style: Adjust display:contents to display:inline for NAC (including ::before/::after).

components/style/matching.rs

@@ -17,7 +17,7 @@ use invalidation::element::restyle_hints::{RESTYLE_CSS_ANIMATIONS, RESTYLE_CSS_T
 use invalidation::element::restyle_hints::{RESTYLE_SMIL, RESTYLE_STYLE_ATTRIBUTE};
 use invalidation::element::restyle_hints::RestyleHint;
 use log::LogLevel::Trace;
-use properties::{ALLOW_SET_ROOT_FONT_SIZE, SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP};
+use properties::{ALLOW_SET_ROOT_FONT_SIZE, PROHIBIT_DISPLAY_CONTENTS, SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP};
 use properties::{AnimationRules, CascadeFlags, ComputedValues};
 use properties::{VISITED_DEPENDENT_ONLY, cascade};
 use properties::longhands::display::computed_value as display;
@@ -29,15 +29,23 @@ use sharing::StyleSharingBehavior;
 use stylearc::Arc;
 use stylist::RuleInclusion;
 
-/// The way a style should be inherited.
+/// Whether we are cascading for an eager pseudo-element or something else.
-enum InheritMode {
+///
+/// Controls where we inherit styles from, and whether display:contents is
+/// prohibited.
+#[derive(PartialEq, Copy, Clone)]
+enum CascadeTarget {
     /// Inherit from the parent element, as normal CSS dictates, _or_ from the
     /// closest non-Native Anonymous element in case this is Native Anonymous
-    /// Content.
+    /// Content. display:contents is allowed.
     Normal,
     /// Inherit from the primary style, this is used while computing eager
     /// pseudos, like ::before and ::after when we're traversing the parent.
-    FromPrimaryStyle,
+    /// Also prohibits display:contents from having an effect.
+    ///
+    /// TODO(emilio) display:contents really should apply to ::before/::after.
+    /// https://github.com/w3c/csswg-drafts/issues/1345
+    EagerPseudo,
 }
 
 /// Represents the result of comparing an element's old and new style.
@@ -251,7 +259,7 @@ trait PrivateMatchMethods: TElement {
                           font_metrics_provider: &FontMetricsProvider,
                           rule_node: &StrongRuleNode,
                           primary_style: &ComputedStyle,
-                          inherit_mode: InheritMode,
+                          cascade_target: CascadeTarget,
                           cascade_visited: CascadeVisitedMode,
                           visited_values_to_insert: Option<Arc<ComputedValues>>)
                           -> Arc<ComputedValues> {
@@ -263,15 +271,17 @@ trait PrivateMatchMethods: TElement {
         if cascade_visited.visited_dependent_only() {
             cascade_flags.insert(VISITED_DEPENDENT_ONLY);
         }
-        if !self.is_native_anonymous() {
+        if self.is_native_anonymous() || cascade_target == CascadeTarget::EagerPseudo {
+            cascade_flags.insert(PROHIBIT_DISPLAY_CONTENTS);
+        } else {
             cascade_flags.insert(ALLOW_SET_ROOT_FONT_SIZE);
         }
 
         // Grab the inherited values.
         let parent_el;
         let parent_data;
-        let style_to_inherit_from = match inherit_mode {
+        let style_to_inherit_from = match cascade_target {
-            InheritMode::Normal => {
+            CascadeTarget::Normal => {
                 parent_el = self.inheritance_parent();
                 parent_data = parent_el.as_ref().and_then(|e| e.borrow_data());
                 let parent_style = parent_data.as_ref().map(|d| {
@@ -287,7 +297,7 @@ trait PrivateMatchMethods: TElement {
                 });
                 parent_style.map(|s| cascade_visited.values(s))
             }
-            InheritMode::FromPrimaryStyle => {
+            CascadeTarget::EagerPseudo => {
                 parent_el = Some(self.clone());
                 Some(cascade_visited.values(primary_style))
             }
@@ -390,17 +400,17 @@ trait PrivateMatchMethods: TElement {
         // Grab the rule node.
         let style = eager_pseudo_style.unwrap_or(primary_style);
         let rule_node = cascade_visited.rules(style);
-        let inherit_mode = if eager_pseudo_style.is_some() {
+        let cascade_target = if eager_pseudo_style.is_some() {
-            InheritMode::FromPrimaryStyle
+            CascadeTarget::EagerPseudo
         } else {
-            InheritMode::Normal
+            CascadeTarget::Normal
         };
 
