Working multitouch example

Cargo.toml

@@ -72,6 +72,7 @@ members = [
     "examples/geometry",
     "examples/integration_opengl",
     "examples/integration_wgpu",
+    "examples/multitouch",
     "examples/pane_grid",
     "examples/pick_list",
     "examples/pokedex",

examples/game_of_life/src/main.rs

@@ -204,6 +204,7 @@ fn view_controls<'a>(
 
 mod grid {
     use crate::Preset;
+    use iced::touch;
     use iced::widget::canvas;
     use iced::widget::canvas::event::{self, Event};
     use iced::widget::canvas::{
@@ -423,6 +424,22 @@ mod grid {
             };
 
             match event {
+                Event::Touch(touch_event) => match touch_event {
+                    touch::Event::FingerMoved { .. } => {
+                        let message = {
+                            *interaction = if is_populated {
+                                Interaction::Erasing
+                            } else {
+                                Interaction::Drawing
+                            };
+
+                            populate.or(unpopulate)
+                        };
+
+                        (event::Status::Captured, message)
+                    }
+                    _ => (event::Status::Ignored, None),
+                },
                 Event::Mouse(mouse_event) => match mouse_event {
                     mouse::Event::ButtonPressed(button) => {
                         let message = match button {

examples/multitouch/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "multitouch"
+version = "0.1.0"
+authors = ["Artur Sapek <artur@kraken.com>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+iced = { path = "../..", features = ["canvas", "tokio", "debug"] }
+tokio = { version = "1.0", features = ["sync"] }
+env_logger = "0.9"

examples/multitouch/src/main.rs

@@ -0,0 +1,150 @@
+//! This example shows how to use touch events in `Canvas` to draw
+//! a circle around each fingertip. This only works on touch-enabled
+//! computers like Microsoft Surface.
+use iced::widget::canvas::event;
+use iced::widget::canvas::{self, Canvas, Cursor, Geometry, Path, Stroke};
+use iced::{
+    executor, touch, window, Application, Color, Command, Element, Length,
+    Point, Rectangle, Settings, Subscription, Theme,
+};
+
+use std::collections::HashMap;
+
+pub fn main() -> iced::Result {
+    env_logger::builder().format_timestamp(None).init();
+
+    Multitouch::run(Settings {
+        antialiasing: true,
+        window: window::Settings {
+            position: window::Position::Centered,
+            ..window::Settings::default()
+        },
+        ..Settings::default()
+    })
+}
+
+struct Multitouch {
+    state: State,
+}
+
+#[derive(Debug)]
+struct State {
+    cache: canvas::Cache,
+    fingers: HashMap<touch::Finger, Point>,
+}
+
+impl State {
+    fn new() -> Self {
+        Self {
+            cache: canvas::Cache::new(),
+            fingers: HashMap::new(),
+        }
+    }
+}
+
+#[derive(Debug)]
+enum Message {
+    FingerPressed { id: touch::Finger, position: Point },
+    FingerLifted { id: touch::Finger },
+}
+
+impl Application for Multitouch {
+    type Executor = executor::Default;
+    type Message = Message;
+    type Theme = Theme;
+    type Flags = ();
+
+    fn new(_flags: ()) -> (Self, Command<Message>) {
+        (
+            Multitouch {
+                state: State::new(),
+            },
+            Command::none(),
+        )
+    }
+
+    fn title(&self) -> String {
+        String::from("Multitouch - Iced")
+    }
+
+    fn update(&mut self, message: Message) -> Command<Message> {
+        match message {
+            Message::FingerPressed { id, position } => {
+                self.state.fingers.insert(id, position.clone());
+                self.state.cache.clear();
+            }
+            Message::FingerLifted { id } => {
+                self.state.fingers.remove(&id);
+                self.state.cache.clear();
+            }
+        }
+
+        Command::none()
+    }
+
+    fn subscription(&self) -> Subscription<Message> {
+        Subscription::none()
+    }
+
+    fn view(&self) -> Element<Message> {
+        Canvas::new(&self.state)
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .into()
+    }
+}
+
+impl<'a> canvas::Program<Message> for State {
+    type State = ();
+
+    fn update(
+        &self,
+        _state: &mut Self::State,
+        event: event::Event,
+        _bounds: Rectangle,
+        _cursor: Cursor,
+    ) -> (event::Status, Option<Message>) {
+        match event {
+            event::Event::Touch(touch_event) => match touch_event {
+                touch::Event::FingerPressed { id, position }
+                | touch::Event::FingerMoved { id, position } => (
+                    event::Status::Captured,
+                    Some(Message::FingerPressed { id, position }),
+                ),
+                touch::Event::FingerLifted { id, .. }
+                | touch::Event::FingerLost { id, .. } => (
+                    event::Status::Captured,
+                    Some(Message::FingerLifted { id }),
+                ),
+            },
+            _ => (event::Status::Ignored, None),
+        }
+    }
+
+    fn draw(
+        &self,
+        _state: &Self::State,
+        _theme: &Theme,
+        bounds: Rectangle,
+        _cursor: Cursor,
+    ) -> Vec<Geometry> {
+        let fingerweb = self.cache.draw(bounds.size(), |frame| {
+            for finger in &self.fingers {
+                dbg!(&finger);
+
+                let circle = Path::new(|p| p.circle(*finger.1, 50.0));
+
+                frame.stroke(
+                    &circle,
+                    Stroke {
+                        color: Color::BLACK,
+                        width: 3.0,
+                        ..Stroke::default()
+                    },
+                );
+            }
+        });
+
+        vec![fingerweb]
+    }
+}