cranpose_ui/widgets/
icon.rs

1//! Generic vector icons and clickable icon buttons.
2
3#![allow(non_snake_case)]
4
5use cranpose_core::{NodeId, rememberKeyed};
6use cranpose_ui_graphics::{Brush, Color, VectorPath};
7use cranpose_ui_layout::Alignment;
8
9use crate::{
10    Modifier, SemanticsWidgetRole, Size, composable,
11    interaction::{MutableInteractionSource, rememberMutableInteractionSource},
12    widgets::{Box, BoxSpec},
13};
14
15/// The coordinate system every icon path is authored in.
16const ICON_VIEW_BOX: f32 = 24.0;
17
18/// The size an icon is drawn at when the caller states none.
19pub const DEFAULT_ICON_SIZE: f32 = 24.0;
20
21/// The smallest square a pointer target may be.
22///
23/// Every platform's accessibility guidance lands on the same number, and it is
24/// why an icon button is bigger than its icon: the glyph is 24dp and the target
25/// around it is 48dp, so a 24dp icon is still comfortable to hit.
26pub const MINIMUM_TOUCH_TARGET: f32 = 48.0;
27
28/// How an icon is drawn.
29#[derive(Clone, Copy, Debug, PartialEq)]
30pub struct IconSpec {
31    /// The square the icon is drawn in.
32    pub size: f32,
33    /// The tint. `None` leaves the path's own colouring, which is what a
34    /// multi-colour illustration wants.
35    pub tint: Option<Color>,
36}
37
38impl Default for IconSpec {
39    fn default() -> Self {
40        Self {
41            size: DEFAULT_ICON_SIZE,
42            tint: None,
43        }
44    }
45}
46
47impl IconSpec {
48    /// An icon of `size`, untinted.
49    pub const fn sized(size: f32) -> Self {
50        Self { size, tint: None }
51    }
52
53    /// Sets the drawn size.
54    pub const fn with_size(mut self, size: f32) -> Self {
55        self.size = size;
56        self
57    }
58
59    /// Sets the tint.
60    pub const fn with_tint(mut self, tint: Color) -> Self {
61        self.tint = Some(tint);
62        self
63    }
64}
65
66/// Draws an SVG path in the standard 24dp icon coordinate system.
67///
68/// An icon is decorative by default: it carries no content description, because
69/// the control around it names the action. Use [`IconWith`] to give a
70/// standalone icon a description a screen reader reads out.
71#[composable]
72pub fn Icon(
73    path: &'static str,
74    content_description: Option<String>,
75    size: f32,
76    color: Color,
77) -> NodeId {
78    IconWith(
79        Modifier::empty(),
80        path,
81        IconSpec::sized(size).with_tint(color),
82        content_description,
83    )
84}
85
86/// An icon with a modifier, a spec, and an optional content description.
87#[composable]
88pub fn IconWith(
89    modifier: Modifier,
90    path: &'static str,
91    spec: IconSpec,
92    content_description: Option<String>,
93) -> NodeId {
94    let parsed = rememberKeyed(path, |value| VectorPath::parse(value).ok());
95    let size = spec.size;
96    let tint = spec.tint;
97    let modifier = modifier
98        .size(Size::new(size, size))
99        .draw_behind(move |scope| {
100            if let Some(path) = &parsed {
101                let scaled = path.scaled(size / ICON_VIEW_BOX);
102                match tint {
103                    Some(tint) => scope.draw_vector_path(&scaled, Brush::solid(tint)),
104                    None => {
105                        scope.draw_vector_path(&scaled, Brush::solid(Color(0.0, 0.0, 0.0, 1.0)))
106                    }
107                }
108            }
109        });
110    let modifier = match content_description {
111        Some(description) => modifier.semantics_spec(
112            cranpose_foundation::SemanticsSpec::new()
113                .content_description(description)
114                .role(SemanticsWidgetRole::Image),
115        ),
116        None => modifier,
117    };
118    Box(modifier, BoxSpec::default(), || {})
119}
120
121/// The colours an icon button paints itself with.
122#[derive(Clone, Copy, Debug, Default, PartialEq)]
123pub struct IconButtonColors {
124    /// The surface behind the icon at rest.
125    pub background: Option<Color>,
126    /// The surface while the button is held.
127    pub pressed_background: Option<Color>,
128    /// The surface while the button is disabled.
129    pub disabled_background: Option<Color>,
130}
131
132impl IconButtonColors {
133    /// Sets the resting surface.
134    pub const fn with_background(mut self, color: Color) -> Self {
135        self.background = Some(color);
136        self
137    }
138
139    /// Sets the held surface.
140    pub const fn with_pressed_background(mut self, color: Color) -> Self {
141        self.pressed_background = Some(color);
142        self
143    }
144
145    /// Sets the disabled surface.
146    pub const fn with_disabled_background(mut self, color: Color) -> Self {
147        self.disabled_background = Some(color);
148        self
149    }
150
151    fn surface(&self, enabled: bool, pressed: bool) -> Option<Color> {
152        if !enabled {
153            return self.disabled_background.or(self.background);
154        }
155        if pressed {
156            return self.pressed_background.or(self.background);
157        }
158        self.background
159    }
160}
161
162/// How an icon button behaves and looks.
163#[derive(Clone, Copy, Debug, PartialEq)]
164pub struct IconButtonSpec {
165    /// Whether the button accepts input. A disabled button still publishes
166    /// itself to a screen reader, which is how the user learns it exists.
167    pub enabled: bool,
168    /// The square the pointer target occupies, never smaller than
169    /// [`MINIMUM_TOUCH_TARGET`].
170    pub touch_target: f32,
171    /// The surfaces the button paints.
