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Rust bindings for the FLTK Graphical User Interface library.

The fltk crate is a crossplatform lightweight gui library which can be statically linked to produce small, self-contained and fast gui applications.


Why choose FLTK?

Here is a list of software using FLTK. For software using fltk-rs, check here.


Just add the following to your project’s Cargo.toml file:

fltk = "^1"

To use the latest changes in the repo:

fltk = { version = "^1", git = "https://github.com/fltk-rs/fltk-rs" }

To use the bundled libs (available for x64 windows (msvc & gnu (msys2-mingw)), x64 linux & macos):

fltk = { version = "^1", features = ["fltk-bundled"] }

The library is automatically built and statically linked to your binary.

For faster builds you can enable ninja builds for the C++ source using the “use-ninja” feature.

An example hello world application:

use fltk::{app, prelude::*, window::Window};

fn main() {
    let app = app::App::default();
    let mut wind = Window::new(100, 100, 400, 300, "Hello from rust");

Another example showing the basic callback functionality:

use fltk::{app, button::Button, frame::Frame, prelude::*, window::Window};

fn main() {
    let app = app::App::default();
    let mut wind = Window::new(100, 100, 400, 300, "Hello from rust");
    let mut frame = Frame::new(0, 0, 400, 200, "");
    let mut but = Button::new(160, 210, 80, 40, "Click me!");
    but.set_callback(move |_| frame.set_label("Hello World!"));

Please check the examples directory for more examples. You will notice that all widgets are instantiated with a new() method, taking the x and y coordinates, the width and height of the widget, as well as a label which can be left blank if needed. Another way to initialize a widget is using the builder pattern: (The following buttons are equivalent)

let but1 = Button::new(10, 10, 80, 40, "Button 1");

let but2 = Button::default()
    .with_pos(10, 10)
    .with_size(80, 40)
    .with_label("Button 2");

An example of a counter showing use of the builder pattern:

fn main() {
    let app = app::App::default();
    let mut wind = Window::default()
        .with_size(160, 200)
    let mut frame = Frame::default()
        .with_size(100, 40)
    let mut but_inc = Button::default()
        .above_of(&frame, 0)
    let mut but_dec = Button::default()
        .below_of(&frame, 0)
    /* Event handling */

Alternatively, you can use packs to layout your widgets:

    let mut wind = Window::default().with_size(160, 200).with_label("Counter");
    // Vertical is default. You can choose horizontal using pack.set_type(PackType::Horizontal);
    let mut pack = Pack::default().with_size(120, 140).center_of(&wind);
    let mut but_inc = Button::default().with_size(0, 40).with_label("+");
    let mut frame = Frame::default().with_size(0, 40).with_label("0");
    let mut but_dec = Button::default().with_size(0, 40).with_label("-");


Events can be handled using the set_callback method (as above) or the available fltk::app::set_callback() free function, which will handle the default trigger of each widget(like clicks for buttons):

    /* previous hello world code */
    but.set_callback(move |_| frame.set_label("Hello World!"));

Another way is to use message passing:

    /* previous counter code */
    let (s, r) = app::channel::<Message>();

    but_inc.emit(s, Message::Increment);
    but_dec.emit(s, Message::Decrement);
    while app.wait() {
        let label: i32 = frame.label().parse().unwrap();
        match r.recv() {
            Some(Message::Increment) => frame.set_label(&(label + 1).to_string()),
            Some(Message::Decrement) => frame.set_label(&(label - 1).to_string()),
            None => (),

For the remainder of the code, check the full example here.

For custom event handling, the handle() method can be used:

    some_widget.handle(move |widget, ev: Event| {
        match ev {
            /* handle ev */

Handled or ignored events using the handle method should return true, unhandled events should return false. More examples are available in the fltk/examples directory.


FLTK offers 4 application themes (called schemes):

These can be set using the App::with_scheme() method.

let app = app::App::default().with_scheme(app::Scheme::Gleam);

Themes of individual widgets can be optionally modified using the provided methods in the WidgetExt trait, such as set_color(), set_label_font(), set_frame() etc:

    some_button.set_color(Color::Light1); // You can use one of the provided colors in the fltk enums
    some_button.set_color(Color::from_rgb(255, 0, 0)); // Or you can specify a color by rgb or hex/u32 value


The following are the features offered by the crate:


Rust (version > 1.38), CMake (version > 3.0), Git and a C++11 compiler need to be installed and in your PATH for a crossplatform build from source. This crate also offers a bundled form of fltk on selected platforms (win 10 x64, macos 10.15 x64, linux x64), this can be enabled using the fltk-bundled feature-flag (which requires curl and tar to download and unpack the bundled libraries).

For Debian-based GUI distributions, that means running:

$ sudo apt-get install libx11-dev libxext-dev libxft-dev libxinerama-dev libxcursor-dev libxrender-dev libxfixes-dev libpango1.0-dev libpng-dev libgl1-mesa-dev libglu1-mesa-dev

For RHEL-based GUI distributions, that means running:

$ sudo yum groupinstall "X Software Development" && yum install pango-devel libXinerama-devel libpng-devel

For Arch-based GUI distributions, that means running:

$ sudo pacman -S libx11 libxext libxft libxinerama libxcursor libxrender libxfixes libpng pango cairo libgl mesa --needed

For Alpine linux:

$ apk add pango-dev fontconfig-dev libxinerama-dev libxfixes-dev libxcursor-dev libpng-dev mesa-gl

For NixOS (Linux distribution) this nix-shell environment can be used:

$ nix-shell --packages rustc cmake git gcc xorg.libXext xorg.libXft xorg.libXinerama xorg.libXcursor xorg.libXrender xorg.libXfixes libpng libcerf pango cairo libGL mesa pkg-config


please check the FAQ page for frequently asked questions, encountered issues, guides on deployment, and contribution.


To build, just run:

$ git clone https://github.com/fltk-rs/fltk-rs
$ cd fltk-rs
$ cargo build


To run the examples:

$ cargo run --example editor
$ cargo run --example calculator
$ cargo run --example calculator2
$ cargo run --example terminal
$ cargo run --example counter
$ cargo run --example hello
$ cargo run --example hello_button
$ cargo run --example fb
$ cargo run --example pong
$ cargo run --example custom_widgets
$ cargo run --example custom_dial

Using custom theming and also FLTK provided default themes like Gtk:















Different frame types which can be used with many different widgets such as Frame, Button widgets, In/Output widgets…etc.

More interesting examples can be found in the fltk-rs-demos repo. Also a nice implementation of the 7guis tasks can be found here.

Currently implemented types:

Image types:


Drawing primitives

(In the draw module)

Surface types:


More videos in the playlist here. Some of the demo projects can be found here.