Auto merge of #17001 - birtles:accumulative-animation, r=hiro

Support accumulative animation

These are the Servo side changes for [Mozilla bug 1353202](https://bugzilla.mozilla.org/show_bug.cgi?id=1353202).

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components/style/gecko/generated/atom_macro.rs

@@ -2940,6 +2940,8 @@ cfg_if! {
             pub static nsGkAtoms_foreignObject: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms12fractalNoiseE"]
             pub static nsGkAtoms_fractalNoise: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms2frE"]
+            pub static nsGkAtoms_fr: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms2fxE"]
             pub static nsGkAtoms_fx: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms2fyE"]
@@ -7957,6 +7959,8 @@ cfg_if! {
             pub static nsGkAtoms_foreignObject: *mut nsIAtom;
             #[link_name = "?fractalNoise@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_fractalNoise: *mut nsIAtom;
+            #[link_name = "?fr@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_fr: *mut nsIAtom;
             #[link_name = "?fx@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_fx: *mut nsIAtom;
             #[link_name = "?fy@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -12974,6 +12978,8 @@ cfg_if! {
             pub static nsGkAtoms_foreignObject: *mut nsIAtom;
             #[link_name = "\x01?fractalNoise@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_fractalNoise: *mut nsIAtom;
+            #[link_name = "\x01?fr@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_fr: *mut nsIAtom;
             #[link_name = "\x01?fx@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_fx: *mut nsIAtom;
             #[link_name = "\x01?fy@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -17994,6 +18000,8 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_foreignObject as *mut _) } };
 ("fractalNoise") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_fractalNoise as *mut _) } };
+("fr") =>
+  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_fr as *mut _) } };
 ("fx") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_fx as *mut _) } };
 ("fy") =>

components/style/gecko/generated/bindings.rs

@@ -36,6 +36,7 @@ use gecko_bindings::structs::FontFamilyList;
 use gecko_bindings::structs::FontFamilyType;
 use gecko_bindings::structs::FontSizePrefs;
 use gecko_bindings::structs::GeckoFontMetrics;
+use gecko_bindings::structs::IterationCompositeOperation;
 use gecko_bindings::structs::Keyframe;
 use gecko_bindings::structs::ServoBundledURI;
 use gecko_bindings::structs::ServoElementSnapshot;
@@ -2261,8 +2262,12 @@ extern "C" {
                                   property: nsCSSPropertyID,
                                   animation_segment:
                                       RawGeckoAnimationPropertySegmentBorrowed,
+                                  last_segment:
+                                      RawGeckoAnimationPropertySegmentBorrowed,
                                   computed_timing:
-                                      RawGeckoComputedTimingBorrowed);
+                                      RawGeckoComputedTimingBorrowed,
+                                  iteration_composite:
+                                      IterationCompositeOperation);
 }
 extern "C" {
     pub fn Servo_DeclarationBlock_PropertyIsSet(declarations:

components/style/properties/helpers/animated_properties.mako.rs

@@ -680,6 +680,15 @@ pub trait Animatable: Sized {
         self.add_weighted(other, 1.0, 1.0)
     }
 
+    /// [Accumulates][animation-accumulation] this value onto itself (|count| - 1) times then
+    /// accumulates |other| onto the result.
+    /// If |count| is zero, the result will be |other|.
+    ///
+    /// [animation-accumulation]: https://w3c.github.io/web-animations/#animation-accumulation
+    fn accumulate(&self, other: &Self, count: u64) -> Result<Self, ()> {
+        self.add_weighted(other, count as f64, 1.0)
+    }
+
     /// Compute distance between a value and another for a given property.
     fn compute_distance(&self, _other: &Self) -> Result<f64, ()>  { Err(()) }
 
@@ -1364,11 +1373,16 @@ impl Animatable for FontWeight {
 /// https://drafts.csswg.org/css-fonts/#font-stretch-prop
 impl Animatable for FontStretch {
     #[inline]
-    fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64) -> Result<Self, ()> {
+    fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64)
+        -> Result<Self, ()>
+    {
         let from = f64::from(*self);
-        let to   = f64::from(*other);
-        let interpolated_mapped_index = ((from * self_portion + to * other_portion) + 0.5).floor();
-        Ok(interpolated_mapped_index.into())
+        let to = f64::from(*other);
+        // FIXME: When `const fn` is available in release rust, make |normal|, below, const.
+        let normal = f64::from(FontStretch::normal);
+        let result = (from - normal) * self_portion + (to - normal) * other_portion + normal;
+
+        Ok(result.into())
     }
 
