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Auto merge of #19688 - Manishearth:linebreak, r=mbrubeck

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Detect adjoining text fragments with no line break opportunity between them

First attempt at https://github.com/servo/servo/issues/874

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This commit is contained in:
bors-servo 2018-01-24 22:42:59 -06:00 • committed by GitHub
commit 9c13073075
39 changed files with 172 additions and 81 deletions
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2
components/layout/Cargo.toml
View file

@ -48,6 +48,8 @@ style_traits = {path = "../style_traits"}
unicode-bidi = {version = "0.3", features = ["with_serde"]}
unicode-script = {version = "0.1", features = ["harfbuzz"]}
webrender_api = {git = "https://github.com/servo/webrender", features = ["ipc"]}
xi-unicode = "0.1.0"
[dev-dependencies]
size_of_test = {path = "../size_of_test"}

36
components/layout/fragment.rs
View file

@ -479,6 +479,11 @@ bitflags! {
/// Is this fragment selected?
const SELECTED = 0x02;
/// Suppress line breaking between this and the previous fragment
///
/// This handles cases like Foo<span>bar</span>
const SUPPRESS_LINE_BREAK_BEFORE = 0x04;
}
}
@ -712,13 +717,15 @@ 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<TextRun>)
-> Fragment {
///
/// If this is the first half of a split, `first` is true
pub fn transform_with_split_info(&self, split: &SplitInfo, text_run: Arc<TextRun>,
first: bool) -> Fragment {
let size = LogicalSize::new(self.style.writing_mode,
split.inline_size,
self.border_box.size.block);
// Preserve the insertion point if it is in this fragment's range or it is at line end.
let (flags, insertion_point) = match self.specific {
let (mut flags, insertion_point) = match self.specific {
SpecificFragmentInfo::ScannedText(ref info) => {
match info.insertion_point {
Some(index) if split.range.contains(index) => (info.flags, info.insertion_point),
@ -729,6 +736,11 @@ impl Fragment {
},
_ => (ScannedTextFlags::empty(), None)
};
if !first {
flags.set(ScannedTextFlags::SUPPRESS_LINE_BREAK_BEFORE, false);
}
let info = Box::new(ScannedTextFragmentInfo::new(
text_run,
split.range,
@ -1421,6 +1433,14 @@ impl Fragment {
}
}
pub fn suppress_line_break_before(&self) -> bool {
match self.specific {
SpecificFragmentInfo::ScannedText(ref st) =>
st.flags.contains(ScannedTextFlags::SUPPRESS_LINE_BREAK_BEFORE),
_ => false,
}
}
/// Computes the intrinsic inline-sizes of this fragment.
pub fn compute_intrinsic_inline_sizes(&mut self) -> IntrinsicISizesContribution {
let mut result = self.style_specified_intrinsic_inline_size();
@ -1621,6 +1641,16 @@ impl Fragment {
}
}
/// Does this fragment start on a glyph run boundary?
pub fn is_on_glyph_run_boundary(&self) -> bool {
let text_fragment_info = match self.specific {
SpecificFragmentInfo::ScannedText(ref text_fragment_info)
=> text_fragment_info,
_ => return true,
};
text_fragment_info.run.on_glyph_run_boundary(text_fragment_info.range.begin())
}
/// Truncates this fragment to the given `max_inline_size`, using a character-based breaking
/// strategy. The resulting fragment will have `SpecificFragmentInfo::TruncatedFragment`,
/// preserving the original fragment for use in incremental reflow.

21
components/layout/inline.rs
View file

@ -554,7 +554,6 @@ impl LineBreaker {
layout_context: &LayoutContext) {
// Undo any whitespace stripping from previous reflows.
fragment.reset_text_range_and_inline_size();
// Determine initial placement for the fragment if we need to.
//
// Also, determine whether we can legally break the line before, or
@ -566,7 +565,21 @@ impl LineBreaker {
self.pending_line.green_zone = line_bounds.size;
false
} else {
fragment.white_space().allow_wrap()
// In case of Foo<span style="...">bar</span>, the line breaker will
// set the "suppress line break before" flag for the second fragment.
//
// In case of Foo<span>bar</span> the second fragment ("bar") will
// start _within_ a glyph run, so we also avoid breaking there
//
// is_on_glyph_run_boundary does a binary search, but this is ok
// because the result will be cached and reused in
// `calculate_split_position` later
if fragment.suppress_line_break_before() ||
!fragment.is_on_glyph_run_boundary() {
false
} else {
fragment.white_space().allow_wrap()
}
};
debug!("LineBreaker: trying to append to line {} \
@ -657,10 +670,10 @@ impl LineBreaker {
};
inline_start_fragment = split_result.inline_start.as_ref().map(|x| {
fragment.transform_with_split_info(x, split_result.text_run.clone())
fragment.transform_with_split_info(x, split_result.text_run.clone(), true)
});
inline_end_fragment = split_result.inline_end.as_ref().map(|x| {
fragment.transform_with_split_info(x, split_result.text_run.clone())
fragment.transform_with_split_info(x, split_result.text_run.clone(), false)
});
// Push the first fragment onto the line we're working on and start off the next line with

