cranpose_render_common/
text_measure.rs

1//! Shared CPU [`TextMeasurer`] used by the software rasterizer backends
2//! (pixels, vulkan). Both backends draw text by rasterizing glyphs directly
3//! into a pixel buffer rather than through a GPU glyph atlas, so they share
4//! one font-backed measurer plus its fallback-metrics path for when no font
5//! is installed.
6
7use std::{
8    hash::{Hash, Hasher},
9    sync::{Mutex, MutexGuard, PoisonError},
10};
11
12use cranpose_core::collections::pass_aged::PassAgedCache;
13use cranpose_ui::{TextMeasurer, TextMetrics, text_layout_result::TextLayoutResult};
14
15use crate::{
16    software_text_raster::{
17        SoftwareTextFontSet, annotated_cursor_x_for_offset, annotated_offset_for_position,
18        layout_annotated_text_with_font_set, measure_annotated_text_with_font_set,
19        visit_annotated_line_boxes,
20    },
21    text_cache_key::{TextCacheKey, TextProbe},
22    text_hyphenation::HyphenationDictionaryStore,
23};
24
25/// Renderer-owned text resources: the resolved font used for software
26/// rasterization and measurement, if any.
27#[derive(Clone)]
28pub struct SoftwareTextResources {
29    fonts: SoftwareTextFontSet,
30}
31
32impl SoftwareTextResources {
33    /// Resources that use the embedded default font when the `embedded-default-font` feature is on,
34    /// and draw no text otherwise.
35    pub fn default_font() -> Self {
36        Self::from_fonts(&[])
37    }
38
39    /// Resources that draw text in `fonts`. With none that parses, they use
40    /// the embedded default font when the `embedded-default-font` feature is
41    /// on, and draw no text otherwise.
42    pub fn from_fonts(fonts: &[&'static [u8]]) -> Self {
43        Self {
44            fonts: SoftwareTextFontSet::from_fonts_or_default(fonts),
45        }
46    }
47
48    /// The font set that text is measured and drawn with.
49    pub fn fonts(&self) -> &SoftwareTextFontSet {
50        &self.fonts
51    }
52
53    /// These resources with the faces installed since they were made, or
54    /// `None` while no face was installed since.
55    #[cfg(feature = "installed-fonts")]
56    pub fn with_installed_faces(&self) -> Option<Self> {
57        self.fonts
58            .with_installed_faces()
59            .map(|fonts| Self { fonts })
60    }
61}
62
63impl Default for SoftwareTextResources {
64    fn default() -> Self {
65        Self::default_font()
66    }
67}
68
69/// Character width in logical pixels that the fallback metrics use: 0.55 times `font_size`,
70/// where a font size below one counts as one.
71pub fn fallback_char_width(font_size: f32) -> f32 {
72    font_size.max(1.0) * 0.55
73}
74
75/// Line height in logical pixels that the fallback metrics use: 1.2 times `font_size`, where a
76/// font size below one counts as one.
77pub fn fallback_line_height(font_size: f32) -> f32 {
78    font_size.max(1.0) * 1.2
79}
80
81/// Estimates the metrics of `text` at `font_size` without a font: every character has the
82/// fallback width and every line break starts a line of the fallback height.
83pub fn fallback_text_metrics(text: &str, font_size: f32) -> TextMetrics {
84    let line_height = fallback_line_height(font_size);
85    let mut line_count = 0usize;
86    let mut max_chars = 0usize;
87    for line in text.split('\n') {
88        line_count += 1;
89        max_chars = max_chars.max(line.chars().count());
90    }
91    let line_count = line_count.max(1);
92    TextMetrics {
93        width: max_chars as f32 * fallback_char_width(font_size),
94        height: line_count as f32 * line_height,
95        line_height,
96        line_count,
97    }
98}
99
100/// Estimates the x offset in logical pixels of the caret at `byte_offset` of `text` without a
101/// font: the characters before it times the fallback width. An offset past the end counts as the
102/// end.
103pub fn fallback_cursor_x_for_byte_offset(text: &str, byte_offset: usize, font_size: f32) -> f32 {
104    let clamped = byte_offset.min(text.len());
105    let char_count = if clamped == text.len() {
106        text.chars().count()
107    } else {
108        text.char_indices()
109            .take_while(|(index, _)| *index < clamped)
110            .count()
111    };
112    char_count as f32 * fallback_char_width(font_size)
113}
114
115/// A `TextMeasurer` that measures with the fonts of `SoftwareTextResources` and caches the
116/// metrics by text, font size and style.
117pub struct CachedFontTextMeasurer {
118    text_resources: SoftwareTextResources,
119    cache: Mutex<TextMetricsCache>,
120    hyphenation: HyphenationDictionaryStore,
121}
122
123/// A measurement's parameters besides its text: the font size's bits and
124/// the style hash.
125type TextMetricsParams = (u32, u64);
126
127struct TextMetricsCache {
128    map: PassAgedCache<TextCacheKey<TextMetricsParams>, TextMetrics>,
129}
130
131impl TextMetricsCache {
132    fn new(capacity: usize) -> Self {
133        Self {
134            map: PassAgedCache::with_capacity_at_least_one(capacity),
135        }
136    }
137
138    /// The cached metrics of `text`, measured by `measure` on a miss. A hit
139    /// borrows `text`; only a miss copies it into the key it stores.