     #[inline]
@@ -1401,11 +1415,11 @@ impl From<FontStretch> for f64 {
 impl Into<FontStretch> for f64 {
     fn into(self) -> FontStretch {
         use properties::longhands::font_stretch::computed_value::T::*;
-        debug_assert!(self >= 1.0 && self <= 9.0);
+        let index = (self + 0.5).floor().min(9.0).max(1.0);
         static FONT_STRETCH_ENUM_MAP: [FontStretch; 9] =
             [ ultra_condensed, extra_condensed, condensed, semi_condensed, normal,
               semi_expanded, expanded, extra_expanded, ultra_expanded ];
-        FONT_STRETCH_ENUM_MAP[(self - 1.0) as usize]
+        FONT_STRETCH_ENUM_MAP[(index - 1.0) as usize]
     }
 }
 
@@ -1659,6 +1673,21 @@ fn build_identity_transform_list(list: &[TransformOperation]) -> Vec<TransformOp
     result
 }
 
+/// A wrapper for calling add_weighted that interpolates the distance of the two values from
+/// an initial_value and uses that to produce an interpolated value.
+/// This is used for values such as 'scale' where the initial value is 1 and where if we interpolate
+/// the absolute values, we will produce odd results for accumulation.
+fn add_weighted_with_initial_val<T: Animatable>(a: &T,
+                                                b: &T,
+                                                a_portion: f64,
+                                                b_portion: f64,
+                                                initial_val: &T) -> Result<T, ()> {
+    let a = try!(a.add_weighted(&initial_val, 1.0, -1.0));
+    let b = try!(b.add_weighted(&initial_val, 1.0, -1.0));
+    let result = try!(a.add_weighted(&b, a_portion, b_portion));
+    result.add_weighted(&initial_val, 1.0, 1.0)
+}
+
 /// Add two transform lists.
 /// http://dev.w3.org/csswg/css-transforms/#interpolation-of-transforms
 fn add_weighted_transform_lists(from_list: &[TransformOperation],
@@ -1696,9 +1725,12 @@ fn add_weighted_transform_lists(from_list: &[TransformOperation],
                 }
                 (&TransformOperation::Scale(fx, fy, fz),
                  &TransformOperation::Scale(tx, ty, tz)) => {
-                    let ix = fx.add_weighted(&tx, self_portion, other_portion).unwrap();
-                    let iy = fy.add_weighted(&ty, self_portion, other_portion).unwrap();
-                    let iz = fz.add_weighted(&tz, self_portion, other_portion).unwrap();
+                    let ix = add_weighted_with_initial_val(&fx, &tx, self_portion,
+                                                           other_portion, &1.0).unwrap();
+                    let iy = add_weighted_with_initial_val(&fy, &ty, self_portion,
+                                                           other_portion, &1.0).unwrap();
+                    let iz = add_weighted_with_initial_val(&fz, &tz, self_portion,
+                                                           other_portion, &1.0).unwrap();
                     result.push(TransformOperation::Scale(ix, iy, iz));
                 }
                 (&TransformOperation::Rotate(fx, fy, fz, fa),
@@ -1808,10 +1840,12 @@ pub struct MatrixDecomposed2D {
 impl Animatable for InnerMatrix2D {
     fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64) -> Result<Self, ()> {
         Ok(InnerMatrix2D {
-            m11: try!(self.m11.add_weighted(&other.m11, self_portion, other_portion)),
+            m11: try!(add_weighted_with_initial_val(&self.m11, &other.m11,
+                                                    self_portion, other_portion, &1.0)),
             m12: try!(self.m12.add_weighted(&other.m12, self_portion, other_portion)),
             m21: try!(self.m21.add_weighted(&other.m21, self_portion, other_portion)),
-            m22: try!(self.m22.add_weighted(&other.m22, self_portion, other_portion)),
+            m22: try!(add_weighted_with_initial_val(&self.m22, &other.m22,
+                                                    self_portion, other_portion, &1.0)),
         })
     }
 }
@@ -1828,8 +1862,8 @@ impl Animatable for Translate2D {
 impl Animatable for Scale2D {
     fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64) -> Result<Self, ()> {
         Ok(Scale2D(
-            try!(self.0.add_weighted(&other.0, self_portion, other_portion)),
-            try!(self.1.add_weighted(&other.1, self_portion, other_portion))
+            try!(add_weighted_with_initial_val(&self.0, &other.0, self_portion, other_portion, &1.0)),
+            try!(add_weighted_with_initial_val(&self.1, &other.1, self_portion, other_portion, &1.0))
         ))
     }
 }
@@ -2229,9 +2263,9 @@ impl Animatable for Translate3D {
 impl Animatable for Scale3D {
     fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64) -> Result<Self, ()> {
         Ok(Scale3D(
-            try!(self.0.add_weighted(&other.0, self_portion, other_portion)),
-            try!(self.1.add_weighted(&other.1, self_portion, other_portion)),
-            try!(self.2.add_weighted(&other.2, self_portion, other_portion))
+            try!(add_weighted_with_initial_val(&self.0, &other.0, self_portion, other_portion, &1.0)),
+            try!(add_weighted_with_initial_val(&self.1, &other.1, self_portion, other_portion, &1.0)),
+            try!(add_weighted_with_initial_val(&self.2, &other.2, self_portion, other_portion, &1.0))
         ))
     }
 }
@@ -2252,7 +2286,7 @@ impl Animatable for Perspective {
             try!(self.0.add_weighted(&other.0, self_portion, other_portion)),
             try!(self.1.add_weighted(&other.1, self_portion, other_portion)),
             try!(self.2.add_weighted(&other.2, self_portion, other_portion)),
-            try!(self.3.add_weighted(&other.3, self_portion, other_portion))
+            try!(add_weighted_with_initial_val(&self.3, &other.3, self_portion, other_portion, &1.0))
         ))
     }
 }
@@ -2261,8 +2295,9 @@ impl Animatable for MatrixDecomposed3D {
     /// https://drafts.csswg.org/css-transforms/#interpolation-of-decomposed-3d-matrix-values
     fn add_weighted(&self, other: &Self, self_portion: f64, other_portion: f64)
         -> Result<Self, ()> {
-        assert!(self_portion + other_portion == 1.0f64,
-                "add_weighted should only be used for interpolating transforms");
+        assert!(self_portion + other_portion == 1.0f64 ||
+                other_portion == 1.0f64,
+                "add_weighted should only be used for interpolating or accumulating transforms");
 
