4. More X Configuration

Before taking a look at various configuration mechanisms for X
servers and clients, it should be noted that the advent of Desktop
Environments like KDE have become popular in part because they can
control much of the user interaction configuration themselves with
nice, "user friendly" GUI controls. And in fact, the compliant
applications that are part of the respective Desktops will be best
configured through the Desktop's configuration tools, or the
application's own GUI configuration methods. So, for instance, gtop,
a GNOME client application, is best configured via GNOME or gtop's
own menus. But this is not true of all X applications.
4.1. X Resources

The X server can store various configuration values for client
programs so they are readily available when needed. If the
application supports this, it will use these as defaults whenever
that program is invoked. These are known as "Resources", and are
often used to define user preferences on a per application basis for
fonts, colors, screen placement (geometry) and various other
attributes. This makes it easy to customize applications.

Resources are specified as text strings (e.g.
Netscape*blinkingEnabled: False) that can be read from disk in
various places when X is starting, or even interactively defined on
the command line. Program components are named in a hierarchical
fashion, with each object in the hierarchy identified by a class as
well as an instance name. At the top level of the hierarchy is the
class and instance name of the application itself. Typically, the
class name of the application is the same as the program name, but
with the first letter capitalized (e.g. Vim or Emacs) although some
programs that begin with the letter "X" also capitalize the second
letter for historical reasons (e.g. XTerm). Each definition will
specify a class (or instance), with corresponding resource and
value. Below this in the hierarchy are the various attributes that
make up the definable aspects of the application.

Traditionally, most X programs were configured this way. This is not
as true today with the advent of Desktop Environments which often
have their own configuration mechanisms.

As an example, say we prefer to run xterm with a blue background. So
if we run it from the command line, we would run it as:

xterm -bg blue &



If this is our preference, it would be easier to put this preference
in a file somewhere, and have the system use our preference. That
way whenever we started xterm, it would use our preferred value, and
we wouldn't need the command line options (unless as an override).

The basic X resource syntax is expressed like:

<program><binding><widget><binding><widget><...><resource>:<value>



Which, in real life, typically looks something like:

xterm*fontMenu*background: darkblue



It should be obvious what this does. The use of "*" in the
definition, is called a "loose binding" and acts as a wild-card.
Meaning there may be gaps in the widget hierarchy. For instance:

xterm*background: darkblue



This would also give a dark blue background for the xterm fontMenu,
but also any other xterm properties that also have a "background"
attribute (e.g. window background, etc), no matter where they may be
in the widget hierarchy. Similarly:

*background: darkblue



This would define the background for any and all programs that
support it -- not just xterm. Using a "." in place of a "*" would be
more precise, and will not allow for wild-card gaps in the
hierarchy. Also, the application must support the particular widget
attribute. "Background" is a fairly safe bet, but many applications
will have more specialized resources that are not so obvious. It is
best to check local documentation (man pages, etc), or see if an
application has an included examples. For instance, Netscape
generally comes with an Netscape.ad file that has an extensive set
of resource definitions that can be customized.

X resources are typically stored in more than one place (see below)
and are processed by the xrdb command (see man page).
4.1.1. App Defaults

One way of storing preferred application resources is via files
named for the application in an "app-defaults" directory. For
instance, on my system, these are in
/usr/X11R6/lib/X11/app-defaults/, though this may vary according to
options your vendor has chosen. This directory contains a number of
files for such well known X applications as xterm, xclock, xcalc,
xload, and so on. All in all, it is a relatively small number of
applications in the overall scheme of things. So not all
applications use this scheme. In fact, most do not.

Each file will contain resource definitions for that application.
The X server loads these by itself during start up. A brief example
from XTerm-color:

! $XFree86$

#include "XTerm"

*VT100*colorMode: on
*VT100*dynamicColors: on

! Uncomment this use color for underline attribute
!*VT100*colorULMode: on
!*VT100*underLine: off

! Uncomment this to use color for the bold attribute
!*VT100*colorBDMode: on

*VT100*color0: black
*VT100*color1: red3
*VT100*color2: green3
*VT100*color3: yellow3
*VT100*color4: blue3
*VT100*color5: magenta3
*VT100*color6: cyan3
*VT100*color7: gray90
*VT100*color8: gray30
*VT100*color9: red
*VT100*color10: green
*VT100*color11: yellow
*VT100*color12: blue
*VT100*color13: magenta
*VT100*color14: cyan
*VT100*color15: white
*VT100*colorUL: yellow
*VT100*colorBD: white



