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Refactor inline layout nesting (#30289)

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This makes the nesting architecture of inline layout a lot simpler. Now
PartialInlineBoxFragment and InlineNestingLevelState are replaced by
two structs:

 - InlineContainerState
 - InlineBoxContainerState

InlineContainerState holds state for the root of the inline formatting
context, while InlineBoxContainerState holds state for inline boxes.
InlineBoxContainerState has an InlineContainerState as the first
element, thus "extends" it.

Now the inline iterators are stack variables directly in the `layout()`
method. They are no longer stored in the state. This avoids the weird
nesting of state and instead relies on a normal vector to hold the
stack of state.

Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>
This commit is contained in:
Martin Robinson 2023-09-05 19:12:15 +02:00 • committed by GitHub
parent 8a011a4487
commit 577baea223
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1 changed files with 206 additions and 140 deletions
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346
components/layout_2020/flow/inline.rs
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@ -87,33 +87,6 @@ pub(crate) struct TextRun {
pub has_uncollapsible_content: bool,
}
struct InlineNestingLevelState<'box_tree> {
remaining_boxes: InlineBoxChildIter<'box_tree>,
line_items_so_far: Vec<LineItem>,
/// Whether or not we have processed any content (an atomic element or text) for
/// this inline box on the current line OR any previous line.
has_content: bool,
/// Indicates whether this nesting level have text decorations in effect.
/// From https://drafts.csswg.org/css-text-decor/#line-decoration
// "When specified on or propagated to a block container that establishes
// an IFC..."
text_decoration_line: TextDecorationLine,
}
struct PartialInlineBoxFragment<'box_tree> {
base_fragment_info: BaseFragmentInfo,
style: Arc<ComputedValues>,
pbm: PaddingBorderMargin,
/// Whether or not this inline box has already been part of a previous line.
/// We need to create at least one Fragment for every inline box, but on following
/// lines, if the inline box is totally empty (such as after a preserved line
/// break), then we don't want to create empty Fragments for it.
was_part_of_previous_line: bool,
parent_nesting_level: InlineNestingLevelState<'box_tree>,
}
/// Information about the current line under construction for a particular
/// [`InlineFormattingContextState`]. This tracks position and size information while
/// [`LineItem`]s are collected and is used as input when those [`LineItem`]s are
@ -182,7 +155,44 @@ impl LineUnderConstruction {
}
}
struct InlineFormattingContextState<'box_tree, 'a, 'b> {
struct InlineContainerState {
/// The [`LineItems`]s we have collected so far for this nesting level for
/// the current line.
line_items_so_far: Vec<LineItem>,
/// Whether or not we have processed any content (an atomic element or text) for
/// this inline box on the current line OR any previous line.
has_content: bool,
/// Indicates whether this nesting level have text decorations in effect.
/// From https://drafts.csswg.org/css-text-decor/#line-decoration
// "When specified on or propagated to a block container that establishes
// an IFC..."
text_decoration_line: TextDecorationLine,
}
struct InlineBoxContainerState {
/// The container state common to both [`InlineBox`] and the root of the
/// [`InlineFormattingContext`].
base: InlineContainerState,
/// The style of this inline box.
style: Arc<ComputedValues>,
/// The [`BaseFragmentInfo`] of the [`InlineBox`] that this state tracks.
base_fragment_info: BaseFragmentInfo,
/// The [`PaddingBorderMargin`] of the [`InlineBox`] that this state tracks.
pbm: PaddingBorderMargin,
/// Whether or not this inline box has already been part of a previous line.
