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Diffstat (limited to 'components/layout_2020/flow/inline/construct.rs')
| -rw-r--r-- | components/layout_2020/flow/inline/construct.rs | 610 |
1 files changed, 610 insertions, 0 deletions
diff --git a/components/layout_2020/flow/inline/construct.rs b/components/layout_2020/flow/inline/construct.rs new file mode 100644 index 00000000000..b88b5014f01 --- /dev/null +++ b/components/layout_2020/flow/inline/construct.rs @@ -0,0 +1,610 @@ +/* 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 std::borrow::Cow; +use std::char::{ToLowercase, ToUppercase}; + +use style::computed_values::white_space_collapse::T as WhiteSpaceCollapse; +use style::values::computed::{TextDecorationLine, TextTransform}; +use style::values::specified::text::TextTransformCase; +use unicode_segmentation::UnicodeSegmentation; + +use super::text_run::TextRun; +use super::{InlineBox, InlineFormattingContext, InlineLevelBox}; +use crate::cell::ArcRefCell; +use crate::context::LayoutContext; +use crate::dom::NodeExt; +use crate::dom_traversal::NodeAndStyleInfo; +use crate::flow::float::FloatBox; +use crate::formatting_contexts::IndependentFormattingContext; +use crate::positioned::AbsolutelyPositionedBox; + +#[derive(Default)] +pub(crate) struct InlineFormattingContextBuilder { + pub text_segments: Vec<String>, + current_text_offset: usize, + + /// Whether the last processed node ended with whitespace. This is used to + /// implement rule 4 of <https://www.w3.org/TR/css-text-3/#collapse>: + /// + /// > Any collapsible space immediately following another collapsible space—even one + /// > outside the boundary of the inline containing that space, provided both spaces are + /// > within the same inline formatting context—is collapsed to have zero advance width. + /// > (It is invisible, but retains its soft wrap opportunity, if any.) + last_inline_box_ended_with_collapsible_white_space: bool, + + /// Whether or not the current state of the inline formatting context is on a word boundary + /// for the purposes of `text-transform: capitalize`. + on_word_boundary: bool, + + /// Whether or not this inline formatting context will contain floats. + pub contains_floats: bool, + + /// Inline elements are direct descendants of the element that establishes + /// the inline formatting context that this builder builds. + pub root_inline_boxes: Vec<ArcRefCell<InlineLevelBox>>, + + /// Whether or not the inline formatting context under construction has any + /// uncollapsible text content. + pub has_uncollapsible_text_content: bool, + + /// 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`). + /// + /// When an inline box ends, it's removed from this stack and added to + /// [`Self::root_inline_boxes`]. + inline_box_stack: Vec<InlineBox>, +} + +impl InlineFormattingContextBuilder { + pub(crate) fn new() -> Self { + // For the purposes of `text-transform: capitalize` the start of the IFC is a word boundary. + Self { + on_word_boundary: true, + ..Default::default() + } + } + + pub(crate) fn currently_processing_inline_box(&self) -> bool { + !self.inline_box_stack.is_empty() + } + + /// Return true if this [`InlineFormattingContextBuilder`] is empty for the purposes of ignoring + /// during box tree construction. An IFC is empty if it only contains TextRuns with + /// completely collapsible whitespace. When that happens it can be ignored completely. + pub(crate) fn is_empty(&self) -> bool { + if self.has_uncollapsible_text_content { + return false; + } + + if !self.inline_box_stack.is_empty() { + return false; + } + + fn inline_level_boxes_are_empty(boxes: &[ArcRefCell<InlineLevelBox>]) -> bool { + boxes + .iter() + .all(|inline_level_box| inline_level_box_is_empty(&inline_level_box.borrow())) + } + + fn inline_level_box_is_empty(inline_level_box: &InlineLevelBox) -> bool { + match inline_level_box { + InlineLevelBox::InlineBox(_) => false, + // Text content is handled by `self.has_uncollapsible_text` content above in order + // to avoid having to iterate through the character once again. + InlineLevelBox::TextRun(_) => true, + InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(_) => false, + InlineLevelBox::OutOfFlowFloatBox(_) => false, + InlineLevelBox::Atomic(_) => false, + } + } + + inline_level_boxes_are_empty(&self.root_inline_boxes) + } + + // Retrieves