layout: Simplify and improve the correctness of whitespace stripping in

text layout, and unify the inline layout paths for pre- and
normally-formatted text.

This fixes a lot of "jumpiness" and removes the `new_line_pos` stuff.

Closes #2260.
This commit is contained in:
Patrick Walton 2015-03-30 14:09:37 -07:00
parent 88aa07b7e0
commit 6d61468160
12 changed files with 485 additions and 461 deletions

View file

@ -27,16 +27,11 @@ use geom::{Point2D, Rect, Size2D};
use gfx::display_list::{BLUR_INFLATION_FACTOR, OpaqueNode};
use gfx::text::glyph::CharIndex;
use gfx::text::text_run::{TextRun, TextRunSlice};
use script_traits::UntrustedNodeAddress;
use rustc_serialize::{Encodable, Encoder};
use msg::constellation_msg::{ConstellationChan, Msg, PipelineId, SubpageId};
use net_traits::image::holder::ImageHolder;
use net_traits::local_image_cache::LocalImageCache;
use util::geometry::{self, Au, ZERO_POINT};
use util::logical_geometry::{LogicalRect, LogicalSize, LogicalMargin, WritingMode};
use util::range::*;
use util::smallvec::SmallVec;
use util::str::is_whitespace;
use rustc_serialize::{Encodable, Encoder};
use script_traits::UntrustedNodeAddress;
use std::borrow::ToOwned;
use std::cmp::{max, min};
use std::collections::LinkedList;
@ -56,6 +51,12 @@ use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto};
use style::values::computed::{LengthOrPercentageOrNone};
use text::TextRunScanner;
use url::Url;
use util::geometry::{self, Au, ZERO_POINT};
use util::logical_geometry::{LogicalRect, LogicalSize, LogicalMargin, WritingMode};
use util::range::*;
use util::smallvec::SmallVec;
use util::str::is_whitespace;
use util;
/// Fragments (`struct Fragment`) are the leaves of the layout tree. They cannot position
/// themselves. In general, fragments do not have a simple correspondence with CSS fragments in the
@ -580,36 +581,27 @@ pub struct ScannedTextFragmentInfo {
/// The text run that this represents.
pub run: Arc<Box<TextRun>>,
/// The intrinsic size of the text fragment.
pub content_size: LogicalSize<Au>,
/// The range within the above text run that this represents.
pub range: Range<CharIndex>,
/// The positions of newlines within this scanned text fragment.
///
/// FIXME(#2260, pcwalton): Can't this go somewhere else, like in the text run or something?
/// Or can we just remove it?
pub new_line_pos: Vec<CharIndex>,
/// The new_line_pos is eaten during line breaking. If we need to re-merge
/// fragments, it will have to be restored.
pub original_new_line_pos: Option<Vec<CharIndex>>,
/// The intrinsic size of the text fragment.
pub content_size: LogicalSize<Au>,
/// The endpoint of the above range, including whitespace that was stripped out. This exists
/// so that we can restore the range to its original value (before line breaking occurred) when
/// performing incremental reflow.
pub range_end_including_stripped_whitespace: CharIndex,
}
impl ScannedTextFragmentInfo {
/// Creates the information specific to a scanned text fragment from a range and a text run.
pub fn new(run: Arc<Box<TextRun>>,
range: Range<CharIndex>,
new_line_positions: Vec<CharIndex>,
content_size: LogicalSize<Au>)
pub fn new(run: Arc<Box<TextRun>>, range: Range<CharIndex>, content_size: LogicalSize<Au>)
-> ScannedTextFragmentInfo {
ScannedTextFragmentInfo {
run: run,
range: range,
new_line_pos: new_line_positions,
original_new_line_pos: None,
content_size: content_size,
range_end_including_stripped_whitespace: range.end(),
}
}
}
@ -769,32 +761,6 @@ impl Fragment {
self.margin = LogicalMargin::zero(self.style.writing_mode);
}
/// Saves the new_line_pos vector into a `SpecificFragmentInfo::ScannedText`. This will fail
/// if called on any other type of fragment.
