Crate fltk_sys

source ·
Expand description


Raw bindings for FLTK. These are generated using bindgen on the cfltk headers.


fltk-sys = "1.4"

Example code:

use fltk_sys::*;
use std::os::raw::*;

unsafe extern "C" fn cb(_wid: *mut button::Fl_Widget, data: *mut c_void) {
    let frame = data as *mut frame::Fl_Box;
    frame::Fl_Box_set_label(frame, "Hello World\0".as_ptr() as *const _);

fn main() {
    unsafe {
        let win = window::Fl_Window_new(100, 100, 400, 300, "Window\0".as_ptr() as *const _);
        let frame = frame::Fl_Box_new(0, 0, 400, 200, std::ptr::null());
        let but = button::Fl_Button_new(160, 220, 80, 40, "Click\0".as_ptr() as *const _);

        button::Fl_Button_set_callback(but, Some(cb), frame as *mut _);



CMake > 3.14, git and a C++17 compiler. The dev dependencies are basically the same as for fltk-rs.

§Why you might want to use fltk-sys directly

  • If you need an abi stable cdylib that you can call into (as a plugin system for example).
  • To create your own wrapper around certain elements if you don’t need the whole fltk crate.
  • fltk-sys, although memory and thread unsafe, is panic-safe.
  • You need a no-std gui library, in such case, you can replace the std:: prefix with the libc via bindgen (requires adding libc as a dependency).
  • Wrapping a 3rd-party widget like in fltk-flow.