543 lines
24 KiB
Rust
543 lines
24 KiB
Rust
//! 统一字体发现、文字整形、测量与抗锯齿字形绘制。
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//! 测量与绘制使用同一字体系统和样式，避免布局宽度与屏幕文字不一致；中文与其他字符通过字体回退处理。
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//! 整形和字形缓存有数量/字节预算；极端放大采用有界字形 LOD，最终只遍历裁剪区域内的像素。
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//!
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//! Shared font discovery, shaping, measurement and antialiased rasterization.
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use std::{
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collections::HashMap,
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sync::{Mutex, OnceLock},
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};
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use cosmic_text::{Align, Attrs, Buffer, Family, FontSystem, Metrics, Shaping, SwashCache, Wrap};
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use crate::display_list::Color;
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#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
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/// 界面比例字体与源码等宽字体的选择，不直接指定某个必然安装的系统字体。
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pub enum TextFamily {
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Interface,
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Code,
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/// A registered family loaded through the generic font-resource API.
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Custom(u32),
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}
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#[derive(Clone, Copy, Debug)]
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/// 字号、行高和字体类别，测量与绘制必须使用兼容样式。
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pub struct TextStyle {
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pub font_size: f32,
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pub line_height: f32,
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pub family: TextFamily,
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}
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impl TextStyle {
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/// 生成界面文字的基准字号与行高，size 是协议使用的字号倍率。
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pub fn ui(size: u32) -> Self {
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Self {
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font_size: 14.0 * size as f32,
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line_height: 20.0 * size as f32,
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family: TextFamily::Interface,
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}
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}
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/// 生成源码/Console 使用的等宽风格基础尺寸。
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pub fn code() -> Self {
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Self {
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font_size: 13.0,
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line_height: 18.0,
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family: TextFamily::Code,
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}
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}
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/// 同比缩放字号与行高，保持设备比例变化后的排版比例一致。
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pub fn scaled(self, scale: f32) -> Self {
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Self {
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font_size: self.font_size * scale,
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line_height: self.line_height * scale,
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..self
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}
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}
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}
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#[derive(Clone, Copy, Debug)]
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/// 整形后实际占用的逻辑文字尺寸。
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pub struct TextSize {
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pub width: f32,
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pub height: f32,
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}
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#[derive(Clone, Hash, PartialEq, Eq)]
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/// 文字整形缓存键，包含文本、样式和可选换行宽度。
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struct TextKey {
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value: String,
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// 用浮点原始位模式做键，精确区分整形参数；不是把字号取整为 u32。
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font_size: u32,
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line_height: u32,
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family: TextFamily,
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// None 表示不换行，Some 保存宽度的浮点位模式；同一文本不同宽度必须分开缓存。
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wrap_width: Option<u32>,
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}
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/// 已整形 Buffer 与测量结果，后续测量/绘制复用同一布局。
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struct PreparedText {
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buffer: Buffer,
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size: TextSize,
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}
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/// 共享字体系统、字形缓存和整形缓存；调用通过全局锁串行访问。
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struct TextEngine {
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fonts: FontSystem,
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custom: Vec<(String, u64)>,
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code_family: Option<String>,
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swash: SwashCache,
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buffers: HashMap<TextKey, PreparedText>,
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// 累计缓存文本的 UTF-8 字节数，只衡量源文本预算，并非 Buffer/字形的总内存。
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source_bytes: usize,
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}
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impl TextEngine {
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/// 扫描系统字体，选择可用的界面/等宽字体偏好，并建立空整形和栅格缓存。
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fn new() -> Self {
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let mut fonts = FontSystem::new();
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// Select installed, readable families rather than assuming an OS font
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// name exists. COSMIC Text handles per-glyph fallback (including CJK).
