iced_widget/
slider.rs

1//! Sliders let users set a value by moving an indicator.
2//!
3//! # Example
4//! ```no_run
5//! # mod iced { pub mod widget { pub use iced_widget::*; } pub use iced_widget::Renderer; pub use iced_widget::core::*; }
6//! # pub type Element<'a, Message> = iced_widget::core::Element<'a, Message, iced_widget::Theme, iced_widget::Renderer>;
7//! #
8//! use iced::widget::slider;
9//!
10//! struct State {
11//!    value: f32,
12//! }
13//!
14//! #[derive(Debug, Clone)]
15//! enum Message {
16//!     ValueChanged(f32),
17//! }
18//!
19//! fn view(state: &State) -> Element<'_, Message> {
20//!     slider(0.0..=100.0, state.value, Message::ValueChanged).into()
21//! }
22//!
23//! fn update(state: &mut State, message: Message) {
24//!     match message {
25//!         Message::ValueChanged(value) => {
26//!             state.value = value;
27//!         }
28//!     }
29//! }
30//! ```
31use crate::core::border::{self, Border};
32use crate::core::keyboard;
33use crate::core::keyboard::key::{self, Key};
34use crate::core::layout;
35use crate::core::mouse;
36use crate::core::renderer;
37use crate::core::touch;
38use crate::core::widget::tree::{self, Tree};
39use crate::core::window;
40use crate::core::{
41    self, Background, Clipboard, Color, Element, Event, Layout, Length, Pixels, Point, Rectangle,
42    Shell, Size, Theme, Widget,
43};
44
45use std::ops::RangeInclusive;
46
47/// An horizontal bar and a handle that selects a single value from a range of
48/// values.
49///
50/// A [`Slider`] will try to fill the horizontal space of its container.
51///
52/// The [`Slider`] range of numeric values is generic and its step size defaults
53/// to 1 unit.
54///
55/// # Example
56/// ```no_run
57/// # mod iced { pub mod widget { pub use iced_widget::*; } pub use iced_widget::Renderer; pub use iced_widget::core::*; }
58/// # pub type Element<'a, Message> = iced_widget::core::Element<'a, Message, iced_widget::Theme, iced_widget::Renderer>;
59/// #
60/// use iced::widget::slider;
61///
62/// struct State {
63///    value: f32,
64/// }
65///
66/// #[derive(Debug, Clone)]
67/// enum Message {
68///     ValueChanged(f32),
69/// }
70///
71/// fn view(state: &State) -> Element<'_, Message> {
72///     slider(0.0..=100.0, state.value, Message::ValueChanged).into()
73/// }
74///
75/// fn update(state: &mut State, message: Message) {
76///     match message {
77///         Message::ValueChanged(value) => {
78///             state.value = value;
79///         }
80///     }
81/// }
82/// ```
83pub struct Slider<'a, T, Message, Theme = crate::Theme>
84where
85    Theme: Catalog,
86{
87    range: RangeInclusive<T>,
88    step: T,
89    shift_step: Option<T>,
90    value: T,
91    default: Option<T>,
92    on_change: Box<dyn Fn(T) -> Message + 'a>,
93    on_release: Option<Message>,
94    width: Length,
95    height: f32,
96    class: Theme::Class<'a>,
97    status: Option<Status>,
98}
99
100impl<'a, T, Message, Theme> Slider<'a, T, Message, Theme>
101where
102    T: Copy + From<u8> + PartialOrd,
103    Message: Clone,
104    Theme: Catalog,
105{
106    /// The default height of a [`Slider`].
107    pub const DEFAULT_HEIGHT: f32 = 16.0;
108
109    /// Creates a new [`Slider`].
110    ///
111    /// It expects:
112    ///   * an inclusive range of possible values
113    ///   * the current value of the [`Slider`]
114    ///   * a function that will be called when the [`Slider`] is dragged.
115    ///     It receives the new value of the [`Slider`] and must produce a
116    ///     `Message`.
