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 (~13kLOC)
Focus on portability, efficiency and simplicity
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_panel 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);

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