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Diffstat (limited to 'components/layout/inline.rs')
| -rw-r--r-- | components/layout/inline.rs | 1170 |
1 files changed, 1170 insertions, 0 deletions
diff --git a/components/layout/inline.rs b/components/layout/inline.rs new file mode 100644 index 00000000000..6c22b25746e --- /dev/null +++ b/components/layout/inline.rs @@ -0,0 +1,1170 @@ +/* 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 http://mozilla.org/MPL/2.0/. */ + +#![deny(unsafe_block)] + +use css::node_style::StyledNode; +use context::LayoutContext; +use floats::{FloatLeft, Floats, PlacementInfo}; +use flow::{BaseFlow, FlowClass, Flow, InlineFlowClass}; +use flow; +use fragment::{Fragment, ScannedTextFragment, ScannedTextFragmentInfo, SplitInfo}; +use layout_debug; +use model::IntrinsicISizes; +use text; +use wrapper::ThreadSafeLayoutNode; + +use collections::{Deque, RingBuf}; +use geom::Rect; +use gfx::display_list::ContentLevel; +use gfx::font::FontMetrics; +use gfx::font_context::FontContext; +use gfx::text::glyph::CharIndex; +use servo_util::geometry::Au; +use servo_util::geometry; +use servo_util::logical_geometry::{LogicalRect, LogicalSize}; +use servo_util::range; +use servo_util::range::{EachIndex, Range, RangeIndex, IntRangeIndex}; +use std::fmt; +use std::mem; +use std::num; +use std::u16; +use style::computed_values::{text_align, vertical_align, white_space}; +use style::ComputedValues; +use sync::Arc; + +/// `Line`s are represented as offsets into the child list, rather than +/// as an object that "owns" fragments. Choosing a different set of line +/// breaks requires a new list of offsets, and possibly some splitting and +/// merging of TextFragments. +/// +/// A similar list will keep track of the mapping between CSS fragments and +/// the corresponding fragments in the inline flow. +/// +/// After line breaks are determined, render fragments in the inline flow may +/// overlap visually. For example, in the case of nested inline CSS fragments, +/// outer inlines must be at least as large as the inner inlines, for +/// purposes of drawing noninherited things like backgrounds, borders, +/// outlines. +/// +/// N.B. roc has an alternative design where the list instead consists of +/// things like "start outer fragment, text, start inner fragment, text, end inner +/// fragment, text, end outer fragment, text". This seems a little complicated to +/// serve as the starting point, but the current design doesn't make it +/// hard to try out that alternative. +/// +/// Line fragments also contain some metadata used during line breaking. The +/// green zone is the area that the line can expand to before it collides +/// with a float or a horizontal wall of the containing block. The block-start +/// inline-start corner of the green zone is the same as that of the line, but +/// the green zone can be taller and wider than the line itself. +#[deriving(Encodable)] +pub struct Line { + /// A range of line indices that describe line breaks. + /// + /// For example, consider the following HTML and rendered element with + /// linebreaks: + /// + /// ~~~html + /// <span>I <span>like truffles, <img></span> yes I do.</span> + /// ~~~ + /// + /// ~~~text + /// +------------+ + /// | I like | + /// | truffles, | + /// | +----+ | + /// | | | | + /// | +----+ yes | + /// | I do. | + /// +------------+ + /// ~~~ + /// + /// The ranges that describe these lines would be: + /// + /// | [0.0, 1.4) | [1.5, 2.0) | [2.0, 3.4) | [3.4, 4.0) | + /// |------------|-------------|-------------|------------| + /// | 'I like' | 'truffles,' | '<img> yes' | 'I do.' | + pub range: Range<LineIndices>, + /// The bounds are the exact position and extents of the line with respect + /// to the parent box. + /// + /// For example, for the HTML below... + /// + /// ~~~html + /// <div><span>I <span>like truffles, <img></span></div> + /// ~~~ + /// + /// ...the bounds would be: + /// + /// ~~~text + /// +-----------------------------------------------------------+ + /// | ^ | + /// | | | + /// | origin.y | + /// | | | + /// | v | + /// |< - origin.x ->+ - - - - - - - - +---------+---- | + /// | | | | ^ | + /// | | | <img> | size.block-size | + /// | I like truffles, | | v | + /// | + - - - - - - - - +---------+---- | + /// | | | | + /// | |<------ size.inline-size ------->| | + /// | | + /// | | + /// +-----------------------------------------------------------+ + /// ~~~ + pub bounds: LogicalRect<Au>, + /// The green zone is the greatest extent from wich a line can extend to + /// before it collides with a float. + /// + /// ~~~text + /// +-----------------------+ + /// |::::::::::::::::: | + /// |:::::::::::::::::FFFFFF| + /// |============:::::FFFFFF| + /// |:::::::::::::::::FFFFFF| + /// |:::::::::::::::::FFFFFF| + /// |::::::::::::::::: | + /// | FFFFFFFFF | + /// | FFFFFFFFF | + /// | FFFFFFFFF | + /// | | + /// +-----------------------+ + /// + /// === line + /// ::: green zone + /// FFF float + /// ~~~ + pub green_zone: LogicalSize<Au> +} + +int_range_index! { + #[deriving(Encodable)] + #[doc = "The index of a fragment in a flattened vector of DOM elements."] + struct FragmentIndex(int) +} + +/// A line index consists of two indices: a fragment index that refers to the +/// index of a DOM fragment within a flattened inline element; and a glyph index +/// where the 0th glyph refers to the first glyph of that fragment. +#[deriving(Clone, Encodable, PartialEq, PartialOrd, Eq, Ord, Zero)] +pub struct LineIndices { + /// The index of a fragment into the flattened vector of DOM elements. + /// + /// For example, given the HTML below: + /// + /// ~~~html + /// <span>I <span>like truffles, <img></span> yes I do.