/// We need to create at least one Fragment for every inline box, but on following
/// lines, if the inline box is totally empty (such as after a preserved line
/// break), then we don't want to create empty Fragments for it.
was_part_of_previous_line: bool,
}
struct InlineFormattingContextState<'a, 'b> {
positioning_context: &'a mut PositioningContext,
containing_block: &'b ContainingBlock<'b>,
sequential_layout_state: Option<&'a mut SequentialLayoutState>,
@ -205,11 +215,17 @@ struct InlineFormattingContextState<'box_tree, 'a, 'b> {
/// common ancestor is used.
white_space: WhiteSpace,
partial_inline_boxes_stack: Vec<PartialInlineBoxFragment<'box_tree>>,
current_nesting_level: InlineNestingLevelState<'box_tree>,
/// The [`InlineContainerState`] for the container formed by the root of the
/// [`InlineFormattingContext`].
root_nesting_level: InlineContainerState,
/// A stack of [`InlineBoxContainerState`] that is used to produce [`LineItem`]s either when we
/// reach the end of an inline box or when we reach the end of a line. Only at the end
/// of the inline box is the state popped from the stack.
inline_box_state_stack: Vec<InlineBoxContainerState>,
}
impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
impl<'a, 'b> InlineFormattingContextState<'a, 'b> {
/// Push a completed [LineItem] to the current nesteding level of this
/// [InlineFormattingContext].
fn push_line_item(
@ -225,42 +241,102 @@ impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
.block_size
.max_assign(line_item.block_size());
self.current_nesting_level.line_items_so_far.push(line_item);
self.current_nesting_level.has_content = true;
let current_nesting_level = self.current_inline_container_state_mut();
current_nesting_level.line_items_so_far.push(line_item);
current_nesting_level.has_content = true;
self.propagate_current_nesting_level_white_space_style();
}
fn current_inline_container_state(&self) -> &InlineContainerState {
match self.inline_box_state_stack.last() {
Some(inline_box_state) => &inline_box_state.base,
None => &self.root_nesting_level,
}
}
fn current_inline_container_state_mut(&mut self) -> &mut InlineContainerState {
match self.inline_box_state_stack.last_mut() {
Some(inline_box_state) => &mut inline_box_state.base,
None => &mut self.root_nesting_level,
}
}
fn propagate_current_nesting_level_white_space_style(&mut self) {
let style = match self.partial_inline_boxes_stack.last() {
Some(partial) => &partial.style,
let style = match self.inline_box_state_stack.last() {
Some(inline_box_state) => &inline_box_state.style,
None => self.containing_block.style,
};
self.white_space = style.get_inherited_text().white_space;
}
/// Finish layout of all the partial inline boxes in the current line,
/// finish current line and start a new one.
fn finish_line_and_reset(&mut self, layout_context: &LayoutContext) {
let mut nesting_level = &mut self.current_nesting_level;
for partial in self.partial_inline_boxes_stack.iter_mut().rev() {
partial.finish_layout(
nesting_level,
/// Start laying out a particular [`InlineBox`] into line items. This will push
/// a new [`InlineBoxContainerState`] onto [`Self::inline_box_state_stack`].
fn start_inline_box(&mut self, inline_box: &InlineBox) {
let text_decoration_of_parent = self.current_inline_container_state().text_decoration_line;
self.inline_box_state_stack
.push(InlineBoxContainerState::new(
inline_box,
&mut self.current_line.inline_position,
false, /* at_end_of_inline_element */
);
nesting_level = &mut partial.parent_nesting_level;
}
let line_items = std::mem::take(&mut nesting_level.line_items_so_far);
self.finish_current_line(layout_context, line_items, self.containing_block);
&self.containing_block,
text_decoration_of_parent,
));
}
fn finish_current_line(
&mut self,
layout_context: &LayoutContext,
mut line_items: Vec<LineItem>,
containing_block: &ContainingBlock,
) {
/// Finish laying out a particular [`InlineBox`] into line items. This will add the
/// final [`InlineBoxLineItem`] to the state and pop its state off of
/// [`Self::inline_box_state_stack`].
fn finish_inline_box(&mut self) {
let mut inline_box_state = match self.inline_box_state_stack.pop() {
Some(inline_box_state) => inline_box_state,
None => return, // We are at the root.
