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<h1><a href="../index.html">XSF</a> / How to configure input</h1>
<span id="author">Cyril Brulebois</span><br />
<span id="email"><code><<a href="mailto:kibi@debian.org">kibi@debian.org</a>></code></span><br />
<div id="toc">
<div id="toctitle">Table of Contents</div>
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</div>
<div id="content">
<div class="sect1">
<h2 id="_general_considerations">General considerations</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_foreword">Foreword</h3>
<div class="paragraph"><p>The Debian wiki also contains an
<a href="https://wiki.debian.org/XStrikeForce/InputHotplugGuide">input hotplug guide</a>
which contains some context around X’s input subsystem. The present
document is meant to be an executive summary, and might miss some
bits. (<strong>FIXME:</strong> Merge those bits.)</p></div>
</div>
<div class="sect2">
<h3 id="_rules_of_thumb">Rules of thumb</h3>
<div class="paragraph"><p>In this documentation, only the last part of the driver’s name will be
mentioned, all of them are under the <code>xserver-xorg-input-*</code> namespace.</p></div>
<div class="ulist"><ul>
<li>
<p>
On Linux, <code>evdev</code> is used for both keyboard and mouse
input.
</p>
</li>
<li>
<p>
On Linux as well, <code>synaptics</code> can be used to benefit from extra
features; it takes precedence over <code>evdev</code> automatically if both
are installed.
</p>
</li>
<li>
<p>
On GNU/kFreeBSD and GNU/Hurd, <code>kbd</code> handles the keyboard and
<code>mouse</code> handles mice, unsurprisingly.
</p>
</li>
</ul></div>
</div>
<div class="sect2">
<h3 id="_configuration_snippets">Configuration snippets</h3>
<div class="paragraph"><p>X can now be run without <code>xorg.conf</code>, but sometimes one has to
configure a few settings for this or that driver. Starting with
<code>squeeze</code>, that can be done by adding a file under
<code>/etc/X11/xorg.conf.d</code>, with a <code>.conf</code> suffix, as documented in the
<code>xorg.conf</code> manpage.</p></div>
<div class="paragraph"><p>Some packages ship a default configuration file under
<code>/usr/share/X11/xorg.conf.d</code> with general rules to match appropriate
hardware. The files under <code>/etc/X11/xorg.conf.d</code> take precedence, as
documented in the <code>xorg.conf</code> manpage.</p></div>
<div class="paragraph"><p>It’s probably mostly useful in the <code>synaptics</code> case, in case one wants
to change default settings on a system-wide fashion. See the <em>Pointer
configuration</em> section below for an example.</p></div>
<div style="page-break-after:always"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_basic_keyboard_configuration">Basic keyboard configuration</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <code>keyboard-configuration</code> package ships <code>/etc/default/keyboard</code>
which can be used to set the following <code>xkb</code> items: model, layout,
variant, and options. Here’s an example:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>XKBMODEL="pc105"
XKBLAYOUT="fr"
XKBVARIANT="oss"
XKBOPTIONS="compose:menu,terminate:ctrl_alt_bksp"</code></pre>
</div></div>
<div class="paragraph"><p>Quick words about the options:</p></div>
<div class="ulist"><ul>
<li>
<p>
They are comma-separated.
</p>
</li>
<li>
<p>
The list of options and a short description for each can be found
in the <code>/usr/share/X11/xkb/rules/base.lst</code> file (shipped by the
<code>xkb-data</code> package).
</p>
</li>
<li>
<p>
First option: <code>compose:menu</code>. This sets the <code>menu</code> key as the
Compose key. More information about it can be found in the
<code>Compose</code> manpage.
</p>
</li>
<li>
<p>
Second option: <code>terminate:ctrl_alt_bksp</code>. By default, the X server
is no longer killed through <code>Ctrl+Alt+Backspace</code>. This option
restores the old behaviour.
</p>
</li>
</ul></div>
<div class="paragraph"><p>Two ways to change the configuration:</p></div>
<div class="ulist"><ul>
<li>
<p>
<code>dpkg-reconfigure keyboard-configuration</code> is going to ask questions
through debconf prompts.
</p>
</li>
<li>
<p>
Manually editing <code>/etc/default/keyboard</code> also works.
