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use cosmic_text::fontdb::Source;
use cosmic_text::{Attrs, Buffer, Family, FontSystem, Metrics, Shaping, Style, SwashCache, Weight, Wrap};
use std::sync::Arc;
use crate::layout::{
LineMetrics, ResolvedTextLayout, TextBlockMeasurement, measure_text_block, resolve_text_layout,
};
use crate::params::{FontStyle, FontWeight, TextLayoutParams};
#[derive(Debug, thiserror::Error)]
pub enum TextError {
#[error("failed to load font: {0}")]
FontLoad(String),
}
pub struct TextEngine {
pub(crate) font_system: FontSystem,
pub(crate) swash_cache: SwashCache,
}
pub struct MeasuredTextLayout {
pub resolved: ResolvedTextLayout,
pub lines: Vec<String>,
pub line_metrics: Vec<LineMetrics>,
pub block: TextBlockMeasurement,
pub(crate) buffer: Buffer,
}
impl TextEngine {
pub fn new() -> Self {
Self::from_font_system(FontSystem::new())
}
pub fn with_font_bytes(fonts: &[&[u8]]) -> Self {
let sources = fonts
.iter()
.map(|bytes| Source::Binary(Arc::new(bytes.to_vec())));
Self::from_font_system(FontSystem::new_with_fonts(sources))
}
fn from_font_system(font_system: FontSystem) -> Self {
Self {
font_system,
swash_cache: SwashCache::new(),
}
}
pub fn load_font_bytes(&mut self, bytes: &[u8]) -> Result<(), TextError> {
let loaded = self
.font_system
.db_mut()
.load_font_source(Source::Binary(Arc::new(bytes.to_vec())));
if loaded.is_empty() {
return Err(TextError::FontLoad(
"no faces found in font data".to_string(),
));
}
Ok(())
}
pub fn measure(&mut self, params: &TextLayoutParams, canvas_height: f64) -> MeasuredTextLayout {
self.measure_with_wrap(params, canvas_height, None)
}
pub fn measure_with_wrap(
&mut self,
params: &TextLayoutParams,
canvas_height: f64,
wrap_width: Option<f64>,
) -> MeasuredTextLayout {
let resolved = resolve_text_layout(params, canvas_height);
let mut buffer = self.build_buffer(params, &resolved, wrap_width);
buffer.shape_until_scroll(&mut self.font_system, false);
let mut lines = Vec::new();
let mut line_metrics = Vec::new();
for line_i in 0..buffer.lines.len() {
let line_text = buffer.lines[line_i].text().to_string();
let layouts = buffer
.line_layout(&mut self.font_system, line_i)
.unwrap_or(&[]);
let mut laid_out = false;
for layout_line in layouts {
laid_out = true;
let (text, metrics) = visual_line_metrics(&line_text, layout_line, &resolved);
lines.push(text);
line_metrics.push(metrics);
}
if !laid_out {
lines.push(line_text);
line_metrics.push(empty_line_metrics(&resolved));
}
}
if line_metrics.is_empty() {
lines.push(String::new());
line_metrics.push(empty_line_metrics(&resolved));
}
let block = measure_text_block(&line_metrics, resolved.line_height_px);
MeasuredTextLayout {
resolved,
lines,
line_metrics,
block,
buffer,
}
}
fn build_buffer(
&mut self,
params: &TextLayoutParams,
resolved: &ResolvedTextLayout,
wrap_width: Option<f64>,
) -> Buffer {
let metrics = Metrics::new(
resolved.scaled_font_size as f32,
resolved.line_height_px as f32,
);
let mut buffer = Buffer::new(&mut self.font_system, metrics);
let (wrap, width) = match wrap_width {
Some(width) => (Wrap::WordOrGlyph, Some(width as f32)),
None => (Wrap::None, None),
};
buffer.set_wrap(&mut self.font_system, wrap);
buffer.set_size(&mut self.font_system, width, None);
let attrs = Attrs::new()
.family(Family::Name(¶ms.font_family))
.weight(match params.font_weight {
FontWeight::Normal => Weight::NORMAL,
FontWeight::Bold => Weight::BOLD,
})
.style(match params.font_style {
FontStyle::Normal => Style::Normal,
FontStyle::Italic => Style::Italic,
})
.letter_spacing((resolved.letter_spacing / resolved.scaled_font_size.max(f64::EPSILON)) as f32);
buffer.set_text(
&mut self.font_system,
¶ms.content,
&attrs,
Shaping::Advanced,
None,
);
buffer
}
}
impl Default for TextEngine {
fn default() -> Self {
Self::new()
}
}
fn visual_line_metrics(
line_text: &str,
layout_line: &cosmic_text::LayoutLine,
resolved: &ResolvedTextLayout,
) -> (String, LineMetrics) {
if layout_line.glyphs.is_empty() {
return (line_text.to_string(), empty_line_metrics(resolved));
}
let raw_width = layout_line
.glyphs
.iter()
.fold(0.0_f32, |max, glyph| max.max(glyph.x + glyph.w));
let width = (f64::from(raw_width) - resolved.letter_spacing).max(0.0);
let start = layout_line
.glyphs
.iter()
.map(|glyph| glyph.start)
.min()
.unwrap_or(0);
let end = layout_line
.glyphs
.iter()
.map(|glyph| glyph.end)
.max()
.unwrap_or(line_text.len());
let text = line_text.get(start..end).unwrap_or(line_text).to_string();
let metrics = LineMetrics {
width,
ascent: f64::from(layout_line.max_ascent),
descent: f64::from(layout_line.max_descent),
};
(text, metrics)
}
fn empty_line_metrics(resolved: &ResolvedTextLayout) -> LineMetrics {
LineMetrics {
width: 0.0,
ascent: resolved.scaled_font_size * 0.8,
descent: resolved.scaled_font_size * 0.2,
}
}
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