/* 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/. */
//! Text layout.
use crate::context::LayoutFontContext;
use crate::fragment::{Fragment, ScannedTextFlags};
use crate::fragment::{ScannedTextFragmentInfo, SpecificFragmentInfo, UnscannedTextFragmentInfo};
use crate::inline::{InlineFragmentNodeFlags, InlineFragments};
use crate::linked_list::split_off_head;
use app_units::Au;
use gfx::font::{FontMetrics, FontRef, RunMetrics, ShapingFlags, ShapingOptions};
use gfx::text::glyph::ByteIndex;
use gfx::text::text_run::TextRun;
use gfx::text::util::{self, CompressionMode};
use range::Range;
use servo_atoms::Atom;
use std::borrow::ToOwned;
use std::collections::LinkedList;
use std::mem;
use std::sync::Arc;
use style::computed_values::text_rendering::T as TextRendering;
use style::computed_values::white_space::T as WhiteSpace;
use style::computed_values::word_break::T as WordBreak;
use style::logical_geometry::{LogicalSize, WritingMode};
use style::properties::style_structs::Font as FontStyleStruct;
use style::properties::ComputedValues;
use style::values::generics::text::LineHeight;
use style::values::specified::text::{TextTransform, TextTransformCase};
use unicode_bidi as bidi;
use unicode_script::{get_script, Script};
use xi_unicode::LineBreakLeafIter;
/// 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 {
if let SpecificFragmentInfo::UnscannedText(ref info) = fragment.specific {
if fragment.white_space().preserve_newlines() {
text.push_str(&info.text);
} else {
text.push_str(&info.text.replace("\n", " "));
}
}
}
text
}
/// A stack-allocated object for scanning an inline flow into `TextRun`-containing `TextFragment`s.
pub struct TextRunScanner {
pub clump: LinkedList<Fragment>,
}
impl TextRunScanner {
pub fn new() -> TextRunScanner {
TextRunScanner {
clump: LinkedList::new(),
}
}
pub fn scan_for_runs(
&mut self,
font_context: &mut LayoutFontContext,
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 = bidi::BidiInfo::new(&text, Some(para_level));
// Optimization: If all the text is LTR, don't bother splitting on bidi levels.
let bidi_levels = if bidi_info.has_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 = 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);
self.clump.append(&mut split_off_head(&mut fragments));
while !fragments.is_empty() &&
self.clump
.back()
.unwrap()
.can_merge_with_fragment(fragments.front().unwrap())
{
split_first_fragment_at_newline_if_necessary(&mut fragments);
self.clump.append(&mut split_off_head(&mut fragments));
}
// 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,
&mut linebreaker,
);
}
debug!("TextRunScanner: complete.");
InlineFragments {
fragments: new_fragments,
}
}
/// A "clump" is a range of inline flow leaves that can be merged together into a single
/// fragment. Adjacent text with the same style can be merged, and nothing else can.
///
/// The flow keeps track of the fragments contained by all non-leaf DOM nodes. This is necessary
/// for correct painting order. Since we compress several leaf fragments here, the mapping must
/// be adjusted.
fn flush_clump_to_list(
&mut self,
mut font_context: &mut LayoutFontContext,
out_fragments: &mut Vec<Fragment>,
paragraph_bytes_processed: &mut usize,
bidi_levels: Option<&[bidi::Level]>,
mut last_whitespace: bool,
linebreaker: &mut Option<LineBreakLeafIter>,
) -> bool {
debug!(
"TextRunScanner: flushing {} fragments in range",
self.clump.len()
);
debug_assert!(!self.clump.is_empty());
match self.clump.front().unwrap().specific {
SpecificFragmentInfo::UnscannedText(_) => {},
_ => {
debug_assert!(
self.clump.len() == 1,
"WAT: can't coalesce non-text nodes in flush_clump_to_list()!"