</p>
</li>
</ul></div>
<div class="paragraph"><p>How does it propagate to X?</p></div>
<div class="ulist"><ul>
<li>
<p>
When HAL is used (that is: on GNU/kFreeBSD and GNU/Hurd), one has
to restart it: <code>invoke-rc.d hal restart</code>
</p>
</li>
<li>
<p>
When udev is used (on GNU/Linux, starting with <code>squeeze</code>), one has
to tell udev to reload input-related configuration:
<code>udevadm trigger --subsystem-match=input --action=change</code>
(that can be found in <code>keyboard-configuration</code>’s <code>README.Debian</code>
file). Properties attached to the input devices are then updated,
and X uses those properties when it starts, as can be seen by
searching for <code>xkb_</code> in the X log. Please note that trying
<code>invoke-rc.d udev restart</code> changes nothing, one has to use
<code>udevadm</code>. Properties can be inspected through:
<code>/sbin/udevadm info --export-db</code>
</p>
</li>
</ul></div>
<div style="page-break-after:always"></div>
</div>
</div>
<div class="sect1">
<h2 id="_pointer_configuration">Pointer configuration</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_evdev_configuration">evdev configuration</h3>
<div class="paragraph"><p>Available options are documented in the <code>evdev</code> manpage. Let’s check
what a configuration snippet (mentioned in <em>General considerations</em>)
would look like. Here is a fictional <code>/etc/X11/xorg.conf.d/42-evdev.conf</code>:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>Section "InputClass"
Identifier "evdev pointer tweaked catchall"
MatchIsPointer "on"
Driver "evdev"
Option "Emulate3Buttons" "True"
Option "SwapAxes" "True"
EndSection</code></pre>
</div></div>
<div class="paragraph"><p>Line by line walkthrough:</p></div>
<div class="ulist"><ul>
<li>
<p>
To avoid specifying any device under <code>/dev/input</code> (<code>event$N</code> might
change, remember it’s about hotplug support!), we use an
<code>InputClass</code>.
</p>
</li>
<li>
<p>
We need an identifier, the actual name doesn’t matter.
</p>
</li>
<li>
<p>
We match everything that looks like a touchpad. Meaning no generic
pointer, keyboard, or tablet.
</p>
</li>
<li>
<p>
We specify the driver we want to use for the matched device(s).
</p>
</li>
<li>
<p>
Finally the options we want to set. Here we enable the 3rd button
emulation (clicking left and right buttons at the same time then no
longer acts as if the middle button was clicked). Then we swap x
and y axes, just for the fun of it.
</p>
</li>
</ul></div>
</div>
<div class="sect2">
<h3 id="_synaptics_configuration">synaptics configuration</h3>
<div class="paragraph"><p>The <code>synaptics</code> driver comes with two tools. The more interesting one
is <code>synclient</code>, which can be used to list available options and
current settings: <code>synclient -l</code>. The documentation for each option
can be found in the <code>synaptics</code> manpage.</p></div>
<div class="paragraph"><p><code>synclient</code> can also be used to set options. A common example is
enabling tapping (upstream kept it disabled by default, Debian won’t
deviate, no need to file bugs): <code>synclient TapButton1=1</code>; one can also
disable the touchpad temporarily: <code>synclient TouchpadOff=1</code> to
disable it, <code>synclient TouchpadOff=0</code> to enable it again.</p></div>
<div class="paragraph"><p>Let’s check what a configuration snippet (mentioned in <em>General
considerations</em>) would look like. Here is a fictional
<code>/etc/X11/xorg.conf.d/42-synaptics.conf</code>:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>Section "InputClass"
Identifier "touchpad tweaked catchall"
MatchIsTouchpad "on"
Driver "synaptics"
Option "TapButton1" "1"
Option "HorizEdgeScroll" "1"
EndSection</code></pre>
</div></div>
<div class="paragraph"><p>Line by line walkthrough:</p></div>
<div class="ulist"><ul>
<li>
<p>
To avoid specifying any device under <code>/dev/input</code> (<code>event$N</code> might
change, remember it’s about hotplug support!), we use an
<code>InputClass</code>.
</p>
</li>
<li>
<p>
We need an identifier, the actual name doesn’t matter.
</p>
</li>
<li>
<p>
We match everything that looks like a touchpad. Meaning no generic
pointer, keyboard, or tablet.
</p>
</li>
<li>
<p>
We specify the driver we want to use for the matched device(s).
</p>
</li>
<li>
<p>
Finally the options we want to set. We enable tapping for the first
button. And we enable horizontal scrolling (by default, only
vertical scrolling is enabled).
</p>
</li>
</ul></div>
<div class="paragraph"><p>Settings can also be changed by various settings managers, like
Gnome’s or KDE’s. An example of a graphical user interface making it
possible to set options in a clicky way: <code>gpointing-device-settings</code>.</p></div>
<div class="paragraph"><p>There’s a palm detection setting but that relies on hardware/firmware
support for the touchpad. The other tool shipped with the <code>synaptics</code>
driver is <code>syndaemon</code>, which makes it trivial to disable the touchpad
temporarily, when the keyboard is being used. Here’s an example:
<code>syndaemon -d -i 0.5</code> makes <code>syndaemon</code> start in background (<code>-d</code> for
daemon mode), waiting 0.5 second before enabling the touchpad again
after the last keypress. Warning: it becomes quite difficult to use
things like <code>Ctrl+click</code> in a browser, or <code>Alt+drag</code> to move
windows.</p></div>
</div>
</div>
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Last updated
2020-10-09 09:18:55 UTC
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