This is mostly various color definitions. The application classname
is not explicitly stated, and is assumed from the filename. So think
of each line as starting: XTerm-color*. Also, notice at the top, the
#include "XTerm" line, which "includes" the resource definitions for
XTerm, a much longer file with a more diverse set of definitions.
(Not included due to length, but worth looking at.) These files
provide system wide defaults, and generally speaking, would not
normally be edited by the user.
4.1.2. Xdefaults

Another common method of reading in resource preferences, is with an
Xdefaults file. Or, sometimes the naming scheme may be Xresources
instead. This may exist as a system wide file, such as
/etc/X11/Xresources. Of course, the user is free to create a
personal version in his home directory, e.g. ~/.Xdefaults. The
user's version will over-ride any system wide settings, and will
remain after system upgrades. Obviously, this is the place to put
your own preferences.

Xresources files are read into the resource database with the xrdb
command. Example:

xrdb -merge ~/.Xresources



This can be done interactively at the command line, or placed in a
script and run automatically as the X session is started. In the
case of system wide files, this should be taken care of by the
vendor supplied start up scripts. Generally, such scripts will also
check the user's home directory as well (see the xinitrc example
above). So probably all that need be done, is to create the file
with a text editor.

Here's an example to illustrate a very few of the many things that
might be done with an .Xdefaults file:

! This is a comment ;-)

#ifdef COLOR
*customization: -color
#endif

!! Let's cast a wide net, for any app supporting these
! Blink instead of beeping
*visualBell: True
*scrollTtyOutput: False
*scrollKey:       True

! See Netscape.ad for many settable resources
Netscape*noAboutSplash:        True
Netscape*documentFonts.sizeIncrement: 5
Netscape*documentFonts.xResolution*iso-8859-1: 120
Netscape*documentFonts.yResolution*iso-8859-1: 120
netscape-navigator*geometry: 960x820+240+140

emacs*Background: DarkBlue
emacs*Foreground: Wheat
emacs*pointerColor: Orchid
emacs*cursorColor: Orchid
emacs*bitmapIcon: on
emacs*font: 10x20

! GVim colors, etc
!! GTK versions of gvim will not use all these.
Vim*useSchemes:         all
Vim*sgiMode:            true
Vim*useEnhancedFSB:     true
Vim.foreground:         Black
!Vim.background:        lightyellow2
Vim*background:         white
! geometry: width x height
Vim.geometry:  88x40
Vim*font:  -misc-fixed-medium-r-normal--20-200-75-75-c-100-iso8859-15-*5
Vim*menuBackground: yellow
Vim*menuForeground: black

rxvt*backspacekey: ^?
rxvt*background: Black
rxvt*foreground: wheat
rxvt*cursorColor: Orchid
rxvt*geometry: 100x18+40+300
rxvt*title: Linux
rxvt*reverseVideo: false
!rxvt*backgroundPixmap: ~/penguinitis.xpm
rxvt*scrollBar: true
rxvt*reverseWrap: true
rxvt*font: -*-lucidatypewriter-medium-*-*-*-14-*-*-*-*-*-*-*
rxvt*fullCursor: true
rxvt*saveLines:  1500
rxvt*menu: ~/rxvt.menu

XTerm*saveLines:    1500
! Do not clear the screen after the program exits
XTerm*VT100*titeInhibit: true

! Fix up xterm's keybindings
xterm*VT100.translations:      #override \
      <Key>BackSpace:    string(0x7F) \n\
      <Key>Insert:       string(0x1b) string("[2~")\n\
      <Key>Delete:       string(0x1b) string("[3~")\n\
      <Key>Home:         string(0x1b) string("[1~")\n\
      <Key>End:             string(0x1b) string("[4~")\n\
      <Key>Page_Up:      string(0x1b) string("[5~")\n\
      <Key>Page_Down:    string(0x1b) string("[6~")\n\
      <KeyPress>Prior : scroll-back(1,page)\n\
      <KeyPress>Next : scroll-forw(1,page)

