servo/components/style/animation.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! CSS transitions and animations.

use app_units::Au;
use bezier::Bezier;
use euclid::point::Point2D;
use dom::{OpaqueNode, TRestyleDamage};
use keyframes::KeyframesAnimation;
use keyframes::KeyframesStep;
use properties::animated_properties::{AnimatedProperty, TransitionProperty};
use properties::longhands::transition_timing_function::computed_value::StartEnd;
use properties::longhands::transition_timing_function::computed_value::TransitionTimingFunction;
use properties::longhands::animation_play_state::computed_value::AnimationPlayState;
use properties::longhands::animation_iteration_count::computed_value::AnimationIterationCount;
use properties::style_struct_traits::Box;
use properties::{ComputedValues, ServoComputedValues};
use std::sync::mpsc::Sender;
use std::sync::{Arc, Mutex};
use time;
use values::computed::Time;
use selector_impl::SelectorImplExt;
use context::SharedStyleContext;
use selectors::matching::DeclarationBlock;
use string_cache::Atom;
use properties;

/// This structure represents a keyframes animation current iteration state.
///
/// If the iteration count is infinite, there's no other state, otherwise we
/// have to keep track the current iteration and the max iteration count.
#[derive(Debug, Clone)]
pub enum KeyframesIterationState {
    Infinite,
    // current, max
    Finite(u32, u32),
}

/// This structure represents the current keyframe animation state, i.e., the
/// duration, the current and maximum iteration count, and the state (either
/// playing or paused).
#[derive(Debug, Clone)]
pub struct KeyframesAnimationState {
    pub started_at: f64,
    pub duration: f64,
    pub iteration_state: KeyframesIterationState,
    pub paused: bool,
}

/// State relating to an animation.
#[derive(Clone, Debug)]
pub enum Animation {
    /// A transition is just a single frame triggered at a time, with a reflow.
    ///
    /// the f64 field is the start time as returned by `time::precise_time_s()`.
    Transition(OpaqueNode, f64, AnimationFrame),
    /// A keyframes animation is identified by a name, and can have a
    /// node-dependent state (i.e. iteration count, etc.).
    Keyframes(OpaqueNode, Atom, KeyframesAnimationState),
}

/// A keyframes animation previously sent to layout.

/// A single animation frame of a single property.
#[derive(Debug, Clone)]
pub struct AnimationFrame {
    /// A description of the property animation that is occurring.
    pub property_animation: PropertyAnimation,
    /// The duration of the animation. This is either relative in the keyframes
    /// case (a number between 0 and 1), or absolute in the transition case.
    pub duration: f64,
}

#[derive(Debug, Clone)]
pub struct PropertyAnimation {
    property: AnimatedProperty,
    timing_function: TransitionTimingFunction,
    duration: Time, // TODO: isn't this just repeated?
}

impl PropertyAnimation {
    /// Creates a new property animation for the given transition index and old and new styles.
    /// Any number of animations may be returned, from zero (if the property did not animate) to
    /// one (for a single transition property) to arbitrarily many (for `all`).
    pub fn from_transition<C: ComputedValues>(transition_index: usize,
                                              old_style: &C,
                                              new_style: &mut C)
                                              -> Vec<PropertyAnimation> {
        let mut result = vec![];
        let box_style = new_style.as_servo().get_box();
        let transition_property = box_style.transition_property.0[transition_index];
        let timing_function = *box_style.transition_timing_function.0.get_mod(transition_index);
        let duration = *box_style.transition_duration.0.get_mod(transition_index);


        if transition_property != TransitionProperty::All {
            if let Some(property_animation) =
                    PropertyAnimation::from_transition_property(transition_property,
                                                                timing_function,
                                                                duration,
                                                                old_style,
                                                                new_style) {
                result.push(property_animation)
            }
            return result
        }

        TransitionProperty::each(|transition_property| {
            if let Some(property_animation) =
                    PropertyAnimation::from_transition_property(transition_property,
                                                                timing_function,
                                                                duration,
                                                                old_style,
                                                                new_style) {
                result.push(property_animation)
            }
        });

        result
    }

    fn from_transition_property<C: ComputedValues>(transition_property: TransitionProperty,
                                                   timing_function: TransitionTimingFunction,
                                                   duration: Time,
                                                   old_style: &C,
                                                   new_style: &C)
                                                   -> Option<PropertyAnimation> {
        let animated_property = AnimatedProperty::from_transition_property(&transition_property,
                                                                           old_style,
                                                                           new_style);

        let property_animation = PropertyAnimation {
            property: animated_property,
            timing_function: timing_function,
            duration: duration,
        };

        if property_animation.does_animate() {
            Some(property_animation)
        } else {
            None
        }
    }

    pub fn update<C: ComputedValues>(&self, style: &mut C, time: f64) {
        let progress = match self.timing_function {
            TransitionTimingFunction::CubicBezier(p1, p2) => {
                // See `WebCore::AnimationBase::solveEpsilon(double)` in WebKit.
                let epsilon = 1.0 / (200.0 * (self.duration.seconds() as f64));
                Bezier::new(Point2D::new(p1.x as f64, p1.y as f64),
                            Point2D::new(p2.x as f64, p2.y as f64)).solve(time, epsilon)
            }
            TransitionTimingFunction::Steps(steps, StartEnd::Start) => {
                (time * (steps as f64)).ceil() / (steps as f64)
            }
            TransitionTimingFunction::Steps(steps, StartEnd::End) => {
                (time * (steps as f64)).floor() / (steps as f64)
            }
        };

        self.property.update(style, progress);
    }

    #[inline]
    fn does_animate(&self) -> bool {
        self.property.does_animate() && self.duration != Time(0.0)
    }
}

