1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
//! Operate on widgets that can be scrolled.
use crate::widget::{Id, Operation};
/// The internal state of a widget that can be scrolled.
pub trait Scrollable {
/// Snaps the scroll of the widget to the given `percentage` along the horizontal & vertical axis.
fn snap_to(&mut self, offset: RelativeOffset);
/// Scroll the widget to the given [`AbsoluteOffset`] along the horizontal & vertical axis.
fn scroll_to(&mut self, offset: AbsoluteOffset);
}
/// Produces an [`Operation`] that snaps the widget with the given [`Id`] to
/// the provided `percentage`.
pub fn snap_to<T>(target: Id, offset: RelativeOffset) -> impl Operation<T> {
struct SnapTo {
target: Id,
offset: RelativeOffset,
}
impl<T> Operation<T> for SnapTo {
fn container(
&mut self,
_id: Option<&Id>,
operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
) {
operate_on_children(self)
}
fn scrollable(&mut self, state: &mut dyn Scrollable, id: Option<&Id>) {
if Some(&self.target) == id {
state.snap_to(self.offset);
}
}
}
SnapTo { target, offset }
}
/// Produces an [`Operation`] that scrolls the widget with the given [`Id`] to
/// the provided [`AbsoluteOffset`].
pub fn scroll_to<T>(target: Id, offset: AbsoluteOffset) -> impl Operation<T> {
struct ScrollTo {
target: Id,
offset: AbsoluteOffset,
}
impl<T> Operation<T> for ScrollTo {
fn container(
&mut self,
_id: Option<&Id>,
operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
) {
operate_on_children(self)
}
fn scrollable(&mut self, state: &mut dyn Scrollable, id: Option<&Id>) {
if Some(&self.target) == id {
state.scroll_to(self.offset);
}
}
}
ScrollTo { target, offset }
}
/// The amount of absolute offset in each direction of a [`Scrollable`].
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub struct AbsoluteOffset {
/// The amount of horizontal offset
pub x: f32,
/// The amount of vertical offset
pub y: f32,
}
/// The amount of relative offset in each direction of a [`Scrollable`].
///
/// A value of `0.0` means start, while `1.0` means end.
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub struct RelativeOffset {
/// The amount of horizontal offset
pub x: f32,
/// The amount of vertical offset
pub y: f32,
}
impl RelativeOffset {
/// A relative offset that points to the top-left of a [`Scrollable`].
pub const START: Self = Self { x: 0.0, y: 0.0 };
/// A relative offset that points to the bottom-right of a [`Scrollable`].
pub const END: Self = Self { x: 1.0, y: 1.0 };
}
|
