Auto merge of #27385 - servo:list, r=Manishearth

Add Layout 2020 support for `display: list-item`

components/layout_2020/dom_traversal.rs

@@ -93,7 +93,6 @@ pub(super) enum NonReplacedContents {
 
 pub(super) enum PseudoElementContentItem {
     Text(String),
-    #[allow(dead_code)]
     Replaced(ReplacedContent),
 }
 
@@ -219,7 +218,9 @@ fn traverse_pseudo_element_contents<'dom, Node>(
                 });
                 let display_inline = DisplayGeneratingBox::OutsideInside {
                     outside: DisplayOutside::Inline,
-                    inside: DisplayInside::Flow,
+                    inside: DisplayInside::Flow {
+                        is_list_item: false,
+                    },
                 };
                 // `display` is not inherited, so we get the initial value
                 debug_assert!(
@@ -345,7 +346,6 @@ where
                             vec.push(PseudoElementContentItem::Replaced(replaced_content));
                         }
                     },
-                    _ => (),
                 }
             }
             vec

components/layout_2020/flow/construct.rs

@@ -20,6 +20,7 @@ use rayon_croissant::ParallelIteratorExt;
 use servo_arc::Arc;
 use std::borrow::Cow;
 use std::convert::{TryFrom, TryInto};
+use style::properties::longhands::list_style_position::computed_value::T as ListStylePosition;
 use style::properties::ComputedValues;
 use style::selector_parser::PseudoElement;
 use style::values::specified::text::TextDecorationLine;
@@ -30,12 +31,18 @@ impl BlockFormattingContext {
         info: &NodeAndStyleInfo<Node>,
         contents: NonReplacedContents,
         propagated_text_decoration_line: TextDecorationLine,
+        is_list_item: bool,
     ) -> Self
     where
         Node: NodeExt<'dom>,
     {
-        let (contents, contains_floats) =
-            BlockContainer::construct(context, info, contents, propagated_text_decoration_line);
+        let (contents, contains_floats) = BlockContainer::construct(
+            context,
+            info,
+            contents,
+            propagated_text_decoration_line,
+            is_list_item,
+        );
         let bfc = Self {
             contents,
             contains_floats: contains_floats == ContainsFloats::Yes,
@@ -97,7 +104,11 @@ enum BlockLevelCreator {
 /// Deferring allows using rayon’s `into_par_iter`.
 enum IntermediateBlockContainer {
     InlineFormattingContext(InlineFormattingContext),
-    Deferred(NonReplacedContents, TextDecorationLine),
+    Deferred {
+        contents: NonReplacedContents,
+        propagated_text_decoration_line: TextDecorationLine,
+        is_list_item: bool,
+    },
 }
 
 /// A builder for a block container.
@@ -164,6 +175,7 @@ impl BlockContainer {
         info: &NodeAndStyleInfo<Node>,
         contents: NonReplacedContents,
         propagated_text_decoration_line: TextDecorationLine,
+        is_list_item: bool,
     ) -> (BlockContainer, ContainsFloats)
     where
         Node: NodeExt<'dom>,
@@ -180,6 +192,24 @@ impl BlockContainer {
             contains_floats: ContainsFloats::No,
         };
 
+        if is_list_item {
+            if let Some(marker_contents) = crate::lists::make_marker(context, info) {
+                let _position = info.style.clone_list_style_position();
+                // FIXME: implement support for `outside` and remove this:
+                let position = ListStylePosition::Inside;
+                match position {
+                    ListStylePosition::Inside => {
+                        builder.handle_list_item_marker_inside(info, marker_contents)
+                    },
+                    ListStylePosition::Outside => {
+                        // FIXME: implement layout for this case
+                        // https://github.com/servo/servo/issues/27383
+                        // and enable `list-style-position` and the `list-style` shorthand in Stylo.
+                    },
+                }
+            }
+        }
+
         contents.traverse(context, info, &mut builder);
 
         debug_assert!(builder.ongoing_inline_boxes_stack.is_empty());
@@ -384,13 +414,38 @@ where
         }
     }
 
