dim13 / fenster

The most minimal cross-platform GUI library

Fenster

Fenster /ˈfɛnstɐ/ -- a German word for "window".

This library provides the most minimal and highly opinionated way to display a cross-platform 2D canvas. If you remember Borland BGI or drawing things in QBASIC or INT 10h- you know what I mean. As a nice bonus you also get cross-platform keyboard/mouse input and audio playback in only a few lines of code.

What it does for you

• Single application window of given size with a title.
• Application lifecycle and system events are all handled automatically.
• Minimal 24-bit RGB framebuffer.
• Cross-platform keyboard events (keycodes).
• Cross-platform mouse events (X/Y + mouse click).
• Cross-platform timers to have a stable FPS rate.
• Cross-platform audio playback (WinMM, CoreAudio, ALSA).
• Simple polling API without a need for callbacks or multithreading (like Arduino/Processing).
• One C99 header of ~300LOC, easy to understand and extend.
• Go bindings (import "github.com/zserge/fenster", see godoc)
• Zig bindings (see examples/minimal-zig)
• And, yes, it can run Doom!

Example

Here's how to draw white noise:

// main.c
#include "fenster.h"
#define W 320
#define H 240
int main() {
  uint32_t buf[W * H];
  struct fenster f = { .title = "hello", .width = W, .height = H, .buf = buf };
  fenster_open(&f);
  while (fenster_loop(&f) == 0) {
    for (int i = 0; i < W; i++) {
      for (int j = 0; j < H; j++) {
        fenster_pixel(&f, i, j) = rand();
      }
    }
  }
  fenster_close(&f);
  return 0;
}

Compile it and run:

# Linux
cc main.c -lX11 -lasound -o main && ./main
# macOS
cc main.c -framework Cocoa -framework AudioToolbox -o main && ./main
# windows
cc main.c -lgdi32 -lwinmm -o main.exe && main.exe

That's it.

API

API is designed to be a polling loop, where on every iteration the framebuffer get updated and the user input (mouse/keyboard) can be polled.

struct fenster {
  const char *title; /* window title */
  const int width; /* window width */
  const int height; /* window height */
  uint32_t *buf; /* window pixels, 24-bit RGB, row by row, pixel by pixel */
  int keys[256]; /* keys are mostly ASCII, but arrows are 17..20 */
  int mod;       /* mod is 4 bits mask, ctrl=1, shift=2, alt=4, meta=8 */
  int x;         /* mouse X coordinate */
  int y;         /* mouse Y coordinate */
  int mouse;     /* 0 = no buttons pressed, 1 = left button pressed */
};

• int fenster_open(struct fenster *f) - opens a new app window.
• int fenster_loop(struct fenster *f) - handles system events and refreshes the canvas. Returns negative values when app window is closed.
• void fenster_close(struct fenster *f) - closes the window and exists the graphical app.
• void fenster_sleep(int ms) - pauses for ms milliseconds.
• int64_t fenster_time() - returns current time in milliseconds.
• fenster_pixel(f, x, y) = 0xRRGGBB - set pixel color.
• uint32_t px = fenster_pixel(f, x, y); - get pixel color.

See examples/drawing-c for more old-school drawing primitives, but also feel free to experiment with your own graphical algorithms!

License

Code is distributed under MIT license, feel free to use it in your proprietary projects as well.