zng_view_api/
touch.rs

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1//! Touch types.
2
3use serde::{Deserialize, Serialize};
4
5use zng_unit::DipPoint;
6
7/// Identifier for a continuous touch contact.
8#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
9#[serde(transparent)]
10pub struct TouchId(pub u64);
11
12/// Describes touch-screen input state.
13#[derive(Debug, Hash, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
14pub enum TouchPhase {
15    /// A finger touched the screen.
16    Start,
17    /// A finger moved on the screen.
18    Move,
19    /// A finger was lifted from the screen.
20    End,
21    /// The system cancelled tracking for the touch.
22    Cancel,
23}
24
25/// Identify a new touch contact or a contact update.
26#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq)]
27pub struct TouchUpdate {
28    /// Identify a continuous touch contact or *finger*.
29    ///
30    /// Multiple points of contact can happen in the same device at the same time,
31    /// this ID identifies each uninterrupted contact. IDs are unique only among other concurrent touches
32    /// on the same device, after a touch is ended an ID may be reused.
33    pub touch: TouchId,
34    /// Touch phase for the `id`.
35    pub phase: TouchPhase,
36    /// Touch center, relative to the window top-left in device independent pixels.
37    pub position: DipPoint,
38    /// Touch pressure force and angle.
39    pub force: Option<TouchForce>,
40}
41
42/// Describes the force of a touch event.
43#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
44pub enum TouchForce {
45    /// On iOS, the force is calibrated so that the same number corresponds to
46    /// roughly the same amount of pressure on the screen regardless of the
47    /// device.
48    Calibrated {
49        /// The force of the touch, where a value of 1.0 represents the force of
50        /// an average touch (predetermined by the system, not user-specific).
51        ///
52        /// The force reported by Apple Pencil is measured along the axis of the
53        /// pencil. If you want a force perpendicular to the device, you need to
54        /// calculate this value using the `altitude_angle` value.
55        force: f64,
56        /// The maximum possible force for a touch.
57        ///
58        /// The value of this field is sufficiently high to provide a wide
59        /// dynamic range for values of the `force` field.
60        max_possible_force: f64,
61        /// The altitude (in radians) of the stylus.
62        ///
63        /// A value of 0 radians indicates that the stylus is parallel to the
64        /// surface. The value of this property is Pi/2 when the stylus is
65        /// perpendicular to the surface.
66        altitude_angle: Option<f64>,
67    },
68    /// If the platform reports the force as normalized, we have no way of
69    /// knowing how much pressure 1.0 corresponds to – we know it's the maximum
70    /// amount of force, but as to how much force, you might either have to
71    /// press really hard, or not hard at all, depending on the device.
72    Normalized(f64),
73}
zng_view_api/touch.rs

zng_view_api/
touch.rs