1
components/layout/lib.rs
View file

@ -42,6 +42,7 @@ extern crate style_traits;
extern crate unicode_bidi;
extern crate unicode_script;
extern crate webrender_api;
extern crate xi_unicode;
#[macro_use]
pub mod layout_debug;

45
components/layout/text.rs
View file

@ -32,6 +32,7 @@ use style::properties::style_structs;
use style::values::generics::text::LineHeight;
use unicode_bidi as bidi;
use unicode_script::{Script, get_script};
use xi_unicode::LineBreakLeafIter;
/// Returns the concatenated text of a list of unscanned text fragments.
fn text(fragments: &LinkedList<Fragment>) -> String {
@ -91,6 +92,15 @@ impl TextRunScanner {
let mut last_whitespace = false;
let mut paragraph_bytes_processed = 0;
// The first time we process a text run we will set this
// linebreaker. There is no way for the linebreaker to start
// with an empty state; you must give it its first input immediately.
//
// This linebreaker is shared across text runs, so we can know if
// there is a break at the beginning of a text run or clump, e.g.
// in the case of FooBar<span>Baz</span>
let mut linebreaker = None;
while !fragments.is_empty() {
// Create a clump.
split_first_fragment_at_newline_if_necessary(&mut fragments);
@ -109,7 +119,8 @@ impl TextRunScanner {
&mut new_fragments,
&mut paragraph_bytes_processed,
bidi_levels,
last_whitespace);
last_whitespace,
&mut linebreaker);
}
debug!("TextRunScanner: complete.");
@ -129,7 +140,8 @@ impl TextRunScanner {
out_fragments: &mut Vec<Fragment>,
paragraph_bytes_processed: &mut usize,
bidi_levels: Option<&[bidi::Level]>,
mut last_whitespace: bool)
mut last_whitespace: bool,
linebreaker: &mut Option<LineBreakLeafIter>)
-> bool {
debug!("TextRunScanner: flushing {} fragments in range", self.clump.len());
@ -309,22 +321,26 @@ impl TextRunScanner {
flags: flags,
};
// FIXME(https://github.com/rust-lang/rust/issues/23338)
run_info_list.into_iter().map(|run_info| {
let mut result = Vec::with_capacity(run_info_list.len());
for run_info in run_info_list {
let mut options = options;
options.script = run_info.script;
if run_info.bidi_level.is_rtl() {
options.flags.insert(ShapingFlags::RTL_FLAG);
}
let mut font = fontgroup.fonts.get(run_info.font_index).unwrap().borrow_mut();
ScannedTextRun {
run: Arc::new(TextRun::new(&mut *font,
run_info.text,
&options,
run_info.bidi_level)),
let (run, break_at_zero) = TextRun::new(&mut *font,
run_info.text,
&options,
run_info.bidi_level,
linebreaker);
result.push((ScannedTextRun {
run: Arc::new(run),
insertion_point: run_info.insertion_point,
}
}).collect::<Vec<_>>()
}, break_at_zero))
}
result
};
// Make new fragments with the runs and adjusted text indices.
@ -351,12 +367,17 @@ impl TextRunScanner {
}
};
let mapping = mappings.next().unwrap();
let scanned_run = runs[mapping.text_run_index].clone();
let (scanned_run, break_at_zero) = runs[mapping.text_run_index].clone();
let mut byte_range = Range::new(ByteIndex(mapping.byte_range.begin() as isize),
ByteIndex(mapping.byte_range.length() as isize));
let mut flags = ScannedTextFlags::empty();
if !break_at_zero && mapping.byte_range.begin() == 0 {
// If this is the first segment of the text run,
// and the text run doesn't break at zero, suppress line breaks
flags.insert(ScannedTextFlags::SUPPRESS_LINE_BREAK_BEFORE)
}
let text_size = old_fragment.border_box.size;
let requires_line_break_afterward_if_wrapping_on_newlines =