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android: Add support for android stylus #4503

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81bfa38
android: add support for stylus
Lineoo Mar 5, 2026
466855c
android: stylus hover
Lineoo Mar 5, 2026
1094f91
fix hovering issue
Lineoo Mar 6, 2026
c4232a0
fix the behavior of ACTION_CANCELED
Lineoo Mar 6, 2026
2546cb7
revert the fix
Lineoo Mar 6, 2026
6cc5469
Update changelog
Lineoo Mar 17, 2026
14d14da
add stylus specific-platform notes
Lineoo Mar 23, 2026
bf8d5a5
Merge branch 'master' into master
Lineoo Mar 23, 2026
58147db
Fix formatting in event.rs documentation
Lineoo Mar 26, 2026
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247 changes: 228 additions & 19 deletions winit-android/src/event_loop.rs
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Original file line number Diff line number Diff line change
@@ -1,11 +1,12 @@
use std::cell::Cell;
use std::f32::consts::{FRAC_PI_2, TAU};
use std::fmt;
use std::hash::Hash;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};

use android_activity::input::{InputEvent, KeyAction, Keycode, MotionAction};
use android_activity::input::{Axis, InputEvent, KeyAction, Keycode, MotionAction};
use android_activity::{
AndroidApp, AndroidAppWaker, ConfigurationRef, InputStatus, MainEvent, Rect,
};
Expand Down Expand Up @@ -330,10 +331,12 @@ impl EventLoop {
MotionAction::Down
| MotionAction::PointerDown
| MotionAction::Up
| MotionAction::PointerUp => Some(Box::new(std::iter::once(
| MotionAction::PointerUp
| MotionAction::HoverEnter
| MotionAction::HoverExit => Some(Box::new(std::iter::once(
motion_event.pointer_at_index(motion_event.pointer_index()),
))),
MotionAction::Move | MotionAction::Cancel => {
MotionAction::Move | MotionAction::HoverMove | MotionAction::Cancel => {
Some(Box::new(motion_event.pointers()))
},
// TODO mouse events
Expand All @@ -350,6 +353,15 @@ impl EventLoop {
let finger_id = FingerId::from_raw(pointer.pointer_id() as usize);
let force = Some(Force::Normalized(pointer.pressure() as f64));

// XXX Actually `orientation` is available for finger touch on most mobile
// devices but winit simply ignore it
let tilt = pointer.axis_value(Axis::Tilt);
let orientation = pointer.axis_value(Axis::Orientation);
let angle = event::TabletToolAngle {
altitude: (FRAC_PI_2 - tilt) as f64,
azimuth: (orientation - FRAC_PI_2).rem_euclid(TAU) as f64,
};

match action {
MotionAction::Down | MotionAction::PointerDown => {
let primary = action == MotionAction::Down;
Expand All @@ -364,12 +376,21 @@ impl EventLoop {
android_activity::input::ToolType::Finger => {
event::PointerKind::Touch(finger_id)
},
android_activity::input::ToolType::Stylus => {
event::PointerKind::TabletTool(event::TabletToolKind::Pen)
},
android_activity::input::ToolType::Eraser => {
event::PointerKind::TabletTool(
event::TabletToolKind::Eraser,
)
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerKind::Unknown,
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);

let event = event::WindowEvent::PointerButton {
device_id,
primary,
Expand All @@ -379,6 +400,32 @@ impl EventLoop {
android_activity::input::ToolType::Finger => {
event::ButtonSource::Touch { finger_id, force }
},
android_activity::input::ToolType::Stylus => {
event::ButtonSource::TabletTool {
kind: event::TabletToolKind::Pen,
button: event::TabletToolButton::Contact,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
android_activity::input::ToolType::Eraser => {
event::ButtonSource::TabletTool {
kind: event::TabletToolKind::Eraser,
button: event::TabletToolButton::Contact,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::ButtonSource::Unknown(0),
Expand All @@ -396,6 +443,30 @@ impl EventLoop {
android_activity::input::ToolType::Finger => {
event::PointerSource::Touch { finger_id, force }
},
android_activity::input::ToolType::Stylus => {
event::PointerSource::TabletTool {
kind: event::TabletToolKind::Pen,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
android_activity::input::ToolType::Eraser => {
event::PointerSource::TabletTool {
kind: event::TabletToolKind::Eraser,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerSource::Unknown,
Expand All @@ -412,23 +483,53 @@ impl EventLoop {
self.primary_pointer = None;
}

if let MotionAction::Up | MotionAction::PointerUp = action {
let event = event::WindowEvent::PointerButton {
device_id,
primary,
state: event::ElementState::Released,
position,
button: match tool_type {
android_activity::input::ToolType::Finger => {
event::ButtonSource::Touch { finger_id, force }
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::ButtonSource::Unknown(0),
// TODO We don't actually have a way to indicate user to *cancel* an
// certain event.

