druid 0.8.3

Data-oriented Rust UI design toolkit.
Documentation 
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

// Copyright 2020 The Druid Authors.
//
// 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 at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! An animated spinner widget.

use std::f64::consts::PI;
use tracing::{instrument, trace};

use druid::kurbo::Line;
use druid::widget::prelude::*;
use druid::{theme, Color, Data, KeyOrValue, Point, Vec2};

/// An animated spinner widget for showing a loading state.
///
/// To customize the spinner's size, you can place it inside a [`SizedBox`]
/// that has a fixed width and height.
///
/// [`SizedBox`]: super::SizedBox
pub struct Spinner {
    t: f64,
    color: KeyOrValue<Color>,
}

impl Spinner {
    /// Create a spinner widget
    pub fn new() -> Spinner {
        Spinner::default()
    }

    /// Builder-style method for setting the spinner's color.
    ///
    /// The argument can be either a [`Color`] or a [`Key<Color>`].
    ///
    /// [`Key<Color>`]: crate::Key
    pub fn with_color(mut self, color: impl Into<KeyOrValue<Color>>) -> Self {
        self.color = color.into();
        self
    }

    /// Set the spinner's color.
    ///
    /// The argument can be either a [`Color`] or a [`Key<Color>`].
    ///
    /// [`Key<Color>`]: crate::Key
    pub fn set_color(&mut self, color: impl Into<KeyOrValue<Color>>) {
        self.color = color.into();
    }
}

impl Default for Spinner {
    fn default() -> Self {
        Spinner {
            t: 0.0,
            color: theme::TEXT_COLOR.into(),
        }
    }
}

impl<T: Data> Widget<T> for Spinner {
    #[instrument(name = "Spinner", level = "trace", skip(self, ctx, event, _data, _env))]
    fn event(&mut self, ctx: &mut EventCtx, event: &Event, _data: &mut T, _env: &Env) {
        if let Event::AnimFrame(interval) = event {
            self.t += (*interval as f64) * 1e-9;
            if self.t >= 1.0 {
                self.t = 0.0;
            }
            ctx.request_anim_frame();
            ctx.request_paint();
        }
    }

    #[instrument(name = "Spinner", level = "trace", skip(self, ctx, event, _data, _env))]
    fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, _data: &T, _env: &Env) {
        if let LifeCycle::WidgetAdded = event {
            ctx.request_anim_frame();
            ctx.request_paint();
        }
    }

    #[instrument(
        name = "Spinner",
        level = "trace",
        skip(self, _ctx, _old_data, _data, _env)
    )]
    fn update(&mut self, _ctx: &mut UpdateCtx, _old_data: &T, _data: &T, _env: &Env) {}

    #[instrument(
        name = "Spinner",
        level = "trace",
        skip(self, _layout_ctx, bc, _data, env)
    )]
    fn layout(
        &mut self,
        _layout_ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        _data: &T,
        env: &Env,
    ) -> Size {
        bc.debug_check("Spinner");

        let size = if bc.is_width_bounded() && bc.is_height_bounded() {
            bc.max()
        } else {
            bc.constrain(Size::new(
                env.get(theme::BASIC_WIDGET_HEIGHT),
                env.get(theme::BASIC_WIDGET_HEIGHT),
            ))
        };

        trace!("Computed size: {}", size);
        size
    }

    #[instrument(name = "Spinner", level = "trace", skip(self, ctx, _data, env))]
    fn paint(&mut self, ctx: &mut PaintCtx, _data: &T, env: &Env) {
        let t = self.t;
        let (width, height) = (ctx.size().width, ctx.size().height);
        let center = Point::new(width / 2.0, height / 2.0);
        let (r, g, b, original_alpha) = Color::as_rgba(self.color.resolve(env));
        let scale_factor = width.min(height) / 40.0;

        for step in 1..=12 {
            let step = f64::from(step);
            let fade_t = (t * 12.0 + 1.0).trunc();
            let fade = ((fade_t + step).rem_euclid(12.0) / 12.0) + 1.0 / 12.0;
            let angle = Vec2::from_angle((step / 12.0) * -2.0 * PI);
            let ambit_start = center + (10.0 * scale_factor * angle);
            let ambit_end = center + (20.0 * scale_factor * angle);
            let color = Color::rgba(r, g, b, fade * original_alpha);

            ctx.stroke(
                Line::new(ambit_start, ambit_end),
                &color,
                3.0 * scale_factor,
            );
        }
    }
}