Import files from Victor

fdb11f3e87

components/layout_2020/flow/construct.rs

@@ -0,0 +1,625 @@
+use super::*;
+
+impl BlockFormattingContext {
+    pub fn construct<'a>(
+        context: &'a Context<'a>,
+        style: &'a Arc<ComputedValues>,
+        contents: NonReplacedContents,
+    ) -> Self {
+        let (contents, contains_floats) = BlockContainer::construct(context, style, contents);
+        Self {
+            contents,
+            contains_floats: contains_floats == ContainsFloats::Yes,
+        }
+    }
+}
+
+enum IntermediateBlockLevelBox {
+    SameFormattingContextBlock {
+        style: Arc<ComputedValues>,
+        contents: IntermediateBlockContainer,
+    },
+    Independent {
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+    },
+    OutOfFlowAbsolutelyPositionedBox {
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+    },
+    OutOfFlowFloatBox {
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+    },
+}
+
+/// A block container that may still have to be constructed.
+///
+/// Represents either the inline formatting context of an anonymous block
+/// box or the yet-to-be-computed block container generated from the children
+/// of a given element.
+///
+/// Deferring allows using rayon’s `into_par_iter`.
+enum IntermediateBlockContainer {
+    InlineFormattingContext(InlineFormattingContext),
+    Deferred { contents: NonReplacedContents },
+}
+
+/// A builder for a block container.
+///
+/// This builder starts from the first child of a given DOM node
+/// and does a preorder traversal of all of its inclusive siblings.
+struct BlockContainerBuilder<'a> {
+    context: &'a Context<'a>,
+    block_container_style: &'a Arc<ComputedValues>,
+
+    /// The list of block-level boxes of the final block container.
+    ///
+    /// Contains all the complete block level boxes we found traversing the tree
+    /// so far, if this is empty at the end of the traversal and the ongoing
+    /// inline formatting context is not empty, the block container establishes
+    /// an inline formatting context (see end of `build`).
+    ///
+    /// DOM nodes which represent block-level boxes are immediately pushed
+    /// to this list with their style without ever being traversed at this
+    /// point, instead we just move to their next sibling. If the DOM node
+    /// doesn't have a next sibling, we either reached the end of the container
+    /// root or there are ongoing inline-level boxes
+    /// (see `handle_block_level_element`).
+    block_level_boxes: Vec<(IntermediateBlockLevelBox, BoxSlot<'a>)>,
+
+    /// The ongoing inline formatting context of the builder.
+    ///
+    /// Contains all the complete inline level boxes we found traversing the
+    /// tree so far. If a block-level box is found during traversal,
+    /// this inline formatting context is pushed as a block level box to
+    /// the list of block-level boxes of the builder
+    /// (see `end_ongoing_inline_formatting_context`).
+    ongoing_inline_formatting_context: InlineFormattingContext,
+
+    /// The ongoing stack of inline boxes stack of the builder.
+    ///
+    /// Contains all the currently ongoing inline boxes we entered so far.
+    /// The traversal is at all times as deep in the tree as this stack is,
+    /// which is why the code doesn't need to keep track of the actual
+    /// container root (see `handle_inline_level_element`).
+    ///
+    /// Whenever the end of a DOM element that represents an inline box is
+    /// reached, the inline box at the top of this stack is complete and ready
+    /// to be pushed to the children of the next last ongoing inline box
+    /// the ongoing inline formatting context if the stack is now empty,
+    /// which means we reached the end of a child of the actual
+    /// container root (see `move_to_next_sibling`).
+    ongoing_inline_boxes_stack: Vec<InlineBox>,
+
+    /// The style of the anonymous block boxes pushed to the list of block-level
+    /// boxes, if any (see `end_ongoing_inline_formatting_context`).
+    anonymous_style: Option<Arc<ComputedValues>>,
+
+    /// Whether the resulting block container contains any float box.
