Simple and portable (but not inflexible) GUI library in C that uses the native GUI technologies of each platform it supports.
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_abort Some cleanup of the top-level directory. Feb 17, 2018
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unix Fixed uiImage on GTK+. Also changed it to have cairo manage memory an… Aug 30, 2018
windows Sigh MinGW Sep 2, 2018
.appveyor.yml Okay let's try this again, with deployment keys this time. Aug 11, 2018
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CMakeLists.txt Wait I thought I did PIC already wtf Sep 2, 2018 Updated and moved the old OS X draw text stuff out of… Mar 4, 2018 More future plans. Jun 12, 2016
LICENSE Split into a new repository and added a LICENSE. Apr 17, 2015 Finally got around to merging ANNOUNCE and Changelog into NEWS. May 30, 2018
OLD_uitable.h Trying out a new uiTable API. This will make implementations easier, … Jun 3, 2018 Perl6 NativeCall bindings Sep 20, 2018 Wrote the new uiAttribute code in attribute.c. Feb 19, 2018
stats.osxdrawtext Ugh, Core Text and NSLayoutManager produce inconsistent output :| Jan 21, 2017
ui.h And fixed the documentation and marked Alpha 4.1. Sep 1, 2018
ui_darwin.h Added a facility to the OS X port to be notified when a child's visib… Jun 14, 2016
ui_unix.h Comments related to above. Jun 6, 2017
ui_windows.h Implemented visibility change detection on Windows. Now to refine the… Jun 14, 2016

libui: a portable GUI library for C

This README is being written.
Build Status, Linux and macOS
Build Status, Windows


It has come to my attention that I have not been particularly clear about how usable or feature-complete libui is, and that this has fooled many people into expecting more from libui right this moment than I have explicitly promised to make available. I apologize for not doing this sooner.

libui is currently mid-alpha software. Much of what is currently present runs stabily enough for the examples and perhaps some small programs to work, but the stability is still a work-in-progress, much of what is already there is not feature-complete, some of it will be buggy on certain platforms, and there's a lot of stuff missing. In short, here's a list of features that I would like to add to libui, but that aren't in yet:

  • trees
  • clipboard support, including drag and drop
  • more and better dialogs
  • printing
  • accessibility for uiArea and custom controls
  • document-based programs
  • tighter OS integration (especially for document-based programs), to allow programs to fully feel native, rather than merely look and act native
  • better support for standard dialogs and features (search bars, etc.)
  • OpenGL support

In addition, here is a list of issues generalizing existing problems.

Furthermore, libui is not properly fully documented yet. This is mainly due to the fact that the API was initially unstable enough so as to result in rewriting documentation multiple times, in addition to me not being happy with really any existing C code documentation tool. That being said, I have started to pin down my ideal code documentation style in parts of ui.h, most notably in the uiAttributedString APIs. Over time, I plan on extending this to the rest of the headers. You can also use the documentation for libui's Go bindings as a reference, though it is somewhat stale and not optimally written.

But libui is not dead; I am working on it whenever I can, and I hope to get it to a point of real quality soon!


Note that today's entry (Eastern Time) may be updated later today.

  • 1 September 2018

    • Alpha 4.1 is here. This is an emergency fix to Alpha 4 to fix uiImageAppend() not working as documented. It now works properly, with one important difference you'll need to care about: it now requires image data to be alpha-premultiplied. In addition, uiImage also is implemented slightly more nicely now, and ui.h has minor documentation typo fixes.
    • Alpha 4.1 also tries to make everything properly PIC-enabled.
  • 10 August 2018

    • Alpha 4 is finally here. Everything from Alpha 3.5 and what's listed below is in this release; the two biggest changes are still the new text drawing API and new uiTable control. In between all that is a whole bunch of bugfixes, and hopefully more stability too. Thanks to everybody who helped contribute!
    • Alpha 4 should hopefully also include automated binary releases via CI. Thanks to those who helped set that up!
  • 8 August 2018

    • Finally introduced an API for loading images, uiImage, and a new control, uiTable, for displaying tabular data. These provide enough basic functionality for now, but will be improved over time. You can read the documentation for the new features as they are here. Thanks to everyone who helped get to this point, in particular @bcampbell for the initial Windows code, and to everyone else for their patience!
  • 30 May 2018

    • Merged the previous Announcements and Updates section of this README into a single News section, and merged the respective archive files into a single file.
  • 16 May 2018

    • Thanks to @parro-it and @msink, libui now has better CI, including AppVeyor for Windows CI, and automated creation of binary releases when I make a tagged release.
  • 13 May 2018

    • Added new functions to work with uiDateTimePickers: uiDateTimePickerTime(), uiDateTimePickerSetTime(), and uiDateTimePickerOnChanged(). These operate on standard <time.h> struct tms. Thanks @cody271!
    • Release builds on Windows with MSVC should be fixed now; thanks @l0calh05t, @slahn, @mischnic, and @zentner-kyle.
  • 12 May 2018

    • GTK+ and OS X now have a cleaner build process for static libraries which no longer has intermediate files and differing configurations. As a result, certain issues should no longer be present. New naming rules for internal symbols of libui have also started being drafted; runtime symbols and edge cases still need to be handled (and the rules applied to Windows) before this can become a regular thing.
  • 2 May 2018

