style/values/animated/
grid.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! Animation implementation for various grid-related types.
6
7// Note: we can implement Animate on their generic types directly, but in this case we need to
8// make sure two trait bounds, L: Clone and I: PartialEq, are satisfied on almost all the
9// grid-related types and their other trait implementations because Animate needs them. So in
10// order to avoid adding these two trait bounds (or maybe more..) everywhere, we implement
11// Animate for the computed types, instead of the generic types.
12
13use super::{Animate, Procedure, ToAnimatedZero};
14use crate::values::computed::Integer;
15use crate::values::computed::LengthPercentage;
16use crate::values::computed::{GridTemplateComponent, TrackList, TrackSize};
17use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
18use crate::values::generics::grid as generics;
19
20fn discrete<T: Clone>(from: &T, to: &T, procedure: Procedure) -> Result<T, ()> {
21    if let Procedure::Interpolate { progress } = procedure {
22        Ok(if progress < 0.5 {
23            from.clone()
24        } else {
25            to.clone()
26        })
27    } else {
28        // The discrete animation is not additive, so per spec [1] we should use the |from|, which
29        // is the underlying value. However this mismatches our animation mechanism (see
30        // composite_endpoint() in servo/ports/geckolib/glues.rs), which uses the effect value
31        // (i.e. |to| value here) [2]. So in order to match the behavior of other properties and
32        // other browsers, we use |to| value for addition and accumulation, i.e. Vresult = Vb.
33        //
34        // [1] https://drafts.csswg.org/css-values-4/#not-additive
35        // [2] https://github.com/w3c/csswg-drafts/issues/9070
36        Ok(to.clone())
37    }
38}
39
40fn animate_with_discrete_fallback<T: Animate + Clone>(
41    from: &T,
42    to: &T,
43    procedure: Procedure,
44) -> Result<T, ()> {
45    from.animate(to, procedure)
46        .or_else(|_| discrete(from, to, procedure))
47}
48
49impl Animate for TrackSize {
50    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
51        match (self, other) {
52            (generics::TrackSize::Breadth(from), generics::TrackSize::Breadth(to)) => {
53                animate_with_discrete_fallback(from, to, procedure)
54                    .map(generics::TrackSize::Breadth)
55            },
56            (
57                generics::TrackSize::Minmax(from_min, from_max),
58                generics::TrackSize::Minmax(to_min, to_max),
59            ) => Ok(generics::TrackSize::Minmax(
60                animate_with_discrete_fallback(from_min, to_min, procedure)?,
61                animate_with_discrete_fallback(from_max, to_max, procedure)?,
62            )),
63            (generics::TrackSize::FitContent(from), generics::TrackSize::FitContent(to)) => {
64                animate_with_discrete_fallback(from, to, procedure)
65                    .map(generics::TrackSize::FitContent)
66            },
67            (_, _) => discrete(self, other, procedure),
68        }
69    }
70}
71
72impl Animate for generics::TrackRepeat<LengthPercentage, Integer> {
73    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
74        // If the keyword, auto-fit/fill, is the same it can result in different
75        // number of tracks. For both auto-fit/fill, the number of columns isn't
76        // known until you do layout since it depends on the container size, item
77        // placement and other factors, so we cannot do the correct interpolation
78        // by computed values. Therefore, return Err(()) if it's keywords. If it
79        // is Number, we support animation only if the count is the same and the
80        // length of track_sizes is the same.
81        // https://github.com/w3c/csswg-drafts/issues/3503
82        match (&self.count, &other.count) {
83            (&generics::RepeatCount::Number(from), &generics::RepeatCount::Number(to))
84                if from == to => {},
85            (_, _) => return Err(()),
86        }
87
88        let count = self.count;
89        let track_sizes = super::lists::by_computed_value::animate(
90            &self.track_sizes,
91            &other.track_sizes,
92            procedure,
93        )?;
94
95        // The length of |line_names| is always 0 or N+1, where N is the length
96        // of |track_sizes|. Besides, <line-names> is always discrete.
97        let line_names = discrete(&self.line_names, &other.line_names, procedure)?;
98
99        Ok(generics::TrackRepeat {
100            count,
101            line_names,
102            track_sizes,
103        })
104    }
105}
106
107impl Animate for TrackList {
108    // Based on https://github.com/w3c/csswg-drafts/issues/3201:
109    // 1. Check interpolation type per track, so we need to handle discrete animations
110    //    in TrackSize, so any Err(()) returned from TrackSize doesn't make all TrackSize
111    //    fallback to discrete animation.
112    // 2. line-names is always discrete.
113    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
114        if self.values.len() != other.values.len() {
115            return Err(());
116        }
117
118        if self.is_explicit() != other.is_explicit() {
119            return Err(());
120        }
121
122        // For now, repeat(auto-fill/auto-fit, ...) is not animatable.
123        // TrackRepeat will return Err(()) if we use keywords. Therefore, we can
124        // early return here to avoid traversing |values| in <auto-track-list>.
125        // This may be updated in the future.
126        // https://github.com/w3c/csswg-drafts/issues/3503
127        if self.has_auto_repeat() || other.has_auto_repeat() {
128            return Err(());
129        }
130
131        let values =
132            super::lists::by_computed_value::animate(&self.values, &other.values, procedure)?;
133
134        // The length of |line_names| is always 0 or N+1, where N is the length
135        // of |track_sizes|. Besides, <line-names> is always discrete.
136        let line_names = discrete(&self.line_names, &other.line_names, procedure)?;
137
138        Ok(TrackList {
139            values,
140            line_names,
141            auto_repeat_index: self.auto_repeat_index,
142        })
143    }
144}
145
146impl ComputeSquaredDistance for GridTemplateComponent {
147    #[inline]
148    fn compute_squared_distance(&self, _other: &Self) -> Result<SquaredDistance, ()> {
149        // TODO: Bug 1518585, we should implement ComputeSquaredDistance.
150        Err(())
151    }
152}
153
154impl ToAnimatedZero for GridTemplateComponent {
155    #[inline]
156    fn to_animated_zero(&self) -> Result<Self, ()> {
157        // It's not clear to get a zero grid track list based on the current definition
158        // of spec, so we return Err(()) directly.
159        Err(())
160    }
161}
style/values/animated/grid.rs

style/values/animated/
grid.rs
