--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,11 +16,11 @@ gui = ["cairo-rs", "gdk", "gio", "glib",
 [dependencies]
 input-linux = "0.3.0"
 bitflags = "1.2.1"
-cairo-rs = { version = "0.9.1", optional = true }
-gdk = { version = "0.13.2", optional = true }
-gio = { version = "0.9.1", optional = true }
-glib = { version = "0.10.2", optional = true }
-gtk = { version = "0.9.2", optional = true }
+cairo-rs = { version = "0.14", optional = true }
+gdk = { version = "0.14", optional = true }
+gio = { version = "0.14", optional = true }
+glib = { version = "0.14", optional = true }
+gtk = { package = "gtk4", version = "0.2", optional = true }
 
 [profile.release]
 lto = true

--- a/src/gtk.rs
+++ b/src/gtk.rs
@@ -27,26 +27,25 @@ use crate::{
     DEFAULT_WIDTH, DEFAULT_HEIGHT,
 };
 
-fn build_main_menu(application: &gtk::Application) {
+fn build_main_menu(app: &gtk::Application) {
     let quit = gio::SimpleAction::new("quit", None);
-    application.set_accels_for_action("app.quit", &["<Control>q"]);
-    application.add_action(&quit);
-    quit.connect_activate(clone!(@weak application => move |_, _| application.quit()));
+    app.set_accels_for_action("app.quit", &["<Control>q"]);
+    app.add_action(&quit);
+    quit.connect_activate(clone!(@weak app => move |_, _| app.quit()));
 
     let about = gio::SimpleAction::new("about", None);
-    application.add_action(&about);
+    app.add_action(&about);
     about.connect_activate(|_, _| {
-        let about = gtk::AboutDialog::new();
-        about.set_program_name("TabletEmu");
-        about.set_logo_icon_name(Some("input-tablet"));
-        about.set_website(Some("https://hg.linkmauve.fr/tablet-emu"));
-        about.set_version(Some("0.1"));
-        about.set_license_type(gtk::License::Agpl30);
-        about.set_copyright(Some("© 2020 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>"));
-        about.run();
-        unsafe {
-            about.destroy();
-        }
+        let about = gtk::AboutDialog::builder()
+            .program_name("TabletEmu")
+            .logo_icon_name("input-tablet")
+            .website("https://hg.linkmauve.fr/tablet-emu")
+            .version("0.1")
+            .license_type(gtk::License::Agpl30)
+            .copyright("© 2020 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>")
+            .build();
+        //about.run();
+        about.destroy();
     });
 
     let menu = gio::Menu::new();
@@ -60,11 +59,11 @@ fn build_main_menu(application: &gtk::Ap
         help.append(Some("_About"), Some("app.about"));
         menu.append_submenu(Some("_Help"), &help);
     }
-    application.set_menubar(Some(&menu));
+    app.set_menubar(Some(&menu));
 }
 
-fn build_ui(application: &gtk::Application) {
-    build_main_menu(application);
+fn build_ui(app: &gtk::Application) {
+    build_main_menu(app);
 
     let state = match State::new() {
         Ok(state) => Arc::new(Mutex::new(state)),
@@ -84,12 +83,12 @@ fn build_ui(application: &gtk::Applicati
         }
     };
 
-    let window = gtk::ApplicationWindow::new(application);
-    window.set_title("tablet-emu");
-    window.set_position(gtk::WindowPosition::Center);
-
-    let hbox = gtk::Box::new(gtk::Orientation::Horizontal, 0);
-    let tools_box = gtk::Box::new(gtk::Orientation::Vertical, 0);
+    let hbox = gtk::Box::builder()
+        .orientation(gtk::Orientation::Horizontal)
+        .build();
+    let tools_box = gtk::Box::builder()
+        .orientation(gtk::Orientation::Vertical)
+        .build();
 
     macro_rules! impl_tool {
         ($tool:tt) => {
@@ -98,7 +97,7 @@ fn build_ui(application: &gtk::Applicati
             tool.connect_clicked(move |b| {
                 let state = state_weak.upgrade().unwrap();
                 let mut state = state.lock().unwrap();
-                let tool = match b.get_label().unwrap().as_str() {
+                let tool = match b.label().unwrap().as_str() {
                     "_Pen" => Key::ButtonToolPen,
                     "_Rubber" => Key::ButtonToolRubber,
                     "_Brush" => Key::ButtonToolBrush,
@@ -108,82 +107,80 @@ fn build_ui(application: &gtk::Applicati
                 };
                 state.select_tool(tool);
             });
-            tools_box.add(&tool);
+            tools_box.append(&tool);
         };
-    };
+    }
     impl_tool!("_Pen");
     impl_tool!("_Rubber");
     impl_tool!("_Brush");
     impl_tool!("P_encil");
     impl_tool!("_Airbrush");
 
