1use std::{borrow::Cow, ops::Range, sync::Arc};
2
3use crate::{
4 color::Color,
5 fonts::{HighlightStyle, TextStyle},
6 geometry::{
7 rect::RectF,
8 vector::{vec2f, Vector2F},
9 },
10 json::{ToJson, Value},
11 text_layout::{Line, RunStyle, ShapedBoundary},
12 DebugContext, Element, Event, EventContext, FontCache, LayoutContext, PaintContext,
13 SizeConstraint, TextLayoutCache,
14};
15use serde_json::json;
16
17pub struct Text {
18 text: String,
19 style: TextStyle,
20 soft_wrap: bool,
21 highlights: Vec<(Range<usize>, HighlightStyle)>,
22}
23
24pub struct LayoutState {
25 shaped_lines: Vec<Line>,
26 wrap_boundaries: Vec<Vec<ShapedBoundary>>,
27 line_height: f32,
28}
29
30impl Text {
31 pub fn new(text: String, style: TextStyle) -> Self {
32 Self {
33 text,
34 style,
35 soft_wrap: true,
36 highlights: Vec::new(),
37 }
38 }
39
40 pub fn with_default_color(mut self, color: Color) -> Self {
41 self.style.color = color;
42 self
43 }
44
45 pub fn with_highlights(mut self, runs: Vec<(Range<usize>, HighlightStyle)>) -> Self {
46 self.highlights = runs;
47 self
48 }
49
50 pub fn with_soft_wrap(mut self, soft_wrap: bool) -> Self {
51 self.soft_wrap = soft_wrap;
52 self
53 }
54}
55
56impl Element for Text {
57 type LayoutState = LayoutState;
58 type PaintState = ();
59
60 fn layout(
61 &mut self,
62 constraint: SizeConstraint,
63 cx: &mut LayoutContext,
64 ) -> (Vector2F, Self::LayoutState) {
65 // Convert the string and highlight ranges into an iterator of highlighted chunks.
66 let mut offset = 0;
67 let mut highlight_ranges = self.highlights.iter().peekable();
68 let chunks = std::iter::from_fn(|| {
69 let result;
70 if let Some((range, highlight_style)) = highlight_ranges.peek() {
71 if offset < range.start {
72 result = Some((&self.text[offset..range.start], None));
73 offset = range.start;
74 } else {
75 result = Some((&self.text[range.clone()], Some(*highlight_style)));
76 highlight_ranges.next();
77 offset = range.end;
78 }
79 } else if offset < self.text.len() {
80 result = Some((&self.text[offset..], None));
81 offset = self.text.len();
82 } else {
83 result = None;
84 }
85 result
86 });
87
88 // Perform shaping on these highlighted chunks
89 let shaped_lines = layout_highlighted_chunks(
90 chunks,
91 &self.style,
92 cx.text_layout_cache,
93 &cx.font_cache,
94 usize::MAX,
95 self.text.matches('\n').count() + 1,
96 );
97
98 // If line wrapping is enabled, wrap each of the shaped lines.
