stylo: Make font base size computation threadsafe

components/layout/animation.rs

@@ -13,6 +13,7 @@ use script_traits::{AnimationState, ConstellationControlMsg, LayoutMsg as Conste
 use std::collections::HashMap;
 use std::sync::mpsc::Receiver;
 use style::animation::{Animation, update_style_for_animation};
+use style::font_metrics::ServoMetricsProvider;
 use style::selector_parser::RestyleDamage;
 use style::timer::Timer;
 
@@ -143,7 +144,8 @@ pub fn recalc_style_for_animations(context: &LayoutContext,
                 let old_style = fragment.style.clone();
                 update_style_for_animation(&context.style_context,
                                            animation,
-                                           &mut fragment.style);
+                                           &mut fragment.style,
+                                           &ServoMetricsProvider);
                 damage |= RestyleDamage::compute(&old_style, &fragment.style);
             }
         }

components/layout/traversal.rs

@@ -53,6 +53,7 @@ impl<'a> RecalcStyleAndConstructFlows<'a> {
 impl<'a, E> DomTraversal<E> for RecalcStyleAndConstructFlows<'a>
     where E: TElement,
           E::ConcreteNode: LayoutNode,
+          E::FontMetricsProvider: Send,
 {
     type ThreadLocalContext = ScopedThreadLocalLayoutContext<E>;
 

components/script/layout_wrapper.rs

@@ -67,6 +67,7 @@ use style::data::ElementData;
 use style::dom::{DescendantsBit, DirtyDescendants, LayoutIterator, NodeInfo, OpaqueNode};
 use style::dom::{PresentationalHintsSynthetizer, TElement, TNode, UnsafeNode};
 use style::element_state::*;
+use style::font_metrics::ServoMetricsProvider;
 use style::properties::{ComputedValues, PropertyDeclarationBlock};
 use style::selector_parser::{NonTSPseudoClass, PseudoElement, SelectorImpl};
 use style::shared_lock::{SharedRwLock as StyleSharedRwLock, Locked as StyleLocked};
@@ -373,6 +374,8 @@ impl<'le> PresentationalHintsSynthetizer for ServoLayoutElement<'le> {
 impl<'le> TElement for ServoLayoutElement<'le> {
     type ConcreteNode = ServoLayoutNode<'le>;
 
+    type FontMetricsProvider = ServoMetricsProvider;
+
     fn as_node(&self) -> ServoLayoutNode<'le> {
         ServoLayoutNode::from_layout_js(self.element.upcast())
     }

components/script_layout_interface/wrapper_traits.rs

@@ -21,6 +21,7 @@ use style::context::SharedStyleContext;
 use style::data::ElementData;
 use style::dom::{LayoutIterator, NodeInfo, PresentationalHintsSynthetizer, TNode};
 use style::dom::OpaqueNode;
+use style::font_metrics::ServoMetricsProvider;
 use style::properties::{CascadeFlags, ServoComputedValues};
 use style::selector_parser::{PseudoElement, PseudoElementCascadeType, SelectorImpl};
 
@@ -411,7 +412,8 @@ pub trait ThreadSafeLayoutElement: Clone + Copy + Sized + Debug +
                                     &context.guards,
                                     &style_pseudo,
                                     Some(data.styles().primary.values()),
-                                    CascadeFlags::empty());
+                                    CascadeFlags::empty(),
+                                    &ServoMetricsProvider);
                             data.styles_mut().cached_pseudos
                                 .insert(style_pseudo.clone(), new_style);
                         }
@@ -426,7 +428,8 @@ pub trait ThreadSafeLayoutElement: Clone + Copy + Sized + Debug +
                                            &context.guards,
                                            unsafe { &self.unsafe_get() },
                                            &style_pseudo,
-                                           data.styles().primary.values());
+                                           data.styles().primary.values(),
+                                           &ServoMetricsProvider);
                             data.styles_mut().cached_pseudos
                                 .insert(style_pseudo.clone(), new_style.unwrap());
                         }

