Zahnrad

This is a minimal state immediate mode graphical user interface toolkit written in ANSI C and licensed under zlib. It was designed as a simple embeddable user interface for application and does not have any direct dependencies, a default renderbackend or OS window and input handling but instead provides a very modular library approach by using simple input state for input and draw commands describing primitive shapes as output. So instead of providing a layered library that tries to abstract over a number of platform and render backends it only focuses on the actual UI.

Features

Immediate mode graphical user interface toolkit
Written in C89 (ANSI C)
Small codebase (~9kLOC)
Focus on portability, efficiency, simplicity and minimal internal state
No dependencies (not even the standard library)
No global or hidden state
Configurable style and colors
UTF-8 support

Optional

Vertex buffer output
Font handling

Building

The library is self-contained within four different files that only have to be copied and compiled into your application. Files zahnrad.c and zahnrad.h make up the core of the library, while stb_rect_pack.h and stb_truetype.h are for a optional font handling implementation and can be removed if not needed.

zahnrad.c
zahnrad.h
stb_rect_pack.h (optional)
stb_truetype.h (optional)

There are no dependencies or a particular building process required. You just have to compile the .c file and #include zahnrad.h into your project. To actually run you have to provide the input state, configuration style and memory for draw commands to the library. After the GUI was executed all draw commands have to be either executed or optionally converted into a vertex buffer to draw the GUI.

Gallery

Example

/* init gui state */
struct zr_context ctx;
zr_init_fixed(&ctx, calloc(1, MAX_MEMORY), MAX_MEMORY, &font);

enum {EASY, HARD};
int op = EASY;
float value = 0.6f;
int i =  20;

struct zr_layout layout;
zr_begin(&ctx, &layout, "Show", zr_rect(50, 50, 220, 220),
    ZR_WINDOW_BORDER|ZR_WINDOW_MOVEABLE|ZR_WINDOW_CLOSEABLE);
{
    /* fixed widget pixel width */
    zr_layout_row_static(&ctx, 30, 80, 1);
    if (zr_button_text(&ctx, "button", ZR_BUTTON_DEFAULT)) {
        /* event handling */
    }

    /* fixed widget window ratio width */
    zr_layout_row_dynamic(&ctx, 30, 2);
    if (zr_option(&ctx, "easy", op == EASY)) op = EASY;
    if (zr_option(&ctx, "hard", op == HARD)) op = HARD;

    /* custom widget pixel width */
    zr_layout_row_begin(&ctx, ZR_STATIC, 30, 2);
    {
        zr_layout_row_push(&ctx, 50);
        zr_label(&ctx, "Volume:", ZR_TEXT_LEFT);
        zr_layout_row_push(&ctx, 110);
        zr_slider_float(&ctx, 0, &value, 1.0f, 0.1f);
    }
    zr_layout_row_end(&ctx);
}
zr_end(ctx);

Documentation

Zahnrad currently relies heavily on documentation provided inside the zahnrad.h header file, consisting of descriptions and important information about modules, data types and functions. While being quite limited in delivering information about the general high-level libray composition it should still offer some understanding about the inner workings and stand as a practical usage reference.

Examples

A number of usage examples can be found inside the example and demo folder which should yield a basic overview how to embed the libray into different platforms with varying APIs and provided functionality and hopefully offer a basic understanding of zahnrad's UI API. In general it is advised to start by reading example/demo. It consists of a basic embedding example into SDL, OpenGL and NanoVG with a very simple set of used widgets and layouting.

As soon as a basic understanding of the library is accumulated it is recommended to look into the demo/ folder with your platform of choice. For now a basic platform layer was implemented for Linux(X11), Windows(win32) and OpenGL with SDL and GLFW. Both platform specific demos (X11, win32) use their respectable window, input, draw and font API and don't have any outside dependencies which should qualify them as the first platform to compile, run and test. For hardware supported rendering, font both the SDL and GLFW version use zahnrad's internal vertex buffer output and font baker.

Up until now you should hopefully have a basic grip of how to use zahnrad UI API and be able to embed zahnrad into your plaform. From here on demo/demo.c should provide a basic reference on how use most widgets and layouting. Finally for some small actual working example apps both example/filex with implementation of a linux only file browser and example/nodedit with a basic node editor skeleton are provided. Especially the nodedit example should show how far you can bend the this library to your own needs.

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