pub fn save_new_line_pos(&mut self) {
match &mut self.specific {
&mut SpecificFragmentInfo::ScannedText(ref mut info) => {
if !info.new_line_pos.is_empty() {
info.original_new_line_pos = Some(info.new_line_pos.clone());
}
}
_ => {}
}
}
pub fn restore_new_line_pos(&mut self) {
match &mut self.specific {
&mut SpecificFragmentInfo::ScannedText(ref mut info) => {
match info.original_new_line_pos.take() {
None => {}
Some(new_line_pos) => info.new_line_pos = new_line_pos,
}
return
}
_ => {}
}
}
/// Returns a debug ID of this fragment. This ID should not be considered stable across
/// multiple layouts or fragment manipulations.
pub fn debug_id(&self) -> u16 {
@ -823,14 +789,12 @@ impl Fragment {
}
/// Transforms this fragment using the given `SplitInfo`, preserving all the other data.
pub fn transform_with_split_info(&self,
split: &SplitInfo,
text_run: Arc<Box<TextRun>>)
pub fn transform_with_split_info(&self, split: &SplitInfo, text_run: Arc<Box<TextRun>>)
-> Fragment {
let size = LogicalSize::new(self.style.writing_mode,
split.inline_size,
self.border_box.size.block);
let info = box ScannedTextFragmentInfo::new(text_run, split.range, Vec::new(), size);
let info = box ScannedTextFragmentInfo::new(text_run, split.range, size);
self.transform(size, SpecificFragmentInfo::ScannedText(info))
}
@ -857,7 +821,6 @@ impl Fragment {
style: Arc<ComputedValues>,
first_frag: bool,
last_frag: bool) {
if self.inline_context.is_none() {
self.inline_context = Some(InlineFragmentContext::new());
}
@ -1179,25 +1142,11 @@ impl Fragment {
}
}
/// Returns true if this element can be split. This is true for text fragments.
/// Returns true if this element can be split. This is true for text fragments, unless
/// `white-space: pre` is set.
pub fn can_split(&self) -> bool {
self.is_scanned_text_fragment()
}
/// Returns the newline positions of this fragment, if it's a scanned text fragment.
pub fn newline_positions(&self) -> Option<&Vec<CharIndex>> {
match self.specific {
SpecificFragmentInfo::ScannedText(ref info) => Some(&info.new_line_pos),
_ => None,
}
}
/// Returns the newline positions of this fragment, if it's a scanned text fragment.
pub fn newline_positions_mut(&mut self) -> Option<&mut Vec<CharIndex>> {
match self.specific {
SpecificFragmentInfo::ScannedText(ref mut info) => Some(&mut info.new_line_pos),
_ => None,
}
self.is_scanned_text_fragment() &&
self.style.get_inheritedtext().white_space != white_space::T::pre
}
/// Returns true if and only if this fragment is a generated content fragment.
@ -1359,64 +1308,6 @@ impl Fragment {
self.border_box - self.border_padding
}
/// Find the split of a fragment that includes a new-line character.
///
/// A return value of `None` indicates that the fragment is not splittable.
/// Otherwise the split information is returned. The right information is
/// optional due to the possibility of it being whitespace.
//
// TODO(bjz): The text run should be removed in the future, but it is currently needed for
// the current method of fragment splitting in the `inline::try_append_*` functions.
pub fn find_split_info_by_new_line(&self)
-> Option<(SplitInfo, Option<SplitInfo>, Arc<Box<TextRun>> /* TODO(bjz): remove */)> {
match self.specific {
SpecificFragmentInfo::Canvas(_) |
SpecificFragmentInfo::Generic |
SpecificFragmentInfo::GeneratedContent(_) |
SpecificFragmentInfo::Iframe(_) |
SpecificFragmentInfo::Image(_) |
SpecificFragmentInfo::Table |
SpecificFragmentInfo::TableCell |
SpecificFragmentInfo::TableRow |
SpecificFragmentInfo::TableWrapper => {
None
}
SpecificFragmentInfo::TableColumn(_) => {
panic!("Table column fragments do not need to split")
}
SpecificFragmentInfo::UnscannedText(_) => {
panic!("Unscanned text fragments should have been scanned by now!")