components/style/animation.rs

@@ -10,6 +10,7 @@ use bezier::Bezier;
 use context::SharedStyleContext;
 use dom::{OpaqueNode, UnsafeNode};
 use euclid::point::Point2D;
+use font_metrics::FontMetricsProvider;
 use keyframes::{KeyframesStep, KeyframesStepValue};
 use properties::{self, CascadeFlags, ComputedValues, Importance};
 use properties::animated_properties::{AnimatedProperty, TransitionProperty};
@@ -410,7 +411,8 @@ pub fn start_transitions_if_applicable(new_animations_sender: &Sender<Animation>
 fn compute_style_for_animation_step(context: &SharedStyleContext,
                                     step: &KeyframesStep,
                                     previous_style: &ComputedValues,
-                                    style_from_cascade: &ComputedValues)
+                                    style_from_cascade: &ComputedValues,
+                                    font_metrics_provider: &FontMetricsProvider)
                                     -> ComputedValues {
     match step.value {
         KeyframesStepValue::ComputedValues => style_from_cascade.clone(),
@@ -433,7 +435,7 @@ fn compute_style_for_animation_step(context: &SharedStyleContext,
                                                previous_style,
                                                /* cascade_info = */ None,
                                                &*context.error_reporter,
-                                               /* Metrics provider */ None,
+                                               font_metrics_provider,
                                                CascadeFlags::empty());
             computed
         }
@@ -534,7 +536,8 @@ pub fn update_style_for_animation_frame(mut new_style: &mut Arc<ComputedValues>,
 /// If `damage` is provided, inserts the appropriate restyle damage.
 pub fn update_style_for_animation(context: &SharedStyleContext,
                                   animation: &Animation,
-                                  style: &mut Arc<ComputedValues>) {
+                                  style: &mut Arc<ComputedValues>,
+                                  font_metrics_provider: &FontMetricsProvider) {
     debug!("update_style_for_animation: entering");
     debug_assert!(!animation.is_expired());
 
@@ -658,7 +661,8 @@ pub fn update_style_for_animation(context: &SharedStyleContext,
             let from_style = compute_style_for_animation_step(context,
                                                               last_keyframe,
                                                               &**style,
-                                                              &state.cascade_style);
+                                                              &state.cascade_style,
+                                                              font_metrics_provider);
 
             // NB: The spec says that the timing function can be overwritten
             // from the keyframe style.
@@ -672,7 +676,8 @@ pub fn update_style_for_animation(context: &SharedStyleContext,
             let target_style = compute_style_for_animation_step(context,
                                                                 target_keyframe,
                                                                 &from_style,
-                                                                &state.cascade_style);
+                                                                &state.cascade_style,
+                                                                font_metrics_provider);
 
             let mut new_style = (*style).clone();
 

components/style/build_gecko.rs

@@ -308,6 +308,7 @@ mod bindings {
             "mozilla::SERVO_PREF_.*",
             "kNameSpaceID_.*",
             "kGenericFont_.*",
+            "kPresContext_.*",
         ];
         let whitelist = [
             "RawGecko.*",
@@ -338,6 +339,7 @@ mod bindings {
             "FontFamilyListRefCnt",
             "FontFamilyName",
             "FontFamilyType",
+            "FontSizePrefs",
             "FragmentOrURL",
             "FrameRequestCallback",
             "GeckoParserExtraData",
@@ -623,6 +625,7 @@ mod bindings {
             "ComputedTimingFunction_BeforeFlag",
             "FontFamilyList",
             "FontFamilyType",
+            "FontSizePrefs",
             "Keyframe",
             "ServoBundledURI",
             "ServoElementSnapshot",

components/style/context.rs

@@ -12,6 +12,7 @@ use data::ElementData;
 use dom::{OpaqueNode, TNode, TElement, SendElement};
 use error_reporting::ParseErrorReporter;
 use euclid::Size2D;
+use font_metrics::FontMetricsProvider;
 #[cfg(feature = "gecko")] use gecko_bindings::structs;
 use matching::StyleSharingCandidateCache;
 use parking_lot::RwLock;
@@ -291,6 +292,9 @@ pub struct ThreadLocalStyleContext<E: TElement> {
     pub statistics: TraversalStatistics,
     /// Information related to the current element, non-None during processing.
     pub current_element_info: Option<CurrentElementInfo>,
+    /// The struct used to compute and cache font metrics from style
+    /// for evaluation of the font-relative em/ch units and font-size
+    pub font_metrics_provider: E::FontMetricsProvider,
 }
 
 impl<E: TElement> ThreadLocalStyleContext<E> {
@@ -303,6 +307,7 @@ impl<E: TElement> ThreadLocalStyleContext<E> {
             tasks: Vec::new(),
             statistics: TraversalStatistics::default(),
             current_element_info: None,
+            font_metrics_provider: E::FontMetricsProvider::create_from(shared),
         }
     }
 

