| Paint the same tree into a terminal, for the machines with no window a7f6202 nandi 17d ago | 1 | //! Two sizes per node, and how a box shares out what it has. |
| 2 | //! |
| 3 | //! Every node answers a *natural* size — what it would like — and a *minimum* |
| 4 | //! — what it can survive on. A container hands out its natural sizes when there |
| 5 | //! is room, shrinks them proportionally toward the minimums when there is not, |
| 6 | //! and gives the surplus to whoever asked to expand. `:width-request` and |
| 7 | //! `:height-request` are a floor on both numbers, so asking for four rows gets |
| 8 | //! four rows even when space is short. |
| 9 | //! |
| 10 | //! Nothing here touches a terminal or the screen grid: sizes are arithmetic on |
| 11 | //! the tree, which is why the layout tests below need no TTY. |
| 12 | |
| 13 | use crate::screen::Rect; |
| 14 | use crate::tree::{Props, Tag, Tree}; |
| 15 | |
| 16 | /// How a child that is not filling its cross axis sits in the space it was |
| 17 | /// given. `:halign` and `:valign` in the props. |
| 18 | #[derive(Clone, Copy, Debug, PartialEq, Eq)] |
| 19 | pub enum Align { |
| 20 | Fill, |
| 21 | Start, |
| 22 | Center, |
| 23 | End, |
| 24 | } |
| 25 | |
| 26 | impl Align { |
| 27 | pub fn parse(text: &str) -> Self { |
| 28 | match text { |
| 29 | "start" => Self::Start, |
| 30 | "center" | "centre" => Self::Center, |
| 31 | "end" => Self::End, |
| 32 | _ => Self::Fill, |
| 33 | } |
| 34 | } |
| 35 | |
| 36 | /// Where a span of `size` sits inside `avail`. |
| 37 | fn offset(self, size: u16, avail: u16) -> u16 { |
| 38 | let slack = avail.saturating_sub(size); |
| 39 | match self { |
| 40 | Self::Fill | Self::Start => 0, |
| 41 | Self::Center => slack / 2, |
| 42 | Self::End => slack, |
| 43 | } |
| 44 | } |
| 45 | } |
| 46 | |
| 47 | /// Whether a box stacks its children across or down. |
| 48 | pub fn horizontal(props: &Props) -> bool { |
| 49 | props.str("orientation") == "horizontal" |
| 50 | } |
| 51 | |
| 52 | /// The cells a node gives up on each side before its content starts. `:margin` |
| 53 | /// and `:padding` are one inset here — a terminal cell has no border between |
| 54 | /// them to tell them apart, and a caller that sets both means both. |
| 55 | pub fn inset(tag: &Tag, props: &Props) -> u16 { |
| 56 | let own = props.cells("margin", 0) + props.cells("padding", 0); |
| 57 | // A frame — and an overlay, which is a frame that floats — spends a cell a |
| 58 | // side on its border. |
| 59 | own + if matches!(tag, Tag::Frame | Tag::Overlay) { |
| 60 | 1 |
| 61 | } else { |
| 62 | 0 |
| 63 | } |
| 64 | } |
| 65 | |
| 66 | /// Break `text` to `width` columns, on spaces where it can and mid-word where |
| 67 | /// it must. Explicit newlines are always breaks. |
| 68 | pub fn wrap(text: &str, width: u16) -> Vec<String> { |
| 69 | if width == 0 { |
| 70 | return Vec::new(); |
| 71 | } |
| 72 | let width = width as usize; |
| 73 | let mut lines = Vec::new(); |
| 74 | for paragraph in text.split('\n') { |
| 75 | let mut line = String::new(); |
| 76 | let mut len = 0usize; |
| 77 | for word in paragraph.split(' ') { |
