Difference between revisions of "Wayland"

Latest revision as of 21:15, 6 September 2017

Wayland is a protocol for a compositor to talk to its clients, as well as a library implementing this protocol. All major Linux desktop systems like Gnome, KDE do support Wayland, and there is also a reference implementation for a compositor called "Weston". XWayland implements a compatibility layer to seamlessly run legacy X11 applications on Wayland.

Requirements

Wayland only works on systems using KMS. As Wayland is only a library, it is useless on its own: to replace the X Server you need a compositor such as #Weston.

Buffer API support

For the GPU driver and Wayland composer to be compatible they must support the same buffer API. There are two main APIs: GBM and EGLStreams.

Weston

Weston is the reference implementation of a Wayland compositor.

Installation

Install the weston package.

Usage

Now that Wayland and its requirements are installed you should be ready to test it out.

It is possible to run Weston inside a running X session:

$ weston

Alternatively, to try to launch Weston natively, switch to a terminal and run:

$ weston-launch

Then at a TTY within Weston, you can run the demos. To launch a terminal emulator:

$ weston-terminal

To move flowers around the screen:

$ weston-flower 

To display images:

$ weston-image image1.jpg image2.jpg...

Configuration

Example configuration file for keyboard layout, module selection and UI modifications. See weston.ini(5) for full details. The Weston outputs differ slightly from xorg.conf's Monitors:

$ ls /sys/class/drm
card0
card0-VGA-1
card1
card1-DVI-I-1
card1-HDMI-A-1
card1-VGA-2

card0 is the unused built-in video adapter. The add-on adapter card1 is cabled to one HDMI and one DVI monitor, so the output names are HDMI-A-1 and DVI-I-1.

~/.config/weston.ini

[core]
# xwayland support
modules=xwayland.so

[libinput]
enable_tap=true

[shell]
background-image=/usr/share/backgrounds/gnome/Aqua.jpg
background-color=0xff002244
panel-color=0x90ff0000
locking=true
animation=zoom
close-animation=fade
focus-animation=dim-layer
#binding-modifier=ctrl
#num-workspaces=6
### for cursor themes install xcursor-themes pkg from Extra. ###
#cursor-theme=whiteglass
#cursor-size=24

### tablet options ###
#lockscreen-icon=/usr/share/icons/gnome/256x256/actions/lock.png
#lockscreen=/usr/share/backgrounds/gnome/Garden.jpg
#homescreen=/usr/share/backgrounds/gnome/Blinds.jpg
#animation=fade

###  for Laptop displays  ###
#[output]
#name=LVDS1
#mode=1680x1050
#transform=90

#[output]
#name=VGA1
# The following sets the mode with a modeline, you can get modelines for your preffered resolutions using the cvt utility
#mode=173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
#transform=flipped

#[output]
#name=X1
#mode=1024x768
#transform=flipped-270

[input-method]
#path=/usr/lib/weston/weston-keyboard

[keyboard]
keymap_rules=evdev
#keymap_layout=gb,de
#keymap_options=caps:ctrl_modifier,shift:both_capslock_cancel
### keymap_options from /usr/share/X11/xkb/rules/base.lst ###
numlock-on=true

[terminal]
#font=DroidSansMono
#font-size=14

[launcher]
icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png
path=/usr/bin/weston-terminal

[launcher]
icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png
path=/usr/bin/gnome-terminal

[launcher]
icon=/usr/share/icons/hicolor/24x24/apps/firefox.png
path=/usr/bin/firefox

[launcher]
icon=/usr/share/weston/icon_flower.png
path=/usr/bin/weston-flower

[screensaver]
# Uncomment path to disable screensaver
path=/usr/libexec/weston-screensaver
duration=600

Minimal weston.ini :

~/.config/weston.ini

[core]
modules=xwayland.so

[keyboard]
keymap_layout=gb

[output]
name=LVDS1
mode=1680x1050
transform=90

[launcher]
icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png
path=/usr/bin/weston-terminal

[launcher]
icon=/usr/share/icons/hicolor/24x24/apps/firefox.png
path=/usr/bin/firefox

XWayland

Install the xorg-server-xwayland package.

When you want to run an X application from within Weston, it spins up Xwayland to service the request. The following configuration is shown above:

~/.config/weston.ini

[core]
modules=xwayland.so

Screencast recording

Weston has build-in screencast recording which can be started and stopped by pressing the Super+r key combination. Screencasts are saved to the file capture.wcap in the current working directory of Weston.

The WCAP format is a lossless video format specific to Weston, which only records the difference in frames. To be able to play the recorded screencast, the WCAP file will need to be converted to a format which a media player can understand. First, convert the capture to the YUV pixel format:

$ wcap-decode capture.wcap --yuv4mpeg2 > capture.y4m

The YUV file can then be transcoded to other formats using FFmpeg.

High DPI displays

For Retina or HiDPI displays, use:

~/.config/weston.ini

[output]
name=...
scale=2

Shell font

Weston uses the default sans-serif font for window title bars, clocks, etc. See Font configuration#Replace or set default fonts for instructions on how to change this font.

