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Basic support for bidirectional text

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This commit is contained in:
Matt Brubeck 2015-06-26 08:19:29 -07:00
parent b386d7ae44
commit dfac8ce4a1
20 changed files with 309 additions and 107 deletions
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134
components/layout/text.rs
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@ -10,7 +10,7 @@ use fragment::{Fragment, SpecificFragmentInfo, ScannedTextFragmentInfo, Unscanne
use inline::InlineFragments;
use gfx::font::{DISABLE_KERNING_SHAPING_FLAG, FontMetrics, IGNORE_LIGATURES_SHAPING_FLAG};
use gfx::font::{RunMetrics, ShapingFlags, ShapingOptions};
use gfx::font::{RTL_FLAG, RunMetrics, ShapingFlags, ShapingOptions};
use gfx::font_context::FontContext;
use gfx::text::glyph::CharIndex;
use gfx::text::text_run::TextRun;
@ -23,11 +23,39 @@ use style::computed_values::{line_height, text_orientation, text_rendering, text
use style::computed_values::{white_space};
use style::properties::ComputedValues;
use style::properties::style_structs::Font as FontStyle;
use unicode_bidi::{is_rtl, process_text};
use util::geometry::Au;
use util::linked_list::split_off_head;
use util::logical_geometry::{LogicalSize, WritingMode};
use util::range::{Range, RangeIndex};
/// Returns the concatenated text of a list of unscanned text fragments.
fn text(fragments: &LinkedList<Fragment>) -> String {
// FIXME: Some of this work is later duplicated in split_first_fragment_at_newline_if_necessary
// and transform_text. This code should be refactored so that the all the scanning for
// newlines is done in a single pass.
let mut text = String::new();
for fragment in fragments {
match fragment.specific {
SpecificFragmentInfo::UnscannedText(ref info) => {
match fragment.white_space() {
white_space::T::normal | white_space::T::nowrap => {
text.push_str(&info.text.replace("\n", " "));
}
white_space::T::pre => {
text.push_str(&info.text);
}
}
}
_ => {}
}
}
text
}
/// A stack-allocated object for scanning an inline flow into `TextRun`-containing `TextFragment`s.
pub struct TextRunScanner {
pub clump: LinkedList<Fragment>,
@ -45,11 +73,26 @@ impl TextRunScanner {
mut fragments: LinkedList<Fragment>)
-> InlineFragments {
debug!("TextRunScanner: scanning {} fragments for text runs...", fragments.len());
debug_assert!(!fragments.is_empty());
// Calculate bidi embedding levels, so we can split bidirectional fragments for reordering.
let text = text(&fragments);
let para_level = fragments.front().unwrap().style.writing_mode.to_bidi_level();
let bidi_info = process_text(&text, Some(para_level));
// Optimization: If all the text is LTR, don't bother splitting on bidi levels.
let bidi_levels = if bidi_info.levels.iter().cloned().any(is_rtl) {
Some(&bidi_info.levels[..])
} else {
None
};
// FIXME(pcwalton): We want to be sure not to allocate multiple times, since this is a
// performance-critical spot, but this may overestimate and allocate too much memory.
let mut new_fragments = Vec::with_capacity(fragments.len());
let mut last_whitespace = true;
let mut paragraph_bytes_processed = 0;
while !fragments.is_empty() {
// Create a clump.
split_first_fragment_at_newline_if_necessary(&mut fragments);
@ -66,6 +109,8 @@ impl TextRunScanner {
// Flush that clump to the list of fragments we're building up.
last_whitespace = self.flush_clump_to_list(font_context,
&mut new_fragments,
&mut paragraph_bytes_processed,
bidi_levels,
last_whitespace);
}
@ -84,6 +129,8 @@ impl TextRunScanner {
fn flush_clump_to_list(&mut self,
font_context: &mut FontContext,
out_fragments: &mut Vec<Fragment>,
paragraph_bytes_processed: &mut usize,
bidi_levels: Option<&[u8]>,
mut last_whitespace: bool)
-> bool {
debug!("TextRunScanner: flushing {} fragments in range", self.clump.len());
@ -137,47 +184,51 @@ impl TextRunScanner {
};
let (mut start_position, mut end_position) = (0, 0);
for character in text.chars() {
// Search for the first font in this font group that contains a glyph for this
// character.
for font_index in 0..fontgroup.fonts.len() {
if font_index < fontgroup.fonts.len() - 1 &&
fontgroup.fonts
.get(font_index)
.unwrap()
.borrow()
.glyph_index(character)
.is_none() {
continue
let mut font_index = 0;
while font_index < fontgroup.fonts.len() - 1 {
if fontgroup.fonts.get(font_index).unwrap().borrow()
.glyph_index(character)
.is_some() {
break
}
// We found the font we want to use. Now, if necessary, flush the mapping
// we were building up.
if run_info.font_index != font_index {
if run_info.text.len() > 0 {
mapping.flush(&mut mappings,
&mut run_info,
&**text,
compression,
text_transform,
&mut last_whitespace,
&mut start_position,
end_position);
run_info_list.push(run_info);
run_info = RunInfo::new();
mapping = RunMapping::new(&run_info_list[..],
&run_info,
fragment_index);
}
run_info.font_index = font_index
}
// Consume this character.
end_position += character.len_utf8();
break
font_index += 1;
}
let bidi_level = match bidi_levels {
Some(levels) => levels[*paragraph_bytes_processed],
None => 0
};
// Now, if necessary, flush the mapping we were building up.
if run_info.font_index != font_index || run_info.bidi_level != bidi_level {
if end_position > start_position {
mapping.flush(&mut mappings,
&mut run_info,
&**text,
compression,
text_transform,
&mut last_whitespace,
&mut start_position,
end_position);
}
if run_info.text.len() > 0 {
run_info_list.push(run_info);
run_info = RunInfo::new();
mapping = RunMapping::new(&run_info_list[..],
&run_info,
fragment_index);
}
run_info.font_index = font_index;
run_info.bidi_level = bidi_level;
}
// Consume this character.
end_position += character.len_utf8();
*paragraph_bytes_processed += character.len_utf8();
}
// If the mapping is zero-length, don't flush it.
@ -220,8 +271,12 @@ impl TextRunScanner {
// FIXME(https://github.com/rust-lang/rust/issues/23338)
run_info_list.into_iter().map(|run_info| {
let mut options = options;
if is_rtl(run_info.bidi_level) {
options.flags.insert(RTL_FLAG);
}
let mut font = fontgroup.fonts.get(run_info.font_index).unwrap().borrow_mut();
Arc::new(box TextRun::new(&mut *font, run_info.text, &options))
Arc::new(box TextRun::new(&mut *font, run_info.text, &options, run_info.bidi_level))
}).collect::<Vec<_>>()
};
@ -364,6 +419,8 @@ struct RunInfo {
font_index: usize,
/// A cached copy of the number of Unicode characters in the text run.
character_length: usize,
/// The bidirection embedding level of this text run.
bidi_level: u8,
}
impl RunInfo {
@ -372,6 +429,7 @@ impl RunInfo {
text: String::new(),
font_index: 0,
character_length: 0,
bidi_level: 0,
}
}
}