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| 1 | //! Two-dimensional layout for equations, from the tree `onestore::page::Math` parses out of |
| 2 | //! the linear text OneNote stores. |
| 3 | |
| 4 | use crate::layout::{LayoutError, TextEngine, TextLayout}; |
| 5 | use onestore::document::Format; |
| 6 | use onestore::page::Math; |
| 7 | use onestore::page::text::Paragraph; |
| 8 | |
| 9 | /// An equation laid out for drawing; coordinates are relative to its top-left. |
| 10 | #[derive(Clone)] |
| 11 | pub struct MathLayout { |
| 12 | pub size: [f32; 2], |
| 13 | /// COLORREF for rules and strokes. |
| 14 | pub color: u32, |
| 15 | /// Distance from the top to the baseline of the equation's main row. |
| 16 | pub baseline: f32, |
| 17 | pub items: Vec<MathItem>, |
| 18 | } |
| 19 | |
| 20 | #[derive(Clone)] |
| 21 | pub enum MathItem { |
| 22 | Text { |
| 23 | layout: TextLayout, |
| 24 | origin: [f32; 2], |
| 25 | }, |
| 26 | Rule([f32; 4]), |
| 27 | /// A pen stroke, for radical signs. |
| 28 | Stroke { |
| 29 | from: [f32; 2], |
| 30 | to: [f32; 2], |
| 31 | width: f32, |
| 32 | }, |
| 33 | } |
| 34 | |
| 35 | /// Items are relative to the box origin on its baseline; y grows downward. |
| 36 | struct Bx { |
| 37 | width: f32, |
| 38 | ascent: f32, |
| 39 | descent: f32, |
| 40 | items: Vec<MathItem>, |
| 41 | } |
| 42 | |
| 43 | impl Bx { |
| 44 | fn empty() -> Self { |
| 45 | Self { |
| 46 | width: 0.0, |
| 47 | ascent: 0.0, |
| 48 | descent: 0.0, |
| 49 | items: Vec::new(), |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | /// Places `other` with its baseline origin at `at` in this box's coordinates. |
| 54 | fn place(&mut self, other: Bx, at: [f32; 2]) { |
| 55 | self.ascent = self.ascent.max(other.ascent - at[1]); |
| 56 | self.descent = self.descent.max(other.descent + at[1]); |
| 57 | self.width = self.width.max(at[0] + other.width); |
| 58 | self.items |
| 59 | .extend(other.items.into_iter().map(|item| offset(item, at))); |
| 60 | } |
| 61 | |
| 62 | fn append(&mut self, other: Bx) { |
| 63 | let x = self.width; |
| 64 | self.place(other, [x, 0.0]); |
| 65 | } |
| 66 | |
| 67 | fn space(&mut self, width: f32) { |
| 68 | self.width += width; |
| 69 | } |
| 70 | |
| 71 | fn height(&self) -> f32 { |
| 72 | self.ascent + self.descent |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | fn offset(item: MathItem, [dx, dy]: [f32; 2]) -> MathItem { |
| 77 | match item { |
| 78 | MathItem::Text { layout, origin } => MathItem::Text { |
| 79 | layout, |
| 80 | origin: [origin[0] + dx, origin[1] + dy], |
| 81 | }, |
| 82 | MathItem::Rule([x0, y0, x1, y1]) => MathItem::Rule([x0 + dx, y0 + dy, x1 + dx, y1 + dy]), |
| 83 | MathItem::Stroke { from, to, width } => MathItem::Stroke { |
| 84 | from: [from[0] + dx, from[1] + dy], |
| 85 | to: [to[0] + dx, to[1] + dy], |
| 86 | width, |
| 87 | }, |
| 88 | } |
| 89 | } |
| 90 | |
| 91 | const SCRIPT: f32 = 0.7; |
| 92 | const AXIS: f32 = 0.25; |
| 93 | const RULE: f32 = 0.06; |
| 94 | |
| 95 | struct Context<'a> { |
| 96 | engine: &'a mut TextEngine, |
| 97 | color: Option<u32>, |
| 98 | } |
| 99 | |
| 100 | impl Context<'_> { |
| 101 | fn text(&mut self, text: &str, size: f32) -> Result<Bx, LayoutError> { |