</span> + /// ~~~ + /// + /// The fragments would be indexed as follows: + /// + /// | 0 | 1 | 2 | 3 | + /// |------|------------------|---------|--------------| + /// | 'I ' | 'like truffles,' | `<img>` | ' yes I do.' | + pub fragment_index: FragmentIndex, + /// The index of a character in a DOM fragment. Continuous runs of whitespace + /// are treated as single characters. Non-breakable DOM fragments such as + /// images are treated as having a range length of `1`. + /// + /// For example, given the HTML below: + /// + /// ~~~html + /// <span>I <span>like truffles, <img></span> yes I do.</span> + /// ~~~ + /// + /// The characters would be indexed as follows: + /// + /// | 0 | 1 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | + /// |---|---|---|---|---|---|---|---|---|---|---|---|----|----|----|----|----| + /// | I | | l | i | k | e | | t | r | u | f | f | l | e | s | , | | + /// + /// | 0 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | + /// |---------|---|---|---|---|---|---|---|---|---|---| + /// | `<img>` | | y | e | s | | I | | d | o | . | + pub char_index: CharIndex, +} + +impl RangeIndex for LineIndices {} + +impl Add<LineIndices, LineIndices> for LineIndices { + fn add(&self, other: &LineIndices) -> LineIndices { + // TODO: use debug_assert! after rustc upgrade + if cfg!(not(ndebug)) { + assert!(other.fragment_index == num::zero() || other.char_index == num::zero(), + "Attempted to add {} to {}. Both the fragment_index and \ + char_index of the RHS are non-zero. This probably was a \ + mistake!", self, other); + } + LineIndices { + fragment_index: self.fragment_index + other.fragment_index, + char_index: self.char_index + other.char_index, + } + } +} + +impl Sub<LineIndices, LineIndices> for LineIndices { + fn sub(&self, other: &LineIndices) -> LineIndices { + // TODO: use debug_assert! after rustc upgrade + if cfg!(not(ndebug)) { + assert!(other.fragment_index == num::zero() || other.char_index == num::zero(), + "Attempted to subtract {} from {}. Both the fragment_index \ + and char_index of the RHS are non-zero. This probably was \ + a mistake!", self, other); + } + LineIndices { + fragment_index: self.fragment_index - other.fragment_index, + char_index: self.char_index - other.char_index, + } + } +} + +impl Neg<LineIndices> for LineIndices { + fn neg(&self) -> LineIndices { + // TODO: use debug_assert! after rustc upgrade + if cfg!(not(ndebug)) { + assert!(self.fragment_index == num::zero() || self.char_index == num::zero(), + "Attempted to negate {}. Both the fragment_index and \ + char_index are non-zero. This probably was a mistake!", + self); + } + LineIndices { + fragment_index: -self.fragment_index, + char_index: -self.char_index, + } + } +} + +impl fmt::Show for LineIndices { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "{}.{}", self.fragment_index, self.char_index) + } +} + +pub fn each_fragment_index(range: &Range<LineIndices>) -> EachIndex<int, FragmentIndex> { + range::each_index(range.begin().fragment_index, range.end().fragment_index) +} + +pub fn each_char_index(range: &Range<LineIndices>) -> EachIndex<int, CharIndex> { + range::each_index(range.begin().char_index, range.end().char_index) +} + +struct LineBreaker { + pub floats: Floats, + pub new_fragments: Vec<Fragment>, + pub work_list: RingBuf<Fragment>, + pub pending_line: Line, + pub lines: Vec<Line>, + pub cur_b: Au, // Current position on the block direction +} + +impl LineBreaker { + pub fn new(float_ctx: Floats) -> LineBreaker { + LineBreaker { + new_fragments: Vec::new(), + work_list: RingBuf::new(), + pending_line: Line { + range: Range::empty(), + bounds: LogicalRect::zero(float_ctx.writing_mode), + green_zone: LogicalSize::zero(float_ctx.writing_mode) + }, + floats: float_ctx, + lines: Vec::new(), + cur_b: Au::new(0) + } + } + + pub fn floats(&mut self) -> Floats { + self.floats.clone() + } + + fn reset_scanner(&mut self) { + debug!("Resetting LineBreaker's state for flow."); + self.lines = Vec::new(); + self.new_fragments = Vec::new(); + self.cur_b = Au(0); + self.reset_line(); + } + + fn reset_line(&mut self) { + self.pending_line.range.reset(num::zero(), num::zero()); + self.pending_line.bounds = LogicalRect::new( + self.floats.writing_mode, Au::new(0), self.cur_b, Au::new(0), Au::new(0)); + self.pending_line.green_zone = LogicalSize::zero(self.floats.writing_mode) + } + + pub fn scan_for_lines(&mut self, flow: &mut InlineFlow, layout_context: &LayoutContext) { + self.reset_scanner(); + + let mut old_fragments = mem::replace(&mut flow.fragments, InlineFragments::new()); + + { // Enter a new scope so that old_fragment_iter's borrow is released + let mut old_fragment_iter = old_fragments.fragments.iter(); + loop { + // acquire the next fragment to lay out from work list or fragment list + let cur_fragment = if self.work_list.is_empty() { + match old_fragment_iter.next() { + None => break, + Some(fragment) => { + debug!("LineBreaker: Working with fragment from flow: b{}", + fragment.debug_id()); + (*fragment).clone() + } + } + } else { + let fragment = self.work_list.pop_front().unwrap(); + debug!