X Applications (Running Linux)

11.4.6. Clocks

How can your screen be complete if it is unadorned by a little clock that tells you how much time you are wasting on customizing the screen's appearance? You can have a clock just the way you want it, square or round, analog or digital, big or small. You can even make it chime.

The .xinit file shown earlier in this chapter contains a line that starts oclock:

oclock -geometry 70x70+5+5 &

Refer to Figure 11-1 to see what this clock looks like. You may prefer the square outline of the xclock program:

xclock -geometry 150x150+5+5 &

Or perhaps a tiny digital clock at the bottom of your screen:

xclock -digital -geometry +10-10

oclock allows you to scatter more colors about, while xclock gives you more control over other aspects of the clock; see the manual pages for more information. To get a beep every half hour, invoke xclock with the -chime option.

11.4.7. Emacs

The X features in Emacs are getting spiffier and spiffier. They include pull-down menus, different typefaces for different parts of your window, and a complete integration of cut-and-paste functions with the X environment.

NOTE

Most distributions nowadays also carry XEmacs, a version of Emacs that integrates even better into the X Window System and has a much nicer and more user-friendly appearance. You might want to try it out. Most of the concepts here apply to XEmacs, too.

Let's start by defining some nice colors for different parts of the Emacs window. Try this command:

eggplant$ emacs  -bg ivory  -fg slateblue  -ms orangered  -cr brown

You are setting the background color, foreground color, mouse color, and cursor color respectively. The cursor is the little rectangle that appears in the window, representing what's called "point" in Emacs--the place where you type in text. We'll return to colors soon.

When you start Emacs, the menu bar on top and the scrollbar on the right side of the window stand out. See Figure 11-10.

Figure 11-10. Emacs window

The scrollbar works just like the xterm scrollbar. The menu bar offers a lot of common functions. Some editing modes, like C and TeX, have their own pull-down menus. The menus are not documented, so you will just have to experiment and try to figure out which Emacs functions they correspond to.

When you want to use a function that doesn't have a simple key sequence--or you've forgotten the sequence--the menus come in handy. For instance, if you rarely use a regular expression search (a quite powerful feature, well worth studying), the easiest way to invoke it is to pull down the Edit menu and choose Regexp Search.

Another useful menu item is Choose Next Paste on the Edit menu. This offers something you can't get any other way: a list of all the pieces of text you've cut recently. In other words, it shows you the kill ring. You can choose the text you want to paste in next, and the next time you press C-y, it's put into your buffer.

If you get tired of the scrollbar and the menu, put the following LISP code in your .emacs file to make them go away:

(if (getenv "DISPLAY")
    (progn (menu-bar-mode -1)
           (scroll-bar-mode -1))
   )

The mouse is the next X feature with interesting possibilities. You can cut and paste text much the same way as in xterm. And you can do this between windows; if you see some output in an xterm you'd like to put in a file, you can copy it from the xterm and paste it into your Emacs buffer. Moreover, any text you cut the normal way (such as through C-w) goes into the same selection as text you cut with the mouse. So you can cut a few words from your Emacs buffer and paste them into an xterm.

The right mouse button works a little unusually. If you select text with the left mouse button, you can click once on the right mouse button to copy it. A second click on the right mouse button removes it. To paste it back, press the middle mouse button. The text goes just before the character the mouse is currently on. Make a mistake? That's all right; the undo command reverses it just as for any other Emacs function. (Choose Undo from the Edit menu or just press the C-_ key.)

If you really love mouse work, you can define the buttons to execute any functions you want, just as with keys. Try putting the following command in your .emacs file. When you hold down the Shift key and press the left mouse button, a buffer for composing a mail message appears:

(define-key global-map [S-mouse-1] 'mail)

We don't recommend you redefine the existing mouse functions, but the Shift, Control, and Meta keys offer plenty of unused possibilities. Combine S-, C-, and M- any way you want in your definitions:

(define-key global-map [S-C-mouse-1] 'mail)

Now let's play around a bit with windows. Emacs has had windows of its own for decades, of course, long before the X Window System existed. So an Emacs window is not the same as an X window. What X considers a window, Emacs calls a frame.

