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    pub fn default_font() -> Self {
34        Self {
35            fonts: SoftwareTextFontSet::from_fonts_or_default(&[]),
36        }
37    }
38
39    pub fn fonts(&self) -> &SoftwareTextFontSet {
40        &self.fonts
41    }
42}
43
44impl Default for SoftwareTextResources {
45    fn default() -> Self {
46        Self::default_font()
47    }
48}
49
50pub fn fallback_char_width(font_size: f32) -> f32 {
51    font_size.max(1.0) * 0.55
52}
53
54pub fn fallback_line_height(font_size: f32) -> f32 {
55    font_size.max(1.0) * 1.2
56}
57
58pub fn fallback_text_metrics(text: &str, font_size: f32) -> TextMetrics {
59    let line_height = fallback_line_height(font_size);
60    let mut line_count = 0usize;
61    let mut max_chars = 0usize;
62    for line in text.split('\n') {
63        line_count += 1;
64        max_chars = max_chars.max(line.chars().count());
65    }
66    let line_count = line_count.max(1);
67    TextMetrics {
68        width: max_chars as f32 * fallback_char_width(font_size),
69        height: line_count as f32 * line_height,
70        line_height,
71        line_count,
72    }
73}
74
75pub fn fallback_cursor_x_for_byte_offset(text: &str, byte_offset: usize, font_size: f32) -> f32 {
76    let clamped = byte_offset.min(text.len());
77    let char_count = if clamped == text.len() {
78        text.chars().count()
79    } else {
80        text.char_indices()
81            .take_while(|(index, _)| *index < clamped)
82            .count()
83    };
84    char_count as f32 * fallback_char_width(font_size)
85}
86
87pub struct CachedFontTextMeasurer {
88    text_resources: SoftwareTextResources,
89    cache: Mutex<TextMetricsCache>,
90    hyphenation: HyphenationDictionaryStore,
91}
92
93/// A measurement's parameters besides its text: the font size's bits and
94/// the style hash.
95type TextMetricsParams = (u32, u64);
96
97struct TextMetricsCache {
98    map: PassAgedCache<TextCacheKey<TextMetricsParams>, TextMetrics>,
99}
100
101impl TextMetricsCache {
102    fn new(capacity: usize) -> Self {
103        Self {
104            map: PassAgedCache::with_capacity_at_least_one(capacity),
105        }
106    }
107
108    /// The cached metrics of `text`, measured by `measure` on a miss. A hit
109    /// borrows `text`; only a miss copies it into the key it stores.
110    fn get_or_measure<F>(
111        &mut self,
112        text: &str,
113        font_size: f32,
114        style_hash: u64,
115        measure: F,
116    ) -> TextMetrics
117    where
118        F: FnOnce(&str, f32) -> TextMetrics,
119    {
120        let probe = TextProbe::new(text, (font_size.to_bits(), style_hash));
121        if let Some(metrics) = self.map.get(probe.key()).copied() {
122            return metrics;
123        }
124
125        let metrics = measure(text, font_size);
126        self.map.push(probe.to_owned_key(), metrics);
127        metrics
128    }
129}
130
131impl CachedFontTextMeasurer {
132    pub fn with_text_resources(text_resources: SoftwareTextResources, capacity: usize) -> Self {
133        Self {
134            text_resources,
135            cache: Mutex::new(TextMetricsCache::new(capacity)),
136            hyphenation: HyphenationDictionaryStore::new(),
137        }
138    }
139
140    fn lock_cache(&self) -> MutexGuard<'_, TextMetricsCache> {
141        self.cache.lock().unwrap_or_else(PoisonError::into_inner)
142    }
143}
144
145fn resolve_font_size(style: &cranpose_ui::text::TextStyle) -> f32 {
146    style.resolve_font_size(14.0)
147}
148
149impl TextMeasurer for CachedFontTextMeasurer {
150    fn begin_layout_pass(&self) {
151        self.lock_cache().map.begin_pass(|_| {});
152    }
153
154    fn glyph_line_box(&self, style: &cranpose_ui::text::TextStyle) -> Option<(f32, f32)> {
155        let font = self.text_resources.fonts().resolve(style)?;
156        Some(crate::software_text_raster::font_glyph_line_box(
157            style, font,
158        ))
159    }
160
161    fn first_baseline(&self, style: &cranpose_ui::text::TextStyle) -> Option<f32> {
162        Some(self.line_box(style)?.baseline)
163    }
164
165    fn line_box(&self, style: &cranpose_ui::text::TextStyle) -> Option<cranpose_ui::text::LineBox> {
166        let font = self.text_resources.fonts().resolve(style)?;
167        Some(crate::software_text_raster::font_line_box(
168            style,
169            font,
170            resolve_font_size(style),
171        ))
172    }
173
174    fn visit_line_boxes(
175        &self,
176        text: &cranpose_ui::text::AnnotatedString,
177        style: &cranpose_ui::text::TextStyle,
178        visit: &mut dyn FnMut(cranpose_ui::text::LineBox),
179    ) -> Option<()> {
180        visit_annotated_line_boxes(text, style, self.text_resources.fonts(), visit)
181    }
182
183    fn measure(
184        &self,
185        text: &cranpose_ui::text::AnnotatedString,
186        style: &cranpose_ui::text::TextStyle,
187    ) -> TextMetrics {
188        let text_str = text.text.as_str();
189        let font_size = resolve_font_size(style);
190        let mut style_hash = style.measurement_hash();
191        if !text.span_styles.is_empty() {
192            let mut hasher = cranpose_ui_graphics::FxHasher::default();
193            style_hash.hash(&mut hasher);
194            text.span_measurement_hash().hash(&mut hasher);
195            style_hash = hasher.finish();
196        }
197        self.lock_cache()
198            .get_or_measure(text_str, font_size, style_hash, |_, size| {
199                measure_annotated_text_with_font_set(text, style, size, self.text_resources.fonts())
200            })
201    }
202
203    fn get_offset_for_position(
204        &self,
205        text: &cranpose_ui::text::AnnotatedString,
206        style: &cranpose_ui::text::TextStyle,
207        x: f32,
208        y: f32,
209    ) -> usize {
210        annotated_offset_for_position(text, style, x, y, self.text_resources.fonts())
211    }
212
213    fn get_cursor_x_for_offset(
214        &self,
215        text: &cranpose_ui::text::AnnotatedString,
216        style: &cranpose_ui::text::TextStyle,
217        offset: usize,
218    ) -> f32 {
219        annotated_cursor_x_for_offset(text, style, offset, self.text_resources.fonts())
220    }
221
222    fn layout(
223        &self,
224        text: &cranpose_ui::text::AnnotatedString,
225        style: &cranpose_ui::text::TextStyle,
226    ) -> TextLayoutResult {
227        layout_annotated_text_with_font_set(text, style, self.text_resources.fonts())
228    }
229
230    fn choose_auto_hyphen_break(
231        &self,
232        line: &str,
233        style: &cranpose_ui::text::TextStyle,
234        segment_start_char: usize,
235        measured_break_char: usize,
236    ) -> Option<usize> {
237        self.hyphenation.choose_auto_hyphen_break(
238            line,
239            style,
240            segment_start_char,
241            measured_break_char,
242        )
243    }
244}
245
246#[cfg(test)]
247#[path = "tests/text_measure_tests.rs"]
248mod tests;
cranpose_render_common/text_measure.rs

cranpose_render_common/
text_measure.rs
