x11: peripheral devices

wiki/linux/x11.md

@@ -1,17 +1,44 @@
 # X11
 
-## Change Keyboardlayout
+X, X Window System and X11 according to the current version is a protocoll for
+handling the display of the most unix-like operating systems.
+[Xorg](https://www.x.org/wiki/) is the most used implementation of the X
+protocoll.
+It is maintained by the [X.Org Foundation](https://x.org/wiki/).
+
+## Peripheral Devices
+
+X also handles various options of peripheral devices.
+In the files of the directory `/etc/X11/xorg.conf.d` and the file
+`/etc/X11/xorg.conf` these settings can be found.
+
+The handling of input devices is achieved by xinput.
+For this the identifier of the device to show the options of is needed.
+By running `xinput list` a list of all devices with identifiers handled by
+xinput is printed.
+Properties and options of a peripheral device can then be shown by running
+`xinput list-props <id>` where `<id>` is the identifier of the
+device.
+
+
+### Keyboard
+
+#### Change Keyboardlayout
 
 To temporarily change the layout of the keyboard just run
 `setxkbmap <your preferred layout>`.
 For a permanent change run `localectl set-x11-keymap <your preferred layout>`.
 
-## Screen Tearing
+### Display
 
-### Intel Graphics
+#### Screen Tearing
 
-Linux can sometimes have problems with screen tearing.
-To get this working you need to change the `/etc/X11/xorg.conf.d/20-intel.conf` to:
+Linux systems that use intel graphics can sometimes have problems with screen
+tearing.
+To get this working you need to change the `/etc/X11/xorg.conf.d/20-intel.conf`
+as explained on
+[maketecheasier](https://www.maketecheasier.com/get-rid-screen-tearing-linux)
+to:
 
 ```txt
 Section "Device"
@@ -21,10 +48,7 @@ Section "Device"
 EndSection
 ```
 
-This was found on
-[maketecheasier](https://www.maketecheasier.com/get-rid-screen-tearing-linux).
-
-## Disable Screen Blanking
+#### Disable Screen Blanking
 
 To save power the screen is set to turn black after a given amount of time.
 This can be disabled temporarily by running `xset s off` or permanently by
@@ -35,3 +59,34 @@ Section "ServerFlags"
     Option "BlankTime" "0"
 EndSection
 ```
+
+### Mouse
+
+#### Enable/Disable the Usage of the Middle Mouse Button
+
+The middle mouse button can be activated or deactivated.
+First the current options have to be confirmed as explained in
+[the peripheral section](#peripheral-devices).
+Important is the property named `libinput Middle Emulation Enabled`.
+To enable the usage of the middle mouse button it should be set to `1`.
+As written by
+[opinion_no9](https://askubuntu.com/questions/160164/how-do-i-enable-middle-mouse-button-emulation-in-12-04-lts/902976#902976)
+there are two ways to change this property.
+If the change is only needed temporarily
+`xinput set-prop <id> "libinput Middle Emulation Enabled" <flag>` can be run.
+`<id>` is the identifier of the mouse and <flag> is `0` for disabling and `1`
+for enabling the middle mouse button.
+For permanent change of the property a change or addition to
+`/etc/X11/xorg.conf.d/40-libinput.conf` can be made.
+If a section for the device is already present the line
+`Option "MiddleEmulation" "true"` should be added to it.
+Otherwise a catchall section for all types of mouses can be created like the
+following:
+
+```txt
+Section "InputClass"
+    Identifier "middle button emulation class"
+    MatchIsPointer "on"
+    Option "MiddleEmulation" "true"
+EndSection
+```