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// 按偏好顺序查询实际安装字体，找到第一个匹配名；找不到则由字体系统默认族处理。
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let choose = |choices: &[&str]| {
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choices.iter().find_map(|choice| {
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fonts
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.db()
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.faces()
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.any(|face| face.families.iter().any(|(name, _)| name == choice))
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.then(|| (*choice).to_owned())
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})
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};
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let sans = choose(&[
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".AppleSystemUIFont",
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"SF Pro Text",
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"Helvetica Neue",
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"Segoe UI",
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"Noto Sans",
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"DejaVu Sans",
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"Liberation Sans",
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]);
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let mono = choose(&["Menlo", "Consolas", "DejaVu Sans Mono", "Liberation Mono"]);
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if let Some(name) = sans {
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fonts.db_mut().set_sans_serif_family(name);
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}
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if let Some(name) = &mono {
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fonts.db_mut().set_monospace_family(name);
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}
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Self {
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fonts,
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custom: Vec::new(),
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code_family: mono,
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swash: SwashCache::new(),
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buffers: HashMap::new(),
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source_bytes: 0,
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}
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}
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/// 对不指定换行宽度的文本复用统一整形准备过程。
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fn prepare(&mut self, value: &str, style: TextStyle) -> TextKey {
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self.prepare_width(value, style, None)
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}
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/// 为文本、字体样式和可选换行宽度建立整形缓存，超过缓存预算先清理旧结果。
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fn prepare_width(&mut self, value: &str, style: TextStyle, wrap_width: Option<f32>) -> TextKey {
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// 键包含全部排版输入；命中后测量与绘制都复用同一 Buffer，避免两套排版产生偏差。
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let key = TextKey {
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value: value.to_owned(),
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font_size: style.font_size.to_bits(),
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line_height: style.line_height.to_bits(),
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family: style.family,
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wrap_width: wrap_width.map(f32::to_bits),
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};
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if self.buffers.contains_key(&key) {
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return key;
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}
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// Cache recent shaped strings, without retaining every submitted source.
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// 采用整批清空而非 LRU；新增前达到条数或文本字节阈值时释放旧整形结果。
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// 单个超大文本仍会被整形，source_bytes 不是对单次输入长度的硬拒绝。
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if self.buffers.len() >= 256 || self.source_bytes + value.len() > 524_288 {
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self.buffers.clear();
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self.source_bytes = 0;
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}
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let family = match style.family {
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TextFamily::Interface => Family::SansSerif,
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TextFamily::Custom(id) => Family::Name(&self.custom[id as usize].0),
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// Keep Latin source on the selected code face, and allow ordinary
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// script fallback for CJK instead of searching all monospace faces.
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TextFamily::Code => self
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.code_family
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.as_deref()
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.map_or(Family::Monospace, Family::Name),
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};
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let mut buffer = Buffer::new(
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&mut self.fonts,
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Metrics::new(style.font_size, style.line_height),
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);
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// 有限宽度使用按词优先、字形兜底的换行策略，兼容中文和无空格长标识符；无宽度则不换行。
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buffer.set_wrap(if wrap_width.is_some() {
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Wrap::WordOrGlyph
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} else {
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Wrap::None
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});
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// 高度不设上限，让测量能得到所有换行后的完整内容高度，而非当前裁剪区域高度。
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buffer.set_size(wrap_width, None);
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buffer.set_text(
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value,
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&Attrs::new().family(family),
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Shaping::Advanced,
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Some(Align::Left),
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);
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// 整形采用高级脚本处理和左对齐；实际字形及回退由同一 FontSystem 决定。
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buffer.shape_until_scroll(&mut self.fonts, false);
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// 即使空文本没有布局 run 也保留一行高度；宽度取各行最大值，高度取最下方行底。
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let mut size = TextSize {
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width: 0.0,
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height: style.line_height,
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};
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for run in buffer.layout_runs() {
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size.width = size.width.max(run.line_w);
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size.height = size.height.max(run.line_top + run.line_height);
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}
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self.source_bytes += value.len();
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self.buffers
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.insert(key.clone(), PreparedText { buffer, size });
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key
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}
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}
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/// 取得全局受锁保护的字体/整形引擎；共享缓存不等于可以并行修改字体状态。
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fn engine() -> &'static Mutex<TextEngine> {
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// 惰性创建全进程引擎；Mutex 同时保护字体库、整形缓存与栅格缓存，测量和绘制不能并发修改它。
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static ENGINE: OnceLock<Mutex<TextEngine>> = OnceLock::new();
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ENGINE.get_or_init(|| Mutex::new(TextEngine::new()))
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}
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/// 返回不受换行宽度约束时的字体整形尺寸。
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pub fn measure(value: &str, style: TextStyle) -> TextSize {
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let mut engine = engine().lock().expect("text engine lock");
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let key = engine.prepare(value, style);
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engine.buffers[&key].size
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}
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/// 按可用宽度整形并测量多行高度，供布局与实际段落绘制共用。
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pub fn measure_wrapped(value: &str, style: TextStyle, width: f32) -> TextSize {
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// 零或负可用宽度直接返回零宽与一行高，避免给整形器无效换行宽度。
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if width <= 0.0 {
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return TextSize {
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width: 0.0,
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height: style.line_height,
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};
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}
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let mut engine = engine().lock().expect("text engine lock");
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let key = engine.prepare_width(value, style, Some(width));
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engine.buffers[&key].size
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}
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/// Rasterize only visible glyph pixels. Large camera zooms use a bounded glyph
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/// bitmap and sample it at the requested size instead of allocating an enormous
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/// font image. Layout and wrapping still use proportionally identical metrics.