+    contains_floats: ContainsFloats,
+}
+
+impl BlockContainer {
+    pub fn construct<'a>(
+        context: &'a Context<'a>,
+        block_container_style: &'a Arc<ComputedValues>,
+        contents: NonReplacedContents,
+    ) -> (BlockContainer, ContainsFloats) {
+        let mut builder = BlockContainerBuilder {
+            context,
+            block_container_style,
+            block_level_boxes: Default::default(),
+            ongoing_inline_formatting_context: Default::default(),
+            ongoing_inline_boxes_stack: Default::default(),
+            anonymous_style: Default::default(),
+            contains_floats: Default::default(),
+        };
+
+        contents.traverse(block_container_style, context, &mut builder);
+
+        debug_assert!(builder.ongoing_inline_boxes_stack.is_empty());
+
+        if !builder
+            .ongoing_inline_formatting_context
+            .inline_level_boxes
+            .is_empty()
+        {
+            if builder.block_level_boxes.is_empty() {
+                let container = BlockContainer::InlineFormattingContext(
+                    builder.ongoing_inline_formatting_context,
+                );
+                return (container, builder.contains_floats);
+            }
+            builder.end_ongoing_inline_formatting_context();
+        }
+
+        let mut contains_floats = builder.contains_floats;
+        let container = BlockContainer::BlockLevelBoxes(
+            builder
+                .block_level_boxes
+                .into_par_iter()
+                .mapfold_reduce_into(
+                    &mut contains_floats,
+                    |contains_floats, (intermediate, box_slot)| {
+                        let (block_level_box, box_contains_floats) = intermediate.finish(context);
+                        *contains_floats |= box_contains_floats;
+                        box_slot.set(LayoutBox::BlockLevel(block_level_box.clone()));
+                        block_level_box
+                    },
+                    |left, right| *left |= right,
+                )
+                .collect(),
+        );
+        (container, contains_floats)
+    }
+}
+
+impl<'a> TraversalHandler<'a> for BlockContainerBuilder<'a> {
+    fn handle_element(
+        &mut self,
+        style: &Arc<ComputedValues>,
+        display: DisplayGeneratingBox,
+        contents: Contents,
+        box_slot: BoxSlot<'a>,
+    ) {
+        match display {
+            DisplayGeneratingBox::OutsideInside { outside, inside } => match outside {
+                DisplayOutside::Inline => box_slot.set(LayoutBox::InlineLevel(
+                    self.handle_inline_level_element(style, inside, contents),
+                )),
+                DisplayOutside::Block => {
+                    // Floats and abspos cause blockification, so they only happen in this case.
+                    // https://drafts.csswg.org/css2/visuren.html#dis-pos-flo
+                    if style.box_.position.is_absolutely_positioned() {
+                        self.handle_absolutely_positioned_element(
+                            style.clone(),
+                            inside,
+                            contents,
+                            box_slot,
+                        )
+                    } else if style.box_.float.is_floating() {
+                        self.handle_float_element(style.clone(), inside, contents, box_slot)
+                    } else {
+                        self.handle_block_level_element(style.clone(), inside, contents, box_slot)
+                    }
+                }
+            },
+        }
+    }
+
+    fn handle_text(&mut self, input: &str, parent_style: &Arc<ComputedValues>) {
+        let (leading_whitespace, mut input) = self.handle_leading_whitespace(input);
+        if leading_whitespace || !input.is_empty() {
+            // This text node should be pushed either to the next ongoing
+            // inline level box with the parent style of that inline level box
+            // that will be ended, or directly to the ongoing inline formatting
+            // context with the parent style of that builder.