172    pub colors: IconButtonColors,
173}
174
175impl Default for IconButtonSpec {
176    fn default() -> Self {
177        Self {
178            enabled: true,
179            touch_target: MINIMUM_TOUCH_TARGET,
180            colors: IconButtonColors::default(),
181        }
182    }
183}
184
185impl IconButtonSpec {
186    /// Sets whether the button accepts input.
187    pub const fn with_enabled(mut self, enabled: bool) -> Self {
188        self.enabled = enabled;
189        self
190    }
191
192    /// Sets the pointer target size. Values below [`MINIMUM_TOUCH_TARGET`] are
193    /// raised to it: a control smaller than that is a control people miss.
194    pub fn with_touch_target(mut self, size: f32) -> Self {
195        self.touch_target = size.max(MINIMUM_TOUCH_TARGET);
196        self
197    }
198
199    /// Sets the surfaces.
200    pub const fn with_colors(mut self, colors: IconButtonColors) -> Self {
201        self.colors = colors;
202        self
203    }
204
205    /// The target size this spec actually uses.
206    pub fn resolved_touch_target(&self) -> f32 {
207        self.touch_target.max(MINIMUM_TOUCH_TARGET)
208    }
209}
210
211/// A semantic icon button with caller-provided content.
212#[composable]
213pub fn IconButton<F>(
214    modifier: Modifier,
215    content_description: impl Into<String>,
216    on_click: impl Fn() + 'static,
217    content: F,
218) -> NodeId
219where
220    F: FnMut() + 'static,
221{
222    IconButtonWith(
223        modifier,
224        content_description,
225        IconButtonSpec::default(),
226        None,
227        on_click,
228        content,
229    )
230}
231
232/// An icon button with an enabled state, colours, a touch target, and an
233/// interaction source the caller can observe.
234///
235/// Passing an interaction source is how a button's visual reacts to being held
236/// without the caller writing pointer handling: read
237/// [`MutableInteractionSource::collectIsPressedAsState`] in the content.
238#[composable]
239pub fn IconButtonWith<F>(
240    modifier: Modifier,
241    content_description: impl Into<String>,
242    spec: IconButtonSpec,
243    interaction_source: Option<MutableInteractionSource>,
244    on_click: impl Fn() + 'static,
245    content: F,
246) -> NodeId
247where
248    F: FnMut() + 'static,
249{
250    let description = content_description.into();
251    let enabled = spec.enabled;
252    let target = spec.resolved_touch_target();
253    let source = interaction_source.unwrap_or_else(rememberMutableInteractionSource);
254    let pressed = source.collectIsPressedAsState().get();
255
256    let mut modifier = modifier
257        .size(Size::new(target, target))
258        .press_interaction_source(source)
259        .semantics(move |config| {
260            config.content_description = Some(description.clone());
261            config.role = Some(SemanticsWidgetRole::Button);
262            config.enabled = enabled;
263            config.is_clickable = enabled;
264        });
265    if let Some(surface) = spec.colors.surface(enabled, pressed) {
266        modifier = modifier.background(surface);
267    }
268    if enabled {
269        modifier = modifier.clickable(move |_| on_click());
270    }
271
272    Box(
273        modifier,
274        BoxSpec::default().content_alignment(Alignment::CENTER),
275        content,
276    )
277}
278
279#[cfg(test)]
280mod tests {
281    use super::*;
282
283    #[test]
284    fn icon_path_is_parseable() {
285        assert!(VectorPath::parse("M0 0h24v24H0z").is_ok());
286    }
287
288    #[test]
289    fn an_icon_button_is_never_smaller_than_the_minimum_touch_target() {
290        let spec = IconButtonSpec::default().with_touch_target(20.0);
291        assert_eq!(spec.resolved_touch_target(), MINIMUM_TOUCH_TARGET);
292        let roomy = IconButtonSpec::default().with_touch_target(64.0);
293        assert_eq!(roomy.resolved_touch_target(), 64.0);
294    }
295
296    #[test]
297    fn colours_follow_the_state_and_fall_back_to_the_resting_surface() {
298        let rest = Color(0.1, 0.1, 0.1, 1.0);
299        let held = Color(0.2, 0.2, 0.2, 1.0);
300        let off = Color(0.3, 0.3, 0.3, 1.0);
301
302        let full = IconButtonColors::default()
303            .with_background(rest)
304            .with_pressed_background(held)
305            .with_disabled_background(off);
306        assert_eq!(full.surface(true, false), Some(rest));
307        assert_eq!(full.surface(true, true), Some(held));
308        assert_eq!(full.surface(false, false), Some(off));
309
310        let plain = IconButtonColors::default().with_background(rest);
311        assert_eq!(plain.surface(true, true), Some(rest));
312        assert_eq!(plain.surface(false, true), Some(rest));
313
314        assert_eq!(IconButtonColors::default().surface(true, true), None);
315    }
316
317    #[test]
318    fn an_icon_states_its_size_and_tint() {
319        assert_eq!(IconSpec::default().size, DEFAULT_ICON_SIZE);
320        assert_eq!(IconSpec::default().tint, None);
321        let spec = IconSpec::sized(16.0).with_tint(Color(1.0, 0.0, 0.0, 1.0));
322        assert_eq!(spec.size, 16.0);
323        assert_eq!(spec.tint, Some(Color(1.0, 0.0, 0.0, 1.0)));
324        assert_eq!(spec.with_size(32.0).size, 32.0);
325    }
326
327    #[test]
328    fn a_disabled_icon_button_still_publishes_itself() {
329        let spec = IconButtonSpec::default().with_enabled(false);
330        assert!(!spec.enabled);
331        assert_eq!(spec.resolved_touch_target(), MINIMUM_TOUCH_TARGET);
332    }
333}
cranpose_ui/widgets/icon.rs

cranpose_ui/widgets/
icon.rs