}
SpecificFragmentInfo::InlineBlock(_) |
SpecificFragmentInfo::InlineAbsoluteHypothetical(_) => {
panic!("Inline blocks or inline absolute hypothetical fragments do not get split")
}
SpecificFragmentInfo::ScannedText(ref text_fragment_info) => {
let mut new_line_pos = text_fragment_info.new_line_pos.clone();
let cur_new_line_pos = new_line_pos.remove(0);
let inline_start_range = Range::new(text_fragment_info.range.begin(),
cur_new_line_pos);
let inline_end_range = Range::new(
text_fragment_info.range.begin() + cur_new_line_pos + CharIndex(1),
text_fragment_info.range.length() - (cur_new_line_pos + CharIndex(1)));
// Left fragment is for inline-start text of first founded new-line character.
let inline_start_fragment = SplitInfo::new(inline_start_range,
&**text_fragment_info);
// Right fragment is for inline-end text of first founded new-line character.
let inline_end_fragment = if inline_end_range.length() > CharIndex(0) {
Some(SplitInfo::new(inline_end_range, &**text_fragment_info))
} else {
None
};
Some((inline_start_fragment, inline_end_fragment, text_fragment_info.run.clone()))
}
}
}
/// Attempts to find the split positions of a text fragment so that its inline-size is no more
/// than `max_inline_size`.
///
@ -1495,13 +1386,13 @@ impl Fragment {
/// A helper method that uses the breaking strategy described by `slice_iterator` (at present,
/// either natural word breaking or character breaking) to split this fragment.
fn calculate_split_position_using_breaking_strategy<'a,I>(&self,
slice_iterator: I,
max_inline_size: Au,
flags: SplitOptions)
-> Option<SplitResult>
where I: Iterator<Item=
TextRunSlice<'a>> {
fn calculate_split_position_using_breaking_strategy<'a,I>(
&self,
slice_iterator: I,
max_inline_size: Au,
flags: SplitOptions)
-> Option<SplitResult>
where I: Iterator<Item=TextRunSlice<'a>> {
let text_fragment_info =
if let SpecificFragmentInfo::ScannedText(ref text_fragment_info) = self.specific {
text_fragment_info
@ -1515,31 +1406,35 @@ impl Fragment {
let mut inline_end_range = None;
let mut overflowing = false;
debug!("calculate_split_position: splitting text fragment (strlen={}, range={:?}, \
max_inline_size={:?})",
debug!("calculate_split_position_using_breaking_strategy: splitting text fragment \
(strlen={}, range={:?}, max_inline_size={:?})",
text_fragment_info.run.text.len(),
text_fragment_info.range,
max_inline_size);
for slice in slice_iterator {
debug!("calculate_split_position: considering slice (offset={:?}, slice range={:?}, \
remaining_inline_size={:?})",
debug!("calculate_split_position_using_breaking_strategy: considering slice \
(offset={:?}, slice range={:?}, remaining_inline_size={:?})",
slice.offset,
slice.range,
remaining_inline_size);
// Use the `remaining_inline_size` to find a split point if possible. If not, go around
// the loop again with the next slice.
let metrics = text_fragment_info.run.metrics_for_slice(slice.glyphs, &slice.range);
let advance = metrics.advance_width;
// Have we found the split point?
if advance <= remaining_inline_size || slice.glyphs.is_whitespace() {
// Keep going; we haven't found the split point yet.
if flags.contains(STARTS_LINE) && pieces_processed_count == 0 &&
if flags.contains(STARTS_LINE) &&
pieces_processed_count == 0 &&
slice.glyphs.is_whitespace() {
debug!("calculate_split_position: skipping leading trimmable whitespace");
debug!("calculate_split_position_using_breaking_strategy: skipping \
leading trimmable whitespace");
inline_start_range.shift_by(slice.range.length());
} else {
debug!("split_to_inline_size: enlarging span");
debug!("calculate_split_position_using_breaking_strategy: enlarging span");
remaining_inline_size = remaining_inline_size - advance;
inline_start_range.extend_by(slice.range.length());
}
@ -1570,60 +1465,31 @@ impl Fragment {
inline_end);
}
break
}
// If we failed to find a suitable split point, we're on the verge of overflowing the
// line.
if inline_start_range.is_empty() || overflowing {
// If we've been instructed to retry at character boundaries (probably via
// `overflow-wrap: break-word`), do so.