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/// 限制字形分辨率并只采样可见像素；保留文字布局比例，同时避免极端相机缩放产生巨型位图。
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pub fn draw_clipped(
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value: &str,
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style: TextStyle,
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color: Color,
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width: Option<f32>,
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clip: crate::geometry::Rect,
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mut pixel: impl FnMut(i32, i32, Color),
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) {
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if clip.width <= 0.
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|| clip.height <= 0.
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|| !style.font_size.is_finite()
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|| style.font_size <= 0.
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{
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return;
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}
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// 超大字号按比例降到最高 512 再栅格化；普通字号保持 1。
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// 字体、行高和换行宽度一起缩小，后续用 1/lod 恢复目标几何比例。
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let lod = (512. / style.font_size).min(1.);
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let mut engine = engine().lock().expect("text engine lock");
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let key = engine.prepare_width(value, style.scaled(lod), width.map(|width| width * lod));
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// 拆借可变字段以便在保留 Buffer 借用时访问字体和 Swash 缓存，不复制整形结果。
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let TextEngine {
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fonts,
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swash,
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buffers,
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..
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} = &mut *engine;
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let buffer = &buffers[&key].buffer;
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// 从已有 image_cache 统计位图字节；不包含整形 Buffer，也不含字体数据库本身。
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let mut cache_bytes: usize = swash
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.image_cache
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.values()
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.flatten()
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.map(|image| image.data.len())
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.sum();
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for run in buffer.layout_runs() {
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for glyph in run.glyphs {
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let physical = glyph.physical((0., run.line_y), 1.);
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// Conservative font-sized guard includes bearings/overhangs. The
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// exact bitmap bounds below determine the actual visible pixels.