/// Accesses an element of an array, "wrapping around" using modular arithmetic. This is needed
/// to handle [repeatable lists][lists] of differing lengths.
///
/// [lists]: https://drafts.csswg.org/css-transitions/#animtype-repeatable-list
pub trait GetMod {
    type Item;
    fn get_mod(&self, i: usize) -> &Self::Item;
}

impl<T> GetMod for Vec<T> {
    type Item = T;
    #[inline]
    fn get_mod(&self, i: usize) -> &T {
        &(*self)[i % self.len()]
    }
}

/// Inserts transitions into the queue of running animations as applicable for
/// the given style difference. This is called from the layout worker threads.
/// Returns true if any animations were kicked off and false otherwise.
//
// TODO(emilio): Take rid of this mutex splitting SharedLayoutContex into a
// cloneable part and a non-cloneable part..
pub fn start_transitions_if_applicable<C: ComputedValues>(new_animations_sender: &Mutex<Sender<Animation>>,
                                                          node: OpaqueNode,
                                                          old_style: &C,
                                                          new_style: &mut C)
                                                          -> bool {
    let mut had_animations = false;
    for i in 0..new_style.get_box().transition_count() {
        // Create any property animations, if applicable.
        let property_animations = PropertyAnimation::from_transition(i, old_style, new_style);
        for property_animation in property_animations {
            // Set the property to the initial value.
            property_animation.update(new_style, 0.0);

            // Kick off the animation.
            let now = time::precise_time_s();
            let box_style = new_style.as_servo().get_box();
            let start_time =
                now + (box_style.transition_delay.0.get_mod(i).seconds() as f64);
            new_animations_sender
                .lock().unwrap()
                .send(Animation::Transition(node, start_time, AnimationFrame {
                    duration: box_style.transition_duration.0.get_mod(i).seconds() as f64,
                    property_animation: property_animation,
                })).unwrap();

            had_animations = true;
        }
    }

    had_animations
}

fn compute_style_for_animation_step<Impl: SelectorImplExt>(context: &SharedStyleContext<Impl>,
                                                           step: &KeyframesStep,
                                                           old_style: &Impl::ComputedValues) -> Impl::ComputedValues {
    let declaration_block = DeclarationBlock {
        declarations: step.declarations.clone(),
        source_order: 0,
        specificity: ::std::u32::MAX,
    };
    let (computed, _) = properties::cascade(context.viewport_size,
                                            &[declaration_block],
                                            false,
                                            Some(old_style),
                                            None,
                                            context.error_reporter.clone());
    computed
}

pub fn maybe_start_animations<Impl: SelectorImplExt>(context: &SharedStyleContext<Impl>,
                                                     node: OpaqueNode,
                                                     new_style: &Impl::ComputedValues) -> bool
{
    let mut had_animations = false;

    let box_style = new_style.as_servo().get_box();
    for (i, name) in box_style.animation_name.0.iter().enumerate() {
        debug!("maybe_start_animations: name={}", name);
        let total_duration = box_style.animation_duration.0.get_mod(i).seconds();
        if total_duration == 0. {
            continue
        }

        if let Some(ref animation) = context.stylist.animations().get(&name) {
            let delay = box_style.animation_delay.0.get_mod(i).seconds();
            let animation_start = time::precise_time_s() + delay as f64;
            let duration = box_style.animation_duration.0.get_mod(i).seconds();
            let iteration_state = match *box_style.animation_iteration_count.0.get_mod(i) {
                AnimationIterationCount::Infinite => KeyframesIterationState::Infinite,
                AnimationIterationCount::Number(n) => KeyframesIterationState::Finite(0, n),
            };
            let paused = *box_style.animation_play_state.0.get_mod(i) == AnimationPlayState::paused;

            context.new_animations_sender
                   .lock().unwrap()
                   .send(Animation::Keyframes(node, name.clone(), KeyframesAnimationState {
                       started_at: animation_start,
                       duration: duration as f64,
                       iteration_state: iteration_state,
                       paused: paused,
                   })).unwrap();
            had_animations = true;
        }
    }