How would you like to edit in two frames at once? Press C-x 5 2, and another frame appears. The new frame is simply another view onto the same editing session. You can edit different buffers in the two frames, but anything you do in one frame is reflected to the corresponding buffer in the other. When you exit Emacs by pressing C-x C-c, both frames disappear; if you want to close just one frame, press C-x 5 0.

To end our exploration of Emacs on the X Window System, we'll look at the exciting things you can do with colors. You can change these during an Emacs session, which makes it easy to play around with different possibilities. Press M-x, then type set-background-color and press the Enter key. At the prompt, type ivory or whatever other color you've chosen. (Remember, Emacs uses the convention M-x where we use Meta-x or Alt-x in the rest of the book.)

Be careful to make the foreground and background different enough so that you can see the text! In addition to set-background-color, Emacs offers set-foreground-color, set-cursor-color, and set-mouse-color.

These settings may seem idle play, but now they show their true colors when you let Emacs highlight different parts of your buffer in different ways. For instance, when you are programming in C or LISP, you can display strings, comments, function names, and keywords in different colors.

To set up color coding, you have to set font-lock mode. The easiest way to do this is in your .emacs start-up file; add lines like the following:

(require 'font-lock)
(setq global-font-lock-mode t)
(setq font-lock-maximum-decoration t)

These rather complicated commands tell each major mode to set the font lock whenever you open a buffer in that mode. So whenever you edit a file ending with the suffix .c, for instance, you automatically set the font lock.

Next, you want to play with the font faces, which are the different kinds of text defined by Emacs. Press M-x and enter the command list-faces-display. You'll see a list like the following:

               bold abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
        bold-italic abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
            default abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
          highlight abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
             italic abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
           modeline abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
             region abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
secondary-selection abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
          underline abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ

You can now set the background and foreground of each face interactively. Here is an example:

Enter M-x set-face-background.
Type modeline at the first prompt.
Type lemonchiffon at the second prompt.

You see the results immediately. Then set the foreground:

Enter M-x set-face-foreground.
Type modeline at the first prompt.
Type green at the second prompt.

No, that probably doesn't offer enough contrast for you to read the words. So do it again and use the color maroon. That looks better.

Find a buffer with C or LISP code in it and try setting each of the other faces. Faces are assigned rather arbitrarily to elements of the code. As you add colors, new dimensions will be revealed in your code. For instance, in C or C++ mode:

Comments and preprocessor keywords appear in italic.
Strings and include filenames appear in underline.
Function names and defined variables appear in bold-italic.

It probably looks best to reserve the bolder colors for short, rarely seen pieces of text.

When you find a set of colors you like, hard-wire them into your .emacs file by using the LISP functions that correspond to the commands you've been experimenting with. Here's a sample set:

(set-background-color "ivory")
(set-foreground-color "slateblue")
(set-cursor-color "brown")
(set-mouse-color "orangered")
(set-face-foreground 'bold "black")
(set-face-background 'bold "lightpink")
(set-face-foreground 'bold-italic "red")
(set-face-background 'bold-italic "wheat")
(set-face-foreground 'italic "darkolivegreen")
(set-face-background 'modeline "lemonchiffon")
(set-face-foreground 'modeline "maroon")
(set-face-foreground 'underline "violet")

You can also set colors in your .Xdefaults file, but that takes a little more effort, so we won't bother to explain it here.

11.4.8. Ghostview: Displaying PostScript

Adobe PostScript, as a standard in its own right, has become one of the most popular formats for exchanging documents in the computer world. Many academics distribute papers in PostScript format. The Linux Documentation Project offers its manuals in PostScript form, among others. This format is useful for people who lack the time to format LaTeX input, or who have immense network bandwidth for transferring files. When you create documents of your own using groff or TeX, you'll want to view them on a screen before you use up precious paper resources by printing them.

Ghostview, a GNU application, offers a pleasant environment for viewing PostScript on the X Window System. It's very simple; invoke it with the name of the file to be displayed, for instance:

eggplant$ ghostview article.ps

The Ghostview window is huge; it can easily take up most of your screen. The first page of the document is displayed with a vertical scrollbar on the right and a horizontal one on the bottom. Menu options appear on the left side of the window, and page numbers just to their right.