// If we add a `cancel` field to `PointerButton` to record the
// cancellation ops we need `FLAG_CANCEL` in API level 33, kinda new.

let event = event::WindowEvent::PointerButton {
device_id,
primary,
state: event::ElementState::Released,
position,
button: match tool_type {
android_activity::input::ToolType::Finger => {
event::ButtonSource::Touch { finger_id, force }
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);
}
android_activity::input::ToolType::Stylus => {
event::ButtonSource::TabletTool {
kind: event::TabletToolKind::Pen,
button: event::TabletToolButton::Contact,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
android_activity::input::ToolType::Eraser => {
event::ButtonSource::TabletTool {
kind: event::TabletToolKind::Eraser,
button: event::TabletToolButton::Contact,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::ButtonSource::Unknown(0),
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);

let event = event::WindowEvent::PointerLeft {
device_id,
Expand All @@ -438,6 +539,114 @@ impl EventLoop {
android_activity::input::ToolType::Finger => {
event::PointerKind::Touch(finger_id)
},
android_activity::input::ToolType::Stylus => {
event::PointerKind::TabletTool(event::TabletToolKind::Pen)
},
android_activity::input::ToolType::Eraser => {
event::PointerKind::TabletTool(
event::TabletToolKind::Eraser,
)
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerKind::Unknown,
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);
},
MotionAction::HoverEnter => {
let primary = true;
if primary {
self.primary_pointer = Some(finger_id);
}
// TODO redundant `-> PointerExit -> PointerEntered ->` events
let event = event::WindowEvent::PointerEntered {
device_id,
primary,
position,
kind: match tool_type {
android_activity::input::ToolType::Finger => {
unreachable!()
},
android_activity::input::ToolType::Stylus => {
event::PointerKind::TabletTool(event::TabletToolKind::Pen)
},
android_activity::input::ToolType::Eraser => {
event::PointerKind::TabletTool(
event::TabletToolKind::Eraser,
)
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerKind::Unknown,
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);
},
MotionAction::HoverMove => {
let primary = self.primary_pointer == Some(finger_id);

let event = event::WindowEvent::PointerMoved {
device_id,
primary,
position,
source: match tool_type {
android_activity::input::ToolType::Finger => {
unreachable!()
},
android_activity::input::ToolType::Stylus => {
event::PointerSource::TabletTool {
kind: event::TabletToolKind::Pen,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
android_activity::input::ToolType::Eraser => {
event::PointerSource::TabletTool {
kind: event::TabletToolKind::Eraser,
data: event::TabletToolData {
force,
tangential_force: None,
twist: None,
tilt: Some(angle.tilt()),
angle: Some(angle),
},
}
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerSource::Unknown,
},
};
app.window_event(&self.window_target, GLOBAL_WINDOW, event);
},
MotionAction::HoverExit => {
let primary = self.primary_pointer == Some(finger_id);
if primary {
self.primary_pointer = None;
}

let event = event::WindowEvent::PointerLeft {
device_id,
primary,
position: Some(position),
kind: match tool_type {
android_activity::input::ToolType::Finger => {
unreachable!()
},
android_activity::input::ToolType::Stylus => {
event::PointerKind::TabletTool(event::TabletToolKind::Pen)
},
android_activity::input::ToolType::Eraser => {
event::PointerKind::TabletTool(
event::TabletToolKind::Eraser,
)
},
// TODO mouse events
android_activity::input::ToolType::Mouse => continue,
_ => event::PointerKind::Unknown,
Expand Down
12 changes: 12 additions & 0 deletions winit-core/src/event.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,11 @@ pub enum WindowEvent {
/// The pointer has entered the window.
///
/// Should be emitted regardless of window focus.
///
/// ## Platform-specific
///
/// - **Android**: Stylus will triggered [`PointerLeft`] and [`PointerEntered`] when it
/// contacts.
PointerEntered {
device_id: Option<DeviceId>,

Expand Down Expand Up @@ -215,6 +220,11 @@ pub enum WindowEvent {
/// The pointer has left the window.
///
/// Should be emitted regardless of window focus.
///
/// ## Platform-specific
///
/// - **Android**: Stylus will triggered [`PointerLeft`] and [`PointerEntered`] when it stop
/// contacts.
PointerLeft {
device_id: Option<DeviceId>,

Expand Down Expand Up @@ -1102,6 +1112,8 @@ pub struct TabletToolData {
///
/// ## Platform-specific
///
/// **Android:** Not supported.
///
/// **Web:** Has no mechanism to detect support, so this will always be [`Some`] with a value
/// of 0.
pub tangential_force: Option<f32>,
Expand Down
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