components/style/dom.rs

@@ -12,6 +12,7 @@ use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
 #[cfg(feature = "gecko")] use context::UpdateAnimationsTasks;
 use data::ElementData;
 use element_state::ElementState;
+use font_metrics::FontMetricsProvider;
 use properties::{ComputedValues, PropertyDeclarationBlock};
 use selector_parser::{ElementExt, PreExistingComputedValues, PseudoElement};
 use selectors::matching::ElementSelectorFlags;
@@ -278,6 +279,12 @@ pub trait TElement : PartialEq + Debug + Sized + Copy + Clone + ElementExt + Pre
     /// The concrete node type.
     type ConcreteNode: TNode<ConcreteElement = Self>;
 
+    /// Type of the font metrics provider
+    ///
+    /// XXXManishearth It would be better to make this a type parameter on
+    /// ThreadLocalStyleContext and StyleContext
+    type FontMetricsProvider: FontMetricsProvider;
+
     /// Get this element as a node.
     fn as_node(&self) -> Self::ConcreteNode;
 

components/style/font_metrics.rs

@@ -8,6 +8,7 @@
 
 use Atom;
 use app_units::Au;
+use context::SharedStyleContext;
 use euclid::Size2D;
 use std::fmt;
 
@@ -31,8 +32,44 @@ pub enum FontMetricsQueryResult {
     NotAvailable,
 }
 
+// TODO: Servo's font metrics provider will probably not live in this crate, so this will
+// have to be replaced with something else (perhaps a trait method on TElement)
+// when we get there
+#[derive(Debug)]
+#[cfg(feature = "servo")]
+/// Dummy metrics provider for Servo. Knows nothing about fonts and does not provide
+/// any metrics.
+pub struct ServoMetricsProvider;
+
+#[cfg(feature = "servo")]
+impl FontMetricsProvider for ServoMetricsProvider {
+    fn create_from(_: &SharedStyleContext) -> Self {
+        ServoMetricsProvider
+    }
+
+    fn get_size(&self, _font_name: &Atom, _font_family: u8) -> Au {
+        unreachable!("Dummy provider should never be used to compute font size")
+    }
+}
+
+// Servo's font metrics provider will probably not live in this crate, so this will
+// have to be replaced with something else (perhaps a trait method on TElement)
+// when we get there
+
+#[cfg(feature = "gecko")]
+/// Construct a font metrics provider for the current product
+pub fn get_metrics_provider_for_product() -> ::gecko::wrapper::GeckoFontMetricsProvider {
+    ::gecko::wrapper::GeckoFontMetricsProvider::new()
+}
+
+#[cfg(feature = "servo")]
+/// Construct a font metrics provider for the current product
+pub fn get_metrics_provider_for_product() -> ServoMetricsProvider {
+    ServoMetricsProvider
+}
+
 /// A trait used to represent something capable of providing us font metrics.
-pub trait FontMetricsProvider: Send + Sync + fmt::Debug {
+pub trait FontMetricsProvider: fmt::Debug {
     /// Obtain the metrics for given font family.
     ///
     /// TODO: We could make this take the full list, I guess, and save a few
@@ -41,4 +78,11 @@ pub trait FontMetricsProvider: Send + Sync + fmt::Debug {
     fn query(&self, _font_name: &Atom) -> FontMetricsQueryResult {
         FontMetricsQueryResult::NotAvailable
     }
+
+    /// Get default size of a given language and generic family
+    fn get_size(&self, font_name: &Atom, font_family: u8) -> Au;
+
+    /// Construct from a shared style context
+    fn create_from(context: &SharedStyleContext) -> Self where Self: Sized;
 }
+

components/style/gecko/media_queries.rs

@@ -7,6 +7,7 @@
 use app_units::Au;
 use cssparser::{CssStringWriter, Parser, Token};
 use euclid::Size2D;
+use font_metrics::get_metrics_provider_for_product;
 use gecko_bindings::bindings;
 use gecko_bindings::structs::{nsCSSValue, nsCSSUnit, nsStringBuffer};
 use gecko_bindings::structs::{nsMediaExpression_Range, nsMediaFeature};
@@ -499,6 +500,8 @@ impl Expression {
 
         let default_values = device.default_computed_values();
 
+        let provider = get_metrics_provider_for_product();
+
         // http://dev.w3.org/csswg/mediaqueries3/#units
         // em units are relative to the initial font-size.
         let context = computed::Context {
@@ -509,7 +512,7 @@ impl Expression {
             // This cloning business is kind of dumb.... It's because Context
             // insists on having an actual ComputedValues inside itself.
             style: default_values.clone(),
-            font_metrics_provider: None,
+            font_metrics_provider: &provider,
         };
 
         let required_value = match self.value {

components/style/gecko/wrapper.rs

@@ -14,13 +14,15 @@
 //! style system it's kind of pointless in the Stylo case, and only Servo forces
 //! the separation between the style system implementation and everything else.
 