    had_animations
}

/// Updates a given computed style for a given animation frame. Returns a bool
/// representing if the style was indeed updated.
pub fn update_style_for_animation_frame<C: ComputedValues>(mut new_style: &mut Arc<C>,
                                                           now: f64,
                                                           start_time: f64,
                                                           frame: &AnimationFrame) -> bool {
    let mut progress = (now - start_time) / frame.duration;
    if progress > 1.0 {
        progress = 1.0
    }

    if progress <= 0.0 {
        return false;
    }

    frame.property_animation.update(Arc::make_mut(&mut new_style), progress);

    true
}
/// Updates a single animation and associated style based on the current time. If `damage` is
/// provided, inserts the appropriate restyle damage.
pub fn update_style_for_animation<Damage, Impl>(context: &SharedStyleContext<Impl>,
                                                animation: &Animation,
                                                style: &mut Arc<Damage::ConcreteComputedValues>,
                                                damage: Option<&mut Damage>)
where Impl: SelectorImplExt,
      Damage: TRestyleDamage<ConcreteComputedValues = Impl::ComputedValues> {
    let now = time::precise_time_s();
    match *animation {
        Animation::Transition(_, start_time, ref frame) => {
            let mut new_style = (*style).clone();
            let updated_style = update_style_for_animation_frame(&mut new_style,
                                                                 now, start_time,
                                                                 frame);
            if updated_style {
                if let Some(damage) = damage {
                    *damage = *damage | Damage::compute(Some(style), &new_style);
                }

                *style = new_style
            }
        }
        Animation::Keyframes(_, ref name, ref state) => {
            debug_assert!(!state.paused);
            let duration = state.duration;
            let started_at = state.started_at;

            let animation = match context.stylist.animations().get(name) {
                None => {
                    warn!("update_style_for_animation: Animation {:?} not found", name);
                    return;
                }
                Some(animation) => animation,
            };

            let maybe_index = style.as_servo()
                                   .get_box().animation_name.0.iter()
                                   .position(|animation_name| name == animation_name);

            let index = match maybe_index {
                Some(index) => index,
                None => {
                    warn!("update_style_for_animation: Animation {:?} not found in style", name);
                    return;
                }
            };

            let total_duration = style.as_servo().get_box().animation_duration.0.get_mod(index).seconds() as f64;
            if total_duration == 0. {
                debug!("update_style_for_animation: zero duration for animation {:?}", name);
                return;
            }

            let mut total_progress = (now - started_at) / total_duration;
            if total_progress < 0. {
                warn!("Negative progress found for animation {:?}", name);
            }
            if total_progress > 1. {
                total_progress = 1.;
            }


            let mut last_keyframe = None;
            let mut target_keyframe = None;

            // TODO: we could maybe binary-search this?
            for i in 1..animation.steps.len() {
                if total_progress as f32 <= animation.steps[i].start_percentage.0 {
                    // We might have found our current keyframe.
                    target_keyframe = Some(&animation.steps[i]);
                    last_keyframe = target_keyframe;
                }
            }

            let target_keyframe = match target_keyframe {
                Some(current) => current,
                None => {
                    warn!("update_style_for_animation: No current keyframe found for animation {:?} at progress {}", name, total_progress);
                    return;
                }
            };

            let last_keyframe = match last_keyframe {
                Some(last_keyframe) => last_keyframe,
                None => {
                    warn!("update_style_for_animation: No last keyframe found for animation {:?} at progress {}", name, total_progress);
                    return;
                }
            };

            let relative_duration = (target_keyframe.start_percentage.0 - last_keyframe.start_percentage.0) as f64 * duration;
            let last_keyframe_ended_at = state.started_at + (total_duration * last_keyframe.start_percentage.0 as f64);
            let relative_progress = (now - last_keyframe_ended_at) / relative_duration;

            // TODO: How could we optimise it? Is it such a big deal?
            let from_style = compute_style_for_animation_step(context,
                                                              last_keyframe,
                                                              &**style);

            // NB: The spec says that the timing function can be overwritten
            // from the keyframe style.
            let mut timing_function = *style.as_servo().get_box().animation_timing_function.0.get_mod(index);
            if !from_style.as_servo().get_box().animation_timing_function.0.is_empty() {
                timing_function = from_style.as_servo().get_box().animation_timing_function.0[0];
            }

            let mut target_style = compute_style_for_animation_step(context,
                                                                    target_keyframe,
                                                                    &from_style);

            let mut new_style = (*style).clone();
            let mut style_changed = false;

            for transition_property in &animation.properties_changed {
                if let Some(property_animation) = PropertyAnimation::from_transition_property(*transition_property,
                                                                                              timing_function,
                                                                                              Time(relative_duration as f32),
                                                                                              &from_style,
                                                                                              &target_style) {
                        debug!("update_style_for_animation: got property animation for prop {:?}", transition_property);
                        property_animation.update(Arc::make_mut(&mut new_style), relative_progress);
                        style_changed = true;
                    }
            }

            if style_changed {
                if let Some(damage) = damage {
                    *damage = *damage | Damage::compute(Some(style), &new_style);
                }

                *style = new_style;
            }
        }
    }
}