         let mut sum = *self;
 
@@ -2275,30 +2310,63 @@ impl Animatable for MatrixDecomposed3D {
                                                              self_portion, other_portion));
 
         // Add quaternions using spherical linear interpolation (Slerp).
-        let mut product = self.quaternion.0 * other.quaternion.0 +
-                          self.quaternion.1 * other.quaternion.1 +
-                          self.quaternion.2 * other.quaternion.2 +
-                          self.quaternion.3 * other.quaternion.3;
+        //
+        // We take a specialized code path for accumulation (where other_portion is 1)
+        if other_portion == 1.0 {
+            if self_portion == 0.0 {
+                return Ok(*other)
+            }
 
-        // Clamp product to -1.0 <= product <= 1.0
-        product = product.min(1.0);
-        product = product.max(-1.0);
+            let clamped_w = self.quaternion.3.min(1.0).max(-1.0);
 
-        if product == 1.0 {
-            return Ok(sum);
+            // Determine the scale factor.
+            let mut theta = clamped_w.acos();
+            let mut scale = if theta == 0.0 { 0.0 } else { 1.0 / theta.sin() };
+            theta *= self_portion as f32;
+            scale *= theta.sin();
+
+            // Scale the self matrix by self_portion.
+            let mut scaled_self = *self;
+            % for i in range(3):
+                scaled_self.quaternion.${i} *= scale;
+            % endfor
+            scaled_self.quaternion.3 = theta.cos();
+
+            // Multiply scaled-self by other.
+            let a = &scaled_self.quaternion;
+            let b = &other.quaternion;
+            sum.quaternion = Quaternion(
+                a.3 * b.0 + a.0 * b.3 + a.1 * b.2 - a.2 * b.1,
+                a.3 * b.1 - a.0 * b.2 + a.1 * b.3 + a.2 * b.0,
+                a.3 * b.2 + a.0 * b.1 - a.1 * b.0 + a.2 * b.3,
+                a.3 * b.3 - a.0 * b.0 - a.1 * b.1 - a.2 * b.2,
+            );
+        } else {
+            let mut product = self.quaternion.0 * other.quaternion.0 +
+                              self.quaternion.1 * other.quaternion.1 +
+                              self.quaternion.2 * other.quaternion.2 +
+                              self.quaternion.3 * other.quaternion.3;
+
+            // Clamp product to -1.0 <= product <= 1.0
+            product = product.min(1.0);
+            product = product.max(-1.0);
+
+            if product == 1.0 {
+                return Ok(sum);
+            }
+
+            let theta = product.acos();
+            let w = (other_portion as f32 * theta).sin() * 1.0 / (1.0 - product * product).sqrt();
+
+            let mut a = *self;
+            let mut b = *other;
+            % for i in range(4):
+                a.quaternion.${i} *= (other_portion as f32 * theta).cos() - product * w;
+                b.quaternion.${i} *= w;
+                sum.quaternion.${i} = a.quaternion.${i} + b.quaternion.${i};
+            % endfor
         }
 
