

        display.get_tab_list(Meta.TabList.NORMAL_ALL, null)
            .forEach((metaWindow, i) => {
                let workspace = metaWindow.get_workspace();
                if (!seen.get(workspace)) {
                    out.push(this.get(workspace));
                    seen.set(workspace, true);
                }
            });

        let workspaces = workspaceManager.get_n_workspaces();
        for (let i=0; i < workspaces; i++) {
            let workspace = workspaceManager.get_workspace_by_index(i);
            if (!seen.get(workspace)) {
                out.push(this.get(workspace));
                seen.set(workspace, true);
           }
        }

        return out;
    }

    window_created(display, metaWindow, user_data) {
        registerWindow(metaWindow);

        debug('window-created', metaWindow.title);
        let actor = metaWindow.get_compositor_private();
        if (metaWindow.get_workspace() !== this.selectedSpace.workspace) {
            metaWindow.redirected = true;
            metaWindow.change_workspace(this.selectedSpace.workspace);
            return;
        }
        let signal = actor.connect(
            'show',
            () =>  {
                actor.disconnect(signal);
                insertWindow(metaWindow, {});
            });
    };

    windowLeftMonitor(screen, index, metaWindow) {
        debug('window-left-monitor', index, metaWindow.title);
    }

    windowEnteredMonitor(screen, index, metaWindow) {
        debug('window-entered-monitor', index, metaWindow.title);
        if (!metaWindow.get_compositor_private()
            || Scratch.isScratchWindow(metaWindow)
            || metaWindow.is_on_all_workspaces()
            || !metaWindow.clone
            || metaWindow.clone.visible)
            return;

        let monitor = Main.layoutManager.monitors[index];
        let space = this.monitors.get(monitor);
        if (space.monitor !== monitor)
            return;
        let focus = metaWindow.has_focus();

        metaWindow.change_workspace(space.workspace);

        // This doesn't play nice with the clickoverlay, disable for now
        if (focus)
            Main.activateWindow(metaWindow);
    }
}
Signals.addSignalMethods(Spaces.prototype);

function registerWindow(metaWindow) {
    let actor = metaWindow.get_compositor_private();
    let clone = new Clutter.Clone({source: actor});
    let container = new Clutter.Actor({
        layout_manager: new WindowCloneLayout()
    });
    container.add_actor(clone);
    clone.meta_window = metaWindow;

    metaWindow.clone = container;

    signals.connect(metaWindow, "focus", focus_wrapper);
    signals.connect(metaWindow, 'notify::minimized', minimizeWrapper);
    signals.connect(metaWindow, 'notify::fullscreen', fullscreenWrapper);
    signals.connect(actor, 'show', showWrapper);

    signals.connect(actor, 'destroy', destroyHandler);
}

function destroyHandler(actor) {
    signals.disconnect(actor);
}

function resizeHandler(metaWindow) {
    let space = spaces.spaceOfWindow(metaWindow);
    if (space.indexOf(metaWindow) === -1)
        return;

    let selected = metaWindow === space.selectedWindow;

    if (noAnimate) {
        space.layout(false);
        if (selected) {
            let frame = metaWindow.get_frame_rect();
            space.selection.width = frame.width + prefs.window_gap;
        }
    } else {
        // Restore window position when eg. exiting fullscreen
        !Navigator.navigating && selected
            && move_to(space, metaWindow, {x: metaWindow.get_frame_rect().x});

        space.layout(true);
        ensureViewport(space.selectedWindow, space, true);
    }
}

function enable() {
    debug('#enable');
    spaces = new Spaces();

    // HACK: couldn't find an other way within a reasonable time budget
    // This state is different from being enabled after startup. Existing
    // windows are not accessible yet for instance.
    let isDuringGnomeShellStartup = Main.actionMode === Shell.ActionMode.NONE;

    function initWorkspaces() {
        spaces.forEach(space => {
            space.addAll(oldSpaces.get(space.workspace));
        });

        spaces.mru().reverse().forEach(s => {
            s.selectedWindow && ensureViewport(s.selectedWindow, s, true);
            s.monitor.clickOverlay.show();
        });

        if (!Scratch.isScratchActive()) {
            Scratch.getScratchWindows().forEach(
                w => w.get_compositor_private().hide());
        }
    }

    if (isDuringGnomeShellStartup) {
        // Defer workspace initialization until existing windows are accessible.
        // Otherwise we're unable to restore the tiling-order. (when restarting
        // gnome-shell)
        Main.layoutManager.connect('startup-complete', function() {
            isDuringGnomeShellStartup = false;
            initWorkspaces();
        });
    } else {
        initWorkspaces();
    }
}

function disable () {
    signals.destroy();
    spaces.destroy();

    oldSpaces.forEach(space => {
        let windows = space.getWindows();
        let selected = windows.indexOf(space.selectedWindow);
        if (selected === -1)
            return;
        // Stack windows correctly for controlled restarts
        for (let i=selected; i<windows.length; i++) {
            windows[i].lower();
        }
        for (let i=selected; i>=0; i--) {
            windows[i].lower();
        }
    });
}