if flags.contains(RETRY_AT_CHARACTER_BOUNDARIES) {
let character_breaking_strategy =
text_fragment_info.run
.character_slices_in_range(&text_fragment_info.range);
let mut flags = flags;
flags.remove(RETRY_AT_CHARACTER_BOUNDARIES);
return self.calculate_split_position_using_breaking_strategy(
character_breaking_strategy,
max_inline_size,
flags)
}
// If we failed to find a suitable split point, we're on the verge of overflowing the line.
if inline_start_range.is_empty() || overflowing {
// If we've been instructed to retry at character boundaries (probably via
// `overflow-wrap: break-word`), do so.
if flags.contains(RETRY_AT_CHARACTER_BOUNDARIES) {
let character_breaking_strategy =
text_fragment_info.run.character_slices_in_range(&text_fragment_info.range);
let mut flags = flags;
flags.remove(RETRY_AT_CHARACTER_BOUNDARIES);
return self.calculate_split_position_using_breaking_strategy(
character_breaking_strategy,
max_inline_size,
flags)
}
// We aren't at the start of the line, so don't overflow. Let inline layout wrap to the
// next line instead.
if !flags.contains(STARTS_LINE) {
return None
}
}
// Remove trailing whitespace from the inline-start split, if necessary.
//
// FIXME(pcwalton): Is there a more clever (i.e. faster) way to do this?
strip_trailing_whitespace(&**text_fragment_info.run, &mut inline_start_range);
// Remove leading whitespace from the inline-end split, if necessary.
//
// FIXME(pcwalton): Is there a more clever (i.e. faster) way to do this?
if let Some(ref mut inline_end_range) = inline_end_range {
let inline_end_fragment_text =
text_fragment_info.run.text.slice_chars(inline_end_range.begin().to_usize(),
inline_end_range.end().to_usize());
let mut leading_whitespace_character_count = 0;
for ch in inline_end_fragment_text.chars() {
if ch.is_whitespace() {
leading_whitespace_character_count += 1
} else {
break
// We aren't at the start of the line, so don't overflow. Let inline layout wrap to
// the next line instead.
if !flags.contains(STARTS_LINE) {
return None
}
}
inline_end_range.adjust_by(CharIndex(leading_whitespace_character_count),
-CharIndex(leading_whitespace_character_count));
}
// Normalize our split so that the inline-end fragment will never be `Some` while the
// inline-start fragment is `None`.
if inline_start_range.is_empty() && inline_end_range.is_some() {
inline_start_range = inline_end_range.unwrap();
inline_end_range = None
break
}
let inline_start = if !inline_start_range.is_empty() {
@ -1642,22 +1508,21 @@ impl Fragment {
})
}
/// Attempts to strip trailing whitespace from this fragment by adjusting the text run range.
/// Returns true if any modifications were made.
pub fn strip_trailing_whitespace_if_necessary(&mut self) -> bool {
let text_fragment_info =
if let SpecificFragmentInfo::ScannedText(ref mut text_fragment_info) = self.specific {
text_fragment_info
} else {
return false
};
let run = text_fragment_info.run.clone();
if strip_trailing_whitespace(&**run, &mut text_fragment_info.range) {
self.border_box.size.inline = run.advance_for_range(&text_fragment_info.range);
return true
/// The opposite of `calculate_split_position_using_breaking_strategy`: merges this fragment
/// with the next one.
pub fn merge_with(&mut self, next_fragment: Fragment) {
match (&mut self.specific, &next_fragment.specific) {
(&mut SpecificFragmentInfo::ScannedText(ref mut this_info),
&SpecificFragmentInfo::ScannedText(ref other_info)) => {
debug_assert!(util::arc_ptr_eq(&this_info.run, &other_info.run));
this_info.range.extend_to(other_info.range_end_including_stripped_whitespace);
this_info.content_size.inline =
this_info.run.metrics_for_range(&this_info.range).advance_width;
self.border_box.size.inline = this_info.content_size.inline +
self.border_padding.inline_start_end();
}
_ => panic!("Can only merge two scanned-text fragments!"),
}
false
}
/// Returns true if this fragment is an unscanned text fragment that consists entirely of
@ -1669,7 +1534,7 @@ impl Fragment {
}
match self.specific {
SpecificFragmentInfo::UnscannedText(ref text_fragment_info) => {
is_whitespace(text_fragment_info.text.as_slice())
util::str::is_whitespace(text_fragment_info.text.as_slice())
}
_ => false,
}
@ -1890,11 +1755,14 @@ impl Fragment {
/// Returns true if this fragment can merge with another adjacent fragment or false otherwise.