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// 先用保守包围范围排除完全不可见字形，尽量避免生成裁剪区外的位图；精确边界由实际位图决定。
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let guard = glyph.font_size * 4. / lod;
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let gx = physical.x as f32 / lod;
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let gy = physical.y as f32 / lod;
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if gx + guard < clip.x
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|| gx - guard > clip.x + clip.width
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|| gy + guard < clip.y
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|| gy - guard > clip.y + clip.height
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{
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continue;
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}
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// 达到条数或约 32 MiB 时替换整个 SwashCache，再生成当前可见字形；预算不因缩放无限增长。
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if swash.image_cache.len() >= 4096 || cache_bytes >= 33_554_432 {
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*swash = SwashCache::new();
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cache_bytes = 0;
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}
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// 只对新生成的图像增加字节统计；缓存中的生成失败项由 None 跳过，不参与绘制。
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let cached = swash.image_cache.contains_key(&physical.cache_key);
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let Some(image) = swash.get_image(fonts, physical.cache_key) else {
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continue;
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};
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if !cached {
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cache_bytes += image.data.len();
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}
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// 位图 placement 包含字形 bearing。顶部使用基线减 top，再除 lod 转回目标绘制空间。
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let left = (physical.x + image.placement.left) as f32 / lod;
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let top = (physical.y - image.placement.top) as f32 / lod;
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let right = left + image.placement.width as f32 / lod;
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let bottom = top + image.placement.height as f32 / lod;
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// 可选字形颜色覆盖 RGB，但透明度始终采用调用方的整体 alpha。彩色位图分支会使用位图自己的 RGB。
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let base = glyph.color_opt.map_or(color, |value| {
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Color::rgba(value.r(), value.g(), value.b(), color.alpha)
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});
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// 循环范围取位图与 clip 交集，只遍历最终可见像素；ceil 与半像素采样共同决定整数像素覆盖。
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for y in top.max(clip.y).ceil() as i32..bottom.min(clip.y + clip.height).ceil() as i32 {
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for x in
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left.max(clip.x).ceil() as i32..right.min(clip.x + clip.width).ceil() as i32
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{
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// 把目标像素中心反映射到低分辨率位图，再钳制到最后一个有效像素，避免边缘采样越界。
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let u = (((x as f32 + 0.5 - left) * lod) as u32)
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.min(image.placement.width.saturating_sub(1));
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let v = (((y as f32 + 0.5 - top) * lod) as u32)
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.min(image.placement.height.saturating_sub(1));
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let index = (v * image.placement.width + u) as usize;
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// 灰度 Mask 把覆盖率乘整体 alpha；Color 保留位图 RGB 并乘其 alpha。
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// SubpixelMask 不适用此软件合成路径，直接跳过。
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let sample = match image.content {
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cosmic_text::SwashContent::Mask => Color::rgba(
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base.red,
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base.green,
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base.blue,
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(u16::from(image.data[index]) * u16::from(color.alpha) / 255) as u8,
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),
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cosmic_text::SwashContent::Color => {
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let i = index * 4;
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Color::rgba(
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image.data[i],
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image.data[i + 1],
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image.data[i + 2],
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(u16::from(image.data[i + 3]) * u16::from(color.alpha) / 255) as u8,
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)
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}
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cosmic_text::SwashContent::SubpixelMask => continue,
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};
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// 只输出采样颜色，最终混合由调用方 pixel 完成；回调在引擎锁持有期间执行，不应重入文字引擎。
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pixel(x, y, sample);
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}
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}
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}
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}
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}
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/// Fit a single displayed source line without slicing a UTF-8/grapheme cluster.
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/// 按真实字体测量截断到给定宽度，以字素簇边界拼接省略号，避免切开组合字符。
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pub fn fit(value: &str, width: f32, style: TextStyle) -> String {
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use unicode_segmentation::UnicodeSegmentation;
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// A source line may include a very large comment. Only shape a bounded
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// preview for the sidebar; the stored source and its AST spans stay intact.
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// 仅预览截断至约 8 KiB 字素边界，不改保存的源码。单个超长字素也不能被拆开。
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let truncated = value.len() > 8192;
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let value = if truncated {
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let end = value
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.grapheme_indices(true)
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.map(|(index, _)| index)
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.take_while(|index| *index <= 8192)
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.last()
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.unwrap_or(0);
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&value[..end]
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} else {
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value
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};
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// 原文本未受预览截断且已能放下时原样返回；受截断文本即使较短也要追加省略号提示。
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if !truncated && measure(value, style).width <= width {
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return value.to_owned();
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}
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let ellipsis = "…";
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if width <= 0.0 || measure(ellipsis, style).width > width {
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return String::new();
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}
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// 保存每个完整字素簇的结束字节位置，后续切片不会拆开组合音标或连字 emoji。
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let ends: Vec<_> = value
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.grapheme_indices(true)
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.map(|(start, part)| start + part.len())
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.collect();
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let mut low = 0;
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let mut high = ends.len();
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// 二分搜索可容纳的最长字素前缀；取上中位数使成功分支能推进 low，避免相邻边界时死循环。
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while low < high {
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let count = (low + high).div_ceil(2);
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let end = ends[count - 1];
|
||
// 省略号也参与真实整形测量，不能简单从总宽度减去字符数估算。
|
||
let candidate = format!("{}{ellipsis}", &value[..end]);
|
||
if measure(&candidate, style).width <= width {
|
||
low = count;
|
||
} else {
|
||
high = count - 1;
|
||
}
|
||
}
|
||
// 没有任何字素能放下时只返回省略号；更早已经检查省略号本身可容纳。
|
||
let end = low.checked_sub(1).map_or(0, |index| ends[index]);
|
||
format!("{}{ellipsis}", &value[..end])
|
||
}
|
||
|
||
/// Register an explicit face for graphics resources. Repeated identical loads
|
||
/// reuse the family; conflicting content and unbounded global growth fail.