| 102 | let layout = self.engine.layout( |
| 103 | &Paragraph::new( |
| 104 | text.into(), |
| 105 | Format { |
| 106 | font: Some("Cambria Math".into()), |
| 107 | font_size: Some(size), |
| 108 | color: self.color, |
| 109 | ..Format::default() |
| 110 | }, |
| 111 | ), |
| 112 | // Atoms never wrap. |
| 113 | f32::MAX / 4.0, |
| 114 | )?; |
| 115 | let (line, bounds) = layout |
| 116 | .lines() |
| 117 | .next() |
| 118 | .ok_or(LayoutError::InvalidFontMetrics)?; |
| 119 | let (width, baseline) = (line.metrics().advance, bounds.baseline); |
| 120 | // Math fonts' line boxes span their tallest glyphs; placement follows the ink instead. |
| 121 | let [ascent, descent] = ink(&layout); |
| 122 | Ok(Bx { |
| 123 | width, |
| 124 | ascent, |
| 125 | descent, |
| 126 | items: vec![MathItem::Text { |
| 127 | layout, |
| 128 | origin: [0.0, -baseline], |
| 129 | }], |
| 130 | }) |
| 131 | } |
| 132 | |
| 133 | fn row(&mut self, nodes: &[Math], size: f32) -> Result<Bx, LayoutError> { |
| 134 | let mut result = Bx::empty(); |
| 135 | for (index, node) in nodes.iter().enumerate() { |
| 136 | let spaced = match node { |
| 137 | Math::Operator(c) if index > 0 => spacing(*c), |
| 138 | _ => 0.0, |
| 139 | } * size; |
| 140 | result.space(spaced); |
| 141 | result.append(self.node(node, size)?); |
| 142 | if index + 1 < nodes.len() { |
| 143 | result.space(spaced); |
| 144 | } |
| 145 | } |
| 146 | Ok(result) |
| 147 | } |
| 148 | |
| 149 | fn node(&mut self, node: &Math, size: f32) -> Result<Bx, LayoutError> { |
| 150 | match node { |
| 151 | Math::Identifier(c) => self.text(&italic(*c).to_string(), size), |
| 152 | Math::Function(name) | Math::Number(name) => self.text(name, size), |
| 153 | Math::Operator(' ') => { |
| 154 | let mut space = Bx::empty(); |
| 155 | space.space(0.2 * size); |
| 156 | Ok(space) |
| 157 | } |
| 158 | Math::Operator(c) => self.text(&c.to_string(), size), |
| 159 | Math::Object { |
| 160 | kind, |
| 161 | symbols, |
| 162 | columns, |
| 163 | arguments, |
| 164 | } => self.object(*kind, symbols, *columns, arguments, size), |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | fn argument( |
| 169 | &mut self, |
| 170 | arguments: &[Vec<Math>], |
| 171 | index: usize, |
| 172 | size: f32, |
| 173 | ) -> Result<Bx, LayoutError> { |
| 174 | self.row(arguments.get(index).map_or(&[][..], Vec::as_slice), size) |
| 175 | } |
| 176 | |
| 177 | fn object( |
| 178 | &mut self, |
| 179 | kind: u32, |
| 180 | symbols: &[char], |
| 181 | columns: Option<u8>, |
| 182 | arguments: &[Vec<Math>], |
| 183 | size: f32, |
| 184 | ) -> Result<Bx, LayoutError> { |
| 185 | let script = size * SCRIPT; |
| 186 | Ok(match (kind, arguments.len()) { |
| 187 | (31, 2) => self.scripts(None, Some(1), arguments, size)?, |
| 188 | (29, 2) => self.scripts(Some(1), None, arguments, size)?, |
| 189 | (30, 3) => self.scripts(Some(1), Some(2), arguments, size)?, |
| 190 | (16, 2) | (26, 2) => { |
| 191 | let numerator = self.argument(arguments, 0, size)?; |
| 192 | let denominator = self.argument(arguments, 1, size)?; |
| 193 | let width = numerator.width.max(denominator.width) + 0.2 * size; |
| 194 | let (axis, rule, gap) = (AXIS * size, RULE * size, 0.12 * size); |
| 195 | let mut result = Bx::empty(); |