);
out_fragments.push(self.clump.pop_front().unwrap());
return false;
},
}
// Concatenate all of the transformed strings together, saving the new character indices.
let mut mappings: Vec<RunMapping> = Vec::new();
let runs = {
let font_group;
let compression;
let text_transform;
let letter_spacing;
let word_spacing;
let text_rendering;
let word_break;
{
let in_fragment = self.clump.front().unwrap();
let font_style = in_fragment.style().clone_font();
let inherited_text_style = in_fragment.style().get_inherited_text();
font_group = font_context.font_group(font_style);
compression = match in_fragment.white_space() {
WhiteSpace::Normal | WhiteSpace::Nowrap => {
CompressionMode::CompressWhitespaceNewline
},
WhiteSpace::Pre | WhiteSpace::PreWrap => CompressionMode::CompressNone,
WhiteSpace::PreLine => CompressionMode::CompressWhitespace,
};
text_transform = inherited_text_style.text_transform;
letter_spacing = inherited_text_style.letter_spacing;
word_spacing = inherited_text_style.word_spacing.to_hash_key();
text_rendering = inherited_text_style.text_rendering;
word_break = inherited_text_style.word_break;
}
// First, transform/compress text of all the nodes.
let (mut run_info_list, mut run_info) = (Vec::new(), RunInfo::new());
let mut insertion_point = None;
for (fragment_index, in_fragment) in self.clump.iter().enumerate() {
debug!(" flushing {:?}", in_fragment);
let mut mapping = RunMapping::new(&run_info_list[..], fragment_index);
let text;
let selection;
match in_fragment.specific {
SpecificFragmentInfo::UnscannedText(ref text_fragment_info) => {
text = &text_fragment_info.text;
selection = text_fragment_info.selection;
},
_ => panic!("Expected an unscanned text fragment!"),
};
insertion_point = match selection {
Some(range) if range.is_empty() => {
// `range` is the range within the current fragment. To get the range
// within the text run, offset it by the length of the preceding fragments.
Some(range.begin() + ByteIndex(run_info.text.len() as isize))
},
_ => None,
};
let (mut start_position, mut end_position) = (0, 0);
for (byte_index, character) in text.char_indices() {
if !character.is_control() {
let font = font_group
.borrow_mut()
.find_by_codepoint(&mut font_context, character);
let bidi_level = match bidi_levels {
Some(levels) => levels[*paragraph_bytes_processed],
None => bidi::Level::ltr(),
};
// Break the run if the new character has a different explicit script than the
// previous characters.
//
// TODO: Special handling of paired punctuation characters.
// http://www.unicode.org/reports/tr24/#Common
let script = get_script(character);
let compatible_script = is_compatible(script, run_info.script);
if compatible_script && !is_specific(run_info.script) && is_specific(script)
{
run_info.script = script;
}
let selected = match selection {
Some(range) => range.contains(ByteIndex(byte_index as isize)),
None => false,
};
// Now, if necessary, flush the mapping we were building up.
let flush_run = !run_info.has_font(&font) ||
run_info.bidi_level != bidi_level ||
!compatible_script;
let new_mapping_needed = flush_run || mapping.selected != selected;
if new_mapping_needed {
// We ignore empty mappings at the very start of a fragment.
// The run info values are uninitialized at this point so
// flushing an empty mapping is pointless.
if end_position > 0 {
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 {
if flush_run {
run_info.flush(&mut run_info_list, &mut insertion_point);
run_info = RunInfo::new();
}
mapping = RunMapping::new(&run_info_list[..], fragment_index);
}
run_info.font = font;
run_info.bidi_level = bidi_level;
run_info.script = script;
mapping.selected = selected;
}
}
// Consume this character.
end_position += character.len_utf8();
*paragraph_bytes_processed += character.len_utf8();
}
// Flush the last mapping we created for this fragment to the list.
mapping.flush(
&mut mappings,
&mut run_info,
&**text,
compression,
text_transform,
&mut last_whitespace,
&mut start_position,
end_position,
);
}
// Push the final run info.
run_info.flush(&mut run_info_list, &mut insertion_point);
// Per CSS 2.1 § 16.4, "when the resultant space between two characters is not the same
// as the default space, user agents should not use ligatures." This ensures that, for
// example, `finally` with a wide `letter-spacing` renders as `f i n a l l y` and not
// `fi n a l l y`.
let mut flags = ShapingFlags::empty();
if letter_spacing.0.px() != 0. {
flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG);
}
if text_rendering == TextRendering::Optimizespeed {
flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG);
flags.insert(ShapingFlags::DISABLE_KERNING_SHAPING_FLAG)
}
if word_break == WordBreak::KeepAll {
flags.insert(ShapingFlags::KEEP_ALL_FLAG);
}
let options = ShapingOptions {
letter_spacing: if letter_spacing.0.px() == 0. {
None
} else {
Some(Au::from(letter_spacing.0))
},
word_spacing,
script: Script::Common,
flags: flags,
};
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);
}
// If no font is found (including fallbacks), there's no way we can render.
let font = run_info
.font
.or_else(|| font_group.borrow_mut().first(&mut font_context))
.expect("No font found for text run!");
let (run, break_at_zero) = TextRun::new(
&mut *font.borrow_mut(),
run_info.text,
&options,
run_info.bidi_level,
linebreaker,
);
result.push((
ScannedTextRun {
run: Arc::new(run),
insertion_point: run_info.insertion_point,
},
break_at_zero,
))
}
result
};
// Make new fragments with the runs and adjusted text indices.
debug!("TextRunScanner: pushing {} fragment(s)", self.clump.len());
let mut mappings = mappings.into_iter().peekable();
let mut prev_fragments_to_meld = Vec::new();
for (logical_offset, old_fragment) in mem::replace(&mut self.clump, LinkedList::new())
.into_iter()
.enumerate()
{
let mut is_first_mapping_of_this_old_fragment = true;
loop {
match mappings.peek() {
Some(mapping) if mapping.old_fragment_index == logical_offset => {},
Some(_) | None => {
if is_first_mapping_of_this_old_fragment {
// There were no mappings for this unscanned fragment. Transfer its
// flags to the previous/next sibling elements instead.
if let Some(ref mut last_fragment) = out_fragments.last_mut() {
last_fragment.meld_with_next_inline_fragment(&old_fragment);
}
prev_fragments_to_meld.push(old_fragment);
}
break;
},
};
let mapping = mappings.next().unwrap();
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 = scanned_run.run.text
[mapping.byte_range.begin()..mapping.byte_range.end()]
.ends_with('\n');
if requires_line_break_afterward_if_wrapping_on_newlines {
byte_range.extend_by(ByteIndex(-1)); // Trim the '\n'
flags.insert(
ScannedTextFlags::REQUIRES_LINE_BREAK_AFTERWARD_IF_WRAPPING_ON_NEWLINES,
);
}
if mapping.selected {
flags.insert(ScannedTextFlags::SELECTED);
}
let insertion_point =
if mapping.contains_insertion_point(scanned_run.insertion_point) {
scanned_run.insertion_point
} else {
None
};
let mut new_text_fragment_info = Box::new(ScannedTextFragmentInfo::new(
scanned_run.run,
byte_range,
text_size,
insertion_point,
flags,
));
let new_metrics = new_text_fragment_info.run.metrics_for_range(&byte_range);
let writing_mode = old_fragment.style.writing_mode;
let bounding_box_size = bounding_box_for_run_metrics(&new_metrics, writing_mode);
new_text_fragment_info.content_size = bounding_box_size;
let mut new_fragment = old_fragment.transform(
bounding_box_size,
SpecificFragmentInfo::ScannedText(new_text_fragment_info),
);
let is_last_mapping_of_this_old_fragment = match mappings.peek() {
Some(mapping) if mapping.old_fragment_index == logical_offset => false,
_ => true,
};
if let Some(ref mut context) = new_fragment.inline_context {
for node in &mut context.nodes {
if !is_last_mapping_of_this_old_fragment {
node.flags
.remove(InlineFragmentNodeFlags::LAST_FRAGMENT_OF_ELEMENT);
}
if !is_first_mapping_of_this_old_fragment {
node.flags
.remove(InlineFragmentNodeFlags::FIRST_FRAGMENT_OF_ELEMENT);
}
}
}
for prev_fragment in prev_fragments_to_meld.drain(..) {
new_fragment.meld_with_prev_inline_fragment(&prev_fragment);
}
is_first_mapping_of_this_old_fragment = false;
out_fragments.push(new_fragment)
}
}
last_whitespace
}
}
#[inline]
fn bounding_box_for_run_metrics(
metrics: &RunMetrics,
writing_mode: WritingMode,
) -> LogicalSize<Au> {
// TODO: When the text-orientation property is supported, the block and inline directions may
// be swapped for horizontal glyphs in vertical lines.
LogicalSize::new(
writing_mode,
metrics.bounding_box.size.width,
metrics.bounding_box.size.height,
)
}
/// Returns the metrics of the font represented by the given `FontStyleStruct`.
///
/// `#[inline]` because often the caller only needs a few fields from the font metrics.
///
/// # Panics
///
/// Panics if no font can be found for the given font style.