140    fn get_or_measure<F>(
141        &mut self,
142        text: &str,
143        font_size: f32,
144        style_hash: u64,
145        measure: F,
146    ) -> TextMetrics
147    where
148        F: FnOnce(&str, f32) -> TextMetrics,
149    {
150        let probe = TextProbe::new(text, (font_size.to_bits(), style_hash));
151        if let Some(metrics) = self.map.get(probe.key()).copied() {
152            return metrics;
153        }
154
155        let metrics = measure(text, font_size);
156        self.map.push(probe.to_owned_key(), metrics);
157        metrics
158    }
159}
160
161impl CachedFontTextMeasurer {
162    /// Creates a measurer for `text_resources` with a metrics cache of `capacity` entries, at least
163    /// one.
164    pub fn with_text_resources(text_resources: SoftwareTextResources, capacity: usize) -> Self {
165        Self {
166            text_resources,
167            cache: Mutex::new(TextMetricsCache::new(capacity)),
168            hyphenation: HyphenationDictionaryStore::new(),
169        }
170    }
171
172    fn lock_cache(&self) -> MutexGuard<'_, TextMetricsCache> {
173        self.cache.lock().unwrap_or_else(PoisonError::into_inner)
174    }
175}
176
177fn resolve_font_size(style: &cranpose_ui::text::TextStyle) -> f32 {
178    style.resolve_font_size(14.0)
179}
180
181impl TextMeasurer for CachedFontTextMeasurer {
182    fn begin_layout_pass(&self) {
183        self.lock_cache().map.begin_pass(|_| {});
184    }
185
186    fn glyph_line_box(&self, style: &cranpose_ui::text::TextStyle) -> Option<(f32, f32)> {
187        let font = self.text_resources.fonts().resolve(style)?;
188        Some(crate::software_text_raster::font_glyph_line_box(
189            style, font,
190        ))
191    }
192
193    fn first_baseline(&self, style: &cranpose_ui::text::TextStyle) -> Option<f32> {
194        Some(self.line_box(style)?.baseline)
195    }
196
197    fn line_box(&self, style: &cranpose_ui::text::TextStyle) -> Option<cranpose_ui::text::LineBox> {
198        let font = self.text_resources.fonts().resolve(style)?;
199        Some(crate::software_text_raster::font_line_box(
200            style,
201            font,
202            resolve_font_size(style),
203        ))
204    }
205
206    fn visit_line_boxes(
207        &self,
208        text: &cranpose_ui::text::AnnotatedString,
209        style: &cranpose_ui::text::TextStyle,
210        visit: &mut dyn FnMut(cranpose_ui::text::LineBox),
211    ) -> Option<()> {
212        visit_annotated_line_boxes(text, style, self.text_resources.fonts(), visit)
213    }
214
215    fn measure(
216        &self,
217        text: &cranpose_ui::text::AnnotatedString,
218        style: &cranpose_ui::text::TextStyle,
219    ) -> TextMetrics {
220        let text_str = text.text.as_str();
221        let font_size = resolve_font_size(style);
222        let mut style_hash = style.measurement_hash();
223        if !text.span_styles.is_empty() {
224            let mut hasher = cranpose_ui_graphics::FxHasher::default();
225            style_hash.hash(&mut hasher);
226            text.span_measurement_hash().hash(&mut hasher);
227            style_hash = hasher.finish();
228        }
229        self.lock_cache()
230            .get_or_measure(text_str, font_size, style_hash, |_, size| {
231                measure_annotated_text_with_font_set(text, style, size, self.text_resources.fonts())
232            })
233    }
234
235    fn get_offset_for_position(
236        &self,
237        text: &cranpose_ui::text::AnnotatedString,
238        style: &cranpose_ui::text::TextStyle,
239        x: f32,
240        y: f32,
241    ) -> usize {
242        annotated_offset_for_position(text, style, x, y, self.text_resources.fonts())
243    }
244
245    fn get_cursor_x_for_offset(
246        &self,
247        text: &cranpose_ui::text::AnnotatedString,
248        style: &cranpose_ui::text::TextStyle,
249        offset: usize,
250    ) -> f32 {
251        annotated_cursor_x_for_offset(text, style, offset, self.text_resources.fonts())
252    }
253
254    fn layout(
255        &self,
256        text: &cranpose_ui::text::AnnotatedString,
257        style: &cranpose_ui::text::TextStyle,
258    ) -> TextLayoutResult {
259        layout_annotated_text_with_font_set(text, style, self.text_resources.fonts())
260    }
261
262    fn choose_auto_hyphen_break(
263        &self,
264        line: &str,
265        style: &cranpose_ui::text::TextStyle,
266        segment_start_char: usize,
267        measured_break_char: usize,
268    ) -> Option<usize> {
269        self.hyphenation.choose_auto_hyphen_break(
270            line,
271            style,
272            segment_start_char,
273            measured_break_char,
274        )
275    }
276}
277
278#[cfg(test)]
279#[path = "tests/text_measure_tests.rs"]
280mod tests;
cranpose_render_common/text_measure.rs

cranpose_render_common/
text_measure.rs