+use app_units::Au;
 use atomic_refcell::AtomicRefCell;
-use context::UpdateAnimationsTasks;
+use context::{SharedStyleContext, UpdateAnimationsTasks};
 use data::ElementData;
 use dom::{self, AnimationRules, DescendantsBit, LayoutIterator, NodeInfo, TElement, TNode, UnsafeNode};
 use dom::{OpaqueNode, PresentationalHintsSynthetizer};
 use element_state::ElementState;
 use error_reporting::StdoutErrorReporter;
+use font_metrics::FontMetricsProvider;
 use gecko::global_style_data::GLOBAL_STYLE_DATA;
 use gecko::selector_parser::{SelectorImpl, NonTSPseudoClass, PseudoElement};
 use gecko::snapshot_helpers;
@@ -60,6 +62,7 @@ use selectors::matching::{ElementSelectorFlags, StyleRelations};
 use selectors::parser::{AttrSelector, NamespaceConstraint};
 use shared_lock::Locked;
 use sink::Push;
+use std::cell::RefCell;
 use std::fmt;
 use std::ptr;
 use std::sync::Arc;
@@ -426,8 +429,65 @@ fn get_animation_rule(element: &GeckoElement,
     }
 }
 
+#[derive(Debug)]
+/// Gecko font metrics provider
+pub struct GeckoFontMetricsProvider {
+    /// Cache of base font sizes for each language
+    ///
+    /// Usually will have 1 element.
+    ///
+    // This may be slow on pages using more languages, might be worth optimizing
+    // by caching lang->group mapping separately and/or using a hashmap on larger
+    // loads.
+    pub font_size_cache: RefCell<Vec<(Atom, ::gecko_bindings::structs::FontSizePrefs)>>,
+}
+
+impl GeckoFontMetricsProvider {
+    /// Construct
+    pub fn new() -> Self {
+        GeckoFontMetricsProvider {
+            font_size_cache: RefCell::new(Vec::new()),
+        }
+    }
+}
+
+impl FontMetricsProvider for GeckoFontMetricsProvider {
+    fn create_from(_: &SharedStyleContext) -> GeckoFontMetricsProvider {
+        GeckoFontMetricsProvider::new()
+    }
+
+    fn get_size(&self, font_name: &Atom, font_family: u8) -> Au {
+        use gecko_bindings::bindings::Gecko_GetBaseSize;
+        let mut cache = self.font_size_cache.borrow_mut();
+        if let Some(sizes) = cache.iter().find(|el| el.0 == *font_name) {
+            return sizes.1.size_for_generic(font_family);
+        }
+        let sizes = unsafe {
+            Gecko_GetBaseSize(font_name.as_ptr())
+        };
+        cache.push((font_name.clone(), sizes));
+        sizes.size_for_generic(font_family)
+    }
+}
+
+impl structs::FontSizePrefs {
+    fn size_for_generic(&self, font_family: u8) -> Au {
+        Au(match font_family {
+            structs::kPresContext_DefaultVariableFont_ID => self.mDefaultVariableSize,
+            structs::kPresContext_DefaultFixedFont_ID => self.mDefaultFixedSize,
+            structs::kGenericFont_serif => self.mDefaultSerifSize,
+            structs::kGenericFont_sans_serif => self.mDefaultSansSerifSize,
+            structs::kGenericFont_monospace => self.mDefaultMonospaceSize,
+            structs::kGenericFont_cursive => self.mDefaultCursiveSize,
+            structs::kGenericFont_fantasy => self.mDefaultFantasySize,
+            x => unreachable!("Unknown generic ID {}", x),
+        })
+    }
+}
+
 impl<'le> TElement for GeckoElement<'le> {
     type ConcreteNode = GeckoNode<'le>;
+    type FontMetricsProvider = GeckoFontMetricsProvider;
 
     fn as_node(&self) -> Self::ConcreteNode {
         unsafe { GeckoNode(&*(self.0 as *const _ as *const RawGeckoNode)) }