-        let theta = product.acos();
-        let w = (other_portion as f32 * theta).sin() * 1.0 / (1.0 - product * product).sqrt();
-
-        let mut a = *self;
-        let mut b = *other;
-        % for i in range(4):
-            a.quaternion.${i} *= (other_portion as f32 * theta).cos() - product * w;
-            b.quaternion.${i} *= w;
-            sum.quaternion.${i} = a.quaternion.${i} + b.quaternion.${i};
-        % endfor
-
         Ok(sum)
     }
 }

ports/geckolib/glue.rs

@@ -68,6 +68,7 @@ use style::gecko_bindings::structs::{RawServoStyleRule, ServoStyleSheet};
 use style::gecko_bindings::structs::{SheetParsingMode, nsIAtom, nsCSSPropertyID};
 use style::gecko_bindings::structs::{nsCSSFontFaceRule, nsCSSCounterStyleRule};
 use style::gecko_bindings::structs::{nsRestyleHint, nsChangeHint};
+use style::gecko_bindings::structs::IterationCompositeOperation;
 use style::gecko_bindings::structs::Loader;
 use style::gecko_bindings::structs::RawGeckoPresContextOwned;
 use style::gecko_bindings::structs::ServoElementSnapshotTable;
@@ -332,7 +333,9 @@ pub extern "C" fn Servo_AnimationCompose(raw_value_map: RawServoAnimationValueMa
                                          base_values: *mut ::std::os::raw::c_void,
                                          css_property: nsCSSPropertyID,
                                          segment: RawGeckoAnimationPropertySegmentBorrowed,
-                                         computed_timing: RawGeckoComputedTimingBorrowed)
+                                         last_segment: RawGeckoAnimationPropertySegmentBorrowed,
+                                         computed_timing: RawGeckoComputedTimingBorrowed,
+                                         iteration_composite: IterationCompositeOperation)
 {
     use style::gecko_bindings::bindings::Gecko_AnimationGetBaseStyle;
     use style::gecko_bindings::bindings::Gecko_GetPositionInSegment;
@@ -342,10 +345,16 @@ pub extern "C" fn Servo_AnimationCompose(raw_value_map: RawServoAnimationValueMa
     let property: TransitionProperty = css_property.into();
     let value_map = AnimationValueMap::from_ffi_mut(raw_value_map);
 
+    // We will need an underlying value if either of the endpoints is null...
     let need_underlying_value = segment.mFromValue.mServo.mRawPtr.is_null() ||
                                 segment.mToValue.mServo.mRawPtr.is_null() ||
+                                // ... or if they have a non-replace composite mode ...
                                 segment.mFromComposite != CompositeOperation::Replace ||
-                                segment.mToComposite != CompositeOperation::Replace;
+                                segment.mToComposite != CompositeOperation::Replace ||
+                                // ... or if we accumulate onto the last value and it is null.
+                                (iteration_composite == IterationCompositeOperation::Accumulate &&
+                                 computed_timing.mCurrentIteration > 0 &&
+                                 last_segment.mToValue.mServo.mRawPtr.is_null());
 
     // If either of the segment endpoints are null, get the underlying value to
     // use from the current value in the values map (set by a lower-priority
@@ -366,39 +375,95 @@ pub extern "C" fn Servo_AnimationCompose(raw_value_map: RawServoAnimationValueMa
         return;
     }
 
-    // Temporaries used in the following if-block whose lifetimes we need to prlong.
+    // Extract keyframe values.
     let raw_from_value;
-    let from_composite_result;
-    let from_value = if !segment.mFromValue.mServo.mRawPtr.is_null() {
+    let keyframe_from_value = if !segment.mFromValue.mServo.mRawPtr.is_null() {
         raw_from_value = unsafe { &*segment.mFromValue.mServo.mRawPtr };
-        match segment.mFromComposite {
-            CompositeOperation::Add => {
-                let value_to_composite = AnimationValue::as_arc(&raw_from_value).as_ref();
-                from_composite_result = underlying_value.as_ref().unwrap().add(value_to_composite);
-                from_composite_result.as_ref().unwrap_or(value_to_composite)
-            }
-            _ => { AnimationValue::as_arc(&raw_from_value) }
-        }
+        Some(AnimationValue::as_arc(&raw_from_value))
     } else {
-        underlying_value.as_ref().unwrap()
+        None
     };
 
