An x11 client library for Zig applications.

X is a protocol for transmitting graphics primitives and user inputs. It's a client/server model. X clients are typically programs that connect to a server. Once connected, the client program will continually receive "user inputs" from the server (like keyboard/mouse events) and send drawing instructions. X has many extensions but the core specification is found here: https://www.x.org/docs/XProtocol/proto.pdf

XClient libraries use the DISPLAY environment variable to know how to connect to the XServer. It uses this format:

[PROTOCOL/][HOST]:DISPLAYNUM[.SCREEN]

Examples:

# connect to unix socket at /tmp/.X11-unix/X0
:0

# connect to "localhost" on port 6003
localhost:3

# connect to myserver port 6007 screen 5
myserver:7.5

Here are some examples of starting XClient programs and settings the DISPLAY environment variable:

# set the XSever
export DISPLAY=:0

# start a couple XClient programs
./my-cool-x-program &
./another-cool-x-program &

# start this program and connect it to the XServer on host "mymachine" running on port 6010 screen 1
DISPLAY=mymachine:10.1 ./yet-another-x-program

# -n means do not copy credentials
xtrace -n -- command

# i.e.
xtrace -n -- zig build hello

Authentication credentials are stored in a file in a binary format. The default path is $HOME/.Xauthority but can be overriden with the XAUTHORITY environment variable.

This binary file contains a list of credentials. Each entry can contain both an address and/or display number to that indicate which server the authorization applies to. Afterwards it contains a name/data pair to be exchanged with the server for authorization. You can build and use the xauth cli program to list the contents of one of these files, i.e.

zig build xauth -- list

https://en.wikipedia.org/wiki/X_Window_authorization

• MIT-MAGIC-COOKIE: implemented for local connections
• XDM-AUTHORIZATION-1: not implemented

For XDM-AUTHORIZATION-1, a secret key is stored in the $HOME/.Xauthority file, the client creates a string by concatenating the current time, a transport identifier and the key, then encrypts the resulting string and sends it to the server.