! Ghostview
Ghostview*Font: *-helvetica-bold-r-normal--12-*-*-*-*-*-*
Ghostview*BorderColor:  white
Ghostview*Text*Font:    rk14
Ghostview*Background:   #d9d9d9
!Ghostview*Foreground:  white
ghostview.form.pageview.page.background: white
ghostview.form.pageview.page.foreground: black
.ghostview.zoom.form.page.background: white
.ghostview.zoom.form.page.foreground: black

! xscreensaver !
! Time out after 12 minutes, cycle mode after each 2
xscreensaver.timeout: 12
xscreensaver.cycle: 5
! Run low priority, and fade between modes
xscreensaver.nice: 12
xscreensaver.fadeSeconds: 2

XFontsel.menu.options.showUnselectable: False



Hopefully, these few examples will give you some ideas to build on.
X does not need to be restarted if xrdb is used interactively from
the command line after making changes. The effects are immediate.

Resources are sometimes available also as command line options. See
below. Command line options will over-ride any existing resource
definitions.  4.2. xmodmap, the Keyboard and Mice

The keyboard and mouse, as well as other possible input devices, are
defined in XF86Config (or XF86Config-4). There is a keyboard layout
that is defined based on the preferred language:

Section "InputDevice"
       Identifier  "Keyboard0"
       Driver      "keyboard"
       Option      "XkbLayout" "us"
EndSection



This gives us our default keyboard layout. Valid layout labels are
listed in /usr/X11R6/lib/X11/xkb/symbols. Also, the setxkbmap
utility can be used to change this interactively.

X is highly customizable, and we can modify the keyboard and mouse
pointer mappings to suit our own preferences. The utility to do this
is xmodmap (see man page). You don't like where the capslock key is?
So move it ;-)

Like xrdb, xmodmap can be run from the command line. Or, preferred
settings can be stored in a file. Typically this is ~/.Xmodmap, or
similar. If your X start up files don't parse this, then edit as
appropriate so that they do (probably from ~/.xinitrc or
~/.xsession).

You can view your current key and mouse mappings with: xmodmap -pk
-pp |less. This will print out all active "keycode" values, with
corresponding "keysym" values, and any keysym names that xmodmap
knows about (e.g. "BackSpace"). And should also give you an idea of
how xmodmap understands key and mouse events. There are two keysyms
per keycode. The second is the shifted value. XFree86's xev utility
can be used to dump a lot of information on key-presses and mouse
events interactively. Pay attention to the "keycode" value. That is
what you will need to know in order to re-map.

xmodmap is often used to make minor keyboard adjustments, like
proper Backspace/Delete mapping. Or can be used make major
adjustments such as for international mappings. You can only re-map
keys and mouse events -- you cannot assign macros to key events
(your Window Manager or Desktop might have some of this
functionality).

Setting up international keyboards in nicely discussed in
http://www.linuxdoc.org/HOWTO/mini/Intkeyb/index.html. Also, a
search of http://google.com/linux will turn up many creative
examples.

The man page has many brief examples of various usages. Here is what
an one hypothetical ~/.Xmodmap might look like:

! /home/hal/.Xmodmap, last change 10/03/01
!
! Force backspace to 22 and Delete to 111
keycode 22 = BackSpace
keycode 111 = Delete
!
! My keyboard handles right and left Alt differently. Make the
! Right act like the Left to avoid digital gymnastics.
keycode 63 = Alt_L
keycode 113 = Meta_L
!
! Hard-code the keypad to numeric values as if numlock is always on
! since I never use it for anything else.
keycode 79=7
keycode 80=8
keycode 81=9
keycode 83=4
keycode 84=5
keycode 85=6
keycode 87=1
keycode 88=2
keycode 89=3
keycode 90=0
keycode 91=period
keycode 86 = plus
! deactivate Num_Lock key since we don't need it now.
keycode 77 =
!
! My capslock is next to tab. I hit it by mistake sometimes,
! and don't use it anyway. So make capslock act like Tab.
keycode 66 = Tab
clear lock
!
! Reverse mouse buttons for left-handed people
pointer = 3 2 1



As with many XFree86 files, the "!" represents a comment. Another
possible use, is to redefine those annoying "Windows" keys to
something useful. Hopefully this gives an idea of some things one
might want to do to make the keyboard more agreeable to us.

