summaryrefslogtreecommitdiffstats
path: root/servo/components/style/stylesheets/origin.rs
blob: 6f8f97b66102da091fce0da53b991ed53d09addb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
/* 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 https://mozilla.org/MPL/2.0/. */

//! [CSS cascade origins](https://drafts.csswg.org/css-cascade/#cascading-origins).

use std::marker::PhantomData;
use std::ops::BitOrAssign;

/// Each style rule has an origin, which determines where it enters the cascade.
///
/// <https://drafts.csswg.org/css-cascade/#cascading-origins>
#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToShmem, PartialOrd, Ord)]
#[repr(u8)]
pub enum Origin {
    /// <https://drafts.csswg.org/css-cascade/#cascade-origin-user-agent>
    UserAgent = 0x1,

    /// <https://drafts.csswg.org/css-cascade/#cascade-origin-user>
    User = 0x2,

    /// <https://drafts.csswg.org/css-cascade/#cascade-origin-author>
    Author = 0x4,
}

impl Origin {
    /// Returns an origin that goes in order for `index`.
    ///
    /// This is used for iterating across origins.
    fn from_index(index: i8) -> Option<Self> {
        Some(match index {
            0 => Origin::Author,
            1 => Origin::User,
            2 => Origin::UserAgent,
            _ => return None,
        })
    }

    fn to_index(self) -> i8 {
        match self {
            Origin::Author => 0,
            Origin::User => 1,
            Origin::UserAgent => 2,
        }
    }

    /// Returns an iterator from this origin, towards all the less specific
    /// origins. So for `UserAgent`, it'd iterate through all origins.
    #[inline]
    pub fn following_including(self) -> OriginSetIterator {
        OriginSetIterator {
            set: OriginSet::ORIGIN_USER | OriginSet::ORIGIN_AUTHOR | OriginSet::ORIGIN_USER_AGENT,
            cur: self.to_index(),
            rev: true,
        }
    }
}

bitflags! {
    /// A set of origins. This is equivalent to Gecko's OriginFlags.
    #[derive(Clone, Copy, PartialEq, MallocSizeOf)]
    pub struct OriginSet: u8 {
        /// <https://drafts.csswg.org/css-cascade/#cascade-origin-user-agent>
        const ORIGIN_USER_AGENT = Origin::UserAgent as u8;
        /// <https://drafts.csswg.org/css-cascade/#cascade-origin-user>
        const ORIGIN_USER = Origin::User as u8;
        /// <https://drafts.csswg.org/css-cascade/#cascade-origin-author>
        const ORIGIN_AUTHOR = Origin::Author as u8;
    }
}

impl OriginSet {
    /// Returns an iterator over the origins present in this `OriginSet`.
    ///
    /// See the `OriginSet` documentation for information about the order
    /// origins are iterated.
    pub fn iter(&self) -> OriginSetIterator {
        OriginSetIterator {
            set: *self,
            cur: 0,
            rev: false,
        }
    }
}

impl From<Origin> for OriginSet {
    fn from(origin: Origin) -> Self {
        Self::from_bits_retain(origin as u8)
    }
}

impl BitOrAssign<Origin> for OriginSet {
    fn bitor_assign(&mut self, origin: Origin) {
        *self |= OriginSet::from(origin);
    }
}

/// Iterates over the origins present in an `OriginSet`, in order from
/// highest priority (author) to lower (user agent).
#[derive(Clone)]
pub struct OriginSetIterator {
    set: OriginSet,
    cur: i8,
    rev: bool,
}

impl Iterator for OriginSetIterator {
    type Item = Origin;

    fn next(&mut self) -> Option<Origin> {
        loop {
            let origin = Origin::from_index(self.cur)?;

            if self.rev {
                self.cur -= 1;
            } else {
                self.cur += 1;
            }

            if self.set.contains(origin.into()) {
                return Some(origin);
            }
        }
    }
}

/// An object that stores a `T` for each origin of the CSS cascade.
#[derive(Debug, Default, MallocSizeOf)]
pub struct PerOrigin<T> {
    /// Data for `Origin::UserAgent`.
    pub user_agent: T,

    /// Data for `Origin::User`.
    pub user: T,

    /// Data for `Origin::Author`.
    pub author: T,
}

impl<T> PerOrigin<T> {
    /// Returns a reference to the per-origin data for the specified origin.
    #[inline]
    pub fn borrow_for_origin(&self, origin: &Origin) -> &T {
        match *origin {
            Origin::UserAgent => &self.user_agent,
            Origin::User => &self.user,
            Origin::Author => &self.author,
        }
    }

    /// Returns a mutable reference to the per-origin data for the specified
    /// origin.
    #[inline]
    pub fn borrow_mut_for_origin(&mut self, origin: &Origin) -> &mut T {
        match *origin {
            Origin::UserAgent => &mut self.user_agent,
            Origin::User => &mut self.user,
            Origin::Author => &mut self.author,
        }
    }

    /// Iterates over references to per-origin extra style data, from highest
    /// level (author) to lowest (user agent).
    pub fn iter_origins(&self) -> PerOriginIter<T> {
        PerOriginIter {
            data: &self,
            cur: 0,
            rev: false,
        }
    }

    /// Iterates over references to per-origin extra style data, from lowest
    /// level (user agent) to highest (author).
    pub fn iter_origins_rev(&self) -> PerOriginIter<T> {
        PerOriginIter {
            data: &self,
            cur: 2,
            rev: true,
        }
    }

    /// Iterates over mutable references to per-origin extra style data, from
    /// highest level (author) to lowest (user agent).
    pub fn iter_mut_origins(&mut self) -> PerOriginIterMut<T> {
        PerOriginIterMut {
            data: self,
            cur: 0,
            _marker: PhantomData,
        }
    }
}

/// Iterator over `PerOrigin<T>`, from highest level (author) to lowest
/// (user agent).
///
/// We rely on this specific order for correctly looking up @font-face,
/// @counter-style and @keyframes rules.
pub struct PerOriginIter<'a, T: 'a> {
    data: &'a PerOrigin<T>,
    cur: i8,
    rev: bool,
}

impl<'a, T> Iterator for PerOriginIter<'a, T>
where
    T: 'a,
{
    type Item = (&'a T, Origin);

    fn next(&mut self) -> Option<Self::Item> {
        let origin = Origin::from_index(self.cur)?;

        self.cur += if self.rev { -1 } else { 1 };

        Some((self.data.borrow_for_origin(&origin), origin))
    }
}

/// Like `PerOriginIter<T>`, but iterates over mutable references to the
/// per-origin data.
///
/// We must use unsafe code here since it's not possible for the borrow
/// checker to know that we are safely returning a different reference
/// each time from `next()`.
pub struct PerOriginIterMut<'a, T: 'a> {
    data: *mut PerOrigin<T>,
    cur: i8,
    _marker: PhantomData<&'a mut PerOrigin<T>>,
}

impl<'a, T> Iterator for PerOriginIterMut<'a, T>
where
    T: 'a,
{
    type Item = (&'a mut T, Origin);

    fn next(&mut self) -> Option<Self::Item> {
        let origin = Origin::from_index(self.cur)?;

        self.cur += 1;

        Some((
            unsafe { (*self.data).borrow_mut_for_origin(&origin) },
            origin,
        ))
    }
}