+            let inlines = self.current_inline_level_boxes();
+
+            fn last_text(inlines: &mut [Arc<InlineLevelBox>]) -> Option<&mut String> {
+                let last = inlines.last_mut()?;
+                if let InlineLevelBox::TextRun(_) = &**last {
+                    // We never clone text run boxes, so the refcount is 1 and unwrap succeeds:
+                    let last = Arc::get_mut(last).unwrap();
+                    if let InlineLevelBox::TextRun(TextRun { text, .. }) = last {
+                        Some(text)
+                    } else {
+                        unreachable!()
+                    }
+                } else {
+                    None
+                }
+            }
+
+            let mut new_text_run_contents;
+            let output;
+            if let Some(text) = last_text(inlines) {
+                // Append to the existing text run
+                new_text_run_contents = None;
+                output = text;
+            } else {
+                new_text_run_contents = Some(String::new());
+                output = new_text_run_contents.as_mut().unwrap();
+            }
+
+            if leading_whitespace {
+                output.push(' ')
+            }
+            loop {
+                if let Some(i) = input.bytes().position(|b| b.is_ascii_whitespace()) {
+                    let (non_whitespace, rest) = input.split_at(i);
+                    output.push_str(non_whitespace);
+                    output.push(' ');
+                    if let Some(i) = rest.bytes().position(|b| !b.is_ascii_whitespace()) {
+                        input = &rest[i..];
+                    } else {
+                        break;
+                    }
+                } else {
+                    output.push_str(input);
+                    break;
+                }
+            }
+
+            if let Some(text) = new_text_run_contents {
+                let parent_style = parent_style.clone();
+                inlines.push(Arc::new(InlineLevelBox::TextRun(TextRun {
+                    parent_style,
+                    text,
+                })))
+            }
+        }
+    }
+}
+
+impl<'a> BlockContainerBuilder<'a> {
+    /// Returns:
+    ///
+    /// * Whether this text run has preserved (non-collapsible) leading whitespace
+    /// * The contents starting at the first non-whitespace character (or the empty string)
+    fn handle_leading_whitespace<'text>(&mut self, text: &'text str) -> (bool, &'text str) {
+        // FIXME: this is only an approximation of
+        // https://drafts.csswg.org/css2/text.html#white-space-model
+        if !text.starts_with(|c: char| c.is_ascii_whitespace()) {
+            return (false, text);
+        }
+        let mut inline_level_boxes = self.current_inline_level_boxes().iter().rev();
+        let mut stack = Vec::new();
+        let preserved = loop {
+            match inline_level_boxes.next().map(|b| &**b) {
+                Some(InlineLevelBox::TextRun(r)) => break !r.text.ends_with(' '),
+                Some(InlineLevelBox::Atomic { .. }) => break false,
+                Some(InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(_))
+                | Some(InlineLevelBox::OutOfFlowFloatBox(_)) => {}
+                Some(InlineLevelBox::InlineBox(b)) => {
+                    stack.push(inline_level_boxes);
+                    inline_level_boxes = b.children.iter().rev()
+                }
+                None => {
+                    if let Some(iter) = stack.pop() {
+                        inline_level_boxes = iter
+                    } else {
+                        break false; // Paragraph start
+                    }
+                }
+            }
+        };
+        let text = text.trim_start_matches(|c: char| c.is_ascii_whitespace());
+        (preserved, text)
+    }
+
+    fn handle_inline_level_element(
+        &mut self,
+        style: &Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+    ) -> Arc<InlineLevelBox> {
+        let box_ = match contents.try_into() {
+            Err(replaced) => Arc::new(InlineLevelBox::Atomic {
+                style: style.clone(),
+                contents: replaced,
+            }),
+            Ok(non_replaced) => match display_inside {
+                DisplayInside::Flow => {
+                    // Whatever happened before, we just found an inline level element, so
+                    // all we need to do is to remember this ongoing inline level box.
+                    self.ongoing_inline_boxes_stack.push(InlineBox {
+                        style: style.clone(),
+                        first_fragment: true,
+                        last_fragment: false,
+                        children: vec![],
+                    });
+
+                    NonReplacedContents::traverse(non_replaced, &style, self.context, self);
+
+                    let mut inline_box = self
+                        .ongoing_inline_boxes_stack
+                        .pop()
+                        .expect("no ongoing inline level box found");
+                    inline_box.last_fragment = true;
+                    Arc::new(InlineLevelBox::InlineBox(inline_box))
+                }
+                DisplayInside::FlowRoot => {
+                    // a.k.a. `inline-block`
+                    unimplemented!()
+                }
+            },
+        };
+        self.current_inline_level_boxes().push(box_.clone());
+        box_
+    }
+
+    fn handle_block_level_element(
+        &mut self,
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+        box_slot: BoxSlot<'a>,
+    ) {
+        // We just found a block level element, all ongoing inline level boxes
+        // need to be split around it. We iterate on the fragmented inline
+        // level box stack to take their contents and set their first_fragment
+        // field to false, for the fragmented inline level boxes that will
+        // come after the block level element.
+        let mut fragmented_inline_boxes =
+            self.ongoing_inline_boxes_stack
+                .iter_mut()
+                .rev()
+                .map(|ongoing| {
+                    let fragmented = InlineBox {
+                        style: ongoing.style.clone(),
+                        first_fragment: ongoing.first_fragment,
+                        // The fragmented boxes before the block level element
+                        // are obviously not the last fragment.
