vizia_core/views/

slider.rs

use std::ops::Range;

use crate::prelude::*;
use accesskit::ActionData;

/// Internal events for the slider view.
pub(crate) enum SliderEvent {
    Increment,
    Decrement,
    SetMin,
    SetMax,
    ResetDefault,
}

/// The slider control can be used to select from a continuous set of values.
///
/// The slider control consists of three main parts, a **thumb** element which can be moved between the extremes of a linear **track**,
/// and a **range** element which fills the slider to indicate the current value.
///
/// # Examples
///
/// ## Basic Slider
/// In the following example, a slider reads from a value source. The `on_change` callback is used
/// to update that value when the slider thumb is moved, or if the track is clicked on.
/// ```
/// # use vizia_core::prelude::*;
///
/// # let mut cx = &mut Context::default();
/// # #[derive(Default)]
/// # pub struct AppData {
/// #     value: f32,
/// # }
/// # impl Model for AppData {}
/// # let value = Signal::new(0.5);
/// Slider::new(cx, value)
///     .on_change(|cx, value| {
///         let _ = (cx, value);
///     });
/// ```
///
/// ## Slider with Label
/// ```
/// # use vizia_core::prelude::*;
///
/// # let mut cx = &mut Context::default();
/// # #[derive(Default)]
/// # pub struct AppData {
/// #     value: f32,
/// # }
/// # impl Model for AppData {}
/// # let value = Signal::new(0.5);
/// HStack::new(cx, |cx|{
///     Slider::new(cx, value)
///         .on_change(|cx, value| {
///             let _ = (cx, value);
///         });
///     Label::new(cx, value.map(|val| format!("{:.2}", val)));
/// });
/// ```
pub struct Slider<S> {
    value: S,
    is_dragging: bool,
    /// The orientation of the slider.
    orientation: Signal<Orientation>,
    /// The range of the slider.
    range: Signal<Range<f32>>,
    /// The step of the slider.
    step: Signal<f32>,
    /// The value that the slider resets to when double-clicking the thumb.
    default_value: Signal<f32>,
    on_change: Option<Box<dyn Fn(&mut EventContext, f32)>>,
}

impl<S> Slider<S>
where
    S: SignalGet<f32> + SignalMap<f32> + Copy + 'static,
{
    /// Creates a new slider from the provided value source.
    ///
    /// ```
    /// # use vizia_core::prelude::*;
    ///
    /// # let mut cx = &mut Context::default();
    /// # #[derive(Default)]
    /// # pub struct AppData {
    /// #     value: f32,
    /// # }
    /// # impl Model for AppData {}
    /// # let value = Signal::new(0.5);
    /// Slider::new(cx, value)
    ///     .on_change(|cx, value| {
    ///         let _ = (cx, value);
    ///     });
    /// ```
    pub fn new(cx: &mut Context, value: S) -> Handle<Self> {
        let range = Signal::new(0.0..1.0);
        let orientation = Signal::new(Orientation::Horizontal);
        let step = Signal::new(0.01);
        let default_value = Signal::new(value.get());

        Self { value, is_dragging: false, orientation, range, step, default_value, on_change: None }
            .build(cx, move |cx| {
                Keymap::from(vec![
                    (
                        KeyChord::new(Modifiers::empty(), Code::ArrowUp),
                        KeymapEntry::new("Increment", |cx| cx.emit(SliderEvent::Increment)),
                    ),
                    (
                        KeyChord::new(Modifiers::empty(), Code::ArrowRight),
                        KeymapEntry::new("Increment", |cx| cx.emit(SliderEvent::Increment)),
                    ),
                    (
                        KeyChord::new(Modifiers::empty(), Code::ArrowDown),
                        KeymapEntry::new("Decrement", |cx| cx.emit(SliderEvent::Decrement)),
                    ),
                    (
                        KeyChord::new(Modifiers::empty(), Code::ArrowLeft),
                        KeymapEntry::new("Decrement", |cx| cx.emit(SliderEvent::Decrement)),
                    ),
                    (
                        KeyChord::new(Modifiers::empty(), Code::Home),
                        KeymapEntry::new("Set Min", |cx| cx.emit(SliderEvent::SetMin)),
                    ),
                    (
                        KeyChord::new(Modifiers::empty(), Code::End),
                        KeymapEntry::new("Set Max", |cx| cx.emit(SliderEvent::SetMax)),
                    ),
                ])
                .build(cx);