| 196 | let top = -axis - rule / 2.0 - gap - numerator.descent; |
| 197 | let bottom = -axis + rule / 2.0 + gap + denominator.ascent; |
| 198 | result.place(numerator.centered(width), [0.0, top]); |
| 199 | result.place(denominator.centered(width), [0.0, bottom]); |
| 200 | result.items.push(MathItem::Rule([ |
| 201 | 0.0, |
| 202 | -axis - rule / 2.0, |
| 203 | width, |
| 204 | -axis + rule / 2.0, |
| 205 | ])); |
| 206 | result |
| 207 | } |
| 208 | (25, _) => { |
| 209 | let body = self.argument(arguments, arguments.len().saturating_sub(1), size)?; |
| 210 | let degree = (arguments.len() == 2 && !arguments[0].is_empty()) |
| 211 | .then(|| self.row(&arguments[0], size * 0.5)) |
| 212 | .transpose()?; |
| 213 | radical(body, degree, size) |
| 214 | } |
| 215 | (19, 2) | (33, 2) => { |
| 216 | let base = self.argument(arguments, 0, size)?; |
| 217 | let limit = self.argument(arguments, 1, script)?; |
| 218 | if kind == 19 { |
| 219 | stacked(base, Some(limit), None, size) |
| 220 | } else { |
| 221 | stacked(base, None, Some(limit), size) |
| 222 | } |
| 223 | } |
| 224 | (13, _) => { |
| 225 | let body = self.argument(arguments, 0, size)?; |
| 226 | let open = symbols |
| 227 | .first() |
| 228 | .map(|c| self.fence(*c, &body, size)) |
| 229 | .transpose()?; |
| 230 | let close = symbols |
| 231 | .get(1) |
| 232 | .map(|c| self.fence(*c, &body, size)) |
| 233 | .transpose()?; |
| 234 | let mut result = Bx::empty(); |
| 235 | for part in [open, Some(body), close].into_iter().flatten() { |
| 236 | result.append(part); |
| 237 | } |
| 238 | result |
| 239 | } |
| 240 | (10, 1) => { |
| 241 | let base = self.argument(arguments, 0, size)?; |
| 242 | let accent = self.text( |
| 243 | &spacing_accent(symbols.first().copied().unwrap_or('\u{302}')).to_string(), |
| 244 | size, |
| 245 | )?; |
| 246 | let mut result = Bx::empty(); |
| 247 | let width = base.width; |
| 248 | // The accent's ink bottom sits just above the base's ink top. |
| 249 | let lift = -base.ascent - 0.05 * size - accent.descent; |
| 250 | result.place(base, [0.0, 0.0]); |
| 251 | let x = (width - accent.width) / 2.0; |
| 252 | result.place(accent, [x.max(0.0), lift]); |
| 253 | result |
| 254 | } |
| 255 | (23, 1) => { |
| 256 | let base = self.argument(arguments, 0, size)?; |
| 257 | let (rule, gap) = (RULE * size, 0.1 * size); |
| 258 | let mut result = Bx::empty(); |
| 259 | let top = -base.ascent - gap; |
| 260 | let width = base.width; |
| 261 | result.place(base, [0.0, 0.0]); |
| 262 | result |
| 263 | .items |
| 264 | .push(MathItem::Rule([0.0, top - rule, width, top])); |
| 265 | result.ascent = result.ascent.max(-(top - rule)); |
| 266 | result |
| 267 | } |
| 268 | (12, 1) => { |
| 269 | let body = self.argument(arguments, 0, size)?; |
| 270 | let (rule, pad) = (RULE * size, 0.12 * size); |
| 271 | let mut result = Bx::empty(); |
| 272 | let [w, a, d] = [ |
| 273 | body.width + 2.0 * pad, |
| 274 | body.ascent + pad, |
| 275 | body.descent + pad, |
| 276 | ]; |
| 277 | result.place(body, [pad, 0.0]); |
| 278 | for rect in [ |
| 279 | [0.0, -a, w, -a + rule], |
| 280 | [0.0, d - rule, w, d], |
| 281 | [0.0, -a, rule, d], |
| 282 | [w - rule, -a, w, d], |
| 283 | ] { |
| 284 | result.items.push(MathItem::Rule(rect)); |