};
// We reached the end of the remaining boxes in this nesting level, so we finish it and
// start working on the parent nesting level again.
let line_item = inline_box_state.layout_into_line_item(
&mut self.current_line.inline_position,
true, /* at_end_of_inline_element */
);
self.current_inline_container_state_mut()
.line_items_so_far
.push(LineItem::InlineBox(line_item));
// If the inline box that we just finished had any content at all, we want to propagate
// the `white-space` property of its parent to future inline children. This is because
// when a soft wrap opportunity is defined by the boundary between two elements, the
// `white-space` used is that of their nearest common ancestor.
if inline_box_state.base.has_content {
self.propagate_current_nesting_level_white_space_style();
}
}
/// Finish layout of all inline boxes for the current line. This will gather all
/// [`LineItem`]s and turn them into [`Fragment`]s, then reset the
/// [`InlineFormattingContextState`] preparing it for laying out a new line.
fn finish_current_line_and_reset(&mut self, layout_context: &LayoutContext) {
let mut line_item_from_child = None;
for inline_box_state in self.inline_box_state_stack.iter_mut().rev() {
if let Some(line_item_from_child) = line_item_from_child {
inline_box_state
.base
.line_items_so_far
.push(LineItem::InlineBox(line_item_from_child));
}
line_item_from_child = Some(
inline_box_state
.layout_into_line_item(&mut self.current_line.inline_position, false),
);
}
if let Some(line_item_from_child) = line_item_from_child {
self.root_nesting_level
.line_items_so_far
.push(LineItem::InlineBox(line_item_from_child));
}
let mut line_items = std::mem::take(&mut self.root_nesting_level.line_items_so_far);
// From <https://www.w3.org/TR/css-text-3/#white-space-phase-2>:
// > 3. A sequence of collapsible spaces at the end of a line is removed,
// > as well as any trailing U+1680   OGHAM SPACE MARK whose white-space
@ -273,7 +349,7 @@ impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
}
let inline_start_position =
self.calculate_inline_start_for_current_line(containing_block, whitespace_trimmed);
self.calculate_inline_start_for_current_line(self.containing_block, whitespace_trimmed);
let block_start_position = self
.current_line
.line_block_start_considering_placement_among_floats();
@ -294,7 +370,7 @@ impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
inline_position: inline_start_position,
max_block_size: Length::zero(),
inline_start_of_parent: Length::zero(),
ifc_containing_block: containing_block,
ifc_containing_block: self.containing_block,
positioning_context: &mut self.positioning_context,
line_block_start: block_start_position,
};
@ -303,7 +379,7 @@ impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
let fragments = layout_line_items(line_items, layout_context, &mut state);
let size = Vec2 {
inline: containing_block.inline_size,
inline: self.containing_block.inline_size,
block: state.max_block_size,
};
@ -329,7 +405,7 @@ impl<'box_tree, 'a, 'b> InlineFormattingContextState<'box_tree, 'a, 'b> {
.push(Fragment::Anonymous(AnonymousFragment::new(
Rect { start_corner, size },
fragments,
containing_block.style.writing_mode,
self.containing_block.style.writing_mode,
)));
}
@ -722,13 +798,12 @@ impl InlineFormattingContext {
}),
white_space: containing_block.style.get_inherited_text().white_space,
linebreaker: None,
partial_inline_boxes_stack: Vec::new(),
current_nesting_level: InlineNestingLevelState {
remaining_boxes: InlineBoxChildIter::from_formatting_context(self),
root_nesting_level: InlineContainerState {
line_items_so_far: Vec::with_capacity(self.inline_level_boxes.len()),
has_content: false,
text_decoration_line: self.text_decoration_line,
},
inline_box_state_stack: Vec::new(),
};
// FIXME(pcwalton): This assumes that margins never collapse through inline formatting
@ -739,13 +814,15 @@ impl InlineFormattingContext {
// FIXME(mrobinson): Collapse margins in the containing block offsets as well??
