kas_core/event/
response.rs

1// Licensed under the Apache License, Version 2.0 (the "License");
2// you may not use this file except in compliance with the License.
3// You may obtain a copy of the License in the LICENSE-APACHE file or at:
4//     https://www.apache.org/licenses/LICENSE-2.0
5
6//! Event handling: IsUsed and Scroll types
7
8use crate::geom::{Offset, Rect, Vec2};
9
10pub use IsUsed::{Unused, Used};
11
12use super::components::KineticStart;
13
14/// Return type of event-handling methods
15///
16/// This type is convertible to/from `bool` and supports the expected bit-wise
17/// OR operator (`a | b`, `*a |= b`).
18///
19/// The type also implements negation with output type `bool`, thus allowing
20/// `if is_used.into() { ... }` and `if !is_used { ... }`. An implementation of
21/// `Deref` would be preferred, but the trait can only output a reference.
22#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
23pub enum IsUsed {
24    /// Event was unused
25    ///
26    /// Unused events may be used by a parent/ancestor widget or passed to
27    /// another handler until used.
28    Unused,
29    /// Event is used, no other result
30    Used,
31}
32
33impl From<bool> for IsUsed {
34    fn from(is_used: bool) -> Self {
35        match is_used {
36            false => Self::Unused,
37            true => Self::Used,
38        }
39    }
40}
41
42impl From<IsUsed> for bool {
43    fn from(is_used: IsUsed) -> bool {
44        is_used == Used
45    }
46}
47
48impl std::ops::BitOr for IsUsed {
49    type Output = Self;
50    #[inline]
51    fn bitor(self, rhs: Self) -> Self {
52        match (self, rhs) {
53            (Unused, Unused) => Unused,
54            _ => Used,
55        }
56    }
57}
58impl std::ops::BitOrAssign for IsUsed {
59    #[inline]
60    fn bitor_assign(&mut self, rhs: Self) {
61        *self = *self | rhs;
62    }
63}
64
65impl std::ops::Not for IsUsed {
66    type Output = bool;
67    #[inline]
68    fn not(self) -> bool {
69        self != Used
70    }
71}
72
73/// Request to / notification of scrolling from a child
74///
75/// See: [`EventCx::set_scroll`](super::EventCx::set_scroll).
76#[derive(Clone, Debug, Default, PartialEq)]
77#[must_use]
78pub enum Scroll {
79    /// No scrolling
80    #[default]
81    None,
82    /// Child has scrolled; no further scrolling needed
83    ///
84    /// External scroll bars use this as a notification to update self.
85    Scrolled,
86    /// Pan region by the given offset
87    ///
88    /// This may be returned to scroll the closest scrollable ancestor region.
89    /// This region should attempt to scroll self by this offset, then, if all
90    /// the offset was used, return `Scroll::Scrolled`, otherwise return
91    /// `Scroll::Offset(delta)` with the unused offset `delta`.
92    ///
93    /// With the usual scroll offset conventions, this delta must be subtracted
94    /// from the scroll offset.
95    Offset(Vec2),
96    /// Start kinetic scrolling
97    Kinetic(KineticStart),
98    /// Focus the given rect
99    ///
100    /// This is specified in the child's coordinate space. It is assumed that
101    /// any parent with non-zero translation will intercept this value and
102    /// either consume or translate it.
103    Rect(Rect),
104}
105
106impl std::ops::Sub<Offset> for Scroll {
107    type Output = Self;
108
109    #[inline]
110    fn sub(self, rhs: Offset) -> Self {
111        match self {
112            Scroll::Rect(rect) => Scroll::Rect(rect - rhs),
113            other => other,
114        }
115    }
116}
kas_core/event/response.rs

kas_core/event/
response.rs