the mutable reference of inline boxes either from the last + // element of a stack or directly from the formatting context, depending on the situation. + fn current_inline_level_boxes(&mut self) -> &mut Vec<ArcRefCell<InlineLevelBox>> { + match self.inline_box_stack.last_mut() { + Some(last) => &mut last.children, + None => &mut self.root_inline_boxes, + } + } + + pub(crate) fn push_atomic( + &mut self, + independent_formatting_context: IndependentFormattingContext, + ) -> ArcRefCell<InlineLevelBox> { + let inline_level_box = + ArcRefCell::new(InlineLevelBox::Atomic(independent_formatting_context)); + self.current_inline_level_boxes() + .push(inline_level_box.clone()); + self.last_inline_box_ended_with_collapsible_white_space = false; + self.on_word_boundary = true; + inline_level_box + } + + pub(crate) fn push_absolutely_positioned_box( + &mut self, + absolutely_positioned_box: AbsolutelyPositionedBox, + ) -> ArcRefCell<InlineLevelBox> { + let absolutely_positioned_box = ArcRefCell::new(absolutely_positioned_box); + let inline_level_box = ArcRefCell::new(InlineLevelBox::OutOfFlowAbsolutelyPositionedBox( + absolutely_positioned_box, + )); + self.current_inline_level_boxes() + .push(inline_level_box.clone()); + inline_level_box + } + + pub(crate) fn push_float_box(&mut self, float_box: FloatBox) -> ArcRefCell<InlineLevelBox> { + let inline_level_box = ArcRefCell::new(InlineLevelBox::OutOfFlowFloatBox(float_box)); + self.current_inline_level_boxes() + .push(inline_level_box.clone()); + self.contains_floats = true; + inline_level_box + } + + pub(crate) fn start_inline_box<'dom, Node: NodeExt<'dom>>( + &mut self, + info: &NodeAndStyleInfo<Node>, + ) { + self.inline_box_stack.push(InlineBox::new(info)) + } + + pub(crate) fn end_inline_box(&mut self) -> ArcRefCell<InlineLevelBox> { + self.end_inline_box_internal(true) + } + + fn end_inline_box_internal(&mut self, is_last_fragment: bool) -> ArcRefCell<InlineLevelBox> { + let mut inline_box = self + .inline_box_stack + .pop() + .expect("no ongoing inline level box found"); + + if is_last_fragment { + inline_box.is_last_fragment = true; + } + + let inline_box = ArcRefCell::new(InlineLevelBox::InlineBox(inline_box)); + self.current_inline_level_boxes().push(inline_box.clone()); + + inline_box + } + + pub(crate) fn push_text<'dom, Node: NodeExt<'dom>>( + &mut self, + text: Cow<'dom, str>, + info: &NodeAndStyleInfo<Node>, + ) { + let white_space_collapse = info.style.clone_white_space_collapse(); + let collapsed = WhitespaceCollapse::new( + text.chars(), + white_space_collapse, + self.last_inline_box_ended_with_collapsible_white_space, + ); + + let text_transform = info.style.clone_text_transform(); + let capitalized_text: String; + let char_iterator: Box<dyn Iterator<Item = char>> = + if text_transform.case_ == TextTransformCase::Capitalize { + // `TextTransformation` doesn't support capitalization, so we must capitalize the whole + // string at once and make a copy. Here `on_word_boundary` indicates whether or not the + // inline formatting context as a whole is on a word boundary. This is different from + // `last_inline_box_ended_with_collapsible_white_space` because the word boundaries are + // between atomic inlines and at the start of the IFC, and because preserved spaces + // are a word boundary. + let collapsed_string: String = collapsed.collect(); + capitalized_text = capitalize_string(&collapsed_string, self.on_word_boundary); + Box::new(capitalized_text.chars()) + } else if !text_transform.is_none() { + // If `text-transform` is active, wrap the `WhitespaceCollapse` iterator in + // a `TextTransformation` iterator. + Box::new(TextTransformation::new(collapsed, text_transform)) + } else { + Box::new(collapsed) + }; + + let white_space_collapse = info.style.clone_white_space_collapse(); + let new_text: String = char_iterator + .map(|character| { + self.has_uncollapsible_text_content |= matches!