| 285 | } |
| 286 | result.ascent = result.ascent.max(a); |
| 287 | result.descent = result.descent.max(d); |
| 288 | result.width = w; |
| 289 | result |
| 290 | } |
| 291 | (21, 3) => { |
| 292 | let operator = symbols.first().copied().unwrap_or('∑'); |
| 293 | let integral = ('\u{222b}'..='\u{2233}').contains(&operator); |
| 294 | // Display-size operators, as OneNote draws them. |
| 295 | let scale = if integral { 1.9 } else { 1.75 }; |
| 296 | let glyph = self |
| 297 | .text(&operator.to_string(), size * scale)? |
| 298 | .on_axis(size); |
| 299 | let lower = (!arguments[0].is_empty()) |
| 300 | .then(|| self.row(&arguments[0], script)) |
| 301 | .transpose()?; |
| 302 | let upper = (!arguments[1].is_empty()) |
| 303 | .then(|| self.row(&arguments[1], script)) |
| 304 | .transpose()?; |
| 305 | let mut result = if integral { |
| 306 | let mut result = Bx::empty(); |
| 307 | let (ascent, descent, width) = (glyph.ascent, glyph.descent, glyph.width); |
| 308 | result.append(glyph); |
| 309 | let x = width + 0.05 * size; |
| 310 | if let Some(upper) = upper { |
| 311 | let y = -ascent + upper.ascent; |
| 312 | result.place(upper, [x, y]); |
| 313 | } |
| 314 | if let Some(lower) = lower { |
| 315 | let y = descent - lower.descent; |
| 316 | result.place(lower, [x - 0.2 * size, y]); |
| 317 | } |
| 318 | result |
| 319 | } else { |
| 320 | stacked(glyph, lower, upper, size) |
| 321 | }; |
| 322 | result.space(0.15 * size); |
| 323 | result.append(self.argument(arguments, 2, size)?); |
| 324 | result |
| 325 | } |
| 326 | (20, _) | (15, _) => { |
| 327 | let width = if kind == 20 { |
| 328 | usize::from(columns.unwrap_or(1).max(1)) |
| 329 | } else { |
| 330 | 1 |
| 331 | }; |
| 332 | let cells = arguments |
| 333 | .iter() |
| 334 | .map(|cell| { |
| 335 | let cell: Vec<Math> = cell |
| 336 | .iter() |
| 337 | .filter(|n| **n != Math::Operator('&')) |
| 338 | .cloned() |
| 339 | .collect(); |
| 340 | self.row(&cell, size) |
| 341 | }) |
| 342 | .collect::<Result<Vec<_>, _>>()?; |
| 343 | grid(cells, width, kind == 20, size) |
| 344 | } |
| 345 | (11, 1) => self.argument(arguments, 0, size)?, |
| 346 | _ => { |
| 347 | let mut result = Bx::empty(); |
| 348 | for symbol in symbols { |
| 349 | result.append(self.text(&symbol.to_string(), size)?); |
| 350 | } |
| 351 | for index in 0..arguments.len() { |
| 352 | result.append(self.argument(arguments, index, size)?); |
| 353 | } |
| 354 | result |
| 355 | } |
| 356 | }) |
| 357 | } |
| 358 | |
| 359 | /// The first argument with the arguments at `lower` and `upper` as its scripts. |
| 360 | fn scripts( |
| 361 | &mut self, |
| 362 | lower: Option<usize>, |
| 363 | upper: Option<usize>, |
| 364 | arguments: &[Vec<Math>], |
| 365 | size: f32, |
| 366 | ) -> Result<Bx, LayoutError> { |
| 367 | let script = size * SCRIPT; |
| 368 | let mut result = self.argument(arguments, 0, size)?; |
| 369 | let x = result.width + 0.03 * size; |
| 370 | let both = lower.is_some() && upper.is_some(); |
| 371 | if let Some(index) = upper { |
| 372 | let upper = self.argument(arguments, index, script)?; |
| 373 | result.place(upper, [x, -0.4 * size]); |
| 374 | } |
| 375 | if let Some(index) = lower { |
| 376 | let lower = self.argument(arguments, index, script)?; |