| 78 | let word_len = word.chars().count(); |
| 79 | if len > 0 && len + 1 + word_len > width { |
| 80 | lines.push(std::mem::take(&mut line)); |
| 81 | len = 0; |
| 82 | } |
| 83 | if word_len > width { |
| 84 | // Longer than the whole line: break it where the line ends |
| 85 | // rather than let it run off the edge. |
| 86 | for ch in word.chars() { |
| 87 | if len == width { |
| 88 | lines.push(std::mem::take(&mut line)); |
| 89 | len = 0; |
| 90 | } |
| 91 | line.push(ch); |
| 92 | len += 1; |
| 93 | } |
| 94 | continue; |
| 95 | } |
| 96 | if len > 0 { |
| 97 | line.push(' '); |
| 98 | len += 1; |
| 99 | } |
| 100 | line.push_str(word); |
| 101 | len += word_len; |
| 102 | } |
| 103 | lines.push(line); |
| 104 | } |
| 105 | lines |
| 106 | } |
| 107 | |
| 108 | fn columns(text: &str) -> u16 { |
| 109 | text.split('\n') |
| 110 | .map(|line| line.chars().count()) |
| 111 | .max() |
| 112 | .unwrap_or(0) |
| 113 | .min(u16::MAX as usize) as u16 |
| 114 | } |
| 115 | |
| 116 | /// The longest single word — a label cannot usefully be narrower than this. |
| 117 | fn longest_word(text: &str) -> u16 { |
| 118 | text.split([' ', '\n']) |
| 119 | .map(|w| w.chars().count()) |
| 120 | .max() |
| 121 | .unwrap_or(0) |
| 122 | .min(u16::MAX as usize) as u16 |
| 123 | } |
| 124 | |
| 125 | /// The text an entry shows: its own, or its placeholder when it has none. |
| 126 | pub fn entry_text(props: &Props) -> String { |
| 127 | let text = props.str("text"); |
| 128 | if text.is_empty() { |
| 129 | props.str("placeholder").to_owned() |
| 130 | } else { |
| 131 | text.to_owned() |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | /// A node's content size before its own request or inset is applied. |
| 136 | fn intrinsic_width(tree: &Tree, id: u32, minimum: bool) -> u16 { |
| 137 | let tag = tree.tag(id); |
| 138 | let props = tree.props(id); |
| 139 | let text = props.label(); |
| 140 | match tag { |
| 141 | Tag::Button => columns(text).saturating_add(4), |
| 142 | Tag::CheckButton => columns(text).saturating_add(4), |
| 143 | Tag::Entry => { |
| 144 | let want = columns(&entry_text(&props)).saturating_add(1).max(12); |
| 145 | if minimum { |
| 146 | want.min(6) |
| 147 | } else { |
| 148 | want |
| 149 | } |
| 150 | } |
| 151 | Tag::Label | Tag::Title | Tag::DimLabel => { |
| 152 | if minimum { |
| 153 | longest_word(text) |
| 154 | } else { |
| 155 | columns(text) |
| 156 | } |
| 157 | } |
| 158 | Tag::Separator => 1, |
| 159 | Tag::Spacer => props.cells("size", 1), |
| 160 | Tag::Progress => { |
| 161 | if minimum { |
| 162 | 4 |
| 163 | } else { |
| 164 | 20 |
| 165 | } |
| 166 | } |
| 167 | Tag::Spinner => 1, |
| 168 | Tag::Listbox => tree |
| 169 | .children(id) |
| 170 | .iter() |
| 171 | .map(|c| intrinsic_width(tree, *c, minimum).saturating_add(2)) |
| 172 | .max() |
| 173 | .unwrap_or(0), |
| 174 | // Every container measures its children the same way; only the axis |
| 175 | // the sum runs along differs. |
| 176 | Tag::Box | Tag::Window | Tag::Frame | Tag::Scroll | Tag::Overlay | Tag::Unknown(_) => { |
| 177 | let children = tree.children(id); |
| 178 | let spacing = props.cells("spacing", 0); |
| 179 | let sizes = children |