                // Track
                HStack::new(cx, move |cx| {
                    let active_normalized = Memo::new(move |_| {
                        let active_range = range.get();
                        let val = value.get().clamp(active_range.start, active_range.end);
                        (val - active_range.start) / (active_range.end - active_range.start)
                    });

                    let active_width = Memo::new(move |_| {
                        let normal_val = active_normalized.get();
                        if orientation.get() == Orientation::Horizontal {
                            Percentage(normal_val * 100.0)
                        } else {
                            Stretch(1.0)
                        }
                    });

                    let active_height = Memo::new(move |_| {
                        let normal_val = active_normalized.get();
                        if orientation.get() == Orientation::Horizontal {
                            Stretch(1.0)
                        } else {
                            Percentage(normal_val * 100.0)
                        }
                    });

                    // Range track
                    VStack::new(cx, move |cx| {
                        let dir = cx.environment().direction;

                        let thumb_translate: Memo<Translate> = Memo::new(move |_| {
                            let thumb_range = range.get();
                            let val = value.get().clamp(thumb_range.start, thumb_range.end);
                            let normal_val =
                                (val - thumb_range.start) / (thumb_range.end - thumb_range.start);
                            // Todo: Find a way to react to local direction rather than global direction.
                            // Currently not possible because local direction is a style property
                            // that gets resolved after bindings.
                            // Ideally we need a way to do the translation in css which means changing
                            // a css variable in rust code that gets used in the stylesheet to do the translation
                            // rather than doing it here in code.
                            let is_rtl = dir.get() == Direction::RightToLeft;
                            if orientation.get() == Orientation::Horizontal {
                                if is_rtl {
                                    (Percentage(-100.0 * (1.0 - normal_val)), Pixels(0.0)).into()
                                } else {
                                    (Percentage(100.0 * (1.0 - normal_val)), Pixels(0.0)).into()
                                }
                            } else {
                                (Pixels(0.0), Percentage(-100.0 * (1.0 - normal_val))).into()
                            }
                        });

                        // Thumb
                        Element::new(cx).class("thumb").translate(thumb_translate);
                    })
                    .class("range")
                    .width(active_width)
                    .height(active_height)
                    .layout_type(orientation.map(|o| {
                        if *o == Orientation::Horizontal {
                            LayoutType::Row
                        } else {
                            LayoutType::Column
                        }
                    }))
                    .alignment(orientation.map(|o| {
                        if *o == Orientation::Horizontal {
                            Alignment::Right
                        } else {
                            Alignment::TopCenter
                        }
                    }));
                })
                .class("track");
            })
            .orientation(orientation)
            .role(Role::Slider)
            .numeric_value(value.map(|v| (*v as f64 * 100.0).round() / 100.0))
            .text_value(value.map(|v| format!("{}", (*v as f64 * 100.0).round() / 100.0)))
            .navigable(true)
    }
}

impl<S> View for Slider<S>
where
    S: SignalGet<f32> + 'static,
{
    fn element(&self) -> Option<&'static str> {
        Some("slider")
    }

    fn accessibility(&self, _cx: &mut AccessContext, node: &mut AccessNode) {
        node.set_numeric_value_step(self.step.get() as f64);
        node.set_min_numeric_value(self.range.get().start as f64);
        node.set_max_numeric_value(self.range.get().end as f64);
    }

    fn event(&mut self, cx: &mut EventContext, event: &mut Event) {
        event.map(|slider_event, _| match slider_event {
            SliderEvent::Increment => {
                let min = self.range.get().start;
                let max = self.range.get().end;
                let step = self.step.get();
                let mut val = self.value.get() + step;
                val = val.clamp(min, max);
                if let Some(callback) = &self.on_change {
                    (callback)(cx, val);
                }
            }