+                        last_fragment: false,
+                        children: take(&mut ongoing.children),
+                    };
+                    ongoing.first_fragment = false;
+                    fragmented
+                });
+
+        if let Some(last) = fragmented_inline_boxes.next() {
+            // There were indeed some ongoing inline level boxes before
+            // the block, we accumulate them as a single inline level box
+            // to be pushed to the ongoing inline formatting context.
+            let mut fragmented_inline = InlineLevelBox::InlineBox(last);
+            for mut fragmented_parent_inline_box in fragmented_inline_boxes {
+                fragmented_parent_inline_box
+                    .children
+                    .push(Arc::new(fragmented_inline));
+                fragmented_inline = InlineLevelBox::InlineBox(fragmented_parent_inline_box);
+            }
+
+            self.ongoing_inline_formatting_context
+                .inline_level_boxes
+                .push(Arc::new(fragmented_inline));
+        }
+
+        // We found a block level element, so the ongoing inline formatting
+        // context needs to be ended.
+        self.end_ongoing_inline_formatting_context();
+
+        let intermediate_box = match contents.try_into() {
+            Ok(contents) => match display_inside {
+                DisplayInside::Flow => IntermediateBlockLevelBox::SameFormattingContextBlock {
+                    style,
+                    contents: IntermediateBlockContainer::Deferred { contents },
+                },
+                _ => IntermediateBlockLevelBox::Independent {
+                    style,
+                    display_inside,
+                    contents: contents.into(),
+                },
+            },
+            Err(contents) => {
+                let contents = Contents::Replaced(contents);
+                IntermediateBlockLevelBox::Independent {
+                    style,
+                    display_inside,
+                    contents,
+                }
+            }
+        };
+        self.block_level_boxes.push((intermediate_box, box_slot))
+    }
+
+    fn handle_absolutely_positioned_element(
+        &mut self,
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+        box_slot: BoxSlot<'a>,
+    ) {
+        if !self.has_ongoing_inline_formatting_context() {
+            let box_ = IntermediateBlockLevelBox::OutOfFlowAbsolutelyPositionedBox {
+                style,
+                contents,
+                display_inside,
+            };
+            self.block_level_boxes.push((box_, box_slot))
+        } else {
+            let box_ = Arc::new(InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(
+                AbsolutelyPositionedBox {
+                    contents: IndependentFormattingContext::construct(
+                        self.context,
+                        &style,
+                        display_inside,
+                        contents,
+                    ),
+                    style,
+                },
+            ));
+            self.current_inline_level_boxes().push(box_.clone());
+            box_slot.set(LayoutBox::InlineLevel(box_))
+        }
+    }
+
+    fn handle_float_element(
+        &mut self,
+        style: Arc<ComputedValues>,
+        display_inside: DisplayInside,
+        contents: Contents,
+        box_slot: BoxSlot<'a>,
+    ) {
+        self.contains_floats = ContainsFloats::Yes;
+
+        if !self.has_ongoing_inline_formatting_context() {
+            let box_ = IntermediateBlockLevelBox::OutOfFlowFloatBox {
+                style,
+                contents,
+                display_inside,
+            };
+            self.block_level_boxes.push((box_, box_slot));
+        } else {
+            let box_ = Arc::new(InlineLevelBox::OutOfFlowFloatBox(FloatBox {
+                contents: IndependentFormattingContext::construct(
+                    self.context,
+                    &style,
+                    display_inside,
+                    contents,
+                ),
+                style,
+            }));
+            self.current_inline_level_boxes().push(box_.clone());
+            box_slot.set(LayoutBox::InlineLevel(box_))
+        }
+    }
+
+    fn end_ongoing_inline_formatting_context(&mut self) {
+        assert!(
+            self.ongoing_inline_boxes_stack.is_empty(),
+            "there should be no ongoing inline level boxes",
+        );
+
+        if self
+            .ongoing_inline_formatting_context
+            .inline_level_boxes
+            .is_empty()
+        {
+            // There should never be an empty inline formatting context.