/**
   Types of windows which never should be tiled.
 */
function add_filter(meta_window) {
    if (meta_window.get_transient_for()) {
        // Never add transient windows
        return false;
    }
    if (meta_window.window_type !== Meta.WindowType.NORMAL) {
        // And only add Normal windows
        return false;
    }

    if (meta_window.is_on_all_workspaces()) {
        return false;
    }
    if (Scratch.isScratchWindow(meta_window)) {
        return false;
    }

    return true;
}


/**
   Handle windows leaving workspaces.
 */
function remove_handler(workspace, meta_window) {
    debug("window-removed", meta_window, meta_window.title, workspace.index());
    // Note: If `meta_window` was closed and had focus at the time, the next
    // window has already received the `focus` signal at this point.
    // Not sure if we can check directly if _this_ window had focus when closed.

    if (!meta_window.get_compositor_private())
        signals.disconnect(meta_window);

    let space = spaces.spaceOf(workspace);
    space.removeWindow(meta_window);
}


/**
   Handle windows entering workspaces.
*/
function add_handler(ws, metaWindow) {
    debug("window-added", metaWindow, metaWindow.title, metaWindow.window_type, ws.index());

    let actor = metaWindow.get_compositor_private();
    if (actor) {
        // Set position and hookup signals, with `existing` set to true
        insertWindow(metaWindow, {existing: true && !metaWindow.redirected});
        delete metaWindow.redirected;
    }
    // Otherwise we're dealing with a new window, so we let `window-created`
    // handle initial positioning.
}

/**
   Insert the window into its space if appropriate. Requires MetaWindowActor

   This gets called from `Workspace::window-added` if the window already exists,
   and `Display::window-created` through `WindowActor::show` if window is newly
   created to ensure that the WindowActor exists.
*/
function insertWindow(metaWindow, {existing}) {

    let connectSizeChanged = () => {
        !existing && signals.connect(metaWindow, 'size-changed', resizeHandler);
    };

    if (!existing) {
        let scratchIsFocused = Scratch.isScratchWindow(display.focus_window);
        let addToScratch = scratchIsFocused;

        let winprop = find_winprop(metaWindow);
        if (winprop) {
            if (winprop.oneshot) {
                winprops.splice(winprops.indexOf(winprop), 1);
            }
            if (winprop.scratch_layer) {
                debug("#winprops", `Move ${metaWindow.title} to scratch`);
                addToScratch = true;
            }
        }

        if (addToScratch) {
            connectSizeChanged();
            Scratch.makeScratch(metaWindow);
            if (scratchIsFocused) {
                Main.activateWindow(metaWindow);
            }
            return;
        }
    }

    if (!add_filter(metaWindow)) {
        connectSizeChanged();
        return;
    }

    let space = spaces.spaceOfWindow(metaWindow);
    let monitor = space.monitor;

    let index = -1; // (-1 -> at beginning)
    if (space.selectedWindow) {
        index = space.indexOf(space.selectedWindow);
    }
    index++;

    if (!space.addWindow(metaWindow, index))
        return;

    metaWindow.unmake_above();
    if (metaWindow.get_maximized() == Meta.MaximizeFlags.BOTH) {
        metaWindow.unmaximize(Meta.MaximizeFlags.BOTH);
        toggleMaximizeHorizontally(metaWindow);
    }

    let buffer = metaWindow.get_buffer_rect();
    let frame = metaWindow.get_frame_rect();
    let x_offset = frame.x - buffer.x;
    let y_offset = frame.y - buffer.y;
    let clone = metaWindow.clone;