( + white_space_collapse, + WhiteSpaceCollapse::Preserve | WhiteSpaceCollapse::BreakSpaces + ) || !character.is_ascii_whitespace() || + (character == '\n' && white_space_collapse != WhiteSpaceCollapse::Collapse); + character + }) + .collect(); + + if new_text.is_empty() { + return; + } + + if let Some(last_character) = new_text.chars().next_back() { + self.on_word_boundary = last_character.is_whitespace(); + self.last_inline_box_ended_with_collapsible_white_space = + self.on_word_boundary && white_space_collapse != WhiteSpaceCollapse::Preserve; + } + + let new_range = self.current_text_offset..self.current_text_offset + new_text.len(); + self.current_text_offset = new_range.end; + self.text_segments.push(new_text); + + let inlines = self.current_inline_level_boxes(); + if let Some(mut last_box) = inlines.last_mut().map(|last| last.borrow_mut()) { + if let InlineLevelBox::TextRun(ref mut text_run) = *last_box { + text_run.text_range.end = new_range.end; + return; + } + } + + inlines.push(ArcRefCell::new(InlineLevelBox::TextRun(TextRun::new( + info.into(), + info.style.clone(), + new_range, + )))); + } + + pub(crate) fn split_around_block_and_finish( + &mut self, + layout_context: &LayoutContext, + text_decoration_line: TextDecorationLine, + has_first_formatted_line: bool, + ) -> Option<InlineFormattingContext> { + if self.is_empty() { + return None; + } + + // Create a new inline builder which will be active after the block splits this inline formatting + // context. It has the same inline box structure as this builder, except the boxes are + // marked as not being the first fragment. No inline content is carried over to this new + // builder. + let mut inline_buidler_from_before_split = std::mem::replace( + self, + InlineFormattingContextBuilder { + on_word_boundary: true, + inline_box_stack: self + .inline_box_stack + .iter() + .map(|inline_box| inline_box.split_around_block()) + .collect(), + ..Default::default() + }, + ); + + // End all ongoing inline boxes in the first builder, but ensure that they are not + // marked as the final fragments, so that they do not get inline end margin, borders, + // and padding. + while !inline_buidler_from_before_split.inline_box_stack.is_empty() { + inline_buidler_from_before_split.end_inline_box_internal(false); + } + + inline_buidler_from_before_split.finish( + layout_context, + text_decoration_line, + has_first_formatted_line, + ) + } + + /// Finish the current inline formatting context, returning [`None`] if the context was empty. + pub(crate) fn finish( + &mut self, + layout_context: &LayoutContext, + text_decoration_line: TextDecorationLine, + has_first_formatted_line: bool, + ) -> Option<InlineFormattingContext> { + if self.is_empty() { + return None; + } + + let old_builder = std::mem::replace(self, InlineFormattingContextBuilder::new()); + assert!(old_builder.inline_box_stack.is_empty()); + + Some(InlineFormattingContext::new_with_builder( + old_builder, + layout_context, + text_decoration_line, + has_first_formatted_line, + )) + } +} + +fn preserve_segment_break() -> bool { + true +} + +pub struct WhitespaceCollapse<InputIterator> { + char_iterator: InputIterator, + white_space_collapse: WhiteSpaceCollapse, + + /// Whether or not we should collapse white space completely at the start of the string. + /// This is true when the last character handled in our owning [`super::InlineFormattingContext`] + /// was collapsible white space. + remove_collapsible_white_space_at_start: bool, + + /// Whether or not the last character produced was newline. There is special behavior + /// we do after each newline. + following_newline: bool, + + /// Whether or not we have seen any non-white space characters, indicating that we are not + /// in a collapsible white space section at the beginning of the string. + have_seen_non_white_space_characters: bool, + + /// Whether the last character that we processed was a non-newline white space character. When + /// collapsing white space we need to wait until the next non-white space character or the end + /// of the string to push a single white space. + inside_white_space: bool, + + /// When we enter a collapsible white space region, we may need to wait to produce a single + /// white space character as soon as we encounter a non-white space character. When that + /// happens we queue up the non-white space character for the next iterator call. + character_pending_to_return: Option<char>, +} + +impl<InputIterator> WhitespaceCollapse<InputIterator> { + pub fn new( + char_iterator: InputIterator, + white_space_collapse: WhiteSpaceCollapse, + trim_beginning_white_space: bool, + ) -> Self { + Self { + char_iterator, + white_space_collapse, + remove_collapsible_white_space_at_start: trim_beginning_white_space, + inside_white_space: false, + following_newline: false, + have_seen_non_white_space_characters: false, + character_pending_to_return: None, + } + } + + fn is_leading_trimmed_white_space(&self) -> bool { + !self.have_seen_non_white_space_characters && self.remove_collapsible_white_space_at_start + } + + /// Whether or not we need to produce a space character if the next character is not a newline + /// and not white space. This happens when we are exiting a section of white space and we + /// waited to produce a single space character for the entire section of white space (but + /// not following or preceding a newline). + fn need_to_produce_space_character_after_white_space(&self) -> bool { + self.inside_white_space && !self.following_newline && !self.is_leading_trimmed_white_space() + } +} + +impl<InputIterator> Iterator for WhitespaceCollapse<InputIterator> +where + InputIterator: Iterator<Item = char>, +{ + type Item = char; + + fn next(&mut self) -> Option<Self::Item> { + // Point 4.1.1 first bullet: + // > If white-space is set to normal, nowrap, or pre-line, whitespace + // > characters are considered collapsible + // If whitespace is not considered collapsible, it is preserved entirely, which + // means that we can simply return the input string exactly. + if self.white_space_collapse == WhiteSpaceCollapse::Preserve || + self.white_space_collapse == WhiteSpaceCollapse::BreakSpaces + { + // From <https://drafts.csswg.org/css-text-3/#white-space-processing>: + // > Carriage returns (U+000D) are treated identically to spaces (U+0020) in all respects. + // + // In the non-preserved case these are converted to space below. + return match self.char_iterator.next() { + Some('\r') => Some(' '), + next => next, + }; + } + + if let Some(character) = self.character_pending_to_return.take() { + self.inside_white_space = false; + self.have_seen_non_white_space_characters = true; + self.following_newline = false; + return Some(character); + } + + while let Some(character) = self.char_iterator.next() { + // Don't push non-newline whitespace immediately. Instead wait to push it until we + // know that it isn't followed by a newline. See `push_pending_whitespace_if_needed` + // above. + if character.is_ascii_whitespace() && character != '\n' { + self.inside_white_space = true; + continue; + } + + // Point 4.1.1: + // > 2. Collapsible segment breaks are transformed for rendering according to the + // > segment break transformation rules. + if character == '\n' { + // From <https://drafts.csswg.org/css-text-3/#line-break-transform> + // (4.1.3 -- the segment break transformation rules): + // + // > When white-space is pre, pre-wrap, or pre-line, segment breaks are not + // > collapsible and are instead transformed into a preserved line feed" + if self.white_space_collapse != WhiteSpaceCollapse::Collapse { + self.inside_white_space = false; + self.following_newline = true; + return Some(character); + + // Point 4.1.3: + // > 1. First, any collapsible segment break immediately following another + // > collapsible segment break is removed. + // > 2. Then any remaining segment break is either transformed into a space (U+0020) + // > or removed depending on the context before and after the break. + } else if !self.following_newline && + preserve_segment_break() && + !self.is_leading_trimmed_white_space() + { + self.inside_white_space = false; + self.following_newline = true; + return Some(' '); + } else { + self.following_newline = true; + continue; + } + } + + // Point 4.1.1: + // > 2. Any sequence of collapsible spaces and tabs immediately preceding or + // > following a segment break is removed. + // > 3. Every collapsible tab is converted to a collapsible space (U+0020). + // > 4. Any collapsible space immediately following another collapsible space—even + // > one outside the boundary of the inline containing that