+    fn handle_list_item_marker_inside(
+        &mut self,
+        info: &NodeAndStyleInfo<Node>,
+        contents: Vec<crate::dom_traversal::PseudoElementContentItem>,
+    ) {
+        let marker_style = self
+            .context
+            .shared_context()
+            .stylist
+            .style_for_anonymous::<Node::ConcreteElement>(
+                &self.context.shared_context().guards,
+                &PseudoElement::ServoText, // FIMXE: use `PseudoElement::Marker` when we add it
+                &info.style,
+            );
+        self.handle_inline_level_element(
+            &info.new_replacing_style(marker_style),
+            DisplayInside::Flow {
+                is_list_item: false,
+            },
+            Contents::OfPseudoElement(contents),
+        );
+    }
+
     fn handle_inline_level_element(
         &mut self,
         info: &NodeAndStyleInfo<Node>,
         display_inside: DisplayInside,
         contents: Contents,
     ) -> ArcRefCell<InlineLevelBox> {
-        let box_ = if display_inside == DisplayInside::Flow && !contents.is_replaced() {
+        let box_ = if let (DisplayInside::Flow { is_list_item }, false) =
+            (display_inside, contents.is_replaced())
+        {
             // We found un inline box.
             // Whatever happened before, all we need to do before recurring
             // is to remember this ongoing inline level box.
@@ -402,6 +457,15 @@ where
                 children: vec![],
             });
 
+            if is_list_item {
+                if let Some(marker_contents) = crate::lists::make_marker(self.context, info) {
+                    // Ignore `list-style-position` here:
+                    // “If the list item is an inline box: this value is equivalent to `inside`.”
+                    // https://drafts.csswg.org/css-lists/#list-style-position-outside
+                    self.handle_list_item_marker_inside(info, marker_contents)
+                }
+            }
+
             // `unwrap` doesn’t panic here because `is_replaced` returned `false`.
             NonReplacedContents::try_from(contents)
                 .unwrap()
@@ -485,9 +549,15 @@ where
 
         let kind = match contents.try_into() {
             Ok(contents) => match display_inside {
-                DisplayInside::Flow => BlockLevelCreator::SameFormattingContextBlock(
-                    IntermediateBlockContainer::Deferred(contents, propagated_text_decoration_line),
-                ),
+                DisplayInside::Flow { is_list_item } => {
+                    BlockLevelCreator::SameFormattingContextBlock(
+                        IntermediateBlockContainer::Deferred {
+                            contents,
+                            propagated_text_decoration_line,
+                            is_list_item,
+                        },
+                    )
+                },
                 _ => BlockLevelCreator::Independent {
                     display_inside,
                     contents: contents.into(),
@@ -695,9 +765,17 @@ impl IntermediateBlockContainer {
         Node: NodeExt<'dom>,
     {
         match self {
-            IntermediateBlockContainer::Deferred(contents, propagated_text_decoration_line) => {
-                BlockContainer::construct(context, info, contents, propagated_text_decoration_line)
-            },
+            IntermediateBlockContainer::Deferred {
+                contents,
+                propagated_text_decoration_line,
+                is_list_item,
+            } => BlockContainer::construct(
+                context,
+                info,
+                contents,
+                propagated_text_decoration_line,
+                is_list_item,
+            ),
             IntermediateBlockContainer::InlineFormattingContext(ifc) => {
                 // If that inline formatting context contained any float, those
                 // were already taken into account during the first phase of

components/layout_2020/formatting_contexts.rs

@@ -71,13 +71,15 @@ impl IndependentFormattingContext {
         match contents.try_into() {
             Ok(non_replaced) => {
                 let contents = match display_inside {
-                    DisplayInside::Flow | DisplayInside::FlowRoot => {
+                    DisplayInside::Flow { is_list_item } |
+                    DisplayInside::FlowRoot { is_list_item } => {
                         NonReplacedFormattingContextContents::Flow(
                             BlockFormattingContext::construct(
                                 context,
                                 info,
                                 non_replaced,
                                 propagated_text_decoration_line,
+                                is_list_item,
                             ),
                         )
                     },