    let actor = metaWindow.get_compositor_private();
    actor.hide();
    if (!existing) {
        clone.set_position(clone.targetX,
                           panelBox.height + prefs.vertical_margin);
        clone.set_scale(0, 0);
        Tweener.addTween(clone, {
            scale_x: 1,
            scale_y: 1,
            time: 0.25,
            transition: 'easeInOutQuad',
            onComplete: () => {
                space.layout();
                connectSizeChanged();
            }
        });
        space.selection.set_scale(0, 0);
        Tweener.addTween(space.selection, {
            scale_x: 1, scale_y: 1, time: 0.25, transition: 'easeInOutQuad'
        });
    } else {
        clone.set_position(
            frame.x - monitor.x - space.cloneContainer.x,
            frame.y - monitor.y + space.cloneContainer.y);
        clone.show();
    }

    if (metaWindow === display.focus_window ||
        space.workspace === workspaceManager.get_active_workspace()) {
        ensureViewport(metaWindow, space, true);
        Main.activateWindow(metaWindow);
    } else {
        ensureViewport(metaWindow, space, true);
    }
}

function animateDown(metaWindow) {

    let frame = metaWindow.get_frame_rect();
    let buffer = metaWindow.get_buffer_rect();
    let clone = metaWindow.clone;
    Tweener.addTween(metaWindow.clone, {
        y: panelBox.height + prefs.vertical_margin,
        time: 0.25,
        transition: 'easeInOutQuad'
    });
}

/**
   Make sure that `meta_window` is in view, scrolling the space if needed.
 */
function ensureViewport(meta_window, space, force) {
    space = space || spaces.spaceOfWindow(meta_window);
    if (space.moving == meta_window && !force) {
        debug('already moving', meta_window.title);
        return undefined;
    }

    let index = space.indexOf(meta_window);
    if (index === -1 || space.length === 0)
        return undefined;

    debug('Moving', meta_window.title);

    if (space.selectedWindow.fullscreen ||
        space.selectedWindow.get_maximized() === Meta.MaximizeFlags.BOTH) {
        animateDown(space.selectedWindow);
    }

    if (space.selectedWindow !== meta_window) {
        updateSelection(space, meta_window, true);
    }

    space.selectedWindow = meta_window;

    let monitor = space.monitor;
    let frame = meta_window.get_frame_rect();
    let buffer = meta_window.get_buffer_rect();
    let clone = meta_window.clone;

    let x = Math.round(clone.targetX) + space.targetX;
    let y = panelBox.height + prefs.vertical_margin;
    let gap = prefs.window_gap;
    if (index == 0 && x <= 0) {
        // Always align the first window to the display's left edge
        x = 0;
    } else if (index == space.length-1 && x + frame.width >= space.width) {
        // Always align the first window to the display's right edge
        x = space.width - frame.width;
    } else if (frame.width > space.width*0.9 - 2*(prefs.horizontal_margin + prefs.window_gap)) {
        // Consider the window to be wide and center it
        x = Math.round((space.width - frame.width)/2);

    } else if (x + frame.width > space.width) {
        // Align to the right prefs.horizontal_margin
        x = space.width - prefs.horizontal_margin - frame.width;
    } else if (x < 0) {
        // Align to the left prefs.horizontal_margin
        x = prefs.horizontal_margin;
    } else if (x + frame.width === space.width) {
        // When opening new windows at the end, in the background, we want to
        // show some minimup margin
        x = space.width - minimumMargin - frame.width;
    } else if (x === 0) {
        // Same for the start (though the case isn't as common)
        x = minimumMargin;
    }


    let selected = space.selectedWindow;
    if (!inPreview && (selected.fullscreen
        || selected.get_maximized() === Meta.MaximizeFlags.BOTH)) {
        Tweener.addTween(selected.clone,
                         { y: frame.y - monitor.y,
                           time: 0.25,
                           transition: 'easeInOutQuad',
                         });
    }
    move_to(space, meta_window, {
        x, y, force
    });

    updateSelection(space);
    selected.raise();
    space.emit('select');
}

function updateSelection(space, metaWindow, noAnimate){
    metaWindow = metaWindow || space.selectedWindow;
    if (!metaWindow)
        return;

    let clone = metaWindow.clone;
    const frame = metaWindow.get_frame_rect();
    const buffer = metaWindow.get_buffer_rect();
    let protrusion = Math.round(prefs.window_gap/2);
    Tweener.addTween(space.selection,
                     {x: clone.targetX - protrusion,
                      y: clone.targetY - protrusion,
                      width: frame.width + prefs.window_gap,
                      height: frame.height + prefs.window_gap,
                      time: noAnimate ? 0 : 0.25,
                      transition: 'easeInOutQuad'});
}