| 377 | result.place(lower, [x, if both { 0.3 } else { 0.2 } * size]); |
| 378 | } |
| 379 | Ok(result) |
| 380 | } |
| 381 | |
| 382 | /// A delimiter tall enough for `body`, centered on the math axis. |
| 383 | fn fence(&mut self, symbol: char, body: &Bx, size: f32) -> Result<Bx, LayoutError> { |
| 384 | let axis = AXIS * size; |
| 385 | let reach = (body.ascent - axis).max(body.descent + axis); |
| 386 | let grown = (reach * 2.0 / (size * 1.15)).max(1.0) * size; |
| 387 | Ok(self.text(&symbol.to_string(), grown)?.on_axis(size)) |
| 388 | } |
| 389 | } |
| 390 | |
| 391 | impl Bx { |
| 392 | /// This box moved vertically so its extent centers on the math axis. |
| 393 | fn on_axis(self, size: f32) -> Bx { |
| 394 | let shift = (self.ascent - self.descent) / 2.0 - AXIS * size; |
| 395 | Bx { |
| 396 | width: self.width, |
| 397 | ascent: self.ascent - shift, |
| 398 | descent: self.descent + shift, |
| 399 | items: self |
| 400 | .items |
| 401 | .into_iter() |
| 402 | .map(|i| offset(i, [0.0, shift])) |
| 403 | .collect(), |
| 404 | } |
| 405 | } |
| 406 | |
| 407 | /// This box horizontally centered in `width`. |
| 408 | fn centered(self, width: f32) -> Bx { |
| 409 | let dx = (width - self.width) / 2.0; |
| 410 | Bx { |
| 411 | width, |
| 412 | ascent: self.ascent, |
| 413 | descent: self.descent, |
| 414 | items: self |
| 415 | .items |
| 416 | .into_iter() |
| 417 | .map(|i| offset(i, [dx, 0.0])) |
| 418 | .collect(), |
| 419 | } |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | /// `base` with `lower` below and `upper` above, all centered on the widest. |
| 424 | fn stacked(base: Bx, lower: Option<Bx>, upper: Option<Bx>, size: f32) -> Bx { |
| 425 | let gap = 0.08 * size; |
| 426 | let width = [Some(&base), lower.as_ref(), upper.as_ref()] |
| 427 | .into_iter() |
| 428 | .flatten() |
| 429 | .map(|b| b.width) |
| 430 | .fold(0.0, f32::max); |
| 431 | let (ascent, descent) = (base.ascent, base.descent); |
| 432 | let mut result = Bx::empty(); |
| 433 | result.place(base.centered(width), [0.0, 0.0]); |
| 434 | if let Some(lower) = lower { |
| 435 | let y = descent + gap + lower.ascent; |
| 436 | result.place(lower.centered(width), [0.0, y]); |
| 437 | } |
| 438 | if let Some(upper) = upper { |
| 439 | let y = -ascent - gap - upper.descent; |
| 440 | result.place(upper.centered(width), [0.0, y]); |
| 441 | } |
| 442 | result |
| 443 | } |
| 444 | |
| 445 | /// A radical sign drawn with the pen over `body`, with an optional small `degree`. |
| 446 | fn radical(body: Bx, degree: Option<Bx>, size: f32) -> Bx { |
| 447 | let (rule, gap) = (RULE * size, 0.12 * size); |
| 448 | let top = -body.ascent - gap; |
| 449 | let bottom = body.descent; |
| 450 | let sign = 0.55 * size; |
| 451 | let mut result = Bx::empty(); |
| 452 | let lead = degree |
| 453 | .as_ref() |
| 454 | .map_or(0.0, |d| (d.width - sign * 0.4).max(0.0)); |
| 455 | let [x0, x1, x2] = [lead, lead + sign * 0.35, lead + sign * 0.6]; |
| 456 | let mid = bottom - (bottom - top) * 0.45; |
| 457 | for (from, to, width) in [ |
| 458 | ([x0, mid + 0.05 * size], [x0 + sign * 0.12, mid], rule), |
| 459 | ([x0 + sign * 0.12, mid], [x1, bottom], rule * 1.6), |
| 460 | ([x1, bottom], [x2, top + rule / 2.0], rule), |
| 461 | ] { |
