The Panel (Linux in a Nutshell, 4th Edition)

17.2. The Panel

The GNOME panel can contain several different types of objects. The most obvious are the buttons for the menu and application launchers. You also can use a button to open a drawer, which is a subpanel containing additional launchers. There are a few special types of buttons used for logging out of the session and locking the screen. Finally, small programs called applets can be run on the panel. The Workspace Switcher, the Window List, and the clock are examples of panel applets.

As with many other things in GNOME, you can find settings for the panel by looking in the Panel menu under the GNOME menu, or by right-clicking on the panel itself. In both cases, there are options to add new launchers or applets to the panel; to adjust the style, size, and display of the panel; or to create new panels on the desktop. The menu panel does not have a properties dialog, as it is preconfigured. If you wish, you can remove it or replace it with an edge panel that is more to your liking.

17.2.1. Additional Panels

You can create more than one panel on your desktop. This is useful if you have different sets of applications used for specific but common tasks. For example, if you do a lot of work on graphics, you can dedicate a panel to launch your favorite graphics tools. To create a new panel, right-click on the default panel and select Add New Panel, or, from the GNOME menu, select Panel → Add New Panel. There are five different types of panels available from the submenu:

Edge panel: The style of the default panel. It stretches across one entire edge of the screen. Arrow buttons on each end of the panel are used to collapse the panel to the side of the screen. Clicking on the remaining visible arrow button of a collapsed panel will cause the panel to appear again in full.
Corner panel: A panel that is anchored to one corner of the screen and extends just enough to fit the buttons and applets it contains. A corner panel can be hidden by clicking the arrow button that is at the edge of the screen. The arrow button farthest from the edge will anchor an aligned panel on the opposite side of the screen.
Sliding panel: Like a corner panel, except that instead of being anchored to a corner, it can be placed anywhere along the edge of the screen. This is similar to the Dock in Macintosh OS X.
Floating panel: A panel that can be placed anywhere on the screen.
Menu panel: A special type of preconfigured edge panel. It is a thin bar that stretches across the top of the screen and contains drop-down menus and a clock. Users of the Macintosh will find it quite familiar.

All of the panels except the menu panel can be moved by middle-clicking (or clicking the left and right buttons simultaneously) and dragging the panel to another part of the screen. They can also be configured individually from the Panel menu in its context (right-click) menu. Right-click and select Panel → Properties to open a properties dialog. Your options vary depending on panel type, but the complete list is:

Position: This option does not appear for floating panels. For other types, choose a position by clicking the location on a diagram of a screen. You can also move all four configurable types of panels without this dialog by middle-clicking and dragging to a new location.
Orientation: This option is available only for floating panels. It lets you choose whether the panel should be vertical or horizontal. Other panels are aligned with the screen edges.
Autohide: Check this box to have the panel hide itself automatically. A small amount of the panel will be left showing; bring the mouse pointer over that bit, and the panel will reappear. This functions similarly to the Microsoft Windows task bar.
Show Hide Buttons, Arrows on Hide Buttons: At each end of the panel is a hide button with an arrow. Click the button, and the panel shrinks into it. Click again, and the panel reappears. Uncheck these boxes to get rid of the buttons or to remove the arrow labels from them. The buttons are slightly smaller if they are unlabeled.

A second tab of the preferences window allows you to choose a background for your panel. Normally, a panel is light gray, but you can choose a color or even an image to go behind your buttons. If you choose an image, you can also scale or stretch it to fit the panel more accurately.

17.2.2. Adding an Application Launcher to the Panel

One of the conveniences of the panel is creating launcher icons that allow you one-click access to frequently used applications. To add an application, right-click the panel and select Add to Panel → New Launcher. You can also right-click launchers in your menus and choose Add This Launcher to Panel, or simply drag launchers to the panel.

To customize the launcher, right-click on it and select Properties. Here, you can enter a name for the application, a comment to be used as a tooltip, and the command used to open the application. (This is similar to creating a launcher, as shown in Section 17.1.1.) Click on the icon button to select the image to be used for the button on the panel. If the application is to be run in a terminal window—that is, if it is a text-based program normally invoked from the shell—check the box labeled Run in Terminal.

