# XSF / How to configure input

Cyril Brulebois
`<kibi@debian.org>`

## General considerations

### Foreword

The Debian wiki also contains an input hotplug guide which contains some context around X’s input subsystem. The present document is meant to be an executive summary, and might miss some bits. (FIXME: Merge those bits.)

### Rules of thumb

In this documentation, only the last part of the driver’s name will be mentioned, all of them are under the `xserver-xorg-input-*` namespace.

- On Linux, `evdev` is used for both keyboard and mouse input.

- On Linux as well, `synaptics` can be used to benefit from extra features; it takes precedence over `evdev` automatically if both are installed.

- On GNU/kFreeBSD and GNU/Hurd, `kbd` handles the keyboard and `mouse` handles mice, unsurprisingly.

### Configuration snippets

X can now be run without `xorg.conf`, but sometimes one has to configure a few settings for this or that driver. Starting with `squeeze`, that can be done by adding a file under `/etc/X11/xorg.conf.d`, with a `.conf` suffix, as documented in the `xorg.conf` manpage.

Some packages ship a default configuration file under `/usr/share/X11/xorg.conf.d` with general rules to match appropriate hardware. The files under `/etc/X11/xorg.conf.d` take precedence, as documented in the `xorg.conf` manpage.

It’s probably mostly useful in the `synaptics` case, in case one wants to change default settings on a system-wide fashion. See the Pointer configuration section below for an example.

## Basic keyboard configuration

The `keyboard-configuration` package ships `/etc/default/keyboard` which can be used to set the following `xkb` items: model, layout, variant, and options. Here’s an example:

    XKBMODEL="pc105"
    XKBLAYOUT="fr"
    XKBVARIANT="oss"
    XKBOPTIONS="compose:menu,terminate:ctrl_alt_bksp"

Quick words about the options:

- They are comma-separated.

- The list of options and a short description for each can be found in the `/usr/share/X11/xkb/rules/base.lst` file (shipped by the `xkb-data` package).

- First option: `compose:menu`. This sets the `menu` key as the Compose key. More information about it can be found in the `Compose` manpage.

- Second option: `terminate:ctrl_alt_bksp`. By default, the X server is no longer killed through `Ctrl+Alt+Backspace`. This option restores the old behaviour.

Two ways to change the configuration:

- `dpkg-reconfigure keyboard-configuration` is going to ask questions through debconf prompts.

- Manually editing `/etc/default/keyboard` also works.

How does it propagate to X?

- When HAL is used (that is: on GNU/kFreeBSD and GNU/Hurd), one has to restart it: `invoke-rc.d hal restart`

- When udev is used (on GNU/Linux, starting with `squeeze`), one has to tell udev to reload input-related configuration: `udevadm trigger --subsystem-match=input --action=change` (that can be found in `keyboard-configuration`’s `README.Debian` 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 `xkb_` in the X log. Please note that trying `invoke-rc.d udev restart` changes nothing, one has to use `udevadm`. Properties can be inspected through: `/sbin/udevadm info --export-db`

## Pointer configuration

### evdev configuration

Available options are documented in the `evdev` manpage. Let’s check what a configuration snippet (mentioned in General considerations) would look like. Here is a fictional `/etc/X11/xorg.conf.d/42-evdev.conf`:

    Section "InputClass"
        Identifier "evdev pointer tweaked catchall"
        MatchIsPointer "on"
        Driver "evdev"
        Option "Emulate3Buttons" True"
        Option "SwapAxes" "True"
    EndSection

Line by line walkthrough:

- To avoid specifying any device under `/dev/input` (`event$N` might change, remember it’s about hotplug support!), we use an `InputClass`.

- We need an identifier, the actual name doesn’t matter.

- We match everything that looks like a touchpad. Meaning no generic pointer, keyboard, or tablet.

- We specify the driver we want to use for the matched device(s).

- 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.

### synaptics configuration

The `synaptics` driver comes with two tools. The more interesting one is `synclient`, which can be used to list available options and current settings: `synclient -l`. The documentation for each option can be found in the `synaptics` manpage.

`synclient` 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): `synclient TapButton1=1`; one can also disable the touchpad temporarily: `synclient TouchpadOff=1` to disable it, `synclient TouchpadOff=0` to enable it again.

Let’s check what a configuration snippet (mentioned in General considerations) would look like. Here is a fictional `/etc/X11/xorg.conf.d/42-synaptics.conf`:

    Section "InputClass"
        Identifier "touchpad tweaked catchall"
        MatchIsTouchpad "on"
        Driver "synaptics"
        Option "TapButton1" "1"
        Option "HorizEdgeScroll" "1"
    EndSection

Line by line walkthrough:

- To avoid specifying any device under `/dev/input` (`event$N` might change, remember it’s about hotplug support!), we use an `InputClass`.

- We need an identifier, the actual name doesn’t matter.

- We match everything that looks like a touchpad. Meaning no generic pointer, keyboard, or tablet.

- We specify the driver we want to use for the matched device(s).

- 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).

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: `gpointing-device-settings`.

There’s a palm detection setting but that relies on hardware/firmware support for the touchpad. The other tool shipped with the `synaptics` driver is `syndaemon`, which makes it trivial to disable the touchpad temporarily, when the keyboard is being used. Here’s an example: `syndaemon -d -i 0.5` makes `syndaemon` start in background (`-d` 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 `Ctrl+click` in a browser, or `Alt+drag` to move windows.