/**
 * Move the column containing @meta_window to x, y and propagate the change
 * in @space. Coordinates are relative to monitor and y is optional.
 */
function move_to(space, metaWindow, { x, y, delay, transition,
                                       onComplete, onStart, gap, force }) {
    let index = space.indexOf(metaWindow);
    if (index === -1)
        return;

    let clone = metaWindow.clone;
    let delta = Math.round(clone.targetX) + space.targetX - x;
    let target = space.targetX - delta;
    if (!inPreview && delta === 0 && !force) {
        space.moveDone();
        return;
    }

    space.targetX = target;
    space.startAnimate();
    space.moving = metaWindow;
    Tweener.addTween(space.cloneContainer,
                     { x: target,
                       time: 0.25,
                       transition: 'easeInOutQuad',
                       onComplete: () => {
                           space.moving = false;
                           space.moveDone();
                       }
                     });

    // Set up the edge overlays so they're available immediately
    space.monitor.clickOverlay.reset();
    for (let overlay = space.monitor.clickOverlay.right,
             n=index+1 ; n < space.length; n++) {
        let metaWindow = space[n][0];
        let clone = metaWindow.clone;
        let x = clone.targetX + target;
        if (!overlay.target && x + clone.width > space.width) {
            overlay.setTarget(space, n);
            break;
        }
    }

    for (let overlay = space.monitor.clickOverlay.left,
             n=index-1; n >= 0; n--) {
        let metaWindow = space[n][0];
        let clone = metaWindow.clone;
        let x = clone.targetX + target;
        if (!overlay.target && x < 0) {
            overlay.setTarget(space, n);
            break;
        }
    }
}

var noAnimate = false;
var grabSignals = new utils.Signals();

function grabBegin(metaWindow, type) {
    // Don't handle pushModal grabs
    if (type === Meta.GrabOp.COMPOSITOR)
        return;
    let space = spaces.spaceOfWindow(metaWindow);
    if (space.indexOf(metaWindow) === -1)
        return;
    space.startAnimate(metaWindow);
    let frame = metaWindow.get_frame_rect();
    let anchor = metaWindow.clone.targetX + space.monitor.x;
    let handler = getGrab(space, anchor);
    grabSignals.connect(metaWindow, 'position-changed', handler);
    Tweener.removeTweens(space.cloneContainer);
    // Turn size/position animation off when grabbing a window with the mouse
    noAnimate = true;
}

function grabEnd(metaWindow, type) {
    if (type === Meta.GrabOp.COMPOSITOR)
        return;
    let space = spaces.spaceOfWindow(metaWindow);
    let frame = metaWindow.get_frame_rect();
    if (space.indexOf(metaWindow) === -1)
        return;
    grabSignals.destroy();
    noAnimate = false;
    let buffer = metaWindow.get_buffer_rect();
    let clone = metaWindow.clone;
    space.targetX = space.cloneContainer.x;
    clone.set_position(frame.x - space.monitor.x - space.targetX,
                       frame.y - space.monitor.y);
    space.layout();
    ensureViewport(metaWindow, space, true);
}
function getGrab(space, anchor) {
    let gap = Math.round(prefs.window_gap/2);
    return (metaWindow) => {
        let frame = metaWindow.get_frame_rect();
        space.cloneContainer.x = frame.x - anchor;
        space.selection.y = frame.y - space.monitor.y - gap;
    };
}

// `MetaWindow::focus` handling
function focus_handler(meta_window, user_data) {
    debug("focus:", meta_window.title, utils.framestr(meta_window.get_frame_rect()));

    if (meta_window.fullscreen) {
        TopBar.hide();
    } else {
        TopBar.show();
    }

    if (Scratch.isScratchWindow(meta_window)) {
        Scratch.makeScratch(meta_window);
        return;
    }

    // If meta_window is a transient window ensure the parent window instead
    let transientFor = meta_window.get_transient_for();
    if (transientFor !== null) {
        meta_window = transientFor;
    }

    let space = spaces.spaceOfWindow(meta_window);
    space.monitor.clickOverlay.show();
    ensureViewport(meta_window, space);
    fixStack(space, meta_window);
}
var focus_wrapper = utils.dynamic_function_ref('focus_handler', Me);