|
||
pub fn register_font(bytes: Vec<u8>, family: &str) -> anyhow::Result<TextFamily> {
|
||
use std::hash::{Hash, Hasher};
|
||
let mut hash = std::collections::hash_map::DefaultHasher::new();
|
||
bytes.hash(&mut hash);
|
||
let hash = hash.finish();
|
||
let mut e = engine().lock().expect("text engine lock");
|
||
if let Some((id, (_, old))) = e.custom.iter().enumerate().find(|(_, v)| v.0 == family) {
|
||
anyhow::ensure!(*old == hash, "font family already has different content");
|
||
return Ok(TextFamily::Custom(id as u32));
|
||
}
|
||
anyhow::ensure!(e.custom.len() < 32, "font registry exceeds 32 families");
|
||
let previous = e.fonts.db().clone();
|
||
e.fonts.db_mut().load_font_data(bytes);
|
||
if !e
|
||
.fonts
|
||
.db()
|
||
.faces()
|
||
.any(|f| f.families.iter().any(|(n, _)| n == family))
|
||
{
|
||
*e.fonts.db_mut() = previous;
|
||
anyhow::bail!("font data does not contain requested family");
|
||
}
|
||
let id = e.custom.len() as u32;
|
||
e.custom.push((family.into(), hash));
|
||
e.buffers.clear();
|
||
e.source_bytes = 0;
|
||
Ok(TextFamily::Custom(id))
|
||
}
|
||
|
||
#[cfg(test)]
|
||
mod tests {
|
||
use super::*;
|
||
use unicode_segmentation::UnicodeSegmentation;
|
||
|
||
#[test]
|
||
/// 用一万倍缩放检验绘制回调被限制在32x32裁剪内，同时检查字形缓存字号不超过512以控制中间资源。
|
||
fn extreme_zoom_rasterizes_only_the_clip_with_bounded_glyph_sizes() {
|
||
// 极端缩放测试限制实际回调在 32×32 裁剪区，同时检查缓存字号不超过 512。
|
||
let mut count = 0;
|
||
draw_clipped(
|
||
"M",
|
||
TextStyle::ui(1).scaled(10_000.),
|
||
Color::rgba(1, 2, 3, 255),
|
||
None,
|
||
crate::geometry::Rect::new(50_000., 60_000., 32., 32.),
|
||
|x, y, _| {
|
||
assert!((50_000..50_032).contains(&x));
|
||
assert!((60_000..60_032).contains(&y));
|
||
count += 1;
|
||
},
|
||
);
|
||
assert_eq!(count, 1024);
|
||
let engine = engine().lock().unwrap();
|
||
assert!(
|
||
engine
|
||
.swash
|
||
.image_cache
|
||
.keys()
|
||
.all(|key| f32::from_bits(key.font_size_bits) <= 512.)