| 462 | result.items.push(MathItem::Stroke { from, to, width }); |
| 463 | } |
| 464 | let body_width = body.width; |
| 465 | result.place(body, [x2 + 0.05 * size, 0.0]); |
| 466 | result.items.push(MathItem::Rule([ |
| 467 | x2, |
| 468 | top, |
| 469 | x2 + 0.05 * size + body_width + 0.05 * size, |
| 470 | top + rule, |
| 471 | ])); |
| 472 | result.width = x2 + 0.1 * size + body_width; |
| 473 | result.ascent = result.ascent.max(-top); |
| 474 | result.descent = result.descent.max(bottom); |
| 475 | if let Some(degree) = degree { |
| 476 | let y = mid - 0.1 * size - degree.descent; |
| 477 | result.place(degree, [0.0, y]); |
| 478 | } |
| 479 | result |
| 480 | } |
| 481 | |
| 482 | /// Cells in rows of `width` columns, centered in each column (left-aligned for equation |
| 483 | /// arrays), the whole grid centered on the math axis. |
| 484 | fn grid(cells: Vec<Bx>, width: usize, centered: bool, size: f32) -> Bx { |
| 485 | let (column_gap, row_gap) = (0.8 * size, 0.2 * size); |
| 486 | let mut columns = vec![0.0_f32; width]; |
| 487 | for (index, cell) in cells.iter().enumerate() { |
| 488 | columns[index % width] = columns[index % width].max(cell.width); |
| 489 | } |
| 490 | let rows: Vec<(f32, f32)> = cells |
| 491 | .chunks(width) |
| 492 | .map(|row| { |
| 493 | row.iter().fold((0.0_f32, 0.0_f32), |(a, d), cell| { |
| 494 | (a.max(cell.ascent), d.max(cell.descent)) |
| 495 | }) |
| 496 | }) |
| 497 | .collect(); |
| 498 | let height: f32 = rows.iter().map(|(a, d)| a + d).sum::<f32>() |
| 499 | + row_gap * rows.len().saturating_sub(1) as f32; |
| 500 | let mut y = -AXIS * size - height / 2.0; |
| 501 | let mut result = Bx::empty(); |
| 502 | let mut cells = cells.into_iter(); |
| 503 | for (ascent, descent) in rows { |
| 504 | let mut x = 0.0; |
| 505 | for column in &columns { |
| 506 | let Some(cell) = cells.next() else { break }; |
| 507 | let dx = if centered { |
| 508 | (column - cell.width) / 2.0 |
| 509 | } else { |
| 510 | 0.0 |
| 511 | }; |
| 512 | result.place(cell, [x + dx, y + ascent]); |
| 513 | x += column + column_gap; |
| 514 | } |
| 515 | y += ascent + descent + row_gap; |
| 516 | } |
| 517 | result.width = columns.iter().sum::<f32>() + column_gap * width.saturating_sub(1) as f32; |
| 518 | result |
| 519 | } |
| 520 | |
| 521 | /// Extra space each side of an operator, in em: medium for binary operators, thick for |
| 522 | /// relations and arrows. |
| 523 | fn spacing(c: char) -> f32 { |
| 524 | match c { |
| 525 | '+' | '-' | '−' | '±' | '∓' | '×' | '÷' | '·' | '∙' | '*' => 4.0 / 18.0, |
| 526 | '=' | '<' | '>' | '≤' | '≥' | '≠' | '≈' | '≡' | '→' | '←' | '↔' | '⇒' | '∈' | '∉' => { |
| 527 | 5.0 / 18.0 |
| 528 | } |
| 529 | _ => 0.0, |
| 530 | } |
| 531 | } |
| 532 | |
| 533 | /// The spacing form of a combining accent, drawn above its base. |
| 534 | fn spacing_accent(c: char) -> char { |
| 535 | match c { |
| 536 | '\u{302}' => 'ˆ', |
| 537 | '\u{303}' => '˜', |
| 538 | '\u{307}' => '˙', |
| 539 | '\u{308}' => '¨', |
| 540 | '\u{301}' => '´', |
| 541 | '\u{300}' => '`', |
| 542 | '\u{306}' => '˘', |
| 543 | '\u{30c}' => 'ˇ', |
| 544 | '\u{20d7}' => '→', |
| 545 | c => c, |
| 546 | } |
| 547 | } |
| 548 | |