("LineBreaker: Working with fragment from work list: b{}", + fragment.debug_id()); + fragment + }; + + let fragment_was_appended = match cur_fragment.white_space() { + white_space::normal => self.try_append_to_line(cur_fragment, flow, layout_context), + white_space::pre => self.try_append_to_line_by_new_line(cur_fragment), + }; + + if !fragment_was_appended { + debug!("LineBreaker: Fragment wasn't appended, because line {:u} was full.", + self.lines.len()); + self.flush_current_line(); + } else { + debug!("LineBreaker: appended a fragment to line {:u}", self.lines.len()); + } + } + + if self.pending_line.range.length() > num::zero() { + debug!("LineBreaker: Partially full line {:u} inline_start at end of scanning.", + self.lines.len()); + self.flush_current_line(); + } + } + + old_fragments.fragments = mem::replace(&mut self.new_fragments, vec![]); + flow.fragments = old_fragments; + flow.lines = mem::replace(&mut self.lines, Vec::new()); + } + + fn flush_current_line(&mut self) { + debug!("LineBreaker: Flushing line {:u}: {:?}", + self.lines.len(), self.pending_line); + + // clear line and add line mapping + debug!("LineBreaker: Saving information for flushed line {:u}.", self.lines.len()); + self.lines.push(self.pending_line); + self.cur_b = self.pending_line.bounds.start.b + self.pending_line.bounds.size.block; + self.reset_line(); + } + + // FIXME(eatkinson): this assumes that the tallest fragment in the line determines the line block-size + // This might not be the case with some weird text fonts. + fn new_block_size_for_line(&self, new_fragment: &Fragment, layout_context: &LayoutContext) -> Au { + let fragment_block_size = new_fragment.content_block_size(layout_context); + if fragment_block_size > self.pending_line.bounds.size.block { + fragment_block_size + } else { + self.pending_line.bounds.size.block + } + } + + /// Computes the position of a line that has only the provided fragment. Returns the bounding + /// rect of the line's green zone (whose origin coincides with the line's origin) and the actual + /// inline-size of the first fragment after splitting. + fn initial_line_placement(&self, first_fragment: &Fragment, ceiling: Au, flow: &InlineFlow) + -> (LogicalRect<Au>, Au) { + debug!("LineBreaker: Trying to place first fragment of line {}", self.lines.len()); + + let first_fragment_size = first_fragment.border_box.size; + let splittable = first_fragment.can_split(); + debug!("LineBreaker: fragment size: {}, splittable: {}", first_fragment_size, splittable); + + // Initally, pretend a splittable fragment has 0 inline-size. + // We will move it later if it has nonzero inline-size + // and that causes problems. + let placement_inline_size = if splittable { + Au::new(0) + } else { + first_fragment_size.inline + }; + + let info = PlacementInfo { + size: LogicalSize::new( + self.floats.writing_mode, placement_inline_size, first_fragment_size.block), + ceiling: ceiling, + max_inline_size: flow.base.position.size.inline, + kind: FloatLeft, + }; + + let line_bounds = self.floats.place_between_floats(&info); + + debug!("LineBreaker: found position for line: {} using placement_info: {:?}", + line_bounds, + info); + + // Simple case: if the fragment fits, then we can stop here + if line_bounds.size.inline > first_fragment_size.inline { + debug!("LineBreaker: case=fragment fits"); + return (line_bounds, first_fragment_size.inline); + } + + // If not, but we can't split the fragment, then we'll place + // the line here and it will overflow. + if !splittable { + debug!("LineBreaker: case=line doesn't fit, but is unsplittable"); + return (line_bounds, first_fragment_size.inline); + } + + debug!("LineBreaker: used to call split_to_inline_size here"); + return (line_bounds, first_fragment_size.inline); + } + + /// Performs float collision avoidance. This is called when adding a fragment is going to increase + /// the block-size, and because of that we will collide with some floats. + /// + /// We have two options here: + /// 1) Move the entire line so that it doesn't collide any more. + /// 2) Break the line and put the new fragment on the next line. + /// + /// The problem with option 1 is that we might move the line and then wind up breaking anyway, + /// which violates the standard. + /// But option 2 is going to look weird sometimes. + /// + /// So we'll try to move the line whenever we can, but break if we have to. + /// + /// Returns false if and only if we should break the line. + fn avoid_floats(&mut self, + in_fragment: Fragment, + flow: &InlineFlow, + new_block_size: Au, + line_is_empty: bool) + -> bool { + debug!("LineBreaker: entering float collision avoider!"); + + // First predict where the next line is going to be. + let this_line_y = self.pending_line.bounds.start.b; + let (next_line, first_fragment_inline_size) = self.initial_line_placement(&in_fragment, this_line_y, flow); + let next_green_zone = next_line.size; + + let new_inline_size = self.pending_line.bounds.size.inline + first_fragment_inline_size; + + // Now, see if everything can fit at the new location. + if next_green_zone.inline >= new_inline_size && next_green_zone.block >= new_block_size { + debug!("LineBreaker: case=adding fragment collides vertically with floats: moving line"); + + self.pending_line.bounds.start = next_line.start; + self.pending_line.green_zone = next_green_zone; + + assert!