Touch support implementation (#696)

Adds a basic touch input system

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 ### Added
+- [Touch Input][696]
 - [Do not depend on spirv on wasm32 target][689]
 - [Another fast compile flag for macOS][552]
 
@@ -15,6 +16,7 @@
   - Individual color-components must now be accessed through setters and getters: `.r`, `.g`, `.b`, `.a`, `.set_r`, `.set_g`, `.set_b`, `.set_a`, and the corresponding methods with the `*_linear` suffix.
 - Despawning an entity multiple times causes a debug-level log message to be emitted instead of a panic [649] [651]
 
+[696]: https://github.com/bevyengine/bevy/pull/696
 [689]: https://github.com/bevyengine/bevy/pull/689
 [552]: https://github.com/bevyengine/bevy/pull/552
 [616]: https://github.com/bevyengine/bevy/pull/616

Cargo.toml

@@ -230,6 +230,14 @@ path = "examples/input/keyboard_input_events.rs"
 name = "gamepad_input"
 path = "examples/input/gamepad_input.rs"
 
+[[example]]
+name = "touch_input"
+path = "examples/input/touch_input.rs"
+
+[[example]]
+name = "touch_input_highlevel"
+path = "examples/input/touch_input_highlevel.rs"
+
 [[example]]
 name = "scene"
 path = "examples/scene/scene.rs"

crates/bevy_input/src/lib.rs

@@ -4,6 +4,7 @@ mod input;
 pub mod keyboard;
 pub mod mouse;
 pub mod system;
+pub mod touch;
 
 pub use axis::*;
 pub use input::*;
@@ -23,6 +24,7 @@ pub mod prelude {
 use bevy_app::prelude::*;
 use keyboard::{keyboard_input_system, KeyCode, KeyboardInput};
 use mouse::{mouse_button_input_system, MouseButton, MouseButtonInput, MouseMotion, MouseWheel};
+use touch::{touch_screen_input_system, TouchInput, Touches};
 
 use bevy_ecs::IntoQuerySystem;
 use gamepad::{GamepadAxis, GamepadButton, GamepadEvent};
@@ -50,6 +52,12 @@ impl Plugin for InputPlugin {
             .add_event::<GamepadEvent>()
             .init_resource::<Input<GamepadButton>>()
             .init_resource::<Axis<GamepadAxis>>()
-            .init_resource::<Axis<GamepadButton>>();
+            .init_resource::<Axis<GamepadButton>>()
+            .add_event::<TouchInput>()
+            .init_resource::<Touches>()
+            .add_system_to_stage(
+                bevy_app::stage::EVENT_UPDATE,
+                touch_screen_input_system.system(),
+            );
     }
 }

crates/bevy_input/src/touch.rs

@@ -0,0 +1,147 @@
+use bevy_app::{EventReader, Events};
+use bevy_ecs::{Local, Res, ResMut};
+use bevy_math::Vec2;
+use bevy_utils::{HashMap, HashSet};
+
+/// A touch input event
+#[derive(Debug, Clone)]
+pub struct TouchInput {
+    pub phase: TouchPhase,
+    pub position: Vec2,
+    ///
+    /// ## Platform-specific
+    ///
+    /// Unique identifier of a finger.
+    pub id: u64,
+}
+
+/// Describes touch-screen input state.
+#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy)]
+#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
+pub enum TouchPhase {
+    Started,
+    Moved,
+    Ended,
+    Cancelled,
+}
+
+#[derive(Default)]
+pub struct TouchSystemState {
+    touch_event_reader: EventReader<TouchInput>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Touch {
+    pub id: u64,
+    pub start_position: Vec2,
+    pub previous_position: Vec2,
+    pub position: Vec2,
+}
+
+impl Touch {
+    pub fn delta(&self) -> Vec2 {
+        self.position - self.previous_position
+    }
+
+    pub fn distance(&self) -> Vec2 {
+        self.position - self.start_position
+    }
+}
+
+#[derive(Default)]
+pub struct Touches {
+    active_touches: HashMap<u64, Touch>,
+    just_pressed: HashSet<u64>,
+    just_released: HashSet<u64>,
+    just_cancelled: HashSet<u64>,
+}
+
+impl Touches {
+    pub fn iter(&self) -> impl Iterator<Item = &Touch> + '_ {
+        self.active_touches.values()
+    }
+
+    pub fn just_pressed(&self, id: u64) -> bool {
+        self.just_pressed.contains(&id)
+    }
+
+    pub fn iter_just_pressed(&self) -> impl Iterator<Item = &Touch> + '_ {
+        self.just_pressed
+            .iter()
+            .map(move |id| self.active_touches.get(id).unwrap())
+    }
+
+    pub fn just_released(&self, id: u64) -> bool {
+        self.just_released.contains(&id)
+    }
+
+    pub fn iter_just_released(&self) -> impl Iterator<Item = &Touch> + '_ {
+        self.just_released
+            .iter()
+            .map(move |id| self.active_touches.get(id).unwrap())
+    }
+
+    pub fn just_cancelled(&self, id: u64) -> bool {
+        self.just_cancelled.contains(&id)
+    }
+
+    pub fn iter_just_cancelled(&self) -> impl Iterator<Item = &Touch> + '_ {
+        self.just_cancelled
+            .iter()
+            .map(move |id| self.active_touches.get(id).unwrap())
+    }
+}
+
+/// Updates the Touches resource with the latest TouchInput events
+pub fn touch_screen_input_system(
+    mut state: Local<TouchSystemState>,
+    mut touch_state: ResMut<Touches>,
+    touch_input_events: Res<Events<TouchInput>>,
+) {
+    touch_state.just_pressed.clear();
+
+    let released_touch_ids: HashSet<_> = touch_state.just_released.iter().cloned().collect();
+    let cancelled_touch_ids: HashSet<_> = touch_state.just_released.iter().cloned().collect();
+
+    touch_state.just_released.clear();
+    touch_state.just_cancelled.clear();
+
+    for released_id in released_touch_ids {
+        touch_state.active_touches.remove(&released_id);
+    }
+
+    for cancelled_id in cancelled_touch_ids {
+        touch_state.active_touches.remove(&cancelled_id);
+    }
+
+    for event in state.touch_event_reader.iter(&touch_input_events) {
+        let active_touch = touch_state.active_touches.get(&event.id);
+        match event.phase {
+            TouchPhase::Started => {
+                touch_state.active_touches.insert(
+                    event.id,
+                    Touch {
+                        id: event.id,
+                        start_position: event.position,
+                        previous_position: event.position,
+                        position: event.position,
+                    },
+                );
+                touch_state.just_pressed.insert(event.id);
+            }
+            TouchPhase::Moved => {
+                let old_touch = active_touch.unwrap();
+                let mut new_touch = old_touch.clone();
+                new_touch.previous_position = new_touch.position;
+                new_touch.position = event.position;
+                touch_state.active_touches.insert(event.id, new_touch);
+            }
+            TouchPhase::Ended => {
+                touch_state.just_released.insert(event.id);
+            }
+            TouchPhase::Cancelled => {
+                touch_state.just_cancelled.insert(event.id);
+            }
+        };
+    }
+}