117    pub fn new<F>(range: RangeInclusive<T>, value: T, on_change: F) -> Self
118    where
119        F: 'a + Fn(T) -> Message,
120    {
121        let value = if value >= *range.start() {
122            value
123        } else {
124            *range.start()
125        };
126
127        let value = if value <= *range.end() {
128            value
129        } else {
130            *range.end()
131        };
132
133        Slider {
134            value,
135            default: None,
136            range,
137            step: T::from(1),
138            shift_step: None,
139            on_change: Box::new(on_change),
140            on_release: None,
141            width: Length::Fill,
142            height: Self::DEFAULT_HEIGHT,
143            class: Theme::default(),
144            status: None,
145        }
146    }
147
148    /// Sets the optional default value for the [`Slider`].
149    ///
150    /// If set, the [`Slider`] will reset to this value when ctrl-clicked or command-clicked.
151    pub fn default(mut self, default: impl Into<T>) -> Self {
152        self.default = Some(default.into());
153        self
154    }
155
156    /// Sets the release message of the [`Slider`].
157    /// This is called when the mouse is released from the slider.
158    ///
159    /// Typically, the user's interaction with the slider is finished when this message is produced.
160    /// This is useful if you need to spawn a long-running task from the slider's result, where
161    /// the default on_change message could create too many events.
162    pub fn on_release(mut self, on_release: Message) -> Self {
163        self.on_release = Some(on_release);
164        self
165    }
166
167    /// Sets the width of the [`Slider`].
168    pub fn width(mut self, width: impl Into<Length>) -> Self {
169        self.width = width.into();
170        self
171    }
172
173    /// Sets the height of the [`Slider`].
174    pub fn height(mut self, height: impl Into<Pixels>) -> Self {
175        self.height = height.into().0;
176        self
177    }
178
179    /// Sets the step size of the [`Slider`].
180    pub fn step(mut self, step: impl Into<T>) -> Self {
181        self.step = step.into();
182        self
183    }
184
185    /// Sets the optional "shift" step for the [`Slider`].
186    ///
187    /// If set, this value is used as the step while the shift key is pressed.
188    pub fn shift_step(mut self, shift_step: impl Into<T>) -> Self {
189        self.shift_step = Some(shift_step.into());
190        self
191    }
192
193    /// Sets the style of the [`Slider`].
194    #[must_use]
195    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
196    where
197        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
198    {
199        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
200        self
201    }
202
203    /// Sets the style class of the [`Slider`].
204    #[cfg(feature = "advanced")]
205    #[must_use]
206    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
207        self.class = class.into();
208        self
209    }
210}
211
212impl<T, Message, Theme, Renderer> Widget<Message, Theme, Renderer> for Slider<'_, T, Message, Theme>
213where
214    T: Copy + Into<f64> + num_traits::FromPrimitive,
215    Message: Clone,
216    Theme: Catalog,
217    Renderer: core::Renderer,
218{
219    fn tag(&self) -> tree::Tag {
220        tree::Tag::of::<State>()
221    }
222
223    fn state(&self) -> tree::State {
224        tree::State::new(State::default())
225    }
226
227    fn size(&self) -> Size<Length> {
228        Size {
229            width: self.width,
230            height: Length::Shrink,
231        }
232    }
233
234    fn layout(
235        &mut self,
236        _tree: &mut Tree,
237        _renderer: &Renderer,
238        limits: &layout::Limits,
239    ) -> layout::Node {
240        layout::atomic(limits, self.width, self.height)
241    }
242
243    fn update(
244        &mut self,
245        tree: &mut Tree,
246        event: &Event,
247        layout: Layout<'_>,
248        cursor: mouse::Cursor,
249        _renderer: &Renderer,
250        _clipboard: &mut dyn Clipboard,
251        shell: &mut Shell<'_, Message>,
252        _viewport: &Rectangle,
253    ) {
254        let state = tree.state.downcast_mut::<State>();
255
256        let mut update = || {
257            let current_value = self.value;
258
259            let locate = |cursor_position: Point| -> Option<T> {
260                let bounds = layout.bounds();
261
262                if cursor_position.x <= bounds.x {
263                    Some(*self.range.start())
264                } else if cursor_position.x >= bounds.x + bounds.width {
265                    Some(*self.range.end())
266                } else {
267                    let step = if state.keyboard_modifiers.shift() {
268                        self.shift_step.unwrap_or(self.step)
269                    } else {
270                        self.step
271                    }
272                    .into();
273
274                    let start = (*self.range.start()).into();
275                    let end = (*self.range.end()).into();
276
277                    let percent = f64::from(cursor_position.x - bounds.x) / f64::from(bounds.width);