| 549 | /// Latin letters draw in mathematical italic, as OneNote's equation editor stores them. |
| 550 | fn italic(c: char) -> char { |
| 551 | match c { |
| 552 | 'h' => '\u{210e}', |
| 553 | 'a'..='z' => char::from_u32(0x1d44e + (c as u32 - 'a' as u32)).unwrap(), |
| 554 | 'A'..='Z' => char::from_u32(0x1d434 + (c as u32 - 'A' as u32)).unwrap(), |
| 555 | c => c, |
| 556 | } |
| 557 | } |
| 558 | |
| 559 | /// Height above and depth below the baseline of the glyphs' outlines; the depth is negative |
| 560 | /// for ink that floats above the baseline, as an accent's does. |
| 561 | fn ink(layout: &TextLayout) -> [f32; 2] { |
| 562 | use skrifa::{MetadataProvider, instance::Size}; |
| 563 | let mut extent = [f32::NEG_INFINITY; 2]; |
| 564 | for line in layout.shaped.lines() { |
| 565 | for item in line.items() { |
| 566 | let parley::PositionedLayoutItem::GlyphRun(glyphs) = item else { |
| 567 | continue; |
| 568 | }; |
| 569 | let run = glyphs.run(); |
| 570 | let font = &run.font().font; |
| 571 | let Ok(font) = skrifa::FontRef::from_index(font.data.as_ref(), font.index) else { |
| 572 | continue; |
| 573 | }; |
| 574 | let metrics = font.glyph_metrics( |
| 575 | Size::new(run.font_size()), |
| 576 | skrifa::instance::LocationRef::default(), |
| 577 | ); |
| 578 | for glyph in glyphs.glyphs() { |
| 579 | match metrics.bounds(skrifa::GlyphId::new(glyph.id)) { |
| 580 | // Blank glyphs, such as spaces, have no ink. |
| 581 | Some(bounds) if bounds.y_max > bounds.y_min => { |
| 582 | extent[0] = extent[0].max(bounds.y_max - glyph.y); |
| 583 | extent[1] = extent[1].max(glyph.y - bounds.y_min); |
| 584 | } |
| 585 | _ => {} |
| 586 | } |
| 587 | } |
| 588 | } |
| 589 | } |
| 590 | extent.map(|v| if v.is_finite() { v } else { 0.0 }) |
| 591 | } |
| 592 | |
| 593 | /// Lays out an equation paragraph at the font size and colour of its first run. |
| 594 | pub fn layout(engine: &mut TextEngine, paragraph: &Paragraph) -> Result<MathLayout, LayoutError> { |
| 595 | let nodes = Math::parse(paragraph).map_err(|_| LayoutError::UnsupportedContent)?; |
| 596 | let format = ¶graph.spans()[0].format; |
| 597 | let size = format.font_size.unwrap_or(11.0); |
| 598 | let color = format.color.filter(|color| *color != 0xff00_0000); |
| 599 | // An equation line is at least as tall as a line of text at its size. |
| 600 | let strut = engine.layout( |
| 601 | &Paragraph::new( |
| 602 | " ".into(), |
| 603 | Format { |
| 604 | font_size: Some(size), |
| 605 | ..Format::default() |
| 606 | }, |
| 607 | ), |
| 608 | 100.0, |
| 609 | )?; |
| 610 | let (_, line) = strut |
| 611 | .lines() |
| 612 | .next() |
| 613 | .ok_or(LayoutError::InvalidFontMetrics)?; |
| 614 | let mut body = Context { engine, color }.row(&nodes, size)?; |
| 615 | body.ascent = body.ascent.max(line.baseline); |
| 616 | body.descent = body.descent.max(line.height - line.baseline); |
| 617 | Ok(MathLayout { |
| 618 | size: [body.width, body.height()], |
| 619 | color: color.unwrap_or(0), |
| 620 | baseline: body.ascent, |
| 621 | items: body |
| 622 | .items |
| 623 | .into_iter() |
| 624 | .map(|item| offset(item, [0.0, body.ascent])) |
| 625 | .collect(), |
| 626 | }) |
| 627 | } |
| 628 | |
| 629 | #[cfg(test)] |
| 630 | mod tests { |
| 631 | use super::*; |
| 632 | |