Speaking of the Numlock key, X will typically disable this when it
starts up. No matter how you have the BIOS set up, or Linux set up
before X starts. So the trick above is one way. There is also a
utility available as either numlockx, or setnumlock, that can be
found on the 'Net, if your distribution does not include one or the
other. This can be put in a start up file to turn Numlock on
automatically if you'd prefer.

Window Managers and Desktop Environments will also allow
customization of the keyboard and mouse (as long as it is recognized
correctly by X). This may be an easier way to configure certain
customizations.
4.2.1. Special Key Mappings

There are several special key mappings traditionally used in XFree86.

   *

     Ctrl-Alt-BackSpace - Will kill the X server process in an
     orderly fashion. This is a quick, easy, legitimate way to
     restart X. Note it does not restart the display manager (if
     used) -- just X itself.
   *

     Ctrl-Alt-Fx - where "x" corresponds to a valid tty number
     (typically 1-6). This is typically used to jump to a text
     console login, while X remains running. To get back to X, then
     it is "Alt-Fx". In this case, "x" represents one plus the last
     tty (e.g. Alt-F7 if there are six available ttys).
   *

     Ctrl-Alt-keypad+ and Ctrl-Alt-keypad- - That is the plus and
     minus keys on the keypad. This will cycle through any existing
     valid screen resolution "Modes", e.g. 1024x768 -> 600x800.
     Note the actual screen size is the same -- just the view and
     resolution changes. Not all that useful for most purposes. You
     cannot permanently change the screen resolution without
     restarting X.

It's possible your Window Manager, Desktop Environment or other
system component may trap these, and alter the standard behavior. In
addition, the Ctrl-Alt-Delete may be trapped as well. This should
shut X (and the system) down orderly, if it is available.  4.2.2.
Mice and Pointers

As mentioned, Linux and Unix make heavy use of three mouse buttons.
If a mouse only has two buttons, then the third (i.e. the middle)
button can be simulated by pressing both buttons simultaneously.
This is a configuration option set in XF86Config as the
"Emulate3Buttons" directive:

Section "InputDevice"
       Identifier  "Mouse0"
       Driver      "mouse"
       Option      "Device" "/dev/mouse"
       Option      "Protocol" "PS/2"
       Option      "Emulate3Buttons" "on"
EndSection



When all is said and done, a third button is quite handy and I would
personally recommend having one. On wheeled mice, the "wheel" acts
as the third button, if pressed. Many standard wheel mice seem to
work with the "IMPS/2" protocol option.

Specifically, the third button (middle) is the "paste" button in
virtually all Linux applications. Copy and paste works a little
different in Linux. The left button is the copy button. Just hold it
down, and drag over text. It is automatically copied to the X
"clipboard". Then, the middle button will paste from there. A very
simple process. A double-click should copy individual words, and a
triple-click individual lines of text. If for some reason, this does
not work, it is either a poorly implemented application, or a bug of
some kind. Some older versions of Netscape were not consistent about
this, for instance. To paste from the keyboard, this should be
shift+insert.

"Drag and Drop" is not natively supported by X itself. But, is
implemented by some toolkits and Desktop Environments. One should
not expect this to work with non-compliant applications (i.e non-KDE
aware applications in KDE for example).  4.3. xset

xset is yet another XFree86 utility to set user preferences. xset is
a bit of a catch-all and is used to change various, unrelated X
server settings. Mostly this is a command line way of configuring
some of the same things that are defined in XF86Config (but not
everything!).

Common usages of xset are to set DPMS on or off and preferred
intervals, to dynamically change the FontPath or re-read it, to
control keyboard LEDs, to adjust mouse (or other pointer) movement
speed, set keyboard "autorepeat" and "repeat" rates, and to control
X's built in screen blanking. See the man page, of course, for
detailed explanations, and other xset usages.

Again, xset can be used interactively from the command line. But
most often preferred settings are stored in one of the start up
configuration files, like .xinitrc or .xsession. A very brief
example:

# Turn off screen blanking
xset s off

# Enable DPMS energy saving
xset +dpms

# Tweak the rodent
xset m 30/10 4

# Speed up keyboard
xset r rate 200 40



Your desktop may have a GUI front-end for xset.

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