-    let drawing_area = gtk::DrawingArea::new();
-    drawing_area.set_size_request(DEFAULT_WIDTH, DEFAULT_HEIGHT);
-    drawing_area.set_hexpand(true);
-    drawing_area.set_events(
-        gdk::EventMask::BUTTON_PRESS_MASK
-            | gdk::EventMask::BUTTON_RELEASE_MASK
-            | gdk::EventMask::POINTER_MOTION_MASK,
-    );
+    let drawing_area = gtk::DrawingArea::builder()
+        .content_width(DEFAULT_WIDTH)
+        .content_height(DEFAULT_HEIGHT)
+        .hexpand(true)
+        .build();
+    let gesture_click = gtk::GestureClick::builder()
+        .build();
+    let event_controller = gtk::EventControllerMotion::builder()
+        .build();
     let state_weak = Arc::downgrade(&state);
-    drawing_area.connect_configure_event(move |_, event| {
+    drawing_area.connect_resize(move |_, width, height| {
         let state = state_weak.upgrade().unwrap();
         let mut state = state.lock().unwrap();
-        state.set_size(event.get_size());
-        true
+        state.set_size(width, height);
     });
     let state_weak = Arc::downgrade(&state);
-    drawing_area.connect_button_press_event(move |_, event| {
-        if event.get_button() != 1 {
-            return Inhibit(false);
+    gesture_click.connect_pressed(move |_, n_press, x, y| {
+        if n_press != 1 {
+            return;
         }
 
         let state = state_weak.upgrade().unwrap();
         let mut state = state.lock().unwrap();
-        let (x, y) = event.get_position();
         state.press(x, y).unwrap();
-        Inhibit(false)
     });
     let state_weak = Arc::downgrade(&state);
-    drawing_area.connect_button_release_event(move |_, event| {
-        if event.get_button() != 1 {
-            return Inhibit(false);
+    gesture_click.connect_released(move |_, n_press, x, y| {
+        if n_press != 1 {
+            return;
         }
 
         let state = state_weak.upgrade().unwrap();
         let mut state = state.lock().unwrap();
-        let (x, y) = event.get_position();
         state.release(x, y).unwrap();
-        Inhibit(false)
     });
-    drawing_area.connect_motion_notify_event(move |_, event| {
+    event_controller.connect_motion(move |_, x, y| {
         let mut state = state.lock().unwrap();
-        let (x, y) = event.get_position();
         state.motion(x, y).unwrap();
-        Inhibit(false)
     });
-    drawing_area.connect_draw(move |_, ctx| {
-        //println!("drawing {}", drawing_area);
+    drawing_area.add_controller(&gesture_click);
+    drawing_area.add_controller(&event_controller);
+    drawing_area.set_draw_func(move |_, ctx, _, _| {
         ctx.set_source_rgb(1., 0., 0.);
         ctx.set_operator(cairo::Operator::Screen);
-        ctx.paint();
-        Inhibit(false)
+        ctx.paint().unwrap();
     });
 
-    hbox.add(&tools_box);
-    hbox.add(&drawing_area);
+    hbox.append(&tools_box);
+    hbox.append(&drawing_area);
 
-    window.add(&hbox);
+    let window = gtk::ApplicationWindow::builder()
+        .application(app)
+        .title("tablet-emu")
+        .default_width(800)
+        .default_height(480)
+        .child(&hbox)
+        .build();
 
-    window.show_all();
+    window.show();
 }
 
-pub fn main(args: &[String]) {
-    let application = gtk::Application::new(
-        Some("fr.linkmauve.TabletEmu"),
-        gio::ApplicationFlags::empty(),
-    )
-    .expect("Initialisation failed…");
-    application.connect_activate(build_ui);
-    application.run(args);
+pub fn main(_args: &[String]) {
+    let app = gtk::Application::builder()
+        .application_id("fr.linkmauve.TabletEmu")
+        .build();
+    app.connect_activate(build_ui);
+    app.run();
 }

--- a/src/server.rs
+++ b/src/server.rs
@@ -92,7 +92,7 @@ pub fn run_server(address: &str) -> io::
 
     let mut event: Event = Default::default();
     let mut last = Some((0., 0.));
-    state.set_size((320, 240));
+    state.set_size(320, 240);
     loop {
         // TODO: Yolo-alignment.
         let buf: &mut [u8; 16] = unsafe { std::mem::transmute(&mut event) };

--- a/src/state.rs
+++ b/src/state.rs
@@ -46,7 +46,7 @@ impl State {
         })
     }
 
-    pub fn set_size(&mut self, (width, height): (u32, u32)) {
+    pub fn set_size(&mut self, width: i32, height: i32) {
         self.width = width as f64;
         self.height = height as f64;
     }