| 180 | .iter() |
| 181 | .map(|c| width(tree, *c, minimum)) |
| 182 | .collect::<Vec<_>>(); |
| 183 | let content = if horizontal(&props) && matches!(tag, Tag::Box) { |
| 184 | let gaps = spacing.saturating_mul(sizes.len().saturating_sub(1) as u16); |
| 185 | sizes.iter().fold(gaps, |a, b| a.saturating_add(*b)) |
| 186 | } else { |
| 187 | sizes.into_iter().max().unwrap_or(0) |
| 188 | }; |
| 189 | // A frame's heading sits in its top edge, so it is part of how wide |
| 190 | // the frame has to be — a box narrower than its own label reads as |
| 191 | // a truncated one. |
| 192 | if matches!(tag, Tag::Frame | Tag::Overlay) { |
| 193 | content.max(columns(props.label()).saturating_add(2)) |
| 194 | } else { |
| 195 | content |
| 196 | } |
| 197 | } |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | /// A node's natural or minimum width, requests and insets included. |
| 202 | pub fn width(tree: &Tree, id: u32, minimum: bool) -> u16 { |
| 203 | let props = tree.props(id); |
| 204 | let pad = inset(&tree.tag(id), &props).saturating_mul(2); |
| 205 | let content = intrinsic_width(tree, id, minimum).saturating_add(pad); |
| 206 | content.max(props.cells("width-request", 0)) |
| 207 | } |
| 208 | |
| 209 | /// How tall `id` is when laid out `avail` columns wide. |
| 210 | /// |
| 211 | /// Height depends on width — that is what wrapping means — so there is no |
| 212 | /// natural height to ask for on its own. |
| 213 | pub fn height_for_width(tree: &Tree, id: u32, avail: u16) -> u16 { |
| 214 | let tag = tree.tag(id); |
| 215 | let props = tree.props(id); |
| 216 | let pad = inset(&tag, &props); |
| 217 | let inner = avail.saturating_sub(pad.saturating_mul(2)); |
| 218 | let content = match tag { |
| 219 | Tag::Label | Tag::Title | Tag::DimLabel => wrap(props.label(), inner).len() as u16, |
| 220 | Tag::Button | Tag::CheckButton | Tag::Separator | Tag::Progress | Tag::Spinner => 1, |
| 221 | Tag::Entry => props.cells("rows", 1).max(1), |
| 222 | Tag::Spacer => props.cells("size", 1), |
| 223 | Tag::Listbox => tree.child_count(id) as u16, |
| 224 | Tag::Box | Tag::Window | Tag::Frame | Tag::Scroll | Tag::Overlay | Tag::Unknown(_) => { |
| 225 | let children = tree.children(id); |
| 226 | let spacing = props.cells("spacing", 0); |
| 227 | if horizontal(&props) && matches!(tag, Tag::Box) { |
| 228 | // Across: each child is measured at the width it will get. |
| 229 | let shares = share(tree, id, inner, true); |
| 230 | children |
| 231 | .iter() |
| 232 | .zip(shares) |
| 233 | .map(|(c, w)| height_for_width(tree, *c, w)) |
| 234 | .max() |
| 235 | .unwrap_or(0) |
| 236 | } else { |
| 237 | let gaps = spacing.saturating_mul(children.len().saturating_sub(1) as u16); |
| 238 | children |
| 239 | .iter() |
| 240 | .map(|c| height_for_width(tree, *c, inner)) |
| 241 | .fold(gaps, |a, b| a.saturating_add(b)) |
| 242 | } |
| 243 | } |
| 244 | }; |
| 245 | content |
| 246 | .saturating_add(pad.saturating_mul(2)) |
| 247 | .max(props.cells("height-request", 0)) |
| 248 | } |
| 249 | |
| 250 | /// Share `avail` out among the children of `id` along one axis. |
| 251 | /// |