         self.cascade_with_rules(context.shared,
                                 &context.thread_local.font_metrics_provider,
                                 rule_node,
                                 primary_style,
-                                inherit_mode,
+                                cascade_target,
                                 cascade_visited,
                                 visited_values_to_insert)
     }
@@ -536,7 +546,7 @@ trait PrivateMatchMethods: TElement {
                                      &context.thread_local.font_metrics_provider,
                                      &without_transition_rules,
                                      primary_style,
-                                     InheritMode::Normal,
+                                     CascadeTarget::Normal,
                                      CascadeVisitedMode::Unvisited,
                                      None))
     }
@@ -1480,7 +1490,7 @@ pub trait MatchMethods : TElement {
                                 font_metrics_provider,
                                 &without_animation_rules,
                                 primary_style,
-                                InheritMode::Normal,
+                                CascadeTarget::Normal,
                                 CascadeVisitedMode::Unvisited,
                                 None)
     }

components/style/properties/properties.mako.rs

@@ -2479,6 +2479,10 @@ bitflags! {
         /// ::backdrop and all NAC will resolve rem units against
         /// the toplevel root element now.
         const ALLOW_SET_ROOT_FONT_SIZE = 0x08,
+        /// Whether to convert display:contents into display:inline.  This
+        /// is used by Gecko to prevent display:contents on generated
+        /// content.
+        const PROHIBIT_DISPLAY_CONTENTS = 0x10,
     }
 }
 
@@ -2851,8 +2855,7 @@ pub fn apply_declarations<'a, F, I>(device: &Device,
 
     {
         StyleAdjuster::new(&mut style, is_root_element)
-            .adjust(context.layout_parent_style,
+            .adjust(context.layout_parent_style, flags);
-                    flags.contains(SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP));
     }
 
     % if product == "gecko":

components/style/style_adjuster.rs

@@ -6,7 +6,10 @@
 //! for it to adhere to the CSS spec.
 
 use app_units::Au;
-use properties::{self, ComputedValues, StyleBuilder};
+use properties::{self, CascadeFlags, ComputedValues};
+use properties::{SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP, StyleBuilder};
+#[cfg(feature = "gecko")]
+use properties::PROHIBIT_DISPLAY_CONTENTS;
 use properties::longhands::display::computed_value::T as display;
 use properties::longhands::float::computed_value::T as float;
 use properties::longhands::overflow_x::computed_value::T as overflow;
@@ -54,7 +57,7 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
     /// https://drafts.csswg.org/css2/visuren.html#dis-pos-flo
     fn blockify_if_necessary(&mut self,
                              layout_parent_style: &ComputedValues,
-                             skip_root_and_element_display_fixup: bool) {
+                             flags: CascadeFlags) {
         let mut blockify = false;
         macro_rules! blockify_if {
             ($if_what:expr) => {
@@ -64,7 +67,7 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
             }
         }
 
-        if !skip_root_and_element_display_fixup {
+        if !flags.contains(SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP) {
             blockify_if!(self.is_root_element);
             blockify_if!(layout_parent_style.get_box().clone_display().is_item_container());
         }
@@ -275,6 +278,19 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
         }
     }
 
+    /// Native anonymous content converts display:contents into display:inline.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_prohibited_display_contents(&mut self, flags: CascadeFlags) {
+        // TODO: We should probably convert display:contents into display:none
+        // in some cases too: https://drafts.csswg.org/css-display/#unbox
+        if !flags.contains(PROHIBIT_DISPLAY_CONTENTS) ||
+           self.style.get_box().clone_display() != display::contents {
+            return;
+        }
+
+        self.style.mutate_box().set_display(display::inline);
+    }
+
     /// -moz-center, -moz-left and -moz-right are used for HTML's alignment.
     ///
     /// This is covering the <div align="right"><table>...</table></div> case.
@@ -305,10 +321,13 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
     /// `nsStyleContext::ApplyStyleFixups`.
     pub fn adjust(&mut self,
                   layout_parent_style: &ComputedValues,
-                  skip_root_and_element_display_fixup: bool) {
+                  flags: CascadeFlags) {
+        #[cfg(feature = "gecko")]
+        {
+            self.adjust_for_prohibited_display_contents(flags);
+        }
         self.adjust_for_top_layer();
-        self.blockify_if_necessary(layout_parent_style,
+        self.blockify_if_necessary(layout_parent_style, flags);
-                                   skip_root_and_element_display_fixup);
         self.adjust_for_position();
         self.adjust_for_overflow();
         #[cfg(feature = "gecko")]