}
let mut iterator = InlineBoxChildIter::from_formatting_context(self);
let mut parent_iterators = Vec::new();
loop {
if let Some(child) = ifc.current_nesting_level.remaining_boxes.next() {
match &mut *child.borrow_mut() {
InlineLevelBox::InlineBox(inline) => {
let partial =
PartialInlineBoxFragment::new(inline, child.clone(), &mut ifc);
ifc.partial_inline_boxes_stack.push(partial);
match iterator.next() {
Some(child) => match &mut *child.borrow_mut() {
InlineLevelBox::InlineBox(inline_box) => {
ifc.start_inline_box(inline_box);
parent_iterators.push(iterator);
iterator = InlineBoxChildIter::from_inline_level_box(child.clone());
},
InlineLevelBox::TextRun(run) => {
run.layout_into_line_items(layout_context, &mut ifc)
@ -754,43 +831,36 @@ impl InlineFormattingContext {
atomic_formatting_context.layout_into_line_items(layout_context, &mut ifc);
},
InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
ifc.current_nesting_level.line_items_so_far.push(
LineItem::AbsolutelyPositioned(AbsolutelyPositionedLineItem {
absolutely_positioned_box: box_.clone(),
}),
);
ifc.current_inline_container_state_mut()
.line_items_so_far
.push(LineItem::AbsolutelyPositioned(
AbsolutelyPositionedLineItem {
absolutely_positioned_box: box_.clone(),
},
));
},
InlineLevelBox::OutOfFlowFloatBox(float_box) => {
float_box.layout_into_line_items(layout_context, &mut ifc);
},
}
} else if let Some(mut partial) = ifc.partial_inline_boxes_stack.pop() {
// We reached the end of the remaining boxes in this nesting level, so we finish it and
// start working on the parent nesting level again.
partial.finish_layout(
&mut ifc.current_nesting_level,
&mut ifc.current_line.inline_position,
true, /* at_end_of_inline_element */
);
let had_content = ifc.current_nesting_level.has_content;
ifc.current_nesting_level = partial.parent_nesting_level;
// If the inline box that we just finished had any content at all, we want to propagate
// the `white-space` property of its parent to future inline children. This is because
// when a soft wrap opportunity is defined by the boundary between two elements, the
// `white-space` used is that of their nearest common ancestor.
if had_content {
ifc.propagate_current_nesting_level_white_space_style();
}
} else {
// We reached the end of the entire IFC.
break;
},
None => {
match parent_iterators.pop() {
// If we have a parent iterator, then we are working on an
// InlineBox and we just finished it.
Some(parent_iterator) => {
ifc.finish_inline_box();
iterator = parent_iterator;
continue;
},
// If we have no more parents, we are at the end of the root
// iterator ie at the end of this InlineFormattingContext.
None => break,
};
},
}
}
let line_items = std::mem::take(&mut ifc.current_nesting_level.line_items_so_far);
ifc.finish_current_line(layout_context, line_items, containing_block);
ifc.finish_current_line_and_reset(layout_context);
let mut collapsible_margins_in_children = CollapsedBlockMargins::zero();
let content_block_size = ifc.current_line.start_position.block;
@ -828,73 +898,65 @@ impl InlineFormattingContext {
}
}
impl<'box_tree> PartialInlineBoxFragment<'box_tree> {
impl InlineBoxContainerState {
fn new(
inline_box: &InlineBox,
this_inline_level_box: ArcRefCell<InlineLevelBox>,
ifc: &mut InlineFormattingContextState<'box_tree, '_, '_>,
) -> PartialInlineBoxFragment<'box_tree> {
inline_position: &mut Length,
containing_block: &ContainingBlock,
text_decoration_of_parent: TextDecorationLine,
) -> Self {
let style = inline_box.style.clone();
let mut pbm = style.padding_border_margin(&ifc.containing_block);
let mut pbm = style.padding_border_margin(containing_block);
if inline_box.first_fragment {
ifc.current_line.inline_position += pbm.padding.inline_start +
*inline_position += pbm.padding.inline_start +
pbm.border.inline_start +
pbm.margin.inline_start.auto_is(Length::zero)
pbm.margin.inline_start.auto_is(Length::zero);
} else {
pbm.padding.inline_start = Length::zero();
pbm.border.inline_start = Length::zero();
pbm.margin.inline_start = LengthOrAuto::zero();
}
let text_decoration_line =
ifc.current_nesting_level.text_decoration_line | style.clone_text_decoration_line();
PartialInlineBoxFragment {
base_fragment_info: inline_box.base_fragment_info,
let text_decoration_line = text_decoration_of_parent | style.clone_text_decoration_line();
Self {
base: InlineContainerState {
line_items_so_far: Vec::with_capacity(inline_box.children.len()),
has_content: false,
text_decoration_line,
},
style,
base_fragment_info: inline_box.base_fragment_info,
pbm,
was_part_of_previous_line: false,
parent_nesting_level: std::mem::replace(
&mut ifc.current_nesting_level,
InlineNestingLevelState {
remaining_boxes: InlineBoxChildIter::from_inline_level_box(
this_inline_level_box,
),
line_items_so_far: Vec::with_capacity(inline_box.children.len()),
has_content: false,
text_decoration_line: text_decoration_line,
},
),
}
}
fn finish_layout(
fn layout_into_line_item(
&mut self,
nesting_level: &mut InlineNestingLevelState,
inline_position: &mut Length,
at_end_of_inline_element: bool,
) {
) -> InlineBoxLineItem {
// If we are finishing in order to fragment this InlineBox into multiple lines, do
// not add end margins, borders, and padding.