            SliderEvent::Decrement => {
                let min = self.range.get().start;
                let max = self.range.get().end;
                let step = self.step.get();
                let mut val = self.value.get() - step;
                val = val.clamp(min, max);
                if let Some(callback) = &self.on_change {
                    (callback)(cx, val);
                }
            }

            SliderEvent::SetMin => {
                if let Some(callback) = &self.on_change {
                    (callback)(cx, self.range.get().start);
                }
            }

            SliderEvent::SetMax => {
                if let Some(callback) = &self.on_change {
                    (callback)(cx, self.range.get().end);
                }
            }

            SliderEvent::ResetDefault => {
                let min = self.range.get().start;
                let max = self.range.get().end;
                let val = self.default_value.get().clamp(min, max);
                if let Some(callback) = &self.on_change {
                    (callback)(cx, val);
                }
            }
        });

        event.map(|window_event, meta| match window_event {
            WindowEvent::MouseDown(button) if *button == MouseButton::Left => {
                if !cx.is_disabled() {
                    self.is_dragging = true;
                    cx.capture();
                    cx.focus_with_visibility(false);
                    cx.with_current(Entity::root(), |cx| {
                        cx.set_pointer_events(false);
                    });

                    let thumb = cx.get_entities_by_class("thumb").first().copied().unwrap();
                    let current = cx.current();
                    let bounds = cx.transformed_bounds(current);
                    let thumb_bounds = cx.transformed_bounds(thumb);
                    let thumb_size = match self.orientation.get() {
                        Orientation::Horizontal => thumb_bounds.width(),
                        Orientation::Vertical => thumb_bounds.height(),
                    };
                    let min = self.range.get().start;
                    let max = self.range.get().end;
                    let step = self.step.get();

                    let is_rtl = matches!(
                        cx.style.direction.get(current).copied(),
                        Some(Direction::RightToLeft)
                    );

                    let mut dx = match self.orientation.get() {
                        Orientation::Horizontal => {
                            let span = (bounds.width() - thumb_size).max(f32::EPSILON);
                            let raw_dx =
                                (cx.mouse.left.pos_down.0 - bounds.left() - thumb_size / 2.0)
                                    / span;
                            if is_rtl { 1.0 - raw_dx } else { raw_dx }
                        }

                        Orientation::Vertical => {
                            let span = (bounds.height() - thumb_size).max(f32::EPSILON);
                            (bounds.height()
                                - (cx.mouse.left.pos_down.1 - bounds.top())
                                - thumb_size / 2.0)
                                / span
                        }
                    };

                    dx = dx.clamp(0.0, 1.0);

                    let mut val = min + dx * (max - min);

                    val = step * (val / step).ceil();
                    val = val.clamp(min, max);

                    if let Some(callback) = self.on_change.take() {
                        (callback)(cx, val);

                        self.on_change = Some(callback);
                    }
                }
            }

            WindowEvent::MouseUp(button) if *button == MouseButton::Left => {
                self.is_dragging = false;
                cx.focus_with_visibility(false);
                cx.release();
                cx.with_current(Entity::root(), |cx| {
                    cx.set_pointer_events(true);
                });
            }