(!line_is_empty, "Non-terminating line breaking"); + self.work_list.push_front(in_fragment); + return true + } + + debug!("LineBreaker: case=adding fragment collides vertically with floats: breaking line"); + self.work_list.push_front(in_fragment); + false + } + + fn try_append_to_line_by_new_line(&mut self, in_fragment: Fragment) -> bool { + if in_fragment.new_line_pos.len() == 0 { + debug!("LineBreaker: Did not find a new-line character, so pushing the fragment to \ + the line without splitting."); + self.push_fragment_to_line(in_fragment); + true + } else { + debug!("LineBreaker: Found a new-line character, so splitting theline."); + + let (inline_start, inline_end, run) = in_fragment.find_split_info_by_new_line() + .expect("LineBreaker: This split case makes no sense!"); + let writing_mode = self.floats.writing_mode; + + // TODO(bjz): Remove fragment splitting + let split_fragment = |split: SplitInfo| { + let info = ScannedTextFragmentInfo::new(run.clone(), split.range); + let specific = ScannedTextFragment(info); + let size = LogicalSize::new( + writing_mode, split.inline_size, in_fragment.border_box.size.block); + in_fragment.transform(size, specific) + }; + + debug!("LineBreaker: Pushing the fragment to the inline_start of the new-line character \ + to the line."); + let mut inline_start = split_fragment(inline_start); + inline_start.new_line_pos = vec![]; + self.push_fragment_to_line(inline_start); + + for inline_end in inline_end.move_iter() { + debug!("LineBreaker: Deferring the fragment to the inline_end of the new-line \ + character to the line."); + let mut inline_end = split_fragment(inline_end); + inline_end.new_line_pos = in_fragment.new_line_pos.clone(); + self.work_list.push_front(inline_end); + } + false + } + } + + /// Tries to append the given fragment to the line, splitting it if necessary. Returns false only if + /// we should break the line. + fn try_append_to_line(&mut self, in_fragment: Fragment, flow: &InlineFlow, layout_context: &LayoutContext) -> bool { + let line_is_empty = self.pending_line.range.length() == num::zero(); + if line_is_empty { + let (line_bounds, _) = self.initial_line_placement(&in_fragment, self.cur_b, flow); + self.pending_line.bounds.start = line_bounds.start; + self.pending_line.green_zone = line_bounds.size; + } + + debug!("LineBreaker: Trying to append fragment to line {:u} (fragment size: {}, green zone: \ + {}): {}", + self.lines.len(), + in_fragment.border_box.size, + self.pending_line.green_zone, + in_fragment); + + let green_zone = self.pending_line.green_zone; + + // NB: At this point, if `green_zone.inline-size < self.pending_line.bounds.size.inline-size` or + // `green_zone.block-size < self.pending_line.bounds.size.block-size`, then we committed a line + // that overlaps with floats. + + let new_block_size = self.new_block_size_for_line(&in_fragment, layout_context); + if new_block_size > green_zone.block { + // Uh-oh. Float collision imminent. Enter the float collision avoider + return self.avoid_floats(in_fragment, flow, new_block_size, line_is_empty) + } + + // If we're not going to overflow the green zone vertically, we might still do so + // horizontally. We'll try to place the whole fragment on this line and break somewhere if it + // doesn't fit. + + let new_inline_size = self.pending_line.bounds.size.inline + in_fragment.border_box.size.inline; + if new_inline_size <= green_zone.inline { + debug!("LineBreaker: case=fragment fits without splitting"); + self.push_fragment_to_line(in_fragment); + return true + } + + if !in_fragment.can_split() { + // TODO(eatkinson, issue #224): Signal that horizontal overflow happened? + if line_is_empty { + debug!("LineBreaker: case=fragment can't split and line {:u} is empty, so \ + overflowing.", + self.lines.len()); + self.push_fragment_to_line(in_fragment); + return true + } + } + + let available_inline_size = green_zone.inline - self.pending_line.bounds.size.inline; + let split = in_fragment.find_split_info_for_inline_size(CharIndex(0), available_inline_size, line_is_empty); + match split.map(|(inline_start, inline_end, run)| { + // TODO(bjz): Remove fragment splitting + let split_fragment = |split: SplitInfo| { + let info = ScannedTextFragmentInfo::new(run.clone(), split.range); + let specific = ScannedTextFragment(info); + let size = LogicalSize::new( + self.floats.writing_mode, split.inline_size, in_fragment.border_box.size.block); + in_fragment.transform(size, specific) + }; + + (inline_start.map(|x| { debug!("LineBreaker: Left split {}", x); split_fragment(x) }), + inline_end.map(|x| { debug!("LineBreaker: Right split {}", x); split_fragment(x) })) + }) { + None => { + debug!("LineBreaker: Tried to split unsplittable render fragment! Deferring to next \ + line. {}", in_fragment); + self.work_list.push_front(in_fragment); + false + }, + Some((Some(inline_start_fragment), Some(inline_end_fragment))) => { + debug!("LineBreaker: Line break found! Pushing inline_start fragment to line and deferring \ + inline_end fragment to next line."); + self.push_fragment_to_line(inline_start_fragment); + self.work_list.push_front(inline_end_fragment); + true + }, + Some((Some(inline_start_fragment), None)) => { + debug!("LineBreaker: Pushing inline_start fragment to line."); + self.push_fragment_to_line(inline_start_fragment); + true + }, + Some((None, Some(inline_end_fragment))) => { + debug!