99 let font_id = self.style.font_id;
100 let mut line_count = 0;
101 let mut max_line_width = 0_f32;
102 let mut wrap_boundaries = Vec::new();
103 let mut wrapper = cx.font_cache.line_wrapper(font_id, self.style.font_size);
104 for (line, shaped_line) in self.text.lines().zip(&shaped_lines) {
105 if self.soft_wrap {
106 let boundaries = wrapper
107 .wrap_shaped_line(line, shaped_line, constraint.max.x())
108 .collect::<Vec<_>>();
109 line_count += boundaries.len() + 1;
110 wrap_boundaries.push(boundaries);
111 } else {
112 line_count += 1;
113 }
114 max_line_width = max_line_width.max(shaped_line.width());
115 }
116
117 let line_height = cx.font_cache.line_height(font_id, self.style.font_size);
118 let size = vec2f(
119 max_line_width
120 .ceil()
121 .max(constraint.min.x())
122 .min(constraint.max.x()),
123 (line_height * line_count as f32).ceil(),
124 );
125 (
126 size,
127 LayoutState {
128 shaped_lines,
129 wrap_boundaries,
130 line_height,
131 },
132 )
133 }
134
135 fn paint(
136 &mut self,
137 bounds: RectF,
138 visible_bounds: RectF,
139 layout: &mut Self::LayoutState,
140 cx: &mut PaintContext,
141 ) -> Self::PaintState {
142 let mut origin = bounds.origin();
143 let empty = Vec::new();
144 for (ix, line) in layout.shaped_lines.iter().enumerate() {
145 let wrap_boundaries = layout.wrap_boundaries.get(ix).unwrap_or(&empty);
146 let boundaries = RectF::new(
147 origin,
148 vec2f(
149 bounds.width(),
150 (wrap_boundaries.len() + 1) as f32 * layout.line_height,
151 ),
152 );
153
154 if boundaries.intersects(visible_bounds) {
155 if self.soft_wrap {
156 line.paint_wrapped(
157 origin,
158 visible_bounds,
159 layout.line_height,
160 wrap_boundaries.iter().copied(),
161 cx,
162 );
163 } else {
164 line.paint(origin, visible_bounds, layout.line_height, cx);
165 }
166 }
167 origin.set_y(boundaries.max_y());
168 }
169 }
170
171 fn dispatch_event(
172 &mut self,
173 _: &Event,
174 _: RectF,
175 _: &mut Self::LayoutState,
176 _: &mut Self::PaintState,
177 _: &mut EventContext,
178 ) -> bool {
179 false
180 }
181
182 fn debug(
183 &self,
184 bounds: RectF,
185 _: &Self::LayoutState,
186 _: &Self::PaintState,
187 _: &DebugContext,
188 ) -> Value {
189 json!({
190 "type": "Text",
191 "bounds": bounds.to_json(),
192 "text": &self.text,
193 "style": self.style.to_json(),
194 })
195 }
196}
197
198/// Perform text layout on a series of highlighted chunks of text.
199pub fn layout_highlighted_chunks<'a>(
200 chunks: impl Iterator<Item = (&'a str, Option<HighlightStyle>)>,
201 text_style: &'a TextStyle,
202 text_layout_cache: &'a TextLayoutCache,
203 font_cache: &'a Arc<FontCache>,
204 max_line_len: usize,
205 max_line_count: usize,
206) -> Vec<Line> {
207 let mut layouts = Vec::with_capacity(max_line_count);
208 let mut line = String::new();
209 let mut styles = Vec::new();
210 let mut row = 0;
211 let mut line_exceeded_max_len = false;
212 for (chunk, highlight_style) in chunks.chain([("\n", Default::default())]) {
213 for (ix, mut line_chunk) in chunk.split('\n').enumerate() {
214 if ix > 0 {
215 layouts.push(text_layout_cache.layout_str(&line, text_style.font_size, &styles));
216 line.clear();
217 styles.clear();
218 row += 1;
219 line_exceeded_max_len = false;
220 if row == max_line_count {
221 return layouts;
222 }
223 }
224
225 if !line_chunk.is_empty() && !line_exceeded_max_len {
226 let text_style = if let Some(style) = highlight_style {
227 text_style
228 .clone()
229 .highlight(style, font_cache)
230 .map(Cow::Owned)
231 .unwrap_or_else(|_| Cow::Borrowed(text_style))
232 } else {
233 Cow::Borrowed(text_style)
234 };
235
236 if line.len() + line_chunk.len() > max_line_len {
237 let mut chunk_len = max_line_len - line.len();
238 while !line_chunk.is_char_boundary(chunk_len) {
239 chunk_len -= 1;
240 }
241 line_chunk = &line_chunk[..chunk_len];
242 line_exceeded_max_len = true;
243 }
244
245 line.push_str(line_chunk);
246 styles.push((
247 line_chunk.len(),
248 RunStyle {
249 font_id: text_style.font_id,
250 color: text_style.color,
251 underline: text_style.underline,
252 },
253 ));
254 }
255 }
256 }
257
258 layouts
259}