style: Implement the body text color quirk in a more straight-forward way.

This avoids grabbing the document when values that inherit from the body,
whatever that means, aren't under the body.

In that case we'll get a semi-random value, but that's also mishandled by Gecko
anyways (and probably Blink, though haven't tested), and doesn't really make
much sense.

components/layout_thread/dom_wrapper.rs

@@ -547,6 +547,14 @@ impl<'le> TElement for ServoLayoutElement<'le> {
         };
         extended_filtering(&element_lang, &*value)
     }
+
+    fn is_html_document_body_element(&self) -> bool {
+        // This is only used for the "tables inherit from body" quirk, which we
+        // don't implement.
+        //
+        // FIXME(emilio): We should be able to give the right answer though!
+        false
+    }
 }
 
 impl<'le> PartialEq for ServoLayoutElement<'le> {

components/style/dom.rs

@@ -727,6 +727,10 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
         override_lang: Option<Option<AttrValue>>,
         value: &PseudoClassStringArg
     ) -> bool;
+
+    /// Returns whether this element is the main body element of the HTML
+    /// document it is on.
+    fn is_html_document_body_element(&self) -> bool;
 }
 
 /// TNode and TElement aren't Send because we want to be careful and explicit

components/style/gecko/generated/bindings.rs

@@ -1551,8 +1551,7 @@ extern "C" {
                                                  *mut nsCSSCounterStyleRule);
 }
 extern "C" {
-    pub fn Gecko_GetBody(pres_context: RawGeckoPresContextBorrowed)
-     -> RawGeckoElementBorrowedOrNull;
+    pub fn Gecko_IsDocumentBody(element: RawGeckoElementBorrowed) -> bool;
 }
 extern "C" {
     pub fn Gecko_GetLookAndFeelSystemColor(color_id: i32,

components/style/gecko/media_queries.rs

@@ -11,7 +11,7 @@ use cssparser::{CssStringWriter, Parser, RGBA, Token, BasicParseError};
 use euclid::ScaleFactor;
 use euclid::Size2D;
 use font_metrics::get_metrics_provider_for_product;
-use gecko::values::convert_nscolor_to_rgba;
+use gecko::values::{convert_nscolor_to_rgba, convert_rgba_to_nscolor};
 use gecko_bindings::bindings;
 use gecko_bindings::structs;
 use gecko_bindings::structs::{nsCSSKeyword, nsCSSProps_KTableEntry, nsCSSValue, nsCSSUnit};
@@ -27,7 +27,7 @@ use rule_cache::RuleCacheConditions;
 use servo_arc::Arc;
 use std::cell::RefCell;
 use std::fmt::{self, Write};
-use std::sync::atomic::{AtomicBool, AtomicIsize, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicIsize, AtomicUsize, Ordering};
 use str::starts_with_ignore_ascii_case;
 use string_cache::Atom;
 use style_traits::{CSSPixel, DevicePixel};
@@ -54,6 +54,11 @@ pub struct Device {
     /// the parent to compute everything else. So it is correct to just use
     /// a relaxed atomic here.
     root_font_size: AtomicIsize,
+    /// The body text color, stored as an `nscolor`, used for the "tables
+    /// inherit from body" quirk.
+    ///
+    /// https://quirks.spec.whatwg.org/#the-tables-inherit-color-from-body-quirk
+    body_text_color: AtomicUsize,
     /// Whether any styles computed in the document relied on the root font-size
     /// by using rem units.
     used_root_font_size: AtomicBool,
@@ -74,6 +79,7 @@ impl Device {
             default_values: ComputedValues::default_values(unsafe { &*pres_context }),
             // FIXME(bz): Seems dubious?
             root_font_size: AtomicIsize::new(font_size::get_initial_value().0.to_i32_au() as isize),
+            body_text_color: AtomicUsize::new(unsafe { &*pres_context }.mDefaultColor as usize),
             used_root_font_size: AtomicBool::new(false),
             used_viewport_size: AtomicBool::new(false),
         }
@@ -110,6 +116,18 @@ impl Device {
         self.root_font_size.store(size.0 as isize, Ordering::Relaxed)
     }
 
+    /// Sets the body text color for the "inherit color from body" quirk.
+    ///
+    /// https://quirks.spec.whatwg.org/#the-tables-inherit-color-from-body-quirk
+    pub fn set_body_text_color(&self, color: RGBA) {
+        self.body_text_color.store(convert_rgba_to_nscolor(&color) as usize, Ordering::Relaxed)
+    }
+
+    /// Returns the body text color.
+    pub fn body_text_color(&self) -> RGBA {
+        convert_nscolor_to_rgba(self.body_text_color.load(Ordering::Relaxed) as u32)
+    }
+
     /// Gets the pres context associated with this document.
     pub fn pres_context(&self) -> &nsPresContext {
         unsafe { &*self.pres_context }

components/style/gecko/wrapper.rs

@@ -593,6 +593,10 @@ impl<'le> GeckoElement<'le> {
         self.as_node().node_info().mInner.mNamespaceID
     }
 