("LineBreaker: Pushing inline_end fragment to line."); + self.push_fragment_to_line(inline_end_fragment); + true + }, + Some((None, None)) => { + error!("LineBreaker: This split case makes no sense!"); + true + }, + } + } + + // An unconditional push + fn push_fragment_to_line(&mut self, fragment: Fragment) { + debug!("LineBreaker: Pushing fragment {} to line {:u}", fragment.debug_id(), self.lines.len()); + + if self.pending_line.range.length() == num::zero() { + assert!(self.new_fragments.len() <= (u16::MAX as uint)); + self.pending_line.range.reset( + LineIndices { + fragment_index: FragmentIndex(self.new_fragments.len() as int), + char_index: CharIndex(0) /* unused for now */, + }, + num::zero() + ); + } + self.pending_line.range.extend_by(LineIndices { + fragment_index: FragmentIndex(1), + char_index: CharIndex(0) /* unused for now */ , + }); + self.pending_line.bounds.size.inline = self.pending_line.bounds.size.inline + + fragment.border_box.size.inline; + self.pending_line.bounds.size.block = Au::max(self.pending_line.bounds.size.block, + fragment.border_box.size.block); + self.new_fragments.push(fragment); + } +} + +/// Represents a list of inline fragments, including element ranges. +#[deriving(Encodable)] +pub struct InlineFragments { + /// The fragments themselves. + pub fragments: Vec<Fragment>, +} + +impl InlineFragments { + /// Creates an empty set of inline fragments. + pub fn new() -> InlineFragments { + InlineFragments { + fragments: vec![], + } + } + + /// Returns the number of inline fragments. + pub fn len(&self) -> uint { + self.fragments.len() + } + + /// Returns true if this list contains no fragments and false if it contains at least one fragment. + pub fn is_empty(&self) -> bool { + self.len() == 0 + } + + /// Pushes a new inline fragment. + pub fn push(&mut self, fragment: &mut Fragment, style: Arc<ComputedValues>) { + fragment.add_inline_context_style(style); + self.fragments.push(fragment.clone()); + } + + /// Merges another set of inline fragments with this one. + pub fn push_all(&mut self, fragments: InlineFragments) { + self.fragments.push_all_move(fragments.fragments); + } + + /// A convenience function to return the fragment at a given index. + pub fn get<'a>(&'a self, index: uint) -> &'a Fragment { + &self.fragments[index] + } + + /// A convenience function to return a mutable reference to the fragment at a given index. + pub fn get_mut<'a>(&'a mut self, index: uint) -> &'a mut Fragment { + self.fragments.get_mut(index) + } + + /// Strips ignorable whitespace from the start of a list of fragments. + pub fn strip_ignorable_whitespace_from_start(&mut self) { + if self.is_empty() { return }; // Fast path + + // FIXME (rust#16151): This can be reverted back to using skip_while once + // the upstream bug is fixed. + let mut fragments = mem::replace(&mut self.fragments, vec![]).move_iter(); + let mut new_fragments = Vec::new(); + let mut skipping = true; + for fragment in fragments { + if skipping && fragment.is_whitespace_only() { + debug!("stripping ignorable whitespace from start"); + continue + } + + skipping = false; + new_fragments.push(fragment); + } + + self.fragments = new_fragments; + } + + /// Strips ignorable whitespace from the end of a list of fragments. + pub fn strip_ignorable_whitespace_from_end(&mut self) { + if self.is_empty() { + return; + } + + let mut new_fragments = self.fragments.clone(); + while new_fragments.len() > 0 && new_fragments.as_slice().last().get_ref().is_whitespace_only() { + debug!("stripping ignorable whitespace from end"); + drop(new_fragments.pop()); + } + + + self.fragments = new_fragments; + } +} + +/// Flows for inline layout. +#[deriving(Encodable)] +pub struct InlineFlow { + /// Data common to all flows. + pub base: BaseFlow, + + /// A vector of all inline fragments. Several fragments may correspond to one node/element. + pub fragments: InlineFragments, + + /// A vector of ranges into fragments that represents line positions. These ranges are disjoint and + /// are the result of inline layout. This also includes some metadata used for positioning + /// lines. + pub lines: Vec<Line>, + + /// The minimum block-size above the baseline for each line, as specified by the line block-size and + /// font style. + pub minimum_block_size_above_baseline: Au, + + /// The minimum depth below the baseline for each line, as specified by the line block-size and + /// font style. + pub minimum_depth_below_baseline: Au, +} + +impl InlineFlow { + pub fn from_fragments(node: ThreadSafeLayoutNode, fragments: InlineFragments) -> InlineFlow { + InlineFlow { + base: BaseFlow::new(node), + fragments: fragments, + lines: Vec::new(), + minimum_block_size_above_baseline: Au(0), + minimum_depth_below_baseline: Au(0), + } + } + + pub fn build_display_list_inline(&mut self, layout_context: &LayoutContext) { + let size = self.base.position.size.to_physical(self.base.writing_mode); + if !Rect(self.base.abs_position, size).intersects(&layout_context.shared.dirty) { + return + } + + // TODO(#228): Once we form lines and have their cached bounds, we can be smarter and + // not recurse on a line if nothing in it can intersect the dirty region. + debug!