            WindowEvent::MouseMove(x, y) => {
                if self.is_dragging {
                    let thumb = cx.get_entities_by_class("thumb").first().copied().unwrap();
                    let current = cx.current();
                    let bounds = cx.transformed_bounds(current);
                    let thumb_bounds = cx.transformed_bounds(thumb);
                    let thumb_size = match self.orientation.get() {
                        Orientation::Horizontal => thumb_bounds.width(),
                        Orientation::Vertical => thumb_bounds.height(),
                    };

                    let min = self.range.get().start;
                    let max = self.range.get().end;
                    let step = self.step.get();

                    let is_rtl = matches!(
                        cx.style.direction.get(current).copied(),
                        Some(Direction::RightToLeft)
                    );

                    let mut dx = match self.orientation.get() {
                        Orientation::Horizontal => {
                            let span = (bounds.width() - thumb_size).max(f32::EPSILON);
                            let raw_dx = (*x - bounds.left() - thumb_size / 2.0) / span;
                            if is_rtl { 1.0 - raw_dx } else { raw_dx }
                        }

                        Orientation::Vertical => {
                            let span = (bounds.height() - thumb_size).max(f32::EPSILON);
                            (bounds.height() - (*y - bounds.top()) - thumb_size / 2.0) / span
                        }
                    };

                    dx = dx.clamp(0.0, 1.0);

                    let mut val = min + dx * (max - min);

                    val = step * (val / step).ceil();
                    val = val.clamp(min, max);

                    if let Some(callback) = &self.on_change {
                        (callback)(cx, val);
                    }
                }
            }

            WindowEvent::MouseDoubleClick(button) if *button == MouseButton::Left => {
                let is_thumb_target = cx
                    .get_entities_by_class("thumb")
                    .first()
                    .copied()
                    .map(|thumb| thumb == meta.target)
                    .unwrap_or(false);

                if is_thumb_target {
                    cx.focus_with_visibility(false);
                    cx.release();
                    cx.with_current(Entity::root(), |cx| {
                        cx.set_pointer_events(true);
                    });
                    self.is_dragging = false;
                    cx.emit(SliderEvent::ResetDefault);
                }
            }

            WindowEvent::ActionRequest(action) => match action.action {
                Action::Increment => {
                    let min = self.range.get().start;
                    let max = self.range.get().end;
                    let step = self.step.get();
                    let mut val = self.value.get() + step;
                    val = step * (val / step).ceil();
                    val = val.clamp(min, max);
                    if let Some(callback) = &self.on_change {
                        (callback)(cx, val);
                    }
                }

                Action::Decrement => {
                    let min = self.range.get().start;
                    let max = self.range.get().end;
                    let step = self.step.get();
                    let mut val = self.value.get() - step;
                    val = step * (val / step).ceil();
                    val = val.clamp(min, max);
                    if let Some(callback) = &self.on_change {
                        (callback)(cx, val);
                    }
                }

                Action::SetValue => {
                    if let Some(ActionData::NumericValue(val)) = action.data {
                        let min = self.range.get().start;
                        let max = self.range.get().end;
                        let mut v = val as f32;
                        v = v.clamp(min, max);
                        if let Some(callback) = &self.on_change {
                            (callback)(cx, v);
                        }
                    }
                }

                _ => {}
            },

            _ => {}
        });
    }
}

pub trait SliderModifiers: Sized {
    /// Sets the callback triggered when the slider value is changed.
    ///
    /// Takes a closure which triggers when the slider value is changed,
    /// either by pressing the track or dragging the thumb along the track.
    ///
    /// ```
    /// # use vizia_core::prelude::*;
    ///
    /// # let mut cx = &mut Context::default();
    /// # #[derive(Default)]
    /// # pub struct AppData {
    /// #     value: f32,
    /// # }
    /// # impl Model for AppData {}
    /// # let value = Signal::new(0.5);
    /// Slider::new(cx, value)
    ///     .on_change(|cx, value| {
    ///         let _ = (cx, value);
    ///     });
    /// ```
    fn on_change<F>(self, callback: F) -> Self
    where
        F: 'static + Fn(&mut EventContext, f32);

