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(path: &'static str, size: f32, color: Color) -> NodeId {
73    IconWith(
74        Modifier::empty(),
75        path,
76        IconSpec::sized(size).with_tint(color),
77        None,
78    )
79}
80
81/// An icon with a modifier, a spec, and an optional content description.
82#[composable]
83pub fn IconWith(
84    modifier: Modifier,
85    path: &'static str,
86    spec: IconSpec,
87    content_description: Option<String>,
88) -> NodeId {
89    let parsed = rememberKeyed(path, |value| VectorPath::parse(value).ok());
90    let size = spec.size;
91    let tint = spec.tint;
92    let modifier = modifier
93        .size(Size::new(size, size))
94        .draw_behind(move |scope| {
95            if let Some(path) = &parsed {
96                let scaled = path.scaled(size / ICON_VIEW_BOX);
97                match tint {
98                    Some(tint) => scope.draw_vector_path(&scaled, Brush::solid(tint)),
99                    None => {
100                        scope.draw_vector_path(&scaled, Brush::solid(Color(0.0, 0.0, 0.0, 1.0)))
101                    }
102                }
103            }
104        });
105    let modifier = match content_description {
106        Some(description) => modifier.semantics(move |config| {
107            config.content_description = Some(description.clone());
108            config.role = Some(SemanticsWidgetRole::Image);
109        }),
110        None => modifier,
111    };
112    Box(modifier, BoxSpec::default(), || {})
113}
114
115/// The colours an icon button paints itself with.
116#[derive(Clone, Copy, Debug, Default, PartialEq)]
117pub struct IconButtonColors {
118    /// The surface behind the icon at rest.
119    pub background: Option<Color>,
120    /// The surface while the button is held.
121    pub pressed_background: Option<Color>,
122    /// The surface while the button is disabled.
123    pub disabled_background: Option<Color>,
124}
125
126impl IconButtonColors {
127    /// Sets the resting surface.
128    pub const fn with_background(mut self, color: Color) -> Self {
129        self.background = Some(color);
130        self
131    }
132
133    /// Sets the held surface.
134    pub const fn with_pressed_background(mut self, color: Color) -> Self {
135        self.pressed_background = Some(color);
136        self
137    }
138
139    /// Sets the disabled surface.
140    pub const fn with_disabled_background(mut self, color: Color) -> Self {
141        self.disabled_background = Some(color);
142        self
143    }
144
145    fn surface(&self, enabled: bool, pressed: bool) -> Option<Color> {
146        if !enabled {
147            return self.disabled_background.or(self.background);
148        }
149        if pressed {
150            return self.pressed_background.or(self.background);
151        }
152        self.background
153    }
154}
155
156/// How an icon button behaves and looks.
157#[derive(Clone, Copy, Debug, PartialEq)]
158pub struct IconButtonSpec {
159    /// Whether the button accepts input. A disabled button still publishes
160    /// itself to a screen reader, which is how the user learns it exists.
161    pub enabled: bool,
162    /// The square the pointer target occupies, never smaller than
163    /// [`MINIMUM_TOUCH_TARGET`].
164    pub touch_target: f32,
165    /// The surfaces the button paints.
166    pub colors: IconButtonColors,
167}
168
169impl Default for IconButtonSpec {
170    fn default() -> Self {
171        Self {
172            enabled: true,
173            touch_target: MINIMUM_TOUCH_TARGET,
174            colors: IconButtonColors::default(),
175        }
176    }
177}
178
179impl IconButtonSpec {
180    /// Sets whether the button accepts input.
181    pub const fn with_enabled(mut self, enabled: bool) -> Self {
182        self.enabled = enabled;
183        self
184    }
185
186    /// Sets the pointer target size. Values below [`MINIMUM_TOUCH_TARGET`] are
187    /// raised to it: a control smaller than that is a control people miss.
188    pub fn with_touch_target(mut self, size: f32) -> Self {
189        self.touch_target = size.max(MINIMUM_TOUCH_TARGET);
190        self
191    }
192
193    /// Sets the surfaces.
194    pub const fn with_colors(mut self, colors: IconButtonColors) -> Self {
195        self.colors = colors;
196        self
197    }
198
199    /// The target size this spec actually uses.
200    pub fn resolved_touch_target(&self) -> f32 {
201        self.touch_target.max(MINIMUM_TOUCH_TARGET)
202    }
203}
204
205/// A semantic icon button with caller-provided content.