space, provided both + // > spaces are within the same inline formatting context—is collapsed to have zero + // > advance width. + if self.need_to_produce_space_character_after_white_space() { + self.inside_white_space = false; + self.character_pending_to_return = Some(character); + return Some(' '); + } + + self.inside_white_space = false; + self.have_seen_non_white_space_characters = true; + self.following_newline = false; + return Some(character); + } + + if self.need_to_produce_space_character_after_white_space() { + self.inside_white_space = false; + return Some(' '); + } + + None + } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.char_iterator.size_hint() + } + + fn count(self) -> usize + where + Self: Sized, + { + self.char_iterator.count() + } +} + +enum PendingCaseConversionResult { + Uppercase(ToUppercase), + Lowercase(ToLowercase), +} + +impl PendingCaseConversionResult { + fn next(&mut self) -> Option<char> { + match self { + PendingCaseConversionResult::Uppercase(to_uppercase) => to_uppercase.next(), + PendingCaseConversionResult::Lowercase(to_lowercase) => to_lowercase.next(), + } + } +} + +/// This is an interator that consumes a char iterator and produces character transformed +/// by the given CSS `text-transform` value. It currently does not support +/// `text-transform: capitalize` because Unicode segmentation libraries do not support +/// streaming input one character at a time. +pub struct TextTransformation<InputIterator> { + /// The input character iterator. + char_iterator: InputIterator, + /// The `text-transform` value to use. + text_transform: TextTransform, + /// If an uppercasing or lowercasing produces more than one character, this + /// caches them so that they can be returned in subsequent iterator calls. + pending_case_conversion_result: Option<PendingCaseConversionResult>, +} + +impl<InputIterator> TextTransformation<InputIterator> { + pub fn new(char_iterator: InputIterator, text_transform: TextTransform) -> Self { + Self { + char_iterator, + text_transform, + pending_case_conversion_result: None, + } + } +} + +impl<InputIterator> Iterator for TextTransformation<InputIterator> +where + InputIterator: Iterator<Item = char>, +{ + type Item = char; + + fn next(&mut self) -> Option<Self::Item> { + if let Some(character) = self + .pending_case_conversion_result + .as_mut() + .and_then(|result| result.next()) + { + return Some(character); + } + self.pending_case_conversion_result = None; + + for character in self.char_iterator.by_ref() { + match self.text_transform.case_ { + TextTransformCase::None => return Some(character), + TextTransformCase::Uppercase => { + let mut pending_result = + PendingCaseConversionResult::Uppercase(character.to_uppercase()); + if let Some(character) = pending_result.next() { + self.pending_case_conversion_result = Some(pending_result); + return Some(character); + } + }, + TextTransformCase::Lowercase => { + let mut pending_result = + PendingCaseConversionResult::Lowercase(character.to_lowercase()); + if let Some(character) = pending_result.next() { + self.pending_case_conversion_result = Some(pending_result); + return Some(character); + } + }, + // `text-transform: capitalize` currently cannot work on a per-character basis, + // so must be handled outside of this iterator. + // TODO: Add support for `full-width` and `full-size-kana`. + _ => return Some(character), + } + } + None + } +} + +/// Given a string and whether the start of the string represents a word boundary, create a copy of +/// the string with letters after word boundaries capitalized. +fn capitalize_string(string: &str, allow_word_at_start: bool) -> String { + let mut output_string = String::new(); + output_string.reserve(string.len()); + + let mut bounds = string.unicode_word_indices().peekable(); + let mut byte_index = 0; + for character in string.chars() { + let current_byte_index = byte_index; + byte_index += character.len_utf8(); + + if let Some((next_index, _)) = bounds.peek() { + if *next_index == current_byte_index { + bounds.next(); + + if current_byte_index != 0 || allow_word_at_start { + output_string.extend(character.to_uppercase()); + continue; + } + } + } + + output_string.push(character); + } + + output_string +} |