    • On Windows, you no longer need to carry around a libui.res file with static builds. You do need to link in the appropriate manifest file, such as the one in the windows/ folder (I still need to figure out exactly what is needed apart from the Common Controls v6 dependency, or at least to create a complete-ish template), or at least include it alongside your executables. This also means you should no longer see random cmake errors when building the static libraries.
  • 18 April 2018

    • Introduced a new uiTimer() function for running code on a timer on the main thread. (Thanks to @cody271.)
    • Migrated all code in the common/ directory to use uipriv prefixes for everything that isn't static. This is the first step toward fixing static library oddities within libui, allowing libui to truly be safely used as either a static library or a shared library.
  • 18 March 2018

    • Introduced an all-new formatted text API that allows you to process formatted text in ways that the old API wouldn't allow. You can read on the whole API here. There is also a new examples for it: drawtext, which shows the whole API at a glance. It doesn't yet support measuring or manipulating text, nor does it currently support functions that would be necessary for things like text editors; all of this will be added back later.
    • libui also now uses my utf library for UTF-8 and UTF-16 processing, to allow consistent behavior across platforms. This usage is not completely propagated throughout libui, but the Windows port uses it in most places now, and eventually this will become what libui will use throughout.
    • Also introduced a formal set of contribution guidelines, see for details. They are still WIP.
  • 17 February 2018

    • The longstanding Enter+Escape crashes on Windows have finally been fixed (thanks to @lxn).
    • Alpha 3.5 is now here. This is a quickie release primiarly intended to deploy the above fix to package ui itself. It is a partial binary release; sorry! More new things will come in the next release, which will also introduce semver (so it will be called v0.4.0 instead).
    • Alpha 3.5 also includes a new control gallery example. The screenshots below have not been updated yet.

Old announcements can be found in the file.

Runtime Requirements

  • Windows: Windows Vista SP2 with Platform Update or newer
  • Unix: GTK+ 3.10 or newer
  • Mac OS X: OS X 10.8 or newer

Build Requirements

  • All platforms:
    • CMake 3.1.0 or newer
  • Windows: either
    • Microsoft Visual Studio 2013 or newer (2013 is needed for va_copy()) — you can build either a static or a shared library
    • MinGW-w64 (other flavors of MinGW may not work) — you can only build a static library; shared library support will be re-added once the following features come in:
      • Isolation awareness, which is how you get themed controls from a DLL without needing a manifest
  • Unix: nothing else specific
  • Mac OS X: nothing else specific, so long as you can build Cocoa programs


Out-of-tree builds typical of cmake are preferred:

$ # you must be in the top-level libui directory, otherwise this won't work
$ mkdir build
$ cd build
$ cmake ..

Pass -DBUILD_SHARED_LIBS=OFF to cmake to build a static library. The standard cmake build configurations are provided; if none is specified, Debug is used.

If you use a makefile generator with cmake, then

$ make
$ make tester         # for the test program
$ make examples       # for examples

and pass VERBOSE=1 to see build commands. Build targets will be in the build/out folder.

Project file generators should work, but are untested by me.

On Windows, I use the Unix Makefiles generator and GNU make (built using the build_w32.bat script included in the source and run in the Visual Studio command line). In this state, if MinGW-w64 (either 32-bit or 64-bit) is not in your %PATH%, cmake will use MSVC by default; otherwise, cmake will use with whatever MinGW-w64 is in your path. set PATH=%PATH%;c:\msys2\mingw(32/64)\bin should be enough to temporarily change to a MinGW-w64 build for the current command line session only if you installed MinGW-w64 through MSYS2; no need to change global environment variables constantly.


Arch Linux

Can be built from AUR:


Needs to be written. Consult ui.h and the examples for details for now.

Language Bindings

libui was originally written as part of my package ui for Go. Now that libui is separate, package ui has become a binding to libui. As such, package ui is the only official binding.

Other people have made bindings to other languages:

Language Bindings
C++ libui-cpp, cpp-libui-qtlike
C# / .NET Framework LibUI.Binding
C# / .NET Core DevZH.UI, SharpUI, LibUISharp
CHICKEN Scheme wasamasa/libui
Common Lisp jinwoo/cl-ui
Crystal, hedron
D DerelictLibui (flat API), libuid (object-oriented)
Euphoria libui-euphoria
Harbour HBUI
Haskell haskell-libui
JavaScript/Node.js libui-node, libui.js (merged into libui-node?), proton-native, vuido
Julia Libui.jl
Kotlin kotlin-libui
Lua libuilua, libui-lua, lui, lui
Nim ui
Perl6 perl6-libui
PHP ui
Python pylibui, pylibui-cffi
Ruby libui-ruby
Rust libui-rs, arcturu/libui-rs, LeoTindall/libui-rs
Scala scalaui
Swift libui-swift

Frequently Asked Questions

Why does my program start in the background on OS X if I run from the command line?

OS X normally does not start program executables directly; instead, it uses Launch Services to coordinate the launching of the program between the various parts of the system and the loading of info from an .app bundle. One of these coordination tasks is responsible for bringing a newly launched app into the foreground. This is called "activation".

When you run a binary directly from the Terminal, however, you are running it directly, not through Launch Services. Therefore, the program starts in the background, because no one told it to activate! Now, it turns out there is an API that we can use to force our app to be activated. But if we use it, then we'd be trampling over Launch Services, which already knows whether it should activate or not. Therefore, libui does not step over Launch Services, at the cost of requiring an extra user step if running directly from the command line.

See also this and this.




From examples/controlgallery: