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enhance: Implement CanvasRenderingContext2D.measureText (#32704)
Signed-off-by: Chocolate Pie <106949016+chocolate-pie@users.noreply.github.com> Co-authored-by: Martin Robinson <mrobinson@igalia.com>
This commit is contained in:
Chocolate Pie
GitHub
parent
d82232d549
commit
1223335547
14 changed files with 325 additions and 51 deletions
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@ -7,15 +7,16 @@ use std::sync::Arc;
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use app_units::Au;
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use canvas_traits::canvas::*;
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use euclid::default::{Point2D, Rect, Size2D, Transform2D, Vector2D};
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use euclid::default::{Box2D, Point2D, Rect, Size2D, Transform2D, Vector2D};
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use euclid::point2;
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use fonts::{
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FontCacheThread, FontContext, FontMetrics, FontRef, GlyphStore, ShapingFlags, ShapingOptions,
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LAST_RESORT_GLYPH_ADVANCE,
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ByteIndex, FontBaseline, FontCacheThread, FontContext, FontGroup, FontMetrics, FontRef,
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GlyphInfo, GlyphStore, ShapingFlags, ShapingOptions, LAST_RESORT_GLYPH_ADVANCE,
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};
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use ipc_channel::ipc::{IpcSender, IpcSharedMemory};
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use log::{debug, warn};
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use num_traits::ToPrimitive;
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use range::Range;
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use servo_arc::Arc as ServoArc;
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use style::color::AbsoluteColor;
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use style::properties::style_structs::Font as FontStyleStruct;
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@ -277,6 +278,29 @@ pub struct TextRun {
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pub glyphs: Arc<GlyphStore>,
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}
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impl TextRun {
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fn bounding_box(&self) -> Rect<f32> {
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let mut bounding_box = None;
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let mut bounds_offset: f32 = 0.;
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let glyph_ids = self
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.glyphs
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.iter_glyphs_for_byte_range(&Range::new(ByteIndex(0), self.glyphs.len()))
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.map(GlyphInfo::id);
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for glyph_id in glyph_ids {
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let bounds = self.font.typographic_bounds(glyph_id);
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let amount = Vector2D::new(bounds_offset, 0.);
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let bounds = bounds.translate(amount);
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let initiated_bbox = bounding_box.get_or_insert_with(|| {
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let origin = Point2D::new(bounds.min_x(), 0.);
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Box2D::new(origin, origin).to_rect()
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});
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bounding_box = Some(initiated_bbox.union(&bounds));
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bounds_offset = bounds.max_x();
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}
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bounding_box.unwrap_or_default()
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}
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}
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// This defines required methods for a DrawTarget (currently only implemented for raqote). The
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// prototypes are derived from the now-removed Azure backend's methods.
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pub trait GenericDrawTarget {
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@ -523,33 +547,7 @@ impl<'a> CanvasData<'a> {
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return;
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};
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let mut runs = Vec::new();
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let mut current_text_run = UnshapedTextRun::default();
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let mut current_text_run_start_index = 0;
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for (index, character) in text.char_indices() {
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// TODO: This should ultimately handle emoji variation selectors, but raqote does not yet
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// have support for color glyphs.
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let script = Script::from(character);
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let font = font_group.find_by_codepoint(&self.font_context, character, None);
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if !current_text_run.script_and_font_compatible(script, &font) {
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let previous_text_run = mem::replace(
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&mut current_text_run,
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UnshapedTextRun {
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font: font.clone(),
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script,
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..Default::default()
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},
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);
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current_text_run_start_index = index;
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runs.push(previous_text_run)
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}
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current_text_run.string =
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&text[current_text_run_start_index..index + character.len_utf8()];
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}
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runs.push(current_text_run);
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let runs = self.build_unshaped_text_runs(&text, &mut font_group);
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// TODO: This doesn't do any kind of line layout at all. In particular, there needs
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// to be some alignment along a baseline and also support for bidi text.
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let shaped_runs: Vec<_> = runs
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@ -617,6 +615,123 @@ impl<'a> CanvasData<'a> {
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self.fill_text_with_size(text, x, y, max_width, is_rtl, size.px() as f64);
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}
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/// <https://html.spec.whatwg.org/multipage/#text-preparation-algorithm>
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/// <https://html.spec.whatwg.org/multipage/#dom-context-2d-measuretext>
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pub fn measure_text(&mut self, text: String) -> TextMetrics {
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// > Step 2: Replace all ASCII whitespace in text with U+0020 SPACE characters.
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let text = replace_ascii_whitespace(text);
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let Some(ref font_style) = self.state.font_style else {
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return TextMetrics::default();
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};
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let font_group = self.font_context.font_group(font_style.clone());
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let mut font_group = font_group.write();
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let font = font_group
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.first(&self.font_context)
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.expect("couldn't find font");
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let ascent = font.metrics.ascent.to_f32_px();
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let descent = font.metrics.descent.to_f32_px();
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let runs = self.build_unshaped_text_runs(&text, &mut font_group);
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let shaped_runs: Vec<_> = runs
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.into_iter()
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.filter_map(UnshapedTextRun::to_shaped_text_run)
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.collect();
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let total_advance = shaped_runs
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.iter()
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.map(|run| run.glyphs.total_advance())
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.sum::<Au>()
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.to_f32_px();
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let bounding_box = shaped_runs
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.iter()
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.map(TextRun::bounding_box)
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.reduce(|a, b| {
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let amount = Vector2D::new(a.max_x(), 0.);
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let bounding_box = b.translate(amount);
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a.union(&bounding_box)
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})
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.unwrap_or_default();
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let FontBaseline {
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ideographic_baseline,
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alphabetic_baseline,
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hanging_baseline,
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} = match font.get_baseline() {
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Some(baseline) => baseline,
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None => FontBaseline {
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hanging_baseline: ascent * HANGING_BASELINE_DEFAULT,
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ideographic_baseline: -descent * IDEOGRAPHIC_BASELINE_DEFAULT,
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alphabetic_baseline: 0.,
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},
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};
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let anchor_x = match self.state.text_align {
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TextAlign::End => total_advance,
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TextAlign::Center => total_advance / 2.,
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TextAlign::Right => total_advance,
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_ => 0.,
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};
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let anchor_y = match self.state.text_baseline {
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TextBaseline::Top => ascent,
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TextBaseline::Hanging => hanging_baseline,
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TextBaseline::Ideographic => ideographic_baseline,
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TextBaseline::Middle => (ascent - descent) / 2.,
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TextBaseline::Alphabetic => alphabetic_baseline,
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TextBaseline::Bottom => -descent,
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};
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TextMetrics {
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width: total_advance,
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actual_boundingbox_left: anchor_x - bounding_box.min_x(),
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actual_boundingbox_right: bounding_box.max_x() - anchor_x,
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actual_boundingbox_ascent: bounding_box.max_y() - anchor_y,
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actual_boundingbox_descent: anchor_y - bounding_box.min_y(),
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font_boundingbox_ascent: ascent - anchor_y,
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font_boundingbox_descent: descent + anchor_y,
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em_height_ascent: ascent - anchor_y,
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em_height_descent: descent + anchor_y,
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hanging_baseline: hanging_baseline - anchor_y,
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alphabetic_baseline: alphabetic_baseline - anchor_y,
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ideographic_baseline: ideographic_baseline - anchor_y,
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}
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}
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fn build_unshaped_text_runs<'b>(
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&self,
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text: &'b str,
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font_group: &mut FontGroup,
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) -> Vec<UnshapedTextRun<'b>> {
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let mut runs = Vec::new();
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let mut current_text_run = UnshapedTextRun::default();
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let mut current_text_run_start_index = 0;
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for (index, character) in text.char_indices() {
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// TODO: This should ultimately handle emoji variation selectors, but raqote does not yet
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// have support for color glyphs.
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let script = Script::from(character);
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let font = font_group.find_by_codepoint(&self.font_context, character, None);
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if !current_text_run.script_and_font_compatible(script, &font) {
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let previous_text_run = mem::replace(
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&mut current_text_run,
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UnshapedTextRun {
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font: font.clone(),
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script,
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..Default::default()
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},
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);
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current_text_run_start_index = index;
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runs.push(previous_text_run)
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}
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current_text_run.string =
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&text[current_text_run_start_index..index + character.len_utf8()];
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}
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runs.push(current_text_run);
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runs
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}
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/// Find the *anchor_point* for the given parameters of a line of text.
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/// See <https://html.spec.whatwg.org/multipage/#text-preparation-algorithm>.
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fn find_anchor_point_for_line_of_text(
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