/**
   Push all minimized windows to the scratch layer
 */
function minimizeHandler(metaWindow) {
    debug('minimized', metaWindow.title);
    if (metaWindow.minimized) {
        Scratch.makeScratch(metaWindow);
    }
}
var minimizeWrapper = utils.dynamic_function_ref('minimizeHandler', Me);

function fullscreenHandler(metaWindow) {
    let space = spaces.spaceOfWindow(metaWindow);
    if (space.selectedWindow !== metaWindow)
        return;

    if (metaWindow.fullscreen) {
        TopBar.hide();
    } else {
        TopBar.show();
    }
}
var fullscreenWrapper = utils.dynamic_function_ref('fullscreenHandler', Me);

/**
  `WindowActor::show` handling

  Kill any falsely shown WindowActor.
*/
function showHandler(actor) {
    let metaWindow = actor.meta_window;
    let onActive = metaWindow.get_workspace() === workspaceManager.get_active_workspace();

    if (Scratch.isScratchWindow(metaWindow))
        return;

    if (metaWindow.clone.visible || ! onActive || Navigator.navigating
       || inPreview) {
        actor.hide();
        metaWindow.clone.show();
    }
}
var showWrapper = utils.dynamic_function_ref('showHandler', Me);

/**
  We need to stack windows in mru order, since mutter picks from the
  stack, not the mru, when auto choosing focus after closing a window.
 */
function fixStack(space, metaWindow) {
    let windows = space.getWindows();
    let around = windows.indexOf(metaWindow);
    if (around === -1)
        return;

    let neighbours = [windows[around - 1], windows[around + 1]].filter(w => w);
    let stack = display.sort_windows_by_stacking(neighbours);

    stack.forEach(w => w.raise());
    metaWindow.raise();
}

/**
  Modelled after notion/ion3's system

  Examples:

    defwinprop({
        wm_class: "Riot",
        scratch_layer: true
    })
*/
var winprops = [];

function winprop_match_p(meta_window, prop) {
    let wm_class = meta_window.wm_class || "";
    let title = meta_window.title;
    if (prop.wm_class !== wm_class) {
        return false;
    }
    if (prop.title) {
        if (prop.title.constructor === RegExp) {
            if (!title.match(prop.title))
                return false;
        } else {
            if (prop.title !== title)
                return false;
        }
    }

    return true;
}

function find_winprop(meta_window)  {
    let props = winprops.filter(
        winprop_match_p.bind(null, meta_window));

    return props[0];
}

function defwinprop(spec) {
    winprops.push(spec);
}

/* simple utils */

function isStacked(metaWindow) {
    return metaWindow._isStacked;
}

function isUnStacked(metaWindow) {
    return !isStacked(metaWindow);
}

function isFullyVisible(metaWindow) {
    let frame = metaWindow.get_frame_rect();
    let space = spaces.spaceOfWindow(metaWindow);
    return frame.x >= 0 && (frame.x + frame.width) <= space.width;
}

function toggleMaximizeHorizontally(metaWindow) {
    metaWindow = metaWindow || display.focus_window;
    let monitor = Main.layoutManager.monitors[metaWindow.get_monitor()];

    // TODO: make some sort of animation
    // Note: should investigate best-practice for attaching extension-data to meta_windows
    if(metaWindow.unmaximizedRect) {
        let unmaximizedRect = metaWindow.unmaximizedRect;
        metaWindow.move_resize_frame(
            true, unmaximizedRect.x, unmaximizedRect.y,
            unmaximizedRect.width, unmaximizedRect.height);
        metaWindow.unmaximizedRect = undefined;
    } else {
        let frame = metaWindow.get_frame_rect();
        metaWindow.unmaximizedRect = frame;
        metaWindow.move_resize_frame(true, minimumMargin, frame.y, monitor.width - minimumMargin*2, frame.height);
    }
}

function tileVisible(metaWindow) {
    metaWindow = metaWindow || display.focus_window;
    let space = spaces.spaceOfWindow(metaWindow);
    if (!space)
        return;

    let active = space.filter(isUnStacked);
    let requiredWidth =
        utils.sum(active.map(mw => mw.get_frame_rect().width))
        + (active.length-1)*prefs.window_gap + minimumMargin*2;
    let deficit = requiredWidth - primary.width;
    if (deficit > 0) {
        let perWindowReduction = Math.ceil(deficit/active.length);
        active.forEach(mw => {
            let frame = mw.get_frame_rect();
            mw.move_resize_frame(true, frame.x, frame.y, frame.width - perWindowReduction, frame.height);
        });