| 252 | /// `across` picks the axis: true for a horizontal box sharing columns, false |
| 253 | /// for a vertical one sharing rows. The rule is the same either way — natural |
| 254 | /// sizes first, shrink proportionally toward the minimums when short, and the |
| 255 | /// surplus to whoever set `:hexpand` / `:vexpand`. |
| 256 | pub fn share(tree: &Tree, id: u32, avail: u16, across: bool) -> Vec<u16> { |
| 257 | let children = tree.children(id); |
| 258 | if children.is_empty() { |
| 259 | return Vec::new(); |
| 260 | } |
| 261 | let props = tree.props(id); |
| 262 | let spacing = props.cells("spacing", 0); |
| 263 | let gaps = spacing.saturating_mul((children.len() - 1) as u16); |
| 264 | let room = avail.saturating_sub(gaps) as i64; |
| 265 | |
| 266 | let measure = |child: u32, minimum: bool| -> i64 { |
| 267 | if across { |
| 268 | width(tree, child, minimum) as i64 |
| 269 | } else { |
| 270 | // Down the page a child's height depends on the width it gets, |
| 271 | // which the caller has already fixed by the time it asks. |
| 272 | height_for_width(tree, child, avail) as i64 |
| 273 | } |
| 274 | }; |
| 275 | |
| 276 | let nat: Vec<i64> = children.iter().map(|c| measure(*c, false)).collect(); |
| 277 | let min: Vec<i64> = children |
| 278 | .iter() |
| 279 | .zip(&nat) |
| 280 | .map(|(c, n)| measure(*c, true).min(*n)) |
| 281 | .collect(); |
| 282 | let total: i64 = nat.iter().sum(); |
| 283 | let mut out = nat.clone(); |
| 284 | |
| 285 | if total > room { |
| 286 | // Short: take the overrun out of whatever each child is willing to give |
| 287 | // up, in proportion to how much that is. |
| 288 | let mut over = total - room; |
| 289 | let slack: i64 = nat.iter().zip(&min).map(|(n, m)| n - m).sum(); |
| 290 | if slack > 0 { |
| 291 | for i in 0..out.len() { |
| 292 | let give = ((nat[i] - min[i]) * over.min(slack)) / slack; |
| 293 | out[i] -= give; |
| 294 | } |
| 295 | over -= nat.iter().zip(&out).map(|(n, o)| n - o).sum::<i64>(); |
| 296 | } |
| 297 | // Rounding, and children with no slack at all: take the rest off the |
| 298 | // end, which is where a terminal clips anyway. |
| 299 | let mut i = out.len(); |
| 300 | while over > 0 && i > 0 { |
| 301 | i -= 1; |
| 302 | let give = (out[i] - min[i]).min(over); |
| 303 | out[i] -= give; |
| 304 | over -= give; |
| 305 | } |
| 306 | } else if total < room { |
| 307 | let key = if across { "hexpand" } else { "vexpand" }; |
| 308 | let greedy: Vec<usize> = children |
| 309 | .iter() |
| 310 | .enumerate() |
| 311 | .filter(|(_, c)| tree.props(**c).bool(key, false)) |
| 312 | .map(|(i, _)| i) |
| 313 | .collect(); |
| 314 | if !greedy.is_empty() { |
| 315 | let extra = room - total; |
| 316 | let each = extra / greedy.len() as i64; |
| 317 | let mut rest = extra % greedy.len() as i64; |
| 318 | for i in greedy { |
| 319 | out[i] += each + if rest > 0 { 1 } else { 0 }; |
| 320 | rest -= 1; |
| 321 | } |
| 322 | } |
| 323 | } |
| 324 | out.into_iter() |
| 325 | .map(|n| n.clamp(0, u16::MAX as i64) as u16) |
| 326 | .collect() |
| 327 | } |
| 328 | |
| 329 | /// The rect a child of `size` gets inside `avail` on its cross axis. |
| 330 | pub fn place(align: Align, size: u16, avail: u16) -> (u16, u16) { |