278
279                    let steps = (percent * (end - start) / step).round();
280                    let value = steps * step + start;
281
282                    T::from_f64(value.min(end))
283                }
284            };
285
286            let increment = |value: T| -> Option<T> {
287                let step = if state.keyboard_modifiers.shift() {
288                    self.shift_step.unwrap_or(self.step)
289                } else {
290                    self.step
291                }
292                .into();
293
294                let steps = (value.into() / step).round();
295                let new_value = step * (steps + 1.0);
296
297                if new_value > (*self.range.end()).into() {
298                    return Some(*self.range.end());
299                }
300
301                T::from_f64(new_value)
302            };
303
304            let decrement = |value: T| -> Option<T> {
305                let step = if state.keyboard_modifiers.shift() {
306                    self.shift_step.unwrap_or(self.step)
307                } else {
308                    self.step
309                }
310                .into();
311
312                let steps = (value.into() / step).round();
313                let new_value = step * (steps - 1.0);
314
315                if new_value < (*self.range.start()).into() {
316                    return Some(*self.range.start());
317                }
318
319                T::from_f64(new_value)
320            };
321
322            let change = |new_value: T| {
323                if (self.value.into() - new_value.into()).abs() > f64::EPSILON {
324                    shell.publish((self.on_change)(new_value));
325
326                    self.value = new_value;
327                }
328            };
329
330            match &event {
331                Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left))
332                | Event::Touch(touch::Event::FingerPressed { .. }) => {
333                    if let Some(cursor_position) = cursor.position_over(layout.bounds()) {
334                        if state.keyboard_modifiers.command() {
335                            let _ = self.default.map(change);
336                            state.is_dragging = false;
337                        } else {
338                            let _ = locate(cursor_position).map(change);
339                            state.is_dragging = true;
340                        }
341
342                        shell.capture_event();
343                    }
344                }
345                Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left))
346                | Event::Touch(touch::Event::FingerLifted { .. })
347                | Event::Touch(touch::Event::FingerLost { .. }) => {
348                    if state.is_dragging {
349                        if let Some(on_release) = self.on_release.clone() {
350                            shell.publish(on_release);
351                        }
352                        state.is_dragging = false;
353                    }
354                }
355                Event::Mouse(mouse::Event::CursorMoved { .. })
356                | Event::Touch(touch::Event::FingerMoved { .. }) => {
357                    if state.is_dragging {
358                        let _ = cursor.land().position().and_then(locate).map(change);
359
360                        shell.capture_event();
361                    }
362                }
363                Event::Mouse(mouse::Event::WheelScrolled { delta })
364                    if state.keyboard_modifiers.control() =>
365                {
366                    if cursor.is_over(layout.bounds()) {
367                        let delta = match delta {
368                            mouse::ScrollDelta::Lines { x: _, y } => y,
369                            mouse::ScrollDelta::Pixels { x: _, y } => y,
370                        };
371
372                        if *delta < 0.0 {
373                            let _ = decrement(current_value).map(change);
374                        } else {
375                            let _ = increment(current_value).map(change);
376                        }
377
378                        shell.capture_event();
379                    }
380                }
381                Event::Keyboard(keyboard::Event::KeyPressed { key, .. }) => {
382                    if cursor.is_over(layout.bounds()) {
383                        match key {
384                            Key::Named(key::Named::ArrowUp) => {
385                                let _ = increment(current_value).map(change);
386                                shell.capture_event();
387                            }
388                            Key::Named(key::Named::ArrowDown) => {
389                                let _ = decrement(current_value).map(change);
390                                shell.capture_event();
391                            }
392                            _ => (),
393                        }
394                    }
395                }
396                Event::Keyboard(keyboard::Event::ModifiersChanged(modifiers)) => {
397                    state.keyboard_modifiers = *modifiers;
398                }
