Documentation for this library can be found in the included man pages, and in the Xlib spec from the specs subdirectory, also available at:

• https://www.x.org/releases/current/doc/libX11/libX11/libX11.html

• https://www.x.org/releases/current/doc/libX11/libX11/libX11.pdf

and the O'Reilly Xlib books, which they have made freely available online, though only for older versions of X11:

• X Series Volume 2: Xlib Reference Manual (1989, covers X11R3) https://www.archive.org/details/xlibretmanver1102nyemiss

• X Series Volume 2: Xlib Reference Manual, 2nd Edition (1990, covers X11R4) https://www.archive.org/details/xlibrefmanv115ed02nyemiss

All questions regarding this software should be directed at the Xorg mailing list:

https://lists.x.org/mailman/listinfo/xorg

The primary development code repository can be found at:

https://gitlab.freedesktop.org/xorg/lib/libX11

Please submit bug reports and requests to merge patches there.

For patch submission instructions, see:

https://www.x.org/wiki/Development/Documentation/SubmittingPatches

• Security fixes and hardening in XImage and pixmap handling code (CVE-2023-43786, CVE-2023-43787, !234)
• Fix buffer allocation in _XkbReadKeySyms() (CVE-2023-43785)
• Fail XOpenDisplay() if server-provided default visual is invalid (!233)
• Bring XKB docs in line with actual implementation (!231, !228)
• Xutil.h: declare XEmptyRegion() and XEqualRegion() as Bool (!225)
• Assorted updates to en_US.UTF-8 compose keys (!213, !214, !215, !216, !217, !219, !220, !222, !223, !226, !227, !229)

• Add bounds checks in InitExt.c (CVE-2023-3138)

• autoconf & libtool updates (!187, !188)
• Restore missing text in XSetScreenSaver man page (#187, !203)
• Update am_ET.UTF-8 compose keys to use dead-vowel symbols, in coordination with xkeyboard-config 2.39 (!205)
• Assorted updates to en_US.UTF-8 compose keys (!189, !195, !196, !198, !199, !200, !201, !207, !208, !209)

• Revert AddressSanitizer fix from 1.8.3 that caused regression (#176, !180)
• Add two compose sequences for "capital B with stroke", remove others (!179)
• Further improved handling of reentering libX11 via X*IfEvent() calls (!176)

• Improved handling of reentering libX11 via X*IfEvent() calls (!171, !173)
• Fix loading of en_US.UTF-8/XLC_LOCALE (#167, !174)
• Add XFreeThreads() and automatic call from a destructor function when thread-safety-constructor is enabled (!167).
• Address issues found by UBSan and AddressSanitizer
• Fix build with older gcc versions (!169)

• Allow X*IfEvent() to reenter libX11 to avoid deadlock from unsafe calls when thread-safety-constructor is enabled (!150).
• Remove Xlib's pthread function stubs - instead use system provided threads functions, including linking against any needed pthread libraries if thread-safety-constructor is enabled (!155, !156).
• Fix off-by-one error in XKeycodeToKeysym for indexes > 3 (!78).
• Allow XNSpotLocation with OnTheSpot (!127).
• Fix Win32 build when -fno-common is in effect (!140).
• Fix memory leak in XRegisterIMInstantiateCallback (!158).
• Add compose sequences for the double-struck capitals ℕ ℤ ℚ ℝ ℂ (!144), the Samogitian E with dot above and macron (!147), Unicode minus sign (!163).
• Change <^> <-> to mean superscript minus instead of macron (!162).
• Delete compose sequences that mix top-row digits with numpad digits (!139) or mix upper & lower case letters (!144).
• Delete some unuseful compose sequences meant for Bépo layout (!146).
• Delete compose sequences using leftcaret & rightcaret keysyms (!163).
• Remove KOI8-R character set from en_US.UTF-8/XLC_LOCALE (!148).
• Map sr locales to sr_RS compose files (!161).

• Fix --enable-thread-safety-constructor configure option

• Add --enable-thread-safety-constructor configure option (default: enabled) to call XInitThreads() from the library's constructor, thus enabling thread-safety and locking by default. This may expose bugs in clients which did not follow documented rules for calling libX11 functions.
• Fix Ethopian (am_ET.UTF-8) compose sequences.
• Remove 8 compose sequences that generated the input symbols.
• Add compose seuences for abovedot (<period> <space>), diaeresis (<quotedbl> <space>), and ogonek (<semicolon> <space>).

• Avoids a segfault when an invalid name is used for opening a display.

• Fixes the "Unknown sequence number" error by allowing backward jumps in the sequence number when widening it.
• Any changes to virtual modifiers get propagated properly.
• Greek case-conversion tables were updated to Unicode Data 14.0.
• Compose sequences for ☮ 🄯 ⇐ ⇑ ⇓ were added, being the following: OY, ()), =<, =^, and =v.
• Hammer-and-sickle can be composed with question mark plus backslash.

• Fixes a hanging issue in _XReply() where the replying thread would wait for an event when another thread was already waiting for one.
• Avoids a crash when the X connection gets broken while closing down.

This is a bug fix release, correcting a regression introduced by and improving the checks from the fix for CVE-2021-31535.

This is a bug fix release, including a security fix for CVE-2021-31535, nls and documentation corrections.

• Reject string longer than USHRT_MAX before sending them on the wire
• Fix out-of-bound access in KeySymToUcs4()
• nls: allow composing all breved letters also with a lowercase "u"
• nls: add 'C.utf8' as an alias for 'en_US.UTF-8'
• Nroff code fixes
• Comments fixes

Version 1.7.0 includes a new API, hence the change from the 1.6 series to 1.7:

• XSetIOErrorExitHandler which provides a mechanism for applications to recover from I/O error conditions instead of being forced to exit. Thanks to Carlos Garnacho for this.

This release includes a bunch of bug fixes, some of which have been pending for over three years:

• A bunch of nls cleanups to remove obsolete entries and clean up formatting of the list. Thanks to Benno Schulenberg for these.

• Warning fixes and other cleanups across a huge swath of the library. Thanks to Alan Coopersmith for these.

• Memory allocation bugs, including leaks and use after free in the locale code. Thanks to Krzesimir Nowak, Jacek Caban and Vittorio Zecca for these.

• Thread safety fixes in the locale code. Thanks to Jacek Caban for these.

• poll_for_response race condition fix. Thanks to Frediano Ziglio for the bulk of this effort, and to Peter Hutterer for careful review and improvements.

Version 1.7.0 includes a couple of new locales:

• ia and ie locales. Thanks to Carmina16 for these.

There are also numerous compose entries added, including:

• |^ or ^| for ↑, |v or v| for ↓, ~~ for ≈. Thanks to Antti Savolainen for this.

• Allowing use of 'v' for caron, in addition to 'c', so things like vC for Č, vc for č. Thanks to Benno Schulenberg for this.

• Compose sequences LT, lt for '<', and GT, gt for '>' for keyboards where those are difficult to access. Thanks to Jonathan Belsewir for this.