pub fn can_merge_with_fragment(&self, other: &Fragment) -> bool {
match (&self.specific, &other.specific) {
(&SpecificFragmentInfo::UnscannedText(_), &SpecificFragmentInfo::UnscannedText(_)) => {
(&SpecificFragmentInfo::UnscannedText(ref first_unscanned_text),
&SpecificFragmentInfo::UnscannedText(_)) => {
// FIXME: Should probably use a whitelist of styles that can safely differ (#3165)
let length = first_unscanned_text.text.len();
self.style().get_font() == other.style().get_font() &&
self.text_decoration() == other.text_decoration() &&
self.white_space() == other.white_space()
self.white_space() == other.white_space() &&
(length == 0 || first_unscanned_text.text.char_at_reverse(length) != '\n')
}
_ => false,
}
@ -2076,14 +1944,57 @@ impl Fragment {
_ => {}
}
}
pub fn requires_line_break_afterward_if_wrapping_on_newlines(&self) -> bool {
match self.specific {
SpecificFragmentInfo::ScannedText(ref scanned_text) => {
!scanned_text.range.is_empty() &&
scanned_text.run.text.char_at_reverse(scanned_text.range
.end()
.get() as usize) == '\n'
}
_ => false,
}
}
pub fn strip_leading_whitespace_if_necessary(&mut self) {
let mut scanned_text_fragment_info = match self.specific {
SpecificFragmentInfo::ScannedText(ref mut scanned_text_fragment_info) => {
scanned_text_fragment_info
}
_ => return,
};
if self.style.get_inheritedtext().white_space == white_space::T::pre {
return
}
let mut leading_whitespace_character_count = 0;
{
let text = scanned_text_fragment_info.run.text.slice_chars(
scanned_text_fragment_info.range.begin().to_usize(),
scanned_text_fragment_info.range.end().to_usize());
for character in text.chars() {
if util::str::char_is_whitespace(character) {
leading_whitespace_character_count += 1
} else {
break
}
}
}
scanned_text_fragment_info.range.adjust_by(CharIndex(leading_whitespace_character_count),
-CharIndex(leading_whitespace_character_count));
}
}
impl fmt::Debug for Fragment {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
try!(write!(f, "({} {} ", self.debug_id(), self.specific.get_type()));
try!(write!(f, "bp {:?}", self.border_padding));
try!(write!(f, " "));
try!(write!(f, "m {:?}", self.margin));
try!(write!(f, "bb {:?} bp {:?} m {:?}",
self.border_box,
self.border_padding,
self.margin));
write!(f, ")")
}
}
@ -2105,7 +2016,7 @@ bitflags! {
const STARTS_LINE = 0x01,
#[doc="True if we should attempt to split at character boundaries if this split fails. \
This is used to implement `overflow-wrap: break-word`."]
const RETRY_AT_CHARACTER_BOUNDARIES = 0x02
const RETRY_AT_CHARACTER_BOUNDARIES = 0x02,
}
}
@ -2129,25 +2040,3 @@ pub enum CoordinateSystem {
Own,
}
/// Given a range and a text run, adjusts the range to eliminate trailing whitespace. Returns true
/// if any modifications were made.
fn strip_trailing_whitespace(text_run: &TextRun, range: &mut Range<CharIndex>) -> bool {
// FIXME(pcwalton): Is there a more clever (i.e. faster) way to do this?
let text = text_run.text.slice_chars(range.begin().to_usize(), range.end().to_usize());
let mut trailing_whitespace_character_count = 0;
for ch in text.chars().rev() {
if ch.is_whitespace() {
trailing_whitespace_character_count += 1
} else {
break
}
}
if trailing_whitespace_character_count == 0 {
return false
}
range.extend_by(-CharIndex(trailing_whitespace_character_count));
return true
}