components/layout_2020/lib.rs

@@ -22,6 +22,7 @@ mod fragments;
 pub mod geom;
 #[macro_use]
 pub mod layout_debug;
+mod lists;
 mod opaque_node;
 mod positioned;
 pub mod query;

components/layout_2020/lists.rs

@@ -0,0 +1,50 @@
+/* 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/. */
+
+use crate::context::LayoutContext;
+use crate::dom_traversal::{NodeAndStyleInfo, NodeExt, PseudoElementContentItem};
+use crate::replaced::ReplacedContent;
+use style::properties::longhands::list_style_type::computed_value::T as ListStyleType;
+use style::properties::style_structs;
+use style::values::computed::url::UrlOrNone;
+
+/// https://drafts.csswg.org/css-lists/#content-property
+pub(crate) fn make_marker<'dom, Node>(
+    context: &LayoutContext,
+    info: &NodeAndStyleInfo<Node>,
+) -> Option<Vec<PseudoElementContentItem>>
+where
+    Node: NodeExt<'dom>,
+{
+    let style = info.style.get_list();
+
+    // https://drafts.csswg.org/css-lists/#marker-image
+    let marker_image = || match &style.list_style_image {
+        UrlOrNone::Url(url) => Some(vec![
+            PseudoElementContentItem::Replaced(ReplacedContent::from_image_url(
+                info.node, context, url,
+            )?),
+            PseudoElementContentItem::Text(" ".into()),
+        ]),
+        UrlOrNone::None => None,
+    };
+    marker_image().or_else(|| {
+        Some(vec![PseudoElementContentItem::Text(
+            marker_string(style)?.into(),
+        )])
+    })
+}
+
+/// https://drafts.csswg.org/css-lists/#marker-string
+fn marker_string(style: &style_structs::List) -> Option<&'static str> {
+    // FIXME: add support for counters and other style types
+    match style.list_style_type {
+        ListStyleType::None => None,
+        ListStyleType::Disc => Some("• "),
+        ListStyleType::Circle => Some("◦ "),
+        ListStyleType::Square => Some("▪ "),
+        ListStyleType::DisclosureOpen => Some("▾ "),
+        ListStyleType::DisclosureClosed => Some("‣ "),
+    }
+}

components/layout_2020/style_ext.rs

@@ -33,7 +33,6 @@ pub(crate) enum DisplayGeneratingBox {
     OutsideInside {
         outside: DisplayOutside,
         inside: DisplayInside,
-        // list_item: bool,
     },
     // Layout-internal display types go here:
     // https://drafts.csswg.org/css-display-3/#layout-specific-display
@@ -47,8 +46,10 @@ pub(crate) enum DisplayOutside {
 
 #[derive(Clone, Copy, Eq, PartialEq)]
 pub(crate) enum DisplayInside {
-    Flow,
-    FlowRoot,
+    // “list-items are limited to the Flow Layout display types”
+    // https://drafts.csswg.org/css-display/#list-items
+    Flow { is_list_item: bool },
+    FlowRoot { is_list_item: bool },
     Flex,
 }
 
@@ -444,8 +445,12 @@ impl ComputedValuesExt for ComputedValues {
 impl From<stylo::Display> for Display {
     fn from(packed: stylo::Display) -> Self {
         let inside = match packed.inside() {
-            stylo::DisplayInside::Flow => DisplayInside::Flow,
-            stylo::DisplayInside::FlowRoot => DisplayInside::FlowRoot,
+            stylo::DisplayInside::Flow => DisplayInside::Flow {
+                is_list_item: packed.is_list_item(),
+            },
+            stylo::DisplayInside::FlowRoot => DisplayInside::FlowRoot {
+                is_list_item: packed.is_list_item(),
+            },
             stylo::DisplayInside::Flex => DisplayInside::Flex,
 
             // These should not be values of DisplayInside, but oh well
@@ -459,11 +464,7 @@ impl From<stylo::Display> for Display {
             // This should not be a value of DisplayInside, but oh well
             stylo::DisplayOutside::None => return Display::None,
         };
-        Display::GeneratingBox(DisplayGeneratingBox::OutsideInside {
-            outside,
-            inside,
-            // list_item: packed.is_list_item(),
-        })
+        Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { outside, inside })
     }
 }