let mut pbm = self.pbm.clone();
if !at_end_of_inline_element {
self.pbm.padding.inline_end = Length::zero();
self.pbm.border.inline_end = Length::zero();
self.pbm.margin.inline_end = LengthOrAuto::zero();
pbm.padding.inline_end = Length::zero();
pbm.border.inline_end = Length::zero();
pbm.margin.inline_end = LengthOrAuto::zero();
} else {
*inline_position += self.pbm.padding.inline_end +
self.pbm.border.inline_end +
self.pbm.margin.inline_end.auto_is(Length::zero)
}
self.parent_nesting_level
.line_items_so_far
.push(LineItem::InlineBox(InlineBoxLineItem {
base_fragment_info: self.base_fragment_info,
style: self.style.clone(),
pbm: self.pbm.clone(),
children: std::mem::take(&mut nesting_level.line_items_so_far),
always_make_fragment: !self.was_part_of_previous_line,
}));
let new_line_item = InlineBoxLineItem {
base_fragment_info: self.base_fragment_info,
style: self.style.clone(),
pbm,
children: std::mem::take(&mut self.base.line_items_so_far),
always_make_fragment: !self.was_part_of_previous_line,
};
// This InlineBox now has at least one Fragment that corresponds to it, so
// if subsequent lines can ignore it if it is empty on those lines.
@ -905,6 +967,8 @@ impl<'box_tree> PartialInlineBoxFragment<'box_tree> {
self.pbm.padding.inline_start = Length::zero();
self.pbm.border.inline_start = Length::zero();
self.pbm.margin.inline_start = LengthOrAuto::zero();
new_line_item
}
}
@ -1037,7 +1101,7 @@ impl IndependentFormattingContext {
};
if ifc.new_potential_line_size_causes_line_break(&new_potential_line_size) {
ifc.finish_line_and_reset(layout_context);
ifc.finish_current_line_and_reset(layout_context);
}
ifc.push_line_item(
@ -1174,7 +1238,9 @@ impl TextRun {
parent_style: self.parent_style.clone(),
font_metrics,
font_key,
text_decoration_line: ifc.current_nesting_level.text_decoration_line,
text_decoration_line: ifc
.current_inline_container_state()
.text_decoration_line,
}),
Length::from(last_whitespace_advance),
);
@ -1200,7 +1266,7 @@ impl TextRun {
advance_from_text_run,
true,
);
ifc.finish_line_and_reset(layout_context);
ifc.finish_current_line_and_reset(layout_context);
advance_from_text_run = Length::zero();
continue;
}
@ -1230,7 +1296,7 @@ impl TextRun {
advance_from_text_run,
true,
);
ifc.finish_line_and_reset(layout_context);
ifc.finish_current_line_and_reset(layout_context);
advance_from_text_run = Length::zero();
}
@ -1313,7 +1379,7 @@ impl FloatBox {
.replace_placement_among_floats(new_placement);
}
ifc.current_nesting_level
ifc.current_inline_container_state_mut()
.line_items_so_far
.push(LineItem::Float(FloatLineItem {
fragment,