+            return;
+        }
+
+        let block_container_style = self.block_container_style;
+        let anonymous_style = self.anonymous_style.get_or_insert_with(|| {
+            // If parent_style is None, the parent is the document node,
+            // in which case anonymous inline boxes should inherit their
+            // styles from initial values.
+            ComputedValues::anonymous_inheriting_from(Some(block_container_style))
+        });
+
+        let box_ = IntermediateBlockLevelBox::SameFormattingContextBlock {
+            style: anonymous_style.clone(),
+            contents: IntermediateBlockContainer::InlineFormattingContext(take(
+                &mut self.ongoing_inline_formatting_context,
+            )),
+        };
+        self.block_level_boxes.push((box_, BoxSlot::dummy()))
+    }
+
+    fn current_inline_level_boxes(&mut self) -> &mut Vec<Arc<InlineLevelBox>> {
+        match self.ongoing_inline_boxes_stack.last_mut() {
+            Some(last) => &mut last.children,
+            None => &mut self.ongoing_inline_formatting_context.inline_level_boxes,
+        }
+    }
+
+    fn has_ongoing_inline_formatting_context(&self) -> bool {
+        !self
+            .ongoing_inline_formatting_context
+            .inline_level_boxes
+            .is_empty()
+            || !self.ongoing_inline_boxes_stack.is_empty()
+    }
+}
+
+impl IntermediateBlockLevelBox {
+    fn finish(self, context: &Context) -> (Arc<BlockLevelBox>, ContainsFloats) {
+        match self {
+            IntermediateBlockLevelBox::SameFormattingContextBlock { style, contents } => {
+                let (contents, contains_floats) = contents.finish(context, &style);
+                let block_level_box =
+                    Arc::new(BlockLevelBox::SameFormattingContextBlock { contents, style });
+                (block_level_box, contains_floats)
+            }
+            IntermediateBlockLevelBox::Independent {
+                style,
+                display_inside,
+                contents,
+            } => {
+                let contents = IndependentFormattingContext::construct(
+                    context,
+                    &style,
+                    display_inside,
+                    contents,
+                );
+                (
+                    Arc::new(BlockLevelBox::Independent { style, contents }),
+                    ContainsFloats::No,
+                )
+            }
+            IntermediateBlockLevelBox::OutOfFlowAbsolutelyPositionedBox {
+                style,
+                display_inside,
+                contents,
+            } => {
+                let block_level_box = Arc::new(BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(
+                    AbsolutelyPositionedBox {
+                        contents: IndependentFormattingContext::construct(
+                            context,
+                            &style,
+                            display_inside,
+                            contents,
+                        ),
+                        style: style,
+                    },
+                ));
+                (block_level_box, ContainsFloats::No)
+            }
+            IntermediateBlockLevelBox::OutOfFlowFloatBox {
+                style,
+                display_inside,
+                contents,
+            } => {
+                let contents = IndependentFormattingContext::construct(
+                    context,
+                    &style,
+                    display_inside,
+                    contents,
+                );
+                let block_level_box = Arc::new(BlockLevelBox::OutOfFlowFloatBox(FloatBox {
+                    contents,
+                    style,
+                }));
+                (block_level_box, ContainsFloats::Yes)
+            }
+        }
+    }
+}
+
+impl IntermediateBlockContainer {
+    fn finish(
+        self,
+        context: &Context,
+        style: &Arc<ComputedValues>,
+    ) -> (BlockContainer, ContainsFloats) {
+        match self {
+            IntermediateBlockContainer::Deferred { contents } => {
+                BlockContainer::construct(context, style, contents)
+            }
+            IntermediateBlockContainer::InlineFormattingContext(ifc) => {
+                // If that inline formatting context contained any float, those
+                // were already taken into account during the first phase of
+                // box construction.
+                (
+                    BlockContainer::InlineFormattingContext(ifc),
+                    ContainsFloats::No,
+                )
+            }
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(in crate::layout) enum ContainsFloats {
+    No,
+    Yes,
+}
+
+impl std::ops::BitOrAssign for ContainsFloats {
+    fn bitor_assign(&mut self, other: Self) {
+        if other == ContainsFloats::Yes {
+            *self = ContainsFloats::Yes;
+        }
+    }
+}
+
+impl Default for ContainsFloats {
+    fn default() -> Self {
+        ContainsFloats::No
+    }
+}