399                _ => {}
400            }
401        };
402
403        update();
404
405        let current_status = if state.is_dragging {
406            Status::Dragged
407        } else if cursor.is_over(layout.bounds()) {
408            Status::Hovered
409        } else {
410            Status::Active
411        };
412
413        if let Event::Window(window::Event::RedrawRequested(_now)) = event {
414            self.status = Some(current_status);
415        } else if self.status.is_some_and(|status| status != current_status) {
416            shell.request_redraw();
417        }
418    }
419
420    fn draw(
421        &self,
422        _tree: &Tree,
423        renderer: &mut Renderer,
424        theme: &Theme,
425        _style: &renderer::Style,
426        layout: Layout<'_>,
427        _cursor: mouse::Cursor,
428        _viewport: &Rectangle,
429    ) {
430        let bounds = layout.bounds();
431
432        let style = theme.style(&self.class, self.status.unwrap_or(Status::Active));
433
434        let (handle_width, handle_height, handle_border_radius) = match style.handle.shape {
435            HandleShape::Circle { radius } => (radius * 2.0, radius * 2.0, radius.into()),
436            HandleShape::Rectangle {
437                width,
438                border_radius,
439            } => (f32::from(width), bounds.height, border_radius),
440        };
441
442        let value = self.value.into() as f32;
443        let (range_start, range_end) = {
444            let (start, end) = self.range.clone().into_inner();
445
446            (start.into() as f32, end.into() as f32)
447        };
448
449        let offset = if range_start >= range_end {
450            0.0
451        } else {
452            (bounds.width - handle_width) * (value - range_start) / (range_end - range_start)
453        };
454
455        let rail_y = bounds.y + bounds.height / 2.0;
456
457        renderer.fill_quad(
458            renderer::Quad {
459                bounds: Rectangle {
460                    x: bounds.x,
461                    y: rail_y - style.rail.width / 2.0,
462                    width: offset + handle_width / 2.0,
463                    height: style.rail.width,
464                },
465                border: style.rail.border,
466                ..renderer::Quad::default()
467            },
468            style.rail.backgrounds.0,
469        );
470
471        renderer.fill_quad(
472            renderer::Quad {
473                bounds: Rectangle {
474                    x: bounds.x + offset + handle_width / 2.0,
475                    y: rail_y - style.rail.width / 2.0,
476                    width: bounds.width - offset - handle_width / 2.0,
477                    height: style.rail.width,
478                },
479                border: style.rail.border,
480                ..renderer::Quad::default()
481            },
482            style.rail.backgrounds.1,
483        );
484
485        renderer.fill_quad(
486            renderer::Quad {
487                bounds: Rectangle {
488                    x: bounds.x + offset,
489                    y: rail_y - handle_height / 2.0,
490                    width: handle_width,
491                    height: handle_height,
492                },
493                border: Border {
494                    radius: handle_border_radius,
495                    width: style.handle.border_width,
496                    color: style.handle.border_color,
497                },
498                ..renderer::Quad::default()
499            },
500            style.handle.background,
501        );
502    }
503
504    fn mouse_interaction(
505        &self,
506        tree: &Tree,
507        layout: Layout<'_>,
508        cursor: mouse::Cursor,
509        _viewport: &Rectangle,
510        _renderer: &Renderer,
511    ) -> mouse::Interaction {
512        let state = tree.state.downcast_ref::<State>();
513
514        if state.is_dragging {
515            // FIXME: Fall back to `Pointer` on Windows
516            // See https://github.com/rust-windowing/winit/issues/1043
517            if cfg!(target_os = "windows") {
518                mouse::Interaction::Pointer
519            } else {
520                mouse::Interaction::Grabbing
521            }
522        } else if cursor.is_over(layout.bounds()) {
523            if cfg!(target_os = "windows") {
524                mouse::Interaction::Pointer
525            } else {
526                mouse::Interaction::Grab
527            }
528        } else {
529            mouse::Interaction::default()
530        }
531    }
532}
533
534impl<'a, T, Message, Theme, Renderer> From<Slider<'a, T, Message, Theme>>
535    for Element<'a, Message, Theme, Renderer>
536where
537    T: Copy + Into<f64> + num_traits::FromPrimitive + 'a,
538    Message: Clone + 'a,
539    Theme: Catalog + 'a,
540    Renderer: core::Renderer + 'a,
541{
542    fn from(slider: Slider<'a, T, Message, Theme>) -> Element<'a, Message, Theme, Renderer> {
543        Element::new(slider)
544    }
545}
546
547#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
548struct State {
549    is_dragging: bool,
550    keyboard_modifiers: keyboard::Modifiers,
551}
552
553/// The possible status of a [`Slider`].
