CUI

A UI library for C that draws its own components.

Live site · Getting started · Tutorial · Components · Downloads

Every image on this page is drawn by CUI, from plain C.

CUI is an immediate-mode UI library written in C99. You describe the screen with function calls every frame. CUI lays it out, handles the mouse and keyboard, and draws it with OpenGL or its own software renderer, in a window on Windows, macOS or Linux, or in a browser through WebAssembly.

• About 210 components, from buttons and text fields to a data grid, charts, a code editor and docking panels.
• No dependencies. One CMake target, or two files (cui.h and cui.c) dropped into your project.
• Small. A complete app, window, fonts and all, is about 250 KB. There is no browser or runtime inside.
• MIT licensed.

Try it first

• In your browser: the live site runs every component and the example apps. It is the same C code, compiled to WebAssembly.
• On your computer, without a compiler: each release has the example apps built for Windows, macOS and Linux.
• In code: the tutorial builds a to-do app in about 130 lines.

A small program

#include <cui/cui.h>
#include <cui/cui_app.h>

int main(void) {
    cui_app *app = cui_app_create(&(cui_app_desc){
        .title = "Hello", .width = 420, .height = 300 });
    if (!app) return 1;
    bool notifications = true;
    int clicks = 0;

    while (cui_app_frame(app)) {
        cui_ctx *ui = cui_app_ui(app);
        cui_column(ui, .pad = 32, .gap = 16) {
            cui_heading(ui, "Hello, CUI", 2);
            cui_secondary(ui, "A native window, a few components "
                              "and no dependencies.");
            cui_switch(ui, "Notifications", &notifications);
            cui_row(ui, .gap = 8) {
                if (cui_button(ui, "Click me", .variant = CUI_BUTTON_PRIMARY))
                    clicks++;
                cui_textf(ui, "Clicked %d times", clicks);
            }
        }
    }
    cui_app_destroy(app);
    return 0;
}

A component is a function call. It draws itself, handles input and returns what happened: cui_button returns true on the frame it is clicked.

Options are named arguments. Leave one out and it takes its default.

Your variables are the state. The screen is described again every frame, so there are no widgets to create, keep or update.

What it is, and what it is not

CUI draws every component itself. It does not wrap the system's buttons and menus, so an app looks the same on every system and does not look like the system's own apps. "Native" here means compiled code in a real window, with nothing interpreted and no web view.

How it sits beside the libraries you may know:

• Dear ImGui and Nuklear are also immediate-mode. They are aimed mostly at tools and debug panels inside a program that already has a renderer. CUI uses the same model for the app itself: it opens the window, and its components come with the things end users expect, such as full text editing, animation, light and dark themes and right-to-left layouts.
• Qt, GTK and wxWidgets keep a tree of widgets for you and are far more mature. They have screen reader support, complete input-method support and years of use behind them. If you need those today, use one of them.
• Electron and web views ship a browser with your app. CUI ships about 250 KB.

CUI is a good fit for a desktop tool, an editor, a dashboard or a game's interface written in C or C++, where you want it small and want it to look finished without designing every control. Read Limitations before you decide.

Install

With CMake (GCC, Clang, MSVC and MinGW are tested):

include(FetchContent)
FetchContent_Declare(cui
    GIT_REPOSITORY https://github.com/yappologistic/CUI.git
    GIT_TAG v1.4.0)
FetchContent_MakeAvailable(cui)
target_link_libraries(my_app PRIVATE cui::cui)
cui_app_target(my_app)   # no console window on Windows, and only the code your app uses

Without CMake, take cui.h and cui.c from a release and compile them with your program. Getting started has the exact commands for both, and CI runs those commands on every push.

To build the library and run an example:

git clone https://github.com/yappologistic/CUI.git
cmake -S CUI -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
./build/examples/tracker

Linux needs the X11 development headers (libx11-dev). Windows and macOS need nothing beyond the system SDK.

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