Launcher buttons can be placed in any position and order you want on the panel. To move a launcher button, right-click it and select Move, or middle-click and drag it. The mouse pointer will change shape, indicating that you can drag the button to another position. Click to set the new position of the button.

TIP: The middle mouse button has two features that are often overlooked. First, it can be used to paste whatever text is currently selected, without a copy command. Second, it can be used to move items such as the Workspace Switcher Applet that cannot be moved with the left mouse button. (In the Workspace Switcher Applet, left clicking and dragging moves individual windows among the workspaces, rather than moving the applet itself.)

17.2.3. GNOME Panel Applets

As mentioned earlier, GNOME offers small applications that run inside the panel, called panel applets. Some will already be in your panel by default. To add more, right-click on a blank space in the panel and select one of the items under Add to Panel → Applet. The two most important GNOME panel applets are the Workspace Switcher Applet and the Window List Applet.

17.2.3.1. Workspaces and the Workspace Switcher

GNOME allows you to create extra screen real estate by multiplying your desktop with workspaces. You can keep a few windows open in each workspace instead of choosing between clutter and closing windows. For example, you might keep your mail program open in one workspace with a few messages open in separate windows, then have one or two browser windows open in a second workspace, and a spreadsheet in a third.

The workspaces are drawn in miniature on your panel in the Workspace Switcher Applet, which at first looks like a series of small grey boxes. Drawn inside each workspace, you can see the individual windows you have open, and even drag them from one workspace to another with the left mouse button. You can navigate these workspaces with the keyboard shortcuts Ctrl+Alt+Left, Ctrl+Alt+Right, Ctrl+Alt+Up, and Ctrl+Alt+Down, or by clicking one of the workspaces in the Workspace Switcher Applet.

Most systems give you four workspaces by default, although some stick with one or two. To create more, open the Workspace Switcher Applet preferences tool by right-clicking on the Workspace Switcher Applet and selecting Preferences. There, you can select not only the number of workspaces, but also their names and their layout in columns and rows.

17.2.3.2. The Window List Applet

The Window List Applet applet lets you keep track of open windows. It displays a button on the panel for each window you have open. Clicking on a button in the tasklist will bring that window to the foreground, reopening it if it was minimized.

You can right-click on any of the buttons for an application to get a context menu that allows you to interact with the window for that application, and close, minimize, maximize, un-maximize, move, or resize it.

To set the way the Window List Applet behaves, right-click on an empty space in the window list or on the small "handle" on its left side, and select Preferences. This will open a dialog box that allows you to set the following options:

Window List content: You can show the windows from all your workspaces, or just from the workspace you are currently in.
When restoring minimized windows: This setting matters only if you choose to display windows from all your workspaces. The default setting, "Restore to current workspace," means that minimized windows you restore with the Window List Applet will appear on your current workspace. If you select "Restore to native workspace," the windows will appear in the workspace where you were last using them. In other words, you can choose to have your windows appear either where you are now or where you were last using them.
Window grouping: One of the more useful Window List Applet features is window grouping. If you have several windows open for a particular application, the Window List Applet can save space by combining all the entries for that application. Then, instead of a button for each window, you'll have a menu for the whole application. For example, if you have one Galeon web browser window open, you will have a button that shows the Galeon icon and the title of the page for that window. If you have five open, the Window List Applet will show "Galeon (5)," and clicking the button will offer you a choice of which window to focus. You can set the applet never to group windows, to group windows only when it runs out of space, or to group windows whenever it can.
Window List size: Choose a minimum and maximum size for your window list applet. The applet will grow between these sizes depending upon how many windows you have open.

17.2.3.3. Miscellaneous applets

In addition to the Window List and Workspace Switcher Applets, there are roughly a dozen other applets in five categories. You can find the complete list of applets by right-clicking on the panel and selecting Add to Panel → Applet.

Accessories: A clock, a dictionary, a stock ticker, and a weather report.
Amusements: A fish that tells your fortune, and some googly eyes that follow your mouse pointer.
Internet: A modem traffic monitor and a mail checker.
Multimedia: A CD player and volume control.
Utility