+    fn is_html_element(&self) -> bool {
+        self.namespace_id() == (structs::root::kNameSpaceID_XHTML as i32)
+    }
+
     fn is_xul_element(&self) -> bool {
         self.namespace_id() == (structs::root::kNameSpaceID_XUL as i32)
     }
@@ -1502,6 +1506,18 @@ impl<'le> TElement for GeckoElement<'le> {
             Gecko_MatchLang(self.0, override_lang_ptr, override_lang.is_some(), value.as_ptr())
         }
     }
+
+    fn is_html_document_body_element(&self) -> bool {
+        if self.get_local_name() != &*local_name!("body") {
+            return false;
+        }
+
+        if !self.is_html_element() {
+            return false;
+        }
+
+        unsafe { bindings::Gecko_IsDocumentBody(self.0) }
+    }
 }
 
 impl<'le> PartialEq for GeckoElement<'le> {
@@ -2011,10 +2027,8 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
     }
 
     fn is_html_element_in_html_document(&self) -> bool {
-        let node = self.as_node();
-        let node_info = node.node_info();
-        node_info.mInner.mNamespaceID == (structs::root::kNameSpaceID_XHTML as i32) &&
-        node.owner_doc().mType == structs::root::nsIDocument_Type::eHTML
+        self.is_html_element() &&
+        self.as_node().owner_doc().mType == structs::root::nsIDocument_Type::eHTML
     }
 
     fn ignores_nth_child_selectors(&self) -> bool {

components/style/matching.rs

@@ -7,7 +7,8 @@
 #![allow(unsafe_code)]
 #![deny(missing_docs)]
 
-use context::{ElementCascadeInputs, SelectorFlagsMap, SharedStyleContext, StyleContext};
+use context::{ElementCascadeInputs, QuirksMode, SelectorFlagsMap};
+use context::{SharedStyleContext, StyleContext};
 use data::ElementData;
 use dom::TElement;
 use invalidation::element::restyle_hints::{RESTYLE_CSS_ANIMATIONS, RESTYLE_CSS_TRANSITIONS};
@@ -586,6 +587,21 @@ pub trait MatchMethods : TElement {
             }
         }
 
+        if context.shared.stylist.quirks_mode() == QuirksMode::Quirks {
+            if self.is_html_document_body_element() {
+                // NOTE(emilio): We _could_ handle dynamic changes to it if it
+                // changes and before we reach our children the cascade stops,
+                // but we don't track right now whether we use the document body
+                // color, and nobody else handles that properly anyway.
+
+                let device = context.shared.stylist.device();
+
+                // Needed for the "inherit from body" quirk.
+                let text_color = new_primary_style.get_color().clone_color();
+                device.set_body_text_color(text_color);
+            }
+        }
+
         // Don't accumulate damage if we're in a forgetful traversal.
         if context.shared.traversal_flags.contains(traversal_flags::Forgetful) {
             return ChildCascadeRequirement::MustCascadeChildren;

components/style/servo/media_queries.rs

@@ -92,6 +92,13 @@ impl Device {
         self.root_font_size.store(size.0 as isize, Ordering::Relaxed)
     }
 
+    /// Sets the body text color for the "inherit color from body" quirk.
+    ///
+    /// https://quirks.spec.whatwg.org/#the-tables-inherit-color-from-body-quirk
+    pub fn set_body_text_color(&self, _color: RGBA) {
+        // Servo doesn't implement this quirk (yet)
+    }
+
     /// Returns whether we ever looked up the root font size of the Device.
     pub fn used_root_font_size(&self) -> bool {
         self.used_root_font_size.load(Ordering::Relaxed)

components/style/values/specified/color.rs

@@ -289,19 +289,7 @@ impl ToComputedValue for Color {
             }
             #[cfg(feature = "gecko")]
             Color::InheritFromBodyQuirk => {
-                use dom::TElement;
-                use gecko::wrapper::GeckoElement;
-                use gecko_bindings::bindings::Gecko_GetBody;
-                let pres_context = context.device().pres_context();
-                let body = unsafe { Gecko_GetBody(pres_context) }.map(GeckoElement);
-                let data = body.as_ref().and_then(|wrap| wrap.borrow_data());
-                if let Some(data) = data {
-                    ComputedColor::rgba(data.styles.primary()
-                                            .get_color()
-                                            .clone_color())
-                } else {
-                    convert_nscolor_to_computedcolor(pres_context.mDefaultColor)
-                }
+                ComputedColor::rgba(context.device().body_text_color())
             },
         }
     }