GUI libraries

See details on the official website.

GTK+ 3

The gtk3 package has the Wayland backend enabled. GTK+ will default to the X11 backend, but this can be overridden by modifying an environment variable: GDK_BACKEND=wayland.

Qt 5

To enable Wayland support in Qt 5, install the qt5-wayland package.

To run a Qt 5 app with the Wayland plugin, use -platform wayland or set the QT_QPA_PLATFORM=wayland-egl environment variable.

Clutter

The Clutter toolkit has a Wayland backend that allows it to run as a Wayland client. The backend is enabled in the clutter package.

To run a Clutter app on Wayland, set CLUTTER_BACKEND=wayland.

SDL2

To run a SDL2 application on Wayland, set SDL_VIDEODRIVER=wayland.

GLFW

To use GLFW with the Wayland backend, install the glfw-wayland package (instead of glfw-x11).

EFL

EFL has complete Wayland support. To run a EFL application on Wayland, see Wayland project page.

Window managers and desktop shells

Some of installed wayland desktop clients might store information in /usr/share/wayland-sessions/*.desktop files about how to start them in wayland.

Troubleshooting

Running graphical applications as root

Trying to run a graphical application as root via su, sudo or pkexec in a Wayland session (e.g. GParted or Gedit), be it in a terminal emulator or from a graphical component, will fail with an error similar to this:

$ sudo gedit
No protocol specified
Unable to init server: Could not connect: Connection refused

(gedit:2349): Gtk-WARNING **: cannot open display: :0

Before Wayland, running GUI applications with elevated privileges could be properly implemented by creating a Polkit policy, or more dangerously done by running the command in a terminal by prepending the command with sudo; but under (X)Wayland this does not work anymore as the default has been made to only allow the user who started the X server to connect clients to it (see the bug report and the upstream commits it refers to).

The most straightforward workaround is to use xhost to temporarily allow the root user to access the local user's X session. To do so, execute the following command as the current (unprivileged) user[1]:

 xhost si:localuser:root

To remove this access after the application has been closed:

 xhost -si:localuser:root

LLVM assertion failure

If you get an LLVM assertion failure, you need to rebuild mesa without Gallium LLVM until this problem is fixed.

This may imply disabling some drivers which require LLVM. You may also try exporting the following, if having problems with hardware drivers:

$ export EGL_DRIVER=/usr/lib/egl/egl_gallium.so

Slow motion, graphical glitches, and crashes

Gnome-shell users may experience display issues when they switch to Wayland from X. One of the root cause might be the CLUTTER_PAINT=disable-clipped-redraws:disable-culling set by yourself for Xorg-based gnome-shell. Just try to remove it from /etc/environment or other rc files to see if everything goes back to normal.

nemo

(20161229) prevent that the desktop is created <ref>nemo issue 1343</ref>

gsettings set org.nemo.desktop show-desktop-icons false

X11 on tty1, wayland on tty2

(20161209) windows of gnome applications end up on tty2 no matter where started (gnome issue 774775)

gnome wayland on tty1, weston on tty2

(20170106) apps started on gnome with WAYLAND_DISPLAY set to westen make it not respond any more (wayland issue 99489)

weston-terminal

(20161229) core dump when started on gnome

liteide

(20161229) core dump] on gnome and weston.

screen recording

(20161229) As of November 2016 there is an ongoing discussion how to implement screen recording. Currently the compositors implement at least basic functionality.

remote display

(20161229) there was a merge of FreeRDP into weston in 2013, enabled via compile time switch. The arch linux weston package currently has it not enabled.

Input grabbing in games, remote desktop and VM windows

In contrast to Xorg, Wayland does not allow exclusive input device grabbing, also known as active or explicit grab (e.g. keyboard, mouse), instead, it depends on the Wayland compositor to pass keyboard shortcuts and confine the pointer device to the application window.

This change in input grabbing breaks current applications' behavior, meaning:

• Hotkey combinations and modifiers will be caught by the compositor and won't be sent to remote desktop and virtual machine windows.
• The mouse pointer will not be restricted to the application's window which might cause a parallax effect where the location of the mouse pointer inside the window of the virtual machine or remote desktop is displaced from the host's mouse pointer.

Wayland solves this by adding protocol extensions for Wayland and XWayland. Support for these extensions is needed to be added to Wayland compositors, XWayland and in the case of native Wayland clients to widget toolkits (e.g GTK, QT) and probably also to the applications themselves. ATM there is no Wayland compositor which support all of these extensions.

The related extensions are:

• XWayland keyboard grabbing protocol, added in wayland-protocols 1.9, XWayland support already been added to xorg-server 1.20 development tree.
• Compositor shortcuts inhibit protocol (native Wayland only), added in wayland-protocols 1.9
• Relative pointer protocol, added in wayland-protocols 1.1, XWayland support already been added in xorg-server 1.19
• Pointer constraints protocol, added in wayland-protocols 1.1, XWayland support already been added in xorg-server 1.19

See also

• Article about Wayland debugging on Fedora Wiki
• Cursor themes
• Arch Linux forum discussion
• Wayland documentation online