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.

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 timers to have a stable FPS rate.
• It's a single header in plain C99 of ~300LOC with no memory allocations.
• Go bindings (import "github.com/zserge/fenster")

What it might do for you in the next version

• Mouse events (at least left button click + XY)
• Audio playback (WinMM, CoreAudio, ALSA)
• Bindings for other programming languages

What it will never do for you

• GUI widgets - use Qt or Gtk or WxWidgets.
• Complex drawing routines or OpenGL - use Sokol or MiniFB or Tigr.
• Low-latency audio - use PortAudio, RtAudio, libsoundio etc.

In other words, you get a single super tiny C file, with a very simple API and it allows you to build graphical apps (simple games, emulators) in a very low-level retrocomputing manner.

Example

Here's how to draw white noise:

#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 -o main && ./main
# macOS
cc main.c -framework Cocoa -o main && ./main
# windows
# TODO, but link with -lgdi32

That's it.

API

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 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 example.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.