new file mode 100644
--- /dev/null
+++ b/src/client.rs
@@ -0,0 +1,213 @@
+// Tablet emulator, for people who don’t own one
+// Copyright © 2020 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+use crate::{state::FakeState, DEFAULT_HEIGHT, DEFAULT_WIDTH};
+use gio::prelude::*;
+use glib::clone;
+use gtk::prelude::*;
+use input_linux::Key;
+use std::sync::{Arc, Mutex};
+use std::net::UdpSocket;
+use crate::Event;
+use crate::server::Buttons;
+
+fn build_main_menu(app: &gtk::Application) {
+    let quit = gio::SimpleAction::new("quit", None);
+    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);
+    app.add_action(&about);
+    about.connect_activate(|_, _| {
+        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();
+    {
+        let file = gio::Menu::new();
+        file.append(Some("_Quit"), Some("app.quit"));
+        menu.append_submenu(Some("_File"), &file);
+    }
+    {
+        let help = gio::Menu::new();
+        help.append(Some("_About"), Some("app.about"));
+        menu.append_submenu(Some("_Help"), &help);
+    }
+    app.set_menubar(Some(&menu));
+}
+
+fn build_ui(app: &gtk::Application) {
+    build_main_menu(app);
+
+    let address = "127.0.0.1:16150";
+    let socket = Arc::new(Mutex::new(UdpSocket::bind("127.0.0.1:4321").unwrap()));
+    println!("opened {:?}", socket);
+
+    let send = move |event: &Event| {
+        // TODO: Yolo-alignment.
+        let buf: &[u8; std::mem::size_of::<Event>()] = unsafe { std::mem::transmute(event) };
+        let socket = socket.lock().unwrap();
+        let amount = socket.send_to(buf, address).unwrap();
+        assert_eq!(amount, std::mem::size_of::<Event>());
+    };
+    let send2 = send.clone();
+    let send3 = send.clone();
+    let send4 = send.clone();
+
+    let state = Arc::new(Mutex::new(FakeState::new()));
+
+    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 {
+        ($tool:tt) => {
+            let tool = gtk::Button::with_mnemonic($tool);
+            let state_weak = Arc::downgrade(&state);
+            let send = send.clone();
+            tool.connect_clicked(move |b| {
+                let state = state_weak.upgrade().unwrap();
+                let mut state = state.lock().unwrap();
+                let tool = match b.label().unwrap().as_str() {
+                    "_Pen" => Key::ButtonToolPen,
+                    "_Rubber" => Key::ButtonToolRubber,
+                    "_Brush" => Key::ButtonToolBrush,
+                    "P_encil" => Key::ButtonToolPencil,
+                    "_Airbrush" => Key::ButtonToolAirbrush,
+                    _ => unreachable!(),
+                };
+                state.select_tool(tool);
+
+                let mut event: Event = Default::default();
+                event.buttons = match tool {
+                    Key::ButtonToolPen => Buttons::A,
+                    Key::ButtonToolRubber => Buttons::B,
+                    Key::ButtonToolBrush => Buttons::X,
+                    Key::ButtonToolPencil => Buttons::Y,
+                    Key::ButtonToolAirbrush => Buttons::SELECT,
+                    _ => unreachable!(),
+                };
+                send(&event);
+            });
+            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::builder()
+        .content_width(DEFAULT_WIDTH)
+        .content_height(DEFAULT_HEIGHT)
+        .hexpand(true)
+        .build();
+    let gesture_click = gtk::GestureClick::new();
+    let event_controller = gtk::EventControllerMotion::new();
+    let state_weak = Arc::downgrade(&state);
+    drawing_area.connect_resize(move |_, width, height| {
+        let state = state_weak.upgrade().unwrap();
+        let mut state = state.lock().unwrap();
+        state.set_size(width, height);
+
+        let mut event: Event = Default::default();
+        event.buttons = Buttons::RESIZE;
+        event.touch = (width as u16, height as u16);
+        send(&event);
+    });
+    let state_weak = Arc::downgrade(&state);
+    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();
+        state.press(x, y).unwrap();
+
+        let mut event: Event = Default::default();
+        event.buttons = Buttons::TOUCH;
+        event.touch = (x as u16, y as u16);
+        send2(&event);
+    });
+    let state_weak = Arc::downgrade(&state);
+    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();
+        state.release(x, y).unwrap();
+
+        let mut event: Event = Default::default();
+        event.touch = (x as u16, y as u16);
+        send3(&event);
+    });
+    event_controller.connect_motion(move |_, x, y| {
+        let mut state = state.lock().unwrap();
+        state.motion(x, y).unwrap();
+
+        if state.is_pressed() {
+            let mut event: Event = Default::default();
+            event.buttons = Buttons::TOUCH;
+            event.touch = (x as u16, y as u16);
+            send4(&event);
+        }
+    });
+    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().unwrap();
+    });
+
+    hbox.append(&tools_box);
+    hbox.append(&drawing_area);
+
+    let window = gtk::ApplicationWindow::builder()
+        .application(app)
+        .title("tablet-emu")
+        .default_width(800)
+        .default_height(480)
+        .child(&hbox)
+        .build();
+
+    window.show();
+}
+
+pub fn main(_args: &[String]) {
+    let app = gtk::Application::builder()
+        .application_id("fr.linkmauve.TabletEmu")
+        .build();
+    app.connect_activate(build_ui);
+    app.run();
+}