554#[derive(Debug, Clone, Copy, PartialEq, Eq)]
555pub enum Status {
556    /// The [`Slider`] can be interacted with.
557    Active,
558    /// The [`Slider`] is being hovered.
559    Hovered,
560    /// The [`Slider`] is being dragged.
561    Dragged,
562}
563
564/// The appearance of a slider.
565#[derive(Debug, Clone, Copy, PartialEq)]
566pub struct Style {
567    /// The colors of the rail of the slider.
568    pub rail: Rail,
569    /// The appearance of the [`Handle`] of the slider.
570    pub handle: Handle,
571}
572
573impl Style {
574    /// Changes the [`HandleShape`] of the [`Style`] to a circle
575    /// with the given radius.
576    pub fn with_circular_handle(mut self, radius: impl Into<Pixels>) -> Self {
577        self.handle.shape = HandleShape::Circle {
578            radius: radius.into().0,
579        };
580        self
581    }
582}
583
584/// The appearance of a slider rail
585#[derive(Debug, Clone, Copy, PartialEq)]
586pub struct Rail {
587    /// The backgrounds of the rail of the slider.
588    pub backgrounds: (Background, Background),
589    /// The width of the stroke of a slider rail.
590    pub width: f32,
591    /// The border of the rail.
592    pub border: Border,
593}
594
595/// The appearance of the handle of a slider.
596#[derive(Debug, Clone, Copy, PartialEq)]
597pub struct Handle {
598    /// The shape of the handle.
599    pub shape: HandleShape,
600    /// The [`Background`] of the handle.
601    pub background: Background,
602    /// The border width of the handle.
603    pub border_width: f32,
604    /// The border [`Color`] of the handle.
605    pub border_color: Color,
606}
607
608/// The shape of the handle of a slider.
609#[derive(Debug, Clone, Copy, PartialEq)]
610pub enum HandleShape {
611    /// A circular handle.
612    Circle {
613        /// The radius of the circle.
614        radius: f32,
615    },
616    /// A rectangular shape.
617    Rectangle {
618        /// The width of the rectangle.
619        width: u16,
620        /// The border radius of the corners of the rectangle.
621        border_radius: border::Radius,
622    },
623}
624
625/// The theme catalog of a [`Slider`].
626pub trait Catalog: Sized {
627    /// The item class of the [`Catalog`].
628    type Class<'a>;
629
630    /// The default class produced by the [`Catalog`].
631    fn default<'a>() -> Self::Class<'a>;
632
633    /// The [`Style`] of a class with the given status.
634    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
635}
636
637/// A styling function for a [`Slider`].
638pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
639
640impl Catalog for Theme {
641    type Class<'a> = StyleFn<'a, Self>;
642
643    fn default<'a>() -> Self::Class<'a> {
644        Box::new(default)
645    }
646
647    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
648        class(self, status)
649    }
650}
651
652/// The default style of a [`Slider`].
653pub fn default(theme: &Theme, status: Status) -> Style {
654    let palette = theme.extended_palette();
655
656    let color = match status {
657        Status::Active => palette.primary.base.color,
658        Status::Hovered => palette.primary.strong.color,
659        Status::Dragged => palette.primary.weak.color,
660    };
661
662    Style {
663        rail: Rail {
664            backgrounds: (color.into(), palette.background.strong.color.into()),
665            width: 4.0,
666            border: Border {
667                radius: 2.0.into(),
668                width: 0.0,
669                color: Color::TRANSPARENT,
670            },
671        },
672        handle: Handle {
673            shape: HandleShape::Circle { radius: 7.0 },
674            background: color.into(),
675            border_color: Color::TRANSPARENT,
676            border_width: 0.0,
677        },
678    }
679}
iced_widget/slider.rs

iced_widget/
slider.rs
