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
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE-APACHE file or at:
// https://www.apache.org/licenses/LICENSE-2.0
//! `GripPart` control
use std::fmt::Debug;
use kas::event::{CursorIcon, Press};
use kas::prelude::*;
/// A message from a [`GripPart`]
#[derive(Clone, Debug)]
pub enum GripMsg {
/// Widget received [`Event::PressStart`]
///
/// Some parents will call [`EventState::set_nav_focus`] on this event.
PressStart,
/// Widget received [`Event::PressMove`]
///
/// Parameter: the new position of the grip relative to the track.
///
/// The grip position is not adjusted; the caller should also call
/// [`GripPart::set_offset`] to do so. This is separate to allow adjustment of
/// the posision; e.g. `Slider` pins the position to the nearest detent.
PressMove(Offset),
/// Widget received [`Event::PressEnd`]
///
/// Parameter: `success` (see [`Event::PressEnd`]).
PressEnd(bool),
}
impl_scope! {
/// A draggable grip part
///
/// [`Slider`](crate::Slider), [`ScrollBar`](crate::ScrollBar) and
/// [`Splitter`](crate::Splitter) all require a component which supports
/// click+drag behaviour. The appearance differs but event handling is the
/// same: this widget is its implementation.
///
/// # Layout
///
/// This widget is unusual in several ways:
///
/// 1. [`Layout::size_rules`] does not request any size; the parent is expected
/// to do this. (Calling this method is still required to comply with
/// widget model.)
/// 2. [`Layout::set_rect`] sets the *track* within which this grip may move;
/// the parent should always call [`GripPart::set_size_and_offset`]
/// afterwards to set the grip position.
/// 3. [`Layout::draw`] does nothing. The parent should handle all drawing.
///
/// # Event handling
///
/// This widget handles click/touch events on the widget, pushing a
/// [`GripMsg`] to allow the parent to implement further handling.
///
/// Optionally, the parent may call [`GripPart::handle_press_on_track`]
/// when a [`Event::PressStart`] occurs on the track area (which identifies
/// as being the parent widget).
#[derive(Clone, Debug, Default)]
#[widget{
hover_highlight = true;
cursor_icon = CursorIcon::Grab;
}]
pub struct GripPart {
core: widget_core!(),
// The track is the area within which this GripPart may move
track: Rect,
press_coord: Coord,
}
/// This implementation is unusual in that:
///
/// 1. `size_rules` always returns [`SizeRules::EMPTY`]
/// 2. `set_rect` sets the *track* within which this grip may move; the
/// parent should call [`GripPart::set_size_and_offset`] after
/// `set_rect` (otherwise the grip's position will not be updated)
/// 3. `draw` does nothing: the parent is expected to do all drawing
impl Layout for GripPart {
fn size_rules(&mut self, _: SizeCx, _axis: AxisInfo) -> SizeRules {
SizeRules::EMPTY
}
fn set_rect(&mut self, _: &mut ConfigCx, rect: Rect) {
self.track = rect;
}
fn draw(&mut self, _: DrawCx) {}
}
impl Events for GripPart {
type Data = ();
fn handle_event(&mut self, cx: &mut EventCx, _: &Self::Data, event: Event) -> IsUsed {
match event {
Event::PressStart { press, .. } => {
cx.push(GripMsg::PressStart);
press.grab(self.id())
.with_icon(CursorIcon::Grabbing)
.with_cx(cx);
// Event delivery implies coord is over the grip.
self.press_coord = press.coord - self.offset();
Used
}
Event::PressMove { press, .. } => {
let offset = press.coord - self.press_coord;
let offset = offset.clamp(Offset::ZERO, self.max_offset());
cx.push(GripMsg::PressMove(offset));
Used
}
Event::PressEnd { success, .. } => {
cx.push(GripMsg::PressEnd(success));
Used
}
_ => Unused,
}
}
}
}
impl GripPart {
/// Construct
pub fn new() -> Self {
GripPart {
core: Default::default(),
track: Default::default(),
press_coord: Coord::ZERO,
}
}
/// Set a new grip size and position
///
/// Returns [`Action::REDRAW`] if a redraw is required.
pub fn set_size_and_offset(&mut self, size: Size, offset: Offset) -> Action {
self.core.rect.size = size;
self.set_offset(offset).1
}
/// Get the current track `Rect`
#[inline]
pub fn track(&self) -> Rect {
self.track
}
/// Get the current grip position
#[inline]
pub fn offset(&self) -> Offset {
self.core.rect.pos - self.track.pos
}
/// Get the maximum allowed offset
///
/// The grip position is clamped between `ZERO` and this offset relative to
/// the track. This value depends on size of the grip and the track.
#[inline]
pub fn max_offset(&self) -> Offset {
Offset::conv(self.track.size) - Offset::conv(self.core.rect.size)
}
/// Set a new grip position
///
/// Returns the new position (after clamping input) and an action: empty if
/// the grip hasn't moved; `REDRAW` if it has (though this widget is
/// not directly responsible for drawing, so this may not be accurate).
pub fn set_offset(&mut self, offset: Offset) -> (Offset, Action) {
let offset = offset.min(self.max_offset()).max(Offset::ZERO);
let grip_pos = self.track.pos + offset;
if grip_pos != self.core.rect.pos {
self.core.rect.pos = grip_pos;
(offset, Action::REDRAW)
} else {
(offset, Action::empty())
}
}
/// Handle an event on the track itself
///
/// If it is desired to make the grip move when the track area is clicked,
/// then the parent widget should call this method when receiving
/// [`Event::PressStart`].
///
/// Returns the new grip position relative to the track.
///
/// The grip position is not adjusted; the caller should also call
/// [`Self::set_offset`] to do so. This is separate to allow adjustment of
/// the posision; e.g. `Slider` pins the position to the nearest detent.
pub fn handle_press_on_track(&mut self, cx: &mut EventCx, press: &Press) -> Offset {
press
.grab(self.id())
.with_icon(CursorIcon::Grabbing)
.with_cx(cx);
let offset = press.coord - self.track.pos - Offset::conv(self.core.rect.size / 2);
let offset = offset.clamp(Offset::ZERO, self.max_offset());
self.press_coord = press.coord - offset;
offset
}
}