Like most X applications, Ghostview offers both menu options and keys (accelerators) for common functions. Thus, to view the next page, you can pull down the Page menu and choose the Next option. Or you can just press the space bar.

To go back to the previous page, choose Previous from the Page menu. To go to any page you want, press the middle mouse button on its number in the number column. To exit, choose Quit from the File menu or just press q.

Documents from different countries often use different page sizes. The Ghostview default is the standard U.S. letter size (this can be overridden by comments in the PostScript file). You can specify a different size on the command line:

eggplant$ ghostview -a3 article.ps

or in your .Xdefaults file:

Ghostview*pageMedia:            A3

Finally, you can also choose a different size at runtime from the Media menu.

Ghostview lets you enlarge or reduce the size of the page, a useful feature for checking the details of your formatting work. (But be warned that fonts on the screen are different from the fonts on a printer, and therefore the exact layout of characters in Ghostview will not be the same as that in the hard copy.) To zoom in on a small part of the page, press any mouse button on it. (The right mouse button enlarges the most; the left mouse button the least.)

You can also change the default size for displaying the whole document by using the Magstep menu. The higher the number you choose, the more the document is enlarged. Negative numbers reduce the size of the document.

To print a page, choose Print from the File menu or press p anywhere in the window. You are prompted to make sure that you've chosen the right printer; you can erase what is shown there and enter a different name. The name shown comes from your environment. So, if your printer is named doorway, you should have issued a shell command in your startup file like:

export PRINTER=doorway

You can also print several pages. Select individual ones by clicking on their numbers with the middle mouse button. Or select the first page with the left mouse button, and the last page with the right mouse button; the whole range of pages will be printed when you press p.

NOTE

KDE comes with its own version of Ghostview, called kghostview, which is really just Ghostview with a more user-friendly interface and a nicer appearance. You can run kghostview even if you do not plan to run the rest of KDE.

Another option would be to use gv, which has become quite popular lately.

11.4.9. xman: A Point-and-Click Interface to Manual Pages

Manual pages, read through the man command, are the ultimate authority on a Unix system. Other books can describe a significant percentage of any given command's functions--and often describe them in a more readable fashion--but only the manual page has all the details. See the section "Section 4.12, "Manual Pages"" in Chapter 4, "Basic Unix Commands and Concepts" for basic information.

Now there's a simple X interface to manual pages: the xman command. As befits a tool that displays documents, it contains a pretty good description of itself. In order to see this documentation clearly, start up the program with a large page size:

eggplant$ xman -pagesize 650x600

What you see first is a tiny box with three buttons. Click on the Manual Page button to bring up the main screen, where you'll do most of your work.

Now you see the xman documentation. You'll have plenty of time to read this; for now, just pull down the Options menu and choose Search, or press Ctrl-S. (You can also display the options menu by holding down the Control key and pressing the left mouse button.) In the box that pops up, type in a command or function you'd like to read about, then press the Enter key. The contents of the main window are replaced by the corresponding manual page.

If you don't know what to look for, try pulling down the Sections menu or pressing the Control key along with the middle button. Choose a section from the menu that appears. You'll see a long list of manual pages. Click the left button on one of them, and the document will be displayed.

Another time-honored way to look for information is through the apropos command (discussed already in the section "Section 4.12, "Manual Pages"" in Chapter 4, "Basic Unix Commands and Concepts"). Press Ctrl-S again, type in a word about a subject you're interested in, and press the Apropos button. If any manual pages match that word, their names will be displayed along with short descriptions. Unfortunately, you can't call up their manual pages by clicking on them; that little convenience was left out of xman. You have to press Ctrl-S and type in the page that looks interesting.

Within a manual page, scrolling is easy. Use the space bar or f to move down a page, b to move up. You can also use the scrollbar, just as in xterm.

Now you can read the documentation! Press the Help button on the small window that appeared when you started xterm. To exit the program, press Ctrl-Q or the Quit button, or choose Quit from the Options menu.

If you think that xman is still too bare-bones and not much of an improvement over the command-line man command, you can try one of its more advanced companions. For example, tkman has a much nicer user interface and features advanced navigation possibilities. The KDE help system, kdehelp, can display manual and info pages in addition to its own HTML pages and thus unifies the three major documentation formats on Linux.