crates/bevy_winit/src/converters.rs

@@ -1,7 +1,9 @@
 use bevy_input::{
     keyboard::{ElementState, KeyCode, KeyboardInput},
     mouse::MouseButton,
+    touch::{TouchInput, TouchPhase},
 };
+use bevy_math::Vec2;
 
 pub fn convert_keyboard_input(keyboard_input: &winit::event::KeyboardInput) -> KeyboardInput {
     KeyboardInput {
@@ -27,6 +29,19 @@ pub fn convert_mouse_button(mouse_button: winit::event::MouseButton) -> MouseBut
     }
 }
 
+pub fn convert_touch_input(touch_input: winit::event::Touch) -> TouchInput {
+    TouchInput {
+        phase: match touch_input.phase {
+            winit::event::TouchPhase::Started => TouchPhase::Started,
+            winit::event::TouchPhase::Moved => TouchPhase::Moved,
+            winit::event::TouchPhase::Ended => TouchPhase::Ended,
+            winit::event::TouchPhase::Cancelled => TouchPhase::Cancelled,
+        },
+        position: Vec2::new(touch_input.location.x as f32, touch_input.location.y as f32),
+        id: touch_input.id,
+    }
+}
+
 pub fn convert_virtual_key_code(virtual_key_code: winit::event::VirtualKeyCode) -> KeyCode {
     match virtual_key_code {
         winit::event::VirtualKeyCode::Key1 => KeyCode::Key1,

crates/bevy_winit/src/lib.rs

@@ -4,6 +4,7 @@ mod winit_windows;
 use bevy_input::{
     keyboard::KeyboardInput,
     mouse::{MouseButtonInput, MouseMotion, MouseScrollUnit, MouseWheel},
+    touch::TouchInput,
 };
 pub use winit_config::*;
 pub use winit_windows::*;
@@ -258,6 +259,11 @@ pub fn winit_runner(mut app: App) {
                         });
                     }
                 },
+                WindowEvent::Touch(touch) => {
+                    let mut touch_input_events =
+                        app.resources.get_mut::<Events<TouchInput>>().unwrap();
+                    touch_input_events.send(converters::convert_touch_input(touch));
+                }
                 _ => {}
             },
             event::Event::DeviceEvent { ref event, .. } => {

examples/input/touch_input.rs

@@ -0,0 +1,35 @@
+use bevy::{input::touch::*, prelude::*};
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_system(touch_system.system())
+        .run();
+}
+
+fn touch_system(touches: Res<Touches>) {
+    for touch in touches.iter() {
+        println!(
+            "active touch: {} {} {} {}",
+            touch.id, touch.position, touch.previous_position, touch.start_position
+        );
+
+        if touches.just_pressed(touch.id) {
+            println!(
+                "just pressed touch with id: {:?}, at: {:?}",
+                touch.id, touch.position
+            );
+        }
+
+        if touches.just_released(touch.id) {
+            println!(
+                "just released touch with id: {:?}, at: {:?}",
+                touch.id, touch.position
+            );
+        }
+
+        if touches.just_cancelled(touch.id) {
+            println!("cancelled touch with id: {:?}", touch.id);
+        }
+    }
+}

examples/input/touch_input_highlevel.rs

@@ -0,0 +1,28 @@
+use bevy::{input::touch::*, prelude::*};
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_system(touch_system.system())
+        .run();
+}
+
+fn touch_system(touches: Res<Touches>) {
+    for touch in touches.iter_just_pressed() {
+        println!(
+            "just pressed touch with id: {:?}, at: {:?}",
+            touch.id, touch.position
+        );
+    }
+
+    for touch in touches.iter_just_released() {
+        println!(
+            "just released touch with id: {:?}, at: {:?}",
+            touch.id, touch.position
+        );
+    }
+
+    for touch in touches.iter_just_cancelled() {
+        println!("cancelled touch with id: {:?}", touch.id);
+    }
+}