     let raw_to_value;
-    let to_composite_result;
-    let to_value = if !segment.mToValue.mServo.mRawPtr.is_null() {
+    let keyframe_to_value = if !segment.mToValue.mServo.mRawPtr.is_null() {
         raw_to_value = unsafe { &*segment.mToValue.mServo.mRawPtr };
-        match segment.mToComposite {
-            CompositeOperation::Add => {
-                let value_to_composite = AnimationValue::as_arc(&raw_to_value).as_ref();
-                to_composite_result = underlying_value.as_ref().unwrap().add(value_to_composite);
-                to_composite_result.as_ref().unwrap_or(value_to_composite)
-            }
-            _ => { AnimationValue::as_arc(&raw_to_value) }
-        }
+        Some(AnimationValue::as_arc(&raw_to_value))
     } else {
-        underlying_value.as_ref().unwrap()
+        None
     };
 
+    // Composite with underlying value.
+    // A return value of None means, "Just use keyframe_value as-is."
+    let composite_endpoint = |keyframe_value: Option<&Arc<AnimationValue>>,
+                              composite_op: CompositeOperation| -> Option<AnimationValue> {
+        match keyframe_value {
+            Some(keyframe_value) => {
+                match composite_op {
+                    CompositeOperation::Add => {
+                        debug_assert!(need_underlying_value,
+                                      "Should have detected we need an underlying value");
+                        underlying_value.as_ref().unwrap().add(keyframe_value).ok()
+                    },
+                    CompositeOperation::Accumulate => {
+                        debug_assert!(need_underlying_value,
+                                      "Should have detected we need an underlying value");
+                        underlying_value.as_ref().unwrap().accumulate(keyframe_value, 1).ok()
+                    },
+                    _ => None,
+                }
+            },
+            None => {
+                debug_assert!(need_underlying_value,
+                              "Should have detected we need an underlying value");
+                underlying_value.clone()
+            },
+        }
+    };
+    let mut composited_from_value = composite_endpoint(keyframe_from_value, segment.mFromComposite);
+    let mut composited_to_value = composite_endpoint(keyframe_to_value, segment.mToComposite);
+
+    debug_assert!(keyframe_from_value.is_some() || composited_from_value.is_some(),
+                  "Should have a suitable from value to use");
+    debug_assert!(keyframe_to_value.is_some() || composited_to_value.is_some(),
+                  "Should have a suitable to value to use");
+
+    // Apply iteration composite behavior.
+    if iteration_composite == IterationCompositeOperation::Accumulate &&
+       computed_timing.mCurrentIteration > 0 {
+        let raw_last_value;
+        let last_value = if !last_segment.mToValue.mServo.mRawPtr.is_null() {
+            raw_last_value = unsafe { &*last_segment.mToValue.mServo.mRawPtr };
+            AnimationValue::as_arc(&raw_last_value).as_ref()
+        } else {
+            debug_assert!(need_underlying_value,
+                          "Should have detected we need an underlying value");
+            underlying_value.as_ref().unwrap()
+        };
+
+        // As with composite_endpoint, a return value of None means, "Use keyframe_value as-is."
+        let apply_iteration_composite = |keyframe_value: Option<&Arc<AnimationValue>>,
+                                         composited_value: Option<AnimationValue>|
+                                        -> Option<AnimationValue> {
+            let count = computed_timing.mCurrentIteration;
+            match composited_value {
+                Some(endpoint) => last_value.accumulate(&endpoint, count)
+                                            .ok()
+                                            .or(Some(endpoint)),
+                None => last_value.accumulate(keyframe_value.unwrap(), count)
+                                  .ok(),
+            }
+        };
+
+        composited_from_value = apply_iteration_composite(keyframe_from_value,
+                                                          composited_from_value);
+        composited_to_value = apply_iteration_composite(keyframe_to_value,
+                                                        composited_to_value);
+    }
+
+    // Use the composited value if there is one, otherwise, use the original keyframe value.
+    let from_value = composited_from_value.as_ref().unwrap_or_else(|| keyframe_from_value.unwrap());
+    let to_value   = composited_to_value.as_ref().unwrap_or_else(|| keyframe_to_value.unwrap());
+
     let progress = unsafe { Gecko_GetProgressFromComputedTiming(computed_timing) };
     if segment.mToKey == segment.mFromKey {
         if progress < 0. {