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

/* 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/. */

//! A cache from rule node to computed values, in order to cache reset
//! properties.

use fnv::FnvHashMap;
use logical_geometry::WritingMode;
use properties::{ComputedValues, StyleBuilder};
use rule_tree::StrongRuleNode;
use selector_parser::PseudoElement;
use servo_arc::Arc;
use smallvec::SmallVec;
use values::computed::NonNegativeLength;

/// The conditions for caching and matching a style in the rule cache.
#[derive(Clone, Debug, Default)]
pub struct RuleCacheConditions {
    uncacheable: bool,
    font_size: Option<NonNegativeLength>,
    writing_mode: Option<WritingMode>,
}

impl RuleCacheConditions {
    /// Sets the style as depending in the font-size value.
    pub fn set_font_size_dependency(&mut self, font_size: NonNegativeLength) {
        debug_assert!(self.font_size.map_or(true, |f| f == font_size));
        self.font_size = Some(font_size);
    }

    /// Sets the style as uncacheable.
    pub fn set_uncacheable(&mut self) {
        self.uncacheable = true;
    }

    /// Sets the style as depending in the writing-mode value `writing_mode`.
    pub fn set_writing_mode_dependency(&mut self, writing_mode: WritingMode) {
        debug_assert!(self.writing_mode.map_or(true, |wm| wm == writing_mode));
        self.writing_mode = Some(writing_mode);
    }

    /// Returns whether the current style's reset properties are cacheable.
    fn cacheable(&self) -> bool {
        !self.uncacheable
    }

    /// Returns whether `style` matches the conditions.
    fn matches(&self, style: &StyleBuilder) -> bool {
        if self.uncacheable {
            return false;
        }

        if let Some(fs) = self.font_size {
            if style.get_font().clone_font_size().size != fs {
                return false;
            }
        }

        if let Some(wm) = self.writing_mode {
            if style.writing_mode != wm {
                return false;
            }
        }

        true
    }
}

/// A TLS cache from rules matched to computed values.
pub struct RuleCache {
    // FIXME(emilio): Consider using LRUCache or something like that?
    map: FnvHashMap<StrongRuleNode, SmallVec<[(RuleCacheConditions, Arc<ComputedValues>); 1]>>,
}

impl RuleCache {
    /// Creates an empty `RuleCache`.
    pub fn new() -> Self {
        Self {
            map: FnvHashMap::default(),
        }
    }

    /// Finds a node in the properties matched cache.
    ///
    /// This needs to receive a `StyleBuilder` with the `early` properties
    /// already applied.
    pub fn find(
        &self,
        builder_with_early_props: &StyleBuilder,
    ) -> Option<&ComputedValues> {
        if builder_with_early_props.is_style_if_visited() {
            // FIXME(emilio): We can probably do better, does it matter much?
            return None;
        }

        // A pseudo-element with property restrictions can result in different
        // computed values if it's also used for a non-pseudo.
        if builder_with_early_props.pseudo
           .and_then(|p| p.property_restriction())
           .is_some() {
            return None;
        }

        let rules = builder_with_early_props.rules.as_ref()?;
        let cached_values = self.map.get(rules)?;

        for &(ref conditions, ref values) in cached_values.iter() {
            if conditions.matches(builder_with_early_props) {
                debug!("Using cached reset style with conditions {:?}", conditions);
                return Some(&**values)
            }
        }
        None
    }

    /// Inserts a node into the rules cache if possible.
    ///
    /// Returns whether the style was inserted into the cache.
    pub fn insert_if_possible(
        &mut self,
        style: &Arc<ComputedValues>,
        pseudo: Option<&PseudoElement>,
        conditions: &RuleCacheConditions,
    ) -> bool {
        if !conditions.cacheable() {
            return false;
        }

        if style.is_style_if_visited() {
            // FIXME(emilio): We can probably do better, does it matter much?
            return false;
        }

        // A pseudo-element with property restrictions can result in different
        // computed values if it's also used for a non-pseudo.
        if pseudo.and_then(|p| p.property_restriction()).is_some() {
            return false;
        }

        let rules = match style.rules {
            Some(ref r) => r.clone(),
            None => return false,
        };

        debug!("Inserting cached reset style with conditions {:?}", conditions);
        self.map
            .entry(rules)
            .or_insert_with(SmallVec::new)
            .push((conditions.clone(), style.clone()));

        true
    }

}