("Flow: building display list for {:u} inline fragments", self.fragments.len()); + + for fragment in self.fragments.fragments.mut_iter() { + let rel_offset = fragment.relative_position(&self.base + .absolute_position_info + .relative_containing_block_size); + drop(fragment.build_display_list(&mut self.base.display_list, + layout_context, + self.base.abs_position.add_size( + &rel_offset.to_physical(self.base.writing_mode)), + ContentLevel)); + } + + // TODO(#225): Should `inline-block` elements have flows as children of the inline flow or + // should the flow be nested inside the fragment somehow? + + // For now, don't traverse the subtree rooted here. + } + + /// Returns the distance from the baseline for the logical block-start inline-start corner of this fragment, + /// taking into account the value of the CSS `vertical-align` property. Negative values mean + /// "toward the logical block-start" and positive values mean "toward the logical block-end". + /// + /// The extra boolean is set if and only if `biggest_block-start` and/or `biggest_block-end` were updated. + /// That is, if the box has a `block-start` or `block-end` value, true is returned. + fn distance_from_baseline(fragment: &Fragment, + ascent: Au, + parent_text_block_start: Au, + parent_text_block_end: Au, + block_size_above_baseline: &mut Au, + depth_below_baseline: &mut Au, + largest_block_size_for_top_fragments: &mut Au, + largest_block_size_for_bottom_fragments: &mut Au, + layout_context: &LayoutContext) + -> (Au, bool) { + match fragment.vertical_align() { + vertical_align::baseline => (-ascent, false), + vertical_align::middle => { + // TODO: x-block-size value should be used from font info. + let xblock_size = Au(0); + let fragment_block_size = fragment.content_block_size(layout_context); + let offset_block_start = -(xblock_size + fragment_block_size).scale_by(0.5); + *block_size_above_baseline = offset_block_start.scale_by(-1.0); + *depth_below_baseline = fragment_block_size - *block_size_above_baseline; + (offset_block_start, false) + }, + vertical_align::sub => { + // TODO: The proper position for subscripts should be used. Lower the baseline to + // the proper position for subscripts. + let sub_offset = Au(0); + (sub_offset - ascent, false) + }, + vertical_align::super_ => { + // TODO: The proper position for superscripts should be used. Raise the baseline to + // the proper position for superscripts. + let super_offset = Au(0); + (-super_offset - ascent, false) + }, + vertical_align::text_top => { + let fragment_block_size = *block_size_above_baseline + *depth_below_baseline; + let prev_depth_below_baseline = *depth_below_baseline; + *block_size_above_baseline = parent_text_block_start; + *depth_below_baseline = fragment_block_size - *block_size_above_baseline; + (*depth_below_baseline - prev_depth_below_baseline - ascent, false) + }, + vertical_align::text_bottom => { + let fragment_block_size = *block_size_above_baseline + *depth_below_baseline; + let prev_depth_below_baseline = *depth_below_baseline; + *depth_below_baseline = parent_text_block_end; + *block_size_above_baseline = fragment_block_size - *depth_below_baseline; + (*depth_below_baseline - prev_depth_below_baseline - ascent, false) + }, + vertical_align::top => { + *largest_block_size_for_top_fragments = + Au::max(*largest_block_size_for_top_fragments, + *block_size_above_baseline + *depth_below_baseline); + let offset_top = *block_size_above_baseline - ascent; + (offset_top, true) + }, + vertical_align::bottom => { + *largest_block_size_for_bottom_fragments = + Au::max(*largest_block_size_for_bottom_fragments, + *block_size_above_baseline + *depth_below_baseline); + let offset_bottom = -(*depth_below_baseline + ascent); + (offset_bottom, true) + }, + vertical_align::Length(length) => (-(length + ascent), false), + vertical_align::Percentage(p) => { + let line_height = fragment.calculate_line_height(layout_context); + let percent_offset = line_height.scale_by(p); + (-(percent_offset + ascent), false) + } + } + } + + /// Sets fragment X positions based on alignment for one line. + fn set_horizontal_fragment_positions(fragments: &mut InlineFragments, + line: &Line, + line_align: text_align::T) { + // Figure out how much inline-size we have. + let slack_inline_size = Au::max(Au(0), line.green_zone.inline - line.bounds.size.inline); + + // Set the fragment x positions based on that alignment. + let mut offset_x = line.bounds.start.i; + offset_x = offset_x + match line_align { + // So sorry, but justified text is more complicated than shuffling line + // coordinates. + // + // TODO(burg, issue #213): Implement `text-align: justify`. + text_align::left | text_align::justify => Au(0), + text_align::center => slack_inline_size.scale_by(0.5), + text_align::right => slack_inline_size, + }; + + for i in each_fragment_index(&line.range) { + let fragment = fragments.get_mut(i.to_uint()); + let size = fragment.border_box.size; + fragment.border_box = LogicalRect::new( + fragment.style.writing_mode, offset_x, fragment.border_box.start.b, + size.inline, size.block); + offset_x = offset_x + size.inline; + } + } + + /// Computes the minimum ascent and descent for each line. This is done during flow + /// construction. + /// + /// `style` is the style of the block. + pub fn compute_minimum_ascent_and_descent(&self, + font_context: &mut FontContext, + style: &ComputedValues) -> (Au, Au) { + let font_style = text::computed_style_to_font_style(style); + let font_metrics = text::font_metrics_for_style(font_context, &font_style); + let line_height = text::line_height_from_style(style, &font_metrics); + let inline_metrics = InlineMetrics::from_font_metrics(&font_metrics, line_height); + (inline_metrics.block_size_above_baseline, inline_metrics.depth_below_baseline) + } +} + +impl Flow for InlineFlow { + fn class(&self) -> FlowClass { + InlineFlowClass + } + + fn as_immutable_inline<'a>(&'a self) -> &'a InlineFlow { + self + } + + fn as_inline<'a>(&'a mut self) -> &'a mut InlineFlow { + self + } + + fn bubble_inline_sizes(&mut self, _: &LayoutContext) { + let _scope = layout_debug_scope!