206#[composable]
207pub fn IconButton<F>(
208    modifier: Modifier,
209    content_description: impl Into<String>,
210    on_click: impl Fn() + 'static,
211    content: F,
212) -> NodeId
213where
214    F: FnMut() + 'static,
215{
216    IconButtonWith(
217        modifier,
218        content_description,
219        IconButtonSpec::default(),
220        None,
221        on_click,
222        content,
223    )
224}
225
226/// An icon button with an enabled state, colours, a touch target, and an
227/// interaction source the caller can observe.
228///
229/// Passing an interaction source is how a button's visual reacts to being held
230/// without the caller writing pointer handling: read
231/// [`MutableInteractionSource::collectIsPressedAsState`] in the content.
232#[composable]
233pub fn IconButtonWith<F>(
234    modifier: Modifier,
235    content_description: impl Into<String>,
236    spec: IconButtonSpec,
237    interaction_source: Option<MutableInteractionSource>,
238    on_click: impl Fn() + 'static,
239    content: F,
240) -> NodeId
241where
242    F: FnMut() + 'static,
243{
244    let description = content_description.into();
245    let enabled = spec.enabled;
246    let target = spec.resolved_touch_target();
247    let source = interaction_source.unwrap_or_else(rememberMutableInteractionSource);
248    let pressed = source.collectIsPressedAsState().get();
249
250    let mut modifier = modifier
251        .size(Size::new(target, target))
252        .press_interaction_source(source)
253        .semantics(move |config| {
254            config.content_description = Some(description.clone());
255            config.role = Some(SemanticsWidgetRole::Button);
256            config.enabled = enabled;
257            config.is_clickable = enabled;
258        });
259    if let Some(surface) = spec.colors.surface(enabled, pressed) {
260        modifier = modifier.background(surface);
261    }
262    if enabled {
263        modifier = modifier.clickable(move |_| on_click());
264    }
265
266    Box(
267        modifier,
268        BoxSpec::default().content_alignment(Alignment::CENTER),
269        content,
270    )
271}
272
273#[cfg(test)]
274mod tests {
275    use super::*;
276
277    #[test]
278    fn icon_path_is_parseable() {
279        assert!(VectorPath::parse("M0 0h24v24H0z").is_ok());
280    }
281
282    #[test]
283    fn an_icon_button_is_never_smaller_than_the_minimum_touch_target() {
284        let spec = IconButtonSpec::default().with_touch_target(20.0);
285        assert_eq!(spec.resolved_touch_target(), MINIMUM_TOUCH_TARGET);
286        let roomy = IconButtonSpec::default().with_touch_target(64.0);
287        assert_eq!(roomy.resolved_touch_target(), 64.0);
288    }
289
290    #[test]
291    fn colours_follow_the_state_and_fall_back_to_the_resting_surface() {
292        let rest = Color(0.1, 0.1, 0.1, 1.0);
293        let held = Color(0.2, 0.2, 0.2, 1.0);
294        let off = Color(0.3, 0.3, 0.3, 1.0);
295
296        let full = IconButtonColors::default()
297            .with_background(rest)
298            .with_pressed_background(held)
299            .with_disabled_background(off);
300        assert_eq!(full.surface(true, false), Some(rest));
301        assert_eq!(full.surface(true, true), Some(held));
302        assert_eq!(full.surface(false, false), Some(off));
303
304        let plain = IconButtonColors::default().with_background(rest);
305        assert_eq!(plain.surface(true, true), Some(rest));
306        assert_eq!(plain.surface(false, true), Some(rest));
307
308        assert_eq!(IconButtonColors::default().surface(true, true), None);
309    }
310
311    #[test]
312    fn an_icon_states_its_size_and_tint() {
313        assert_eq!(IconSpec::default().size, DEFAULT_ICON_SIZE);
314        assert_eq!(IconSpec::default().tint, None);
315        let spec = IconSpec::sized(16.0).with_tint(Color(1.0, 0.0, 0.0, 1.0));
316        assert_eq!(spec.size, 16.0);
317        assert_eq!(spec.tint, Some(Color(1.0, 0.0, 0.0, 1.0)));
318        assert_eq!(spec.with_size(32.0).size, 32.0);
319    }
320
321    #[test]
322    fn a_disabled_icon_button_still_publishes_itself() {
323        let spec = IconButtonSpec::default().with_enabled(false);
324        assert!(!spec.enabled);
325        assert_eq!(spec.resolved_touch_target(), MINIMUM_TOUCH_TARGET);
326    }
327}
cranpose_ui/widgets/icon.rs

cranpose_ui/widgets/
icon.rs
