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. It does not have a default renderbackend, os window and input handling but instead provides a very modular library approach by providing a simple input state storage 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 (~8kLOC)
• Focus on portability, efficiency, simplicity and minimal internal state
• No global or hidden state
• No direct dependencies
• 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

enum {EASY, HARD};
int option = EASY;
float value = 0.6f;

struct zr_context context;
zr_begin(&context, &window, "Show");
{
    zr_layout_row_static(&context, 30, 80, 1);
    if (zr_button_text(&context, "button", ZR_BUTTON_DEFAULT)) {
        /* event handling */
    }
    zr_layout_row_dynamic(&context, 30, 2);
    if (zr_option(&context, "easy", option == EASY)) option = EASY;
    if (zr_option(&context, "hard", option == HARD)) option = HARD;
    zr_label(&context, "Volume:", ZR_TEXT_LEFT);
    zr_slider_float(&context, 0, &value, 1.0f, 0.1f);
    zr_layout_row_end(&context);
}
zr_end(&context, &window);

Documentation

For code related documentation and information on how to link each single part to a whole I would recommend reading the documentation inside the zahnrad.h header file wich has information and descriptions about each part, struct, members and functions. In addition I would especially recommend reading the examples and the demo.

If you want to dive into the example code I would recommand starting with example/demo/demo.c, even if you don't know or want to use nanovg. It contains the usage code for every simple to use core part of the library while providing a good looking UI. It also introduces a small set of widgets while providing a simple example of how to do layouting.

As soon as you have a basic grip of how to use the library I would recommend looking at demo/demo.c. It only contains the actual UI part of the GUI but offers example ussage code for all widgets in the library. So it functions more as a reference to look how a widget is supposed to be used.

On how to do the platform and render backend depended part I would recommend looking at some example platform implementations for Win32 (demo/win32/win32.c) for windows and X11 (demo/x11.xlib.c) for linux. Both provide the absolute minimum needed platform dependend code without using any libraries. Finally for the most complex plaform demos it is definitely worth it to read the OpenGL examples with demo/sdl/sdl.c for zahnrad integration with SDL2, OpenGL and GLEW and demo/glfw/glfw.c for integration with GLFW, OpenGL and GLEW. They also include usage code for the optional zahnrad font handling and vertex buffer output.

The final two examples example/filex/filex.c and example/nodedit/nodedit.c both provide actual example application use cases for this library. Filex is a simple file browser for Linux and shows how to do window tiling. The node editor on the other hand is probably the more interesting of the two since it shows how far you can bend this library to your specific problem on hand.