("inline::bubble_inline_sizes {:s}", self.base.debug_id()); + + let writing_mode = self.base.writing_mode; + for kid in self.base.child_iter() { + flow::mut_base(kid).floats = Floats::new(writing_mode); + } + + let mut intrinsic_inline_sizes = IntrinsicISizes::new(); + for fragment in self.fragments.fragments.mut_iter() { + debug!("Flow: measuring {}", *fragment); + + let fragment_intrinsic_inline_sizes = + fragment.intrinsic_inline_sizes(); + intrinsic_inline_sizes.minimum_inline_size = geometry::max( + intrinsic_inline_sizes.minimum_inline_size, + fragment_intrinsic_inline_sizes.minimum_inline_size); + intrinsic_inline_sizes.preferred_inline_size = + intrinsic_inline_sizes.preferred_inline_size + + fragment_intrinsic_inline_sizes.preferred_inline_size; + } + + self.base.intrinsic_inline_sizes = intrinsic_inline_sizes; + } + + /// Recursively (top-down) determines the actual inline-size of child contexts and fragments. When called + /// on this context, the context has had its inline-size set by the parent context. + fn assign_inline_sizes(&mut self, _: &LayoutContext) { + let _scope = layout_debug_scope!("inline::assign_inline_sizes {:s}", self.base.debug_id()); + + // Initialize content fragment inline-sizes if they haven't been initialized already. + // + // TODO: Combine this with `LineBreaker`'s walk in the fragment list, or put this into `Fragment`. + + debug!("InlineFlow::assign_inline_sizes: floats in: {:?}", self.base.floats); + + { + let inline_size = self.base.position.size.inline; + let this = &mut *self; + for fragment in this.fragments.fragments.mut_iter() { + fragment.assign_replaced_inline_size_if_necessary(inline_size); + } + } + + assert!(self.base.children.len() == 0, + "InlineFlow: should not have children flows in the current layout implementation."); + + // There are no child contexts, so stop here. + + // TODO(Issue #225): once there are 'inline-block' elements, this won't be + // true. In that case, set the InlineBlockFragment's inline-size to the + // shrink-to-fit inline-size, perform inline flow, and set the block + // flow context's inline-size as the assigned inline-size of the + // 'inline-block' fragment that created this flow before recursing. + } + + /// Calculate and set the block-size of this flow. See CSS 2.1 § 10.6.1. + fn assign_block_size(&mut self, ctx: &LayoutContext) { + let _scope = layout_debug_scope!("inline::assign_block_size {:s}", self.base.debug_id()); + + // Divide the fragments into lines. + // + // TODO(#226): Get the CSS `line-block-size` property from the containing block's style to + // determine minimum line block-size. + // + // TODO(#226): Get the CSS `line-block-size` property from each non-replaced inline element to + // determine its block-size for computing line block-size. + // + // TODO(pcwalton): Cache the line scanner? + debug!("assign_block_size_inline: floats in: {:?}", self.base.floats); + + // assign block-size for inline fragments + for fragment in self.fragments.fragments.mut_iter() { + fragment.assign_replaced_block_size_if_necessary(); + } + + let scanner_floats = self.base.floats.clone(); + let mut scanner = LineBreaker::new(scanner_floats); + scanner.scan_for_lines(self, ctx); + + // All lines use text alignment of the flow. + let text_align = self.base.flags.text_align(); + + // Now, go through each line and lay out the fragments inside. + let mut line_distance_from_flow_block_start = Au(0); + for line in self.lines.mut_iter() { + // Lay out fragments horizontally. + InlineFlow::set_horizontal_fragment_positions(&mut self.fragments, line, text_align); + + // Set the block-start y position of the current line. + // `line_height_offset` is updated at the end of the previous loop. + line.bounds.start.b = line_distance_from_flow_block_start; + + // Calculate the distance from the baseline to the block-start and block-end of the line. + let mut largest_block_size_above_baseline = self.minimum_block_size_above_baseline; + let mut largest_depth_below_baseline = self.minimum_depth_below_baseline; + + // Calculate the largest block-size among fragments with 'top' and 'bottom' values + // respectively. + let (mut largest_block_size_for_top_fragments, mut largest_block_size_for_bottom_fragments) = + (Au(0), Au(0)); + + for fragment_i in each_fragment_index(&line.range) { + let fragment = self.fragments.fragments.get_mut(fragment_i.to_uint()); + + let InlineMetrics { + block_size_above_baseline: mut block_size_above_baseline, + depth_below_baseline: mut depth_below_baseline, + ascent + } = fragment.inline_metrics(ctx); + + // To calculate text-top and text-bottom value when `vertical-align` is involved, + // we should find the top and bottom of the content area of the parent fragment. + // "Content area" is defined in CSS 2.1 § 10.6.1. + // + // TODO: We should extract em-box info from the font size of the parent and + // calculate the distances from the baseline to the block-start and the block-end of the + // parent's content