#[inline]
pub fn font_metrics_for_style(
mut font_context: &mut LayoutFontContext,
style: crate::ServoArc<FontStyleStruct>,
) -> FontMetrics {
let font_group = font_context.font_group(style);
let font = font_group.borrow_mut().first(&mut font_context);
let font = font.as_ref().unwrap().borrow();
font.metrics.clone()
}
/// Returns the line block-size needed by the given computed style and font size.
pub fn line_height_from_style(style: &ComputedValues, metrics: &FontMetrics) -> Au {
let font_size = style.get_font().font_size.size();
match style.get_inherited_text().line_height {
LineHeight::Normal => Au::from(metrics.line_gap),
LineHeight::Number(l) => font_size.scale_by(l.0),
LineHeight::Length(l) => Au::from(l),
}
}
fn split_first_fragment_at_newline_if_necessary(fragments: &mut LinkedList<Fragment>) {
if fragments.is_empty() {
return;
}
let new_fragment = {
let first_fragment = fragments.front_mut().unwrap();
let string_before;
let selection_before;
{
if !first_fragment.white_space().preserve_newlines() {
return;
}
let unscanned_text_fragment_info = match first_fragment.specific {
SpecificFragmentInfo::UnscannedText(ref mut unscanned_text_fragment_info) => {
unscanned_text_fragment_info
},
_ => return,
};
let position = match unscanned_text_fragment_info.text.find('\n') {
Some(position) if position < unscanned_text_fragment_info.text.len() - 1 => {
position
},
Some(_) | None => return,
};
string_before = unscanned_text_fragment_info.text[..(position + 1)].to_owned();
unscanned_text_fragment_info.text = unscanned_text_fragment_info.text[(position + 1)..]
.to_owned()
.into_boxed_str();
let offset = ByteIndex(string_before.len() as isize);
match unscanned_text_fragment_info.selection {
Some(ref mut selection) if selection.begin() >= offset => {
// Selection is entirely in the second fragment.
selection_before = None;
selection.shift_by(-offset);
},
Some(ref mut selection) if selection.end() > offset => {
// Selection is split across two fragments.
selection_before = Some(Range::new(selection.begin(), offset));
*selection = Range::new(ByteIndex(0), selection.end() - offset);
},
_ => {
// Selection is entirely in the first fragment.
selection_before = unscanned_text_fragment_info.selection;
unscanned_text_fragment_info.selection = None;
},
};
}
first_fragment.transform(
first_fragment.border_box.size,
SpecificFragmentInfo::UnscannedText(Box::new(UnscannedTextFragmentInfo::new(
string_before.into_boxed_str(),
selection_before,
))),
)
};
fragments.push_front(new_fragment);
}
/// Information about a text run that we're about to create. This is used in `scan_for_runs`.
struct RunInfo {
/// The text that will go in this text run.
text: String,
/// The insertion point in this text run, if applicable.
insertion_point: Option<ByteIndex>,
/// The font that the text should be rendered with.
font: Option<FontRef>,
/// The bidirection embedding level of this text run.
bidi_level: bidi::Level,
/// The Unicode script property of this text run.
script: Script,
}
impl RunInfo {
fn new() -> RunInfo {
RunInfo {
text: String::new(),
insertion_point: None,
font: None,
bidi_level: bidi::Level::ltr(),
script: Script::Common,
}
}
/// Finish processing this RunInfo and add it to the "done" list.
///
/// * `insertion_point`: The position of the insertion point, in characters relative to the start
/// of this text run.
fn flush(mut self, list: &mut Vec<RunInfo>, insertion_point: &mut Option<ByteIndex>) {
if let Some(idx) = *insertion_point {
let char_len = ByteIndex(self.text.len() as isize);
if idx <= char_len {
// The insertion point is in this text run.
self.insertion_point = insertion_point.take()
} else {
// Continue looking for the insertion point in the next text run.
*insertion_point = Some(idx - char_len)
}
}
list.push(self);
}
fn has_font(&self, font: &Option<FontRef>) -> bool {
fn identifier(font: &Option<FontRef>) -> Option<Atom> {
font.as_ref().map(|f| f.borrow().identifier())
}
identifier(&self.font) == identifier(font)
}
}
/// A mapping from a portion of an unscanned text fragment to the text run we're going to create
/// for it.
#[derive(Clone, Copy, Debug)]
struct RunMapping {
/// The range of byte indices within the text fragment.
byte_range: Range<usize>,
/// The index of the unscanned text fragment that this mapping corresponds to.
old_fragment_index: usize,
/// The index of the text run we're going to create.
text_run_index: usize,
/// Is the text in this fragment selected?
selected: bool,
}
impl RunMapping {
/// Given the current set of text runs, creates a run mapping for the next fragment.
