extension.js

const Main = imports.ui.main;
const PanelMenu = imports.ui.panelMenu;
const St = imports.gi.St;
const Clutter = imports.gi.Clutter;
const Meta = imports.gi.Meta;
const GObject = imports.gi.GObject;
const Config = imports.misc.config;
const Version = parseInt(Config.PACKAGE_VERSION.split('.')[0]);

const ShowAppsButton = Version == 3 ? Main.overview.viewSelector._showAppsButton : Main.overview.dash.showAppsButton;
const MainOverview = Version == 3 ? Main.overview.viewSelector : Main.overview.dash;
const OverviewShowApps = Version == 3 ? Main.overview.viewSelector : Main.overview;

const DirBack = Version == 3 ? Meta.MotionDirection.UP : Meta.MotionDirection.LEFT;
const DirForward = Version == 3 ? Meta.MotionDirection.DOWN : Meta.MotionDirection.RIGHT;

let activities;
let buttonWorkspace;
let buttonApps;

const AppsIcon = GObject.registerClass(
    class AppsIcon extends PanelMenu.Button {

    _init()
    {

        super._init()
        
        this.wm = global.workspace_manager;
        this.box = new St.BoxLayout({style_class: 'activity-box'});

        this.appButton = new St.Button();
        this.appButton.child = new St.Icon({icon_name: 'view-app-grid-symbolic', style_class: 'system-status-icon activity-icon'});
        this.appButton.connect('clicked', () => this._changePage(true));
        this.appButton.connect('scroll-event', (self, event) => this._scrollWindows(self, event));
        this.box.add_child(this.appButton);

        this.add_child(this.box);

    }

    destroy()
    {
        this.parent();
    }

    _changePage(appsButtonChecked)
    {
        // selecting the same view again will hide the overview
        if (Main.overview.visible && appsButtonChecked == ShowAppsButton.checked)
        {
            Main.overview.hide();
            return;
        }

        ShowAppsButton.checked = appsButtonChecked;

        if (!Main.overview.visible)
        {
            if (appsButtonChecked)
                OverviewShowApps.showApps();
            else
                Main.overview.show();
        }
        else
        {
            ShowAppsButton.checked = appsButtonChecked;
            MainOverview._onShowAppsButtonToggled();
        }
    }

    _scrollWindows(actor, event)
    {
        let workspace = this.wm.get_active_workspace();
        let windows = global.display.get_tab_list(Meta.TabList.NORMAL_ALL, workspace);
        if (windows.length < 2)
            return;

        switch (event.get_scroll_direction())
        {
          case Clutter.ScrollDirection.UP:
            windows[windows.length - 1].activate(global.get_current_time());
            break;
          case Clutter.ScrollDirection.DOWN:
            windows[windows.length - windows.length > 2 ? 2 : 1].activate(global.get_current_time());
            //windows[0].lower(); // the windows loses focus using this method
            break;
        }

        return Clutter.EVENT_STOP;
    }

});

const WorkspaceIcon = GObject.registerClass(
    class WorkspaceIcon extends PanelMenu.Button {

    _init()
    {
        super._init();

        this.wm = global.workspace_manager;

        this.box = new St.BoxLayout({style_class: 'activity-box'});

        this.overButton = new St.Button();
        this.overButton.child = new St.Icon({icon_name: 'focus-windows-symbolic', style_class: 'system-status-icon activity-icon-ws'});
        this.overButton.connect('clicked', () => this._changePage(false));
        this.overButton.connect('scroll-event', (self, event) => this._scrollWorkspace(self, event));
        this.box.add_child(this.overButton);

        this.add_child(this.box);
    }

    destroy()
    {
        this.parent();
    }

    _changePage(appsButtonChecked)
    {
        // selecting the same view again will hide the overview
        if (Main.overview.visible && appsButtonChecked == ShowAppsButton.checked)
        {
            Main.overview.hide();
            return;
        }

        ShowAppsButton.checked = appsButtonChecked;

        if (!Main.overview.visible)
        {
            if (appsButtonChecked)
                OverviewShowApps.showApps();
            else
                Main.overview.show();
        }
        else
        {
            ShowAppsButton.checked = appsButtonChecked;
            MainOverview._onShowAppsButtonToggled();
        }
    }

    _scrollWorkspace(self, event)
    {
        let workspace = this.wm.get_active_workspace();

        switch (event.get_scroll_direction())
        {
          case Clutter.ScrollDirection.UP:
            if (workspace.index() == 0)
                return;
            else
                workspace.get_neighbor(DirBack).activate(global.get_current_time());
            break;
          case Clutter.ScrollDirection.DOWN:
            if (workspace.index() + 1 == this.wm.n_workspaces)
                return;
            else
                workspace.get_neighbor(DirForward).activate(global.get_current_time());
            break;
        }

        return Clutter.EVENT_STOP;
    }
});

function init()
{
    activities = Main.panel.statusArea['activities'];
}

function enable()
{
    buttonWorkspace = new WorkspaceIcon();
    buttonApps = new AppsIcon();

    activities.container.hide();
    Main.panel.addToStatusArea('WorskpaceIcon', buttonWorkspace, 1, 'left');
    Main.panel.addToStatusArea('AppsIcon', buttonApps, 0, 'left');
}

function disable()
{
    buttonWorkspace.destroy();
    buttonApps.destroy();
    activities.container.show();
}