area. + + // We should calculate the distance from baseline to the top of parent's content + // area. But for now we assume it's the font size. + // + // CSS 2.1 does not state which font to use. Previous versions of the code used + // the parent's font; this code uses the current font. + let parent_text_top = fragment.style().get_font().font_size; + + // We should calculate the distance from baseline to the bottom of the parent's + // content area. But for now we assume it's zero. + let parent_text_bottom = Au(0); + + // Calculate the final block-size above the baseline for this fragment. + // + // The no-update flag decides whether `largest_block-size_for_top_fragments` and + // `largest_block-size_for_bottom_fragments` are to be updated or not. This will be set + // if and only if the fragment has `vertical-align` set to `top` or `bottom`. + let (distance_from_baseline, no_update_flag) = + InlineFlow::distance_from_baseline( + fragment, + ascent, + parent_text_top, + parent_text_bottom, + &mut block_size_above_baseline, + &mut depth_below_baseline, + &mut largest_block_size_for_top_fragments, + &mut largest_block_size_for_bottom_fragments, + ctx); + + // Unless the current fragment has `vertical-align` set to `top` or `bottom`, + // `largest_block-size_above_baseline` and `largest_depth_below_baseline` are updated. + if !no_update_flag { + largest_block_size_above_baseline = Au::max(block_size_above_baseline, + largest_block_size_above_baseline); + largest_depth_below_baseline = Au::max(depth_below_baseline, + largest_depth_below_baseline); + } + + // Temporarily use `fragment.border_box.start.b` to mean "the distance from the + // baseline". We will assign the real value later. + fragment.border_box.start.b = distance_from_baseline + } + + // Calculate the distance from the baseline to the top of the largest fragment with a + // value for `bottom`. Then, if necessary, update `largest_block-size_above_baseline`. + largest_block_size_above_baseline = + Au::max(largest_block_size_above_baseline, + largest_block_size_for_bottom_fragments - largest_depth_below_baseline); + + // Calculate the distance from baseline to the bottom of the largest fragment with a value + // for `top`. Then, if necessary, update `largest_depth_below_baseline`. + largest_depth_below_baseline = + Au::max(largest_depth_below_baseline, + largest_block_size_for_top_fragments - largest_block_size_above_baseline); + + // Now, the distance from the logical block-start of the line to the baseline can be + // computed as `largest_block-size_above_baseline`. + let baseline_distance_from_block_start = largest_block_size_above_baseline; + + // Compute the final positions in the block direction of each fragment. Recall that + // `fragment.border_box.start.b` was set to the distance from the baseline above. + for fragment_i in each_fragment_index(&line.range) { + let fragment = self.fragments.get_mut(fragment_i.to_uint()); + match fragment.vertical_align() { + vertical_align::top => { + fragment.border_box.start.b = fragment.border_box.start.b + + line_distance_from_flow_block_start + } + vertical_align::bottom => { + fragment.border_box.start.b = fragment.border_box.start.b + + line_distance_from_flow_block_start + baseline_distance_from_block_start + + largest_depth_below_baseline + } + _ => { + fragment.border_box.start.b = fragment.border_box.start.b + + line_distance_from_flow_block_start + baseline_distance_from_block_start + } + } + } + + // This is used to set the block-start y position of the next line in the next loop. + line.bounds.size.block = largest_block_size_above_baseline + largest_depth_below_baseline; + line_distance_from_flow_block_start = line_distance_from_flow_block_start + line.bounds.size.block; + } // End of `lines.each` loop. + + self.base.position.size.block = match self.lines.as_slice().last() { + Some(ref last_line) => last_line.bounds.start.b + last_line.bounds.size.block, + None => Au::new(0) + }; + + self.base.floats = scanner.floats(); + self.base.floats.translate(LogicalSize::new( + self.base.writing_mode, Au::new(0), -self.base.position.size.block)); + } +} + +impl fmt::Show for InlineFlow { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + try!(write!(f, "InlineFlow")); + for (i, fragment) in self.fragments.fragments.iter().enumerate() { + if i == 0 { + try!(write!(f, ": {}", fragment)) + } else { + try!(write!(f, ", {}", fragment)) + } + } + Ok(()) + } +} + +#[deriving(Clone)] +pub struct InlineFragmentContext { + pub styles: Vec<Arc<ComputedValues>>, +} + +impl InlineFragmentContext { + pub fn new() -> InlineFragmentContext { + InlineFragmentContext { + styles: vec!() + } + } +} + +/// BSize above the baseline, depth below the baseline, and ascent for a fragment. See CSS 2.1 § +/// 10.8.1. +pub struct InlineMetrics { + pub block_size_above_baseline: Au, + pub depth_below_baseline: Au, + pub ascent: Au, +} + +impl InlineMetrics { + /// Calculates inline metrics from font metrics and line block-size per CSS 2.1 § 10.8.1. + #[inline] + pub fn from_font_metrics(font_metrics: &FontMetrics, line_height: Au) -> InlineMetrics { + let leading = line_height - (font_metrics.ascent + font_metrics.descent); + InlineMetrics { + block_size_above_baseline: font_metrics.ascent + leading.scale_by(0.5), + depth_below_baseline: font_metrics.descent + leading.scale_by(0.5), + ascent: font_metrics.ascent, + } + } +} + |