/// `run_info_list` describes the set of runs we've seen already.
fn new(run_info_list: &[RunInfo], fragment_index: usize) -> RunMapping {
RunMapping {
byte_range: Range::new(0, 0),
old_fragment_index: fragment_index,
text_run_index: run_info_list.len(),
selected: false,
}
}
/// Flushes this run mapping to the list. `run_info` describes the text run that we're
/// currently working on. `text` refers to the text of this fragment.
fn flush(
mut self,
mappings: &mut Vec<RunMapping>,
run_info: &mut RunInfo,
text: &str,
compression: CompressionMode,
text_transform: TextTransform,
last_whitespace: &mut bool,
start_position: &mut usize,
end_position: usize,
) {
let was_empty = *start_position == end_position;
let old_byte_length = run_info.text.len();
*last_whitespace = util::transform_text(
&text[(*start_position)..end_position],
compression,
*last_whitespace,
&mut run_info.text,
);
// Account for `text-transform`. (Confusingly, this is not handled in "text
// transformation" above, but we follow Gecko in the naming.)
let is_first_run = *start_position == 0;
apply_style_transform_if_necessary(
&mut run_info.text,
old_byte_length,
text_transform,
*last_whitespace,
is_first_run,
);
*start_position = end_position;
let new_byte_length = run_info.text.len();
let is_empty = new_byte_length == old_byte_length;
// Don't save mappings that contain only discarded characters.
// (But keep ones that contained no characters to begin with, since they might have been
// generated by an empty flow to draw its borders/padding/insertion point.)
if is_empty && !was_empty {
return;
}
self.byte_range = Range::new(old_byte_length, new_byte_length - old_byte_length);
mappings.push(self)
}
/// Is the insertion point for this text run within this mapping?
///
/// NOTE: We treat the range as inclusive at both ends, since the insertion point can lie
/// before the first character *or* after the last character, and should be drawn even if the
/// text is empty.
fn contains_insertion_point(&self, insertion_point: Option<ByteIndex>) -> bool {
match insertion_point.map(ByteIndex::to_usize) {
None => false,
Some(idx) => self.byte_range.begin() <= idx && idx <= self.byte_range.end(),
}
}
}
/// Accounts for `text-transform`.
///
/// FIXME(#4311, pcwalton): Title-case mapping can change length of the string;
/// case mapping should be language-specific; `full-width`;
/// use graphemes instead of characters.
fn apply_style_transform_if_necessary(
string: &mut String,
first_character_position: usize,
text_transform: TextTransform,
last_whitespace: bool,
is_first_run: bool,
) {
match text_transform.case_ {
TextTransformCase::None => {},
TextTransformCase::Uppercase => {
let original = string[first_character_position..].to_owned();
string.truncate(first_character_position);
for ch in original.chars().flat_map(|ch| ch.to_uppercase()) {
string.push(ch);
}
},
TextTransformCase::Lowercase => {
let original = string[first_character_position..].to_owned();
string.truncate(first_character_position);
for ch in original.chars().flat_map(|ch| ch.to_lowercase()) {
string.push(ch);
}
},
TextTransformCase::Capitalize => {
let original = string[first_character_position..].to_owned();
string.truncate(first_character_position);
let mut capitalize_next_letter = is_first_run || last_whitespace;
for character in original.chars() {
// FIXME(#4311, pcwalton): Should be the CSS/Unicode notion of a *typographic
// letter unit*, not an *alphabetic* character:
//
// http://dev.w3.org/csswg/css-text/#typographic-letter-unit
if capitalize_next_letter && character.is_alphabetic() {
string.push(character.to_uppercase().next().unwrap());
capitalize_next_letter = false;
continue;
}
string.push(character);
// FIXME(#4311, pcwalton): Try UAX29 instead of just whitespace.
if character.is_whitespace() {
capitalize_next_letter = true
}
}
},
}
}
#[derive(Clone)]
struct ScannedTextRun {
run: Arc<TextRun>,
insertion_point: Option<ByteIndex>,
}
/// Can a character with script `b` continue a text run with script `a`?
fn is_compatible(a: Script, b: Script) -> bool {
a == b || !is_specific(a) || !is_specific(b)
}
/// Returns true if the script is not invalid or inherited.
fn is_specific(script: Script) -> bool {
script != Script::Common && script != Script::Inherited
}