cushy/
tick.rs

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
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use std::time::{Duration, Instant};

use ahash::AHashSet;
use figures::units::Px;
use figures::Point;
use intentional::Assert;
use kludgine::app::winit::event::{ElementState, MouseButton};
use kludgine::app::winit::keyboard::Key;
use parking_lot::{Condvar, Mutex, MutexGuard};

use crate::context::WidgetContext;
use crate::value::{Destination, Dynamic};
use crate::widget::{EventHandling, HANDLED, IGNORED};
use crate::window::KeyEvent;

/// A fixed-rate callback that provides access to tracked input on its
/// associated widget.
#[derive(Clone, Debug)]
#[must_use]
pub struct Tick {
    data: Arc<TickData>,
    handled_keys: AHashSet<Key>,
}

impl Tick {
    /// Signals that this widget has been redrawn.
    pub fn rendered(&self, context: &WidgetContext<'_>) {
        context.redraw_when_changed(&self.data.tick_number);

        self.data.sync.notify_one();
    }

    /// Processes `input`.
    ///
    /// If the event matches a key that has been marked as handled, [`HANDLED`]
    /// will be returned. Otherwise, [`IGNORED`] will be returned,
    #[must_use]
    pub fn key_input(&self, input: &KeyEvent) -> EventHandling {
        let mut state = self.data.state();
        if input.state.is_pressed() {
            state.input.keys.insert(input.logical_key.clone());
        } else {
            state.input.keys.remove(&input.logical_key);
        }
        drop(state);

        if self.handled_keys.contains(&input.logical_key) {
            HANDLED
        } else {
            IGNORED
        }
    }

    /// Sets the cursor position.
    pub fn set_cursor_position(&self, pos: Option<Point<Px>>) {
        let mut state = self.data.state();
        match pos {
            Some(pos) => {
                if state.input.mouse.is_none() {
                    state.input.mouse = Some(Mouse::default());
                }

                state
                    .input
                    .mouse
                    .as_mut()
                    .assert("always initialized")
                    .position = pos;
            }
            None => {
                state.input.mouse = None;
            }
        }
    }

    /// Processes a mouse button event.
    pub fn mouse_button(&self, button: MouseButton, button_state: ElementState) {
        let mut state = self.data.state();
        if let Some(mouse) = &mut state.input.mouse {
            if button_state.is_pressed() {
                mouse.buttons.insert(button);
            } else {
                mouse.buttons.remove(&button);
            }
        }
    }

    /// Returns a new tick that invokes `tick`, aiming to repeat at the given
    /// duration.
    pub fn new<F>(tick_every: Duration, tick: F) -> Self
    where
        F: FnMut(Duration, &InputState) + Send + 'static,
    {
        let now = Instant::now();
        let data = Arc::new(TickData {
            state: Mutex::new(TickState {
                last_time: now,
                next_target: now,
                keep_running: true,
                frame: 0,
                input: InputState::default(),
            }),
            period: tick_every,
            sync: Condvar::new(),
            rendered_frame: AtomicUsize::new(0),
            tick_number: Dynamic::default(),
        });

        std::thread::spawn({
            let data = data.clone();
            move || tick_loop(&data, tick)
        });

        Self {
            data,
            handled_keys: AHashSet::new(),
        }
    }

    /// Returns a new tick that invokes `tick` at a target number of times per
    /// second.
    pub fn times_per_second<F>(times_per_second: u32, tick: F) -> Self
    where
        F: FnMut(Duration, &InputState) + Send + 'static,
    {
        Self::new(Duration::from_secs(1) / times_per_second, tick)
    }

    /// Returns a new tick that redraws its associated widget at a target rate
    /// of `x times_per_second`.
    pub fn redraws_per_second(times_per_second: u32) -> Self {
        Self::times_per_second(times_per_second, |_, _| {})
    }

    /// Adds the collection of [`Key`]s to the list that are handled, and
    /// returns self.
    ///
    /// The list of keys provided will be prevented from propagating.
    pub fn handled_keys(mut self, keys: impl IntoIterator<Item = Key>) -> Self {
        self.handled_keys.extend(keys);
        self
    }
}

/// The current state of input during the execution of a [`Tick`].
#[derive(Default, Debug)]
pub struct InputState {
    /// A collection of all keys currently pressed.
    pub keys: AHashSet<Key>,
    /// The state of the mouse cursor and any buttons pressed.
    pub mouse: Option<Mouse>,
}

#[derive(Debug, Default)]
pub struct Mouse {
    pub position: Point<Px>,
    pub buttons: AHashSet<MouseButton>,
}

#[derive(Debug)]
struct TickData {
    state: Mutex<TickState>,
    period: Duration,
    sync: Condvar,
    rendered_frame: AtomicUsize,
    tick_number: Dynamic<u64>,
}

impl TickData {
    fn state(&self) -> MutexGuard<'_, TickState> {
        self.state.lock()
    }
}

#[derive(Debug)]
struct TickState {
    last_time: Instant,
    next_target: Instant,
    keep_running: bool,
    frame: usize,
    input: InputState,
}

fn tick_loop<F>(data: &TickData, mut tick: F)
where
    F: FnMut(Duration, &InputState),
{
    let mut state = data.state();
    while state.keep_running {
        let mut now = Instant::now();
        match state.next_target.checked_duration_since(now) {
            Some(remaining) if remaining > Duration::ZERO => {
                drop(state);
                std::thread::sleep(remaining);
                state = data.state();

                now = Instant::now();
            }
            _ => {}
        }

        let elapsed = now
            .checked_duration_since(state.last_time)
            .expect("instant never decreases");
        state.frame += 1;

        tick(elapsed, &state.input);
        state.next_target = (state.next_target + data.period).max(now);
        state.last_time = now;

        // Signal that we have a new frame, which will cause the widget to
        // redraw.
        data.tick_number.map_mut(|mut tick| *tick += 1);

        // Wait for a frame to be rendered.
        while state.keep_running {
            let current_frame = data.rendered_frame.load(Ordering::Acquire);
            if state.frame == current_frame {
                data.sync.wait(&mut state);
            } else {
                break;
            }
        }
    }
}