    /// Sets the range of the slider.
    ///
    /// If the source value is outside of the range then the slider will clip to min/max of the range.
    ///
    /// ```
    /// # use vizia_core::prelude::*;
    ///
    /// # let mut cx = &mut Context::default();
    /// # #[derive(Default)]
    /// # pub struct AppData {
    /// #     value: f32,
    /// # }
    /// # impl Model for AppData {}
    /// # let value = Signal::new(0.5);
    /// Slider::new(cx, value)
    ///     .range(-20.0..50.0)
    ///     .on_change(|cx, value| {
    ///         let _ = (cx, value);
    ///     });
    /// ```
    fn range<U: Into<Range<f32>> + Clone + 'static>(self, range: impl Res<U> + 'static) -> Self;

    /// Sets the orientation of the slider to vertical.
    ///
    /// ```
    /// # use vizia_core::prelude::*;
    ///
    /// # let mut cx = &mut Context::default();
    /// # #[derive(Default)]
    /// # pub struct AppData {
    /// #     value: f32,
    /// # }
    /// # impl Model for AppData {}
    /// # let value = Signal::new(0.5);
    /// Slider::new(cx, value)
    ///     .vertical(true)
    ///     .on_change(|cx, value| {
    ///         let _ = (cx, value);
    ///     });
    /// ```
    fn vertical<U: Into<bool> + Clone + 'static>(self, vertical: impl Res<U> + 'static) -> Self;

    /// Set the step value for the slider.
    ///
    /// ```
    /// # use vizia_core::prelude::*;
    ///
    /// # let mut cx = &mut Context::default();
    /// # #[derive(Default)]
    /// # pub struct AppData {
    /// #     value: f32,
    /// # }
    /// # impl Model for AppData {}
    /// # let value = Signal::new(0.5);
    /// Slider::new(cx, value)
    ///     .step(0.1_f32)
    ///     .on_change(|cx, value| {
    ///         let _ = (cx, value);
    ///     });
    /// ```
    fn step<U: Into<f32> + Clone + 'static>(self, step: impl Res<U> + 'static) -> Self;

    /// Sets the value that the slider resets to when the thumb is double-clicked.
    fn default_value<U: Into<f32> + Clone + 'static>(
        self,
        default_value: impl Res<U> + 'static,
    ) -> Self;
}

impl<S> SliderModifiers for Handle<'_, Slider<S>>
where
    S: SignalGet<f32> + 'static,
{
    fn on_change<F>(self, callback: F) -> Self
    where
        F: 'static + Fn(&mut EventContext, f32),
    {
        self.modify(|slider| slider.on_change = Some(Box::new(callback)))
    }

    fn range<U: Into<Range<f32>> + Clone + 'static>(self, range: impl Res<U> + 'static) -> Self {
        let range = range.to_signal(self.cx);
        self.bind(range, move |handle| {
            let range = range.get();
            let range = range.into();
            handle.modify(|slider| {
                slider.range.set(range);
            });
        })
    }

    fn vertical<U: Into<bool> + Clone + 'static>(self, vertical: impl Res<U> + 'static) -> Self {
        let vertical = vertical.to_signal(self.cx);
        self.bind(vertical, move |handle| {
            let vertical = vertical.get().into();

            let orientation =
                if vertical { Orientation::Vertical } else { Orientation::Horizontal };
            handle.modify(|slider| {
                slider.orientation.set(orientation);
            });
        })
    }

    fn step<U: Into<f32> + Clone + 'static>(self, step: impl Res<U> + 'static) -> Self {
        let step = step.to_signal(self.cx);
        self.bind(step, move |handle| {
            let step = step.get();
            let step = step.into();
            handle.modify(|slider| {
                slider.step.set(step);
            });
        })
    }

    fn default_value<U: Into<f32> + Clone + 'static>(
        self,
        default_value: impl Res<U> + 'static,
    ) -> Self {
        let default_value = default_value.to_signal(self.cx);
        self.bind(default_value, move |handle| {
            let default_value = default_value.get().into();
            handle.modify(|slider| {
                slider.default_value.set(default_value);
            });
        })
    }
}