    }
    move_to(space, active[0], { x: minimumMargin, y: active[0].get_frame_rect().y });
}

function cycleWindowWidth(metaWindow) {
    const gr = 1/1.618;
    const ratios = [(1-gr), 1/2, gr];

    function findNext(tr) {
        // Find the first ratio that is significantly bigger than 'tr'
        for (let i = 0; i < ratios.length; i++) {
            let r = ratios[i]
            if (tr <= r) {
                if (tr/r > 0.9) {
                    return (i+1) % ratios.length;
                } else {
                    return i;
                }
            }
        }
        return 0; // cycle
    }
    let frame = metaWindow.get_frame_rect();
    let monitor = Main.layoutManager.monitors[metaWindow.get_monitor()];
    let availableWidth = monitor.width - minimumMargin*2;
    let r = frame.width / availableWidth;
    let nextW = Math.floor(ratios[findNext(r)]*availableWidth);
    let nextX = frame.x;

    if (nextX+nextW > monitor.x+monitor.width - minimumMargin) {
        // Move the window so it remains fully visible
        nextX = monitor.x+monitor.width - minimumMargin - nextW;
    }

    // WEAKNESS: When the navigator is open the window is not moved until the navigator is closed
    metaWindow.move_resize_frame(true, nextX, frame.y, nextW, frame.height);

    delete metaWindow.unmaximized_rect;
}

function activateNthWindow(n, space) {
    space = space || spaces.spaceOf(workspaceManager.get_active_workspace());
    let nth = space[n][0];
    ensureViewport(nth, space);
}

function activateFirstWindow(mw, space) {
    space = space || spaces.spaceOf(workspaceManager.get_active_workspace());
    activateNthWindow(0, space);
}

function activateLastWindow(mw, space) {
    space = space || spaces.spaceOf(workspaceManager.get_active_workspace());
    activateNthWindow(space.length - 1, space);
}

function centerWindowHorizontally(metaWindow) {
    const frame = metaWindow.get_frame_rect();
    const space = spaces.spaceOfWindow(metaWindow);
    const monitor = space.monitor;
    const targetX = Math.round(monitor.width/2 - frame.width/2);
    const dx = targetX - (metaWindow.clone.targetX + space.targetX);

    let [pointerX, pointerY] = utils.getPointerPosition();
    let relPointerX = pointerX - monitor.x - space.cloneContainer.x;
    let relPointerY = pointerY - monitor.y - space.cloneContainer.y;
    if (utils.isPointInsideActor(metaWindow.clone, relPointerX, relPointerY)) {
        utils.warpPointer(pointerX + dx, pointerY)
    }
    if (space.indexOf(metaWindow) === -1) {
        metaWindow.move_frame(true, targetX + monitor.x, frame.y);
    } else {
        move_to(space, metaWindow, { x: targetX,
                                     onComplete: () => space.moveDone()});
        updateSelection(space);
    }
}

function slurp(metaWindow) {
    let space = spaces.spaceOfWindow(metaWindow);
    let index = space.indexOf(metaWindow);
    let rightNeigbour = index < space.length ? space[index+1][0] : null;
    if(!rightNeigbour)
        return;
    space.removeWindow(rightNeigbour);
    let column = space[index];
    space.addWindow(rightNeigbour, index, column.length);
    ensureViewport(space.selectedWindow, space, true);
}

function barf(metaWindow) {
    let space = spaces.spaceOfWindow(metaWindow);
    let index = space.indexOf(metaWindow);
    if (index === -1)
        return;

    let column = space[index];
    if (column.length < 2)
        return;

    let bottom = column[column.length - 1];
    space.removeWindow(bottom);
    space.addWindow(bottom, index + 1);
    ensureViewport(space.selectedWindow, space, true);
}

function clipWindowActor(actor, monitor) {
    const x = Math.max(0, monitor.x - actor.x);
    const y = Math.max(0, monitor.y - actor.y);

    const w = actor.width - x
          - Math.max(0, (actor.x + actor.width) - (monitor.x + monitor.width));
    const h = actor.height - y
          - Math.max(0, (actor.y + actor.height) - (monitor.y + monitor.height));

    actor.set_clip(x, y, w, h);
}


function selectPreviousSpace(mw, space) {
    spaces.selectSpace(Meta.MotionDirection.DOWN);
}

function selectPreviousSpaceBackwards(mw, space) {
    spaces.selectSpace(Meta.MotionDirection.UP);
}

function movePreviousSpace(mw, space) {
    spaces.selectSpace(Meta.MotionDirection.DOWN, true);
}

function movePreviousSpaceBackwards(mw, space) {
    spaces.selectSpace(Meta.MotionDirection.UP, true);
}