|
||
);
|
||
}
|
||
|
||
#[test]
|
||
/// 混合中文、单词、长标识符、组合字符和emoji，检查窄宽约束分别换行/缓存，且不污染无约束自然测量。
|
||
fn width_sensitive_shaping_wraps_words_and_clusters_without_changing_intrinsic_metrics() {
|
||
let style = TextStyle::ui(1);
|
||
// 混合中文、长英文词、组合字符和 emoji，验证窄/宽换行缓存隔离且不改变无换行测量结果。
|
||
let text = "中文段落 with words and long_unbroken_identifier é 👩💻 中文段落";
|
||
let intrinsic = measure(text, style);
|
||
let narrow = measure_wrapped(text, style, 70.0);
|
||
let wide = measure_wrapped(text, style, 240.0);
|
||
assert!(narrow.height > wide.height);
|
||
assert!(wide.height >= style.line_height);
|
||
assert!(narrow.width <= 70.1);
|
||
assert_eq!(measure(text, style).width, intrinsic.width);
|
||
assert_eq!(measure_wrapped(text, style, 0.0).width, 0.0);
|
||
let mut engine = engine().lock().unwrap();
|
||
let narrow_key = engine.prepare_width(text, style, Some(70.0));
|
||
let wide_key = engine.prepare_width(text, style, Some(240.0));
|
||
assert!(narrow_key != wide_key);
|
||
assert!(engine.buffers[&narrow_key].size.height > engine.buffers[&wide_key].size.height);
|
||
}
|
||
|
||
#[test]
|
||
/// 比较比例字体宽窄字母、等宽字体、多行高度与缩放比例，证明尺寸来自字体整形而非按字符数估计。
|
||
fn proportional_metrics_monospace_and_multiline_height_come_from_the_fonts() {
|
||
// 用宽窄拉丁字母验证比例字体差异、等宽字体一致性、多行行高和同比例缩放。
|
||
let ui = TextStyle::ui(1);
|
||
assert!(measure("WWWW", ui).width > measure("iiii", ui).width * 2.0);
|
||
let mono = TextStyle::code();
|
||
assert!((measure("WWWW", mono).width - measure("iiii", mono).width).abs() < 0.1);
|
||
assert_eq!(measure("one\ntwo", ui).height, ui.line_height * 2.0);
|
||
let width = measure("Hello Endor", ui).width;
|
||
assert!((measure("Hello Endor", ui.scaled(1.25)).width - width * 1.25).abs() < 0.5);
|
||
}
|
||
|
||
#[test]
|
||
/// 普通和代码字体都需为四个中文字符产生非零glyph_id；依赖测试环境安装可用CJK回退字体。
|
||
fn system_fallback_shapes_chinese_without_missing_glyphs() {
|
||
let mut engine = engine().lock().unwrap();
|
||
// 两种字体风格都要求四个中文字符生成非零 glyph_id，确保系统回退实际找到了字形。
|
||
for style in [TextStyle::ui(1), TextStyle::code()] {
|
||
let key = engine.prepare("中文字体", style);
|
||
let glyphs: Vec<_> = engine.buffers[&key]
|
||
.buffer
|
||
.layout_runs()
|
||
.flat_map(|run| run.glyphs)
|
||
.collect();
|
||
assert_eq!(glyphs.len(), 4);
|
||
assert!(glyphs.iter().all(|glyph| glyph.glyph_id != 0));
|
||
assert!(engine.buffers[&key].size.width <= style.font_size * 8.0);
|
||
}
|
||
}
|
||
|
||
#[test]
|
||
/// 按实际测量宽度截断带组合字符的文本，结果需是原文字素边界前缀加省略号，且整体不超宽。
|
||
fn ellipsis_fits_actual_width_and_preserves_graphemes() {
|
||
let style = TextStyle::code();
|
||
let short_source = "let s = ui.text(\"中文字体\")";
|
||
assert_eq!(fit(short_source, 365.0, style), short_source);
|
||
let value = "e\u{301}e\u{301}中文字体e\u{301}e\u{301}";
|
||
let width = measure("e\u{301}e\u{301}中…", style).width + 0.01;
|
||
let fitted = fit(value, width, style);
|
||
// 检查结果前缀确实来自原文且结束于字素边界，而不仅是合法 UTF-8 字节边界。
|
||
let prefix = fitted.strip_suffix('…').unwrap();
|
||
assert!(value.starts_with(prefix));
|
||
assert!(
|
||
value
|
||
.grapheme_indices(true)
|
||
.any(|(index, _)| index == prefix.len())
|
||
);
|
||
assert!(measure(&fitted, style).width <= width);
|
||
assert_eq!(fit(value, 0.0, style), "");
|
||
}
|
||
}
|