| 633 | fn object(kind: u32, symbols: &[char], arguments: Vec<Vec<Math>>) -> Math { |
| 634 | Math::Object { |
| 635 | kind, |
| 636 | symbols: symbols.to_vec(), |
| 637 | columns: None, |
| 638 | arguments, |
| 639 | } |
| 640 | } |
| 641 | |
| 642 | /// Each text's left edge and baseline. |
| 643 | fn texts(layout: &MathLayout) -> Vec<[f32; 2]> { |
| 644 | layout |
| 645 | .items |
| 646 | .iter() |
| 647 | .filter_map(|item| match item { |
| 648 | MathItem::Text { origin, layout } => Some([ |
| 649 | origin[0], |
| 650 | origin[1] + layout.lines().next().unwrap().1.baseline, |
| 651 | ]), |
| 652 | _ => None, |
| 653 | }) |
| 654 | .collect() |
| 655 | } |
| 656 | |
| 657 | fn laid_out(nodes: &[Math]) -> MathLayout { |
| 658 | let mut engine = TextEngine::default(); |
| 659 | layout(&mut engine, &Math::paragraph(nodes, &Format::default())).unwrap() |
| 660 | } |
| 661 | |
| 662 | #[test] |
| 663 | fn scripts_fractions_and_accents_stack_as_equations_do() { |
| 664 | let x = || vec![Math::Identifier('x')]; |
| 665 | let scripted = laid_out(&[object( |
| 666 | 30, |
| 667 | &[], |
| 668 | vec![ |
| 669 | x(), |
| 670 | vec![Math::Identifier('i')], |
| 671 | vec![Math::Number("2".into())], |
| 672 | ], |
| 673 | )]); |
| 674 | let [base, upper, lower] = texts(&scripted)[..] else { |
| 675 | panic!() |
| 676 | }; |
| 677 | assert!(lower[0] > base[0] && upper[0] == lower[0]); |
| 678 | assert!(upper[1] < base[1] && lower[1] > base[1]); |
| 679 | |
| 680 | let fraction = laid_out(&[object(16, &[], vec![x(), vec![Math::Identifier('y')]])]); |
| 681 | let [numerator, denominator] = texts(&fraction)[..] else { |
| 682 | panic!() |
| 683 | }; |
| 684 | let bar = fraction.items.iter().find_map(|item| match item { |
| 685 | MathItem::Rule(rect) => Some(*rect), |
| 686 | _ => None, |
| 687 | }); |
| 688 | let [_, top, _, bottom] = bar.unwrap(); |
| 689 | assert!(numerator[1] < top && denominator[1] > numerator[1] && bottom > top); |
| 690 | assert!(fraction.size[1] > laid_out(&[Math::Identifier('x')]).size[1]); |
| 691 | |
| 692 | let accented = laid_out(&[object(10, &['\u{302}'], vec![x()])]); |
| 693 | let [base, accent] = texts(&accented)[..] else { |
| 694 | panic!() |
| 695 | }; |
| 696 | assert!(accent[1] < base[1]); |
| 697 | |
| 698 | let radical = laid_out(&[object(25, &[], vec![vec![], x()])]); |
| 699 | assert!( |
| 700 | radical |
| 701 | .items |
| 702 | .iter() |
| 703 | .any(|item| matches!(item, MathItem::Stroke { .. })) |
| 704 | ); |
| 705 | assert!( |
| 706 | radical |
| 707 | .items |
| 708 | .iter() |
| 709 | .any(|item| matches!(item, MathItem::Rule(_))) |
| 710 | ); |
| 711 | } |
| 712 | |
| 713 | #[test] |
| 714 | fn a_plain_equation_keeps_the_height_of_a_line_of_text() { |
| 715 | let mut engine = TextEngine::default(); |
| 716 | let line = engine |
| 717 | .layout(&Paragraph::new("x".into(), Format::default()), 100.0) |
| 718 | .unwrap(); |
| 719 | let equation = laid_out(&[ |
| 720 | Math::Identifier('x'), |
| 721 | Math::Operator('+'), |
| 722 | Math::Number("1".into()), |
| 723 | ]); |
| 724 | assert!((equation.size[1] - line.height()).abs() < 0.01); |
| 725 | assert!(equation.size[0] > 0.0); |
| 726 | } |
| 727 | } |
clover caruso <git@paperclover.net> 2026-09-24 11:09:12-07:00