| 331 | match align { |
| 332 | Align::Fill => (0, avail), |
| 333 | other => { |
| 334 | let size = size.min(avail); |
| 335 | (other.offset(size, avail), size) |
| 336 | } |
| 337 | } |
| 338 | } |
| 339 | |
| 340 | /// Lay the children of a box out inside `area`. |
| 341 | pub fn children_rects(tree: &Tree, id: u32, area: Rect) -> Vec<Rect> { |
| 342 | let props = tree.props(id); |
| 343 | let across = horizontal(&props) && matches!(tree.tag(id), Tag::Box); |
| 344 | let spacing = props.cells("spacing", 0); |
| 345 | let children = tree.children(id); |
| 346 | let shares = share(tree, id, if across { area.w } else { area.h }, across); |
| 347 | |
| 348 | let mut out = Vec::with_capacity(children.len()); |
| 349 | let mut at = 0u16; |
| 350 | for (child, main) in children.iter().zip(shares) { |
| 351 | let cprops = tree.props(*child); |
| 352 | let rect = if across { |
| 353 | let want = height_for_width(tree, *child, main).max(cprops.cells("height-request", 0)); |
| 354 | let (dy, h) = place(Align::parse(cprops.str("valign")), want, area.h); |
| 355 | Rect::new( |
| 356 | area.x.saturating_add(at), |
| 357 | area.y.saturating_add(dy), |
| 358 | main, |
| 359 | h, |
| 360 | ) |
| 361 | } else { |
| 362 | let want = width(tree, *child, false); |
| 363 | let (dx, w) = place(Align::parse(cprops.str("halign")), want, area.w); |
| 364 | Rect::new( |
| 365 | area.x.saturating_add(dx), |
| 366 | area.y.saturating_add(at), |
| 367 | w, |
| 368 | main, |
| 369 | ) |
| 370 | }; |
| 371 | out.push(rect); |
| 372 | at = at.saturating_add(main).saturating_add(spacing); |
| 373 | } |
| 374 | out |
| 375 | } |
| 376 | |
| 377 | #[cfg(test)] |
| 378 | mod tests { |
| 379 | use super::*; |
| 380 | use crate::tree::Value; |
| 381 | |
| 382 | fn label(tree: &mut Tree, parent: u32, text: &str) -> u32 { |
| 383 | let id = tree.new_node("label"); |
| 384 | tree.set(id, "label", Value::Str(text.into())); |
| 385 | tree.append(parent, id); |
| 386 | id |
| 387 | } |
| 388 | |
| 389 | #[test] |
| 390 | fn wrapping_breaks_on_spaces_and_mid_word_when_it_must() { |
| 391 | assert_eq!(wrap("one two three", 7), vec!["one two", "three"]); |
| 392 | assert_eq!( |
| 393 | wrap("antidisestablishment", 6), |
| 394 | vec!["antidi", "sestab", "lishme", "nt"] |
| 395 | ); |
| 396 | assert_eq!(wrap("a\nb", 10), vec!["a", "b"]); |
| 397 | } |
| 398 | |
| 399 | #[test] |
| 400 | fn a_label_is_as_wide_as_its_text_and_as_narrow_as_its_longest_word() { |
| 401 | let mut tree = Tree::new(); |
| 402 | let root = tree.root(); |
| 403 | let id = label(&mut tree, root, "one two three"); |
| 404 | assert_eq!(width(&tree, id, false), 13); |
| 405 | assert_eq!(width(&tree, id, true), 5); |
| 406 | assert_eq!(height_for_width(&tree, id, 7), 2); |
| 407 | } |
| 408 | |
| 409 | #[test] |
| 410 | fn a_width_request_is_a_floor_on_both_sizes() { |
| 411 | let mut tree = Tree::new(); |
| 412 | let root = tree.root(); |
| 413 | let id = label(&mut tree, root, "hi"); |
| 414 | tree.set(id, "width-request", Value::Num(20.0)); |
| 415 | assert_eq!(width(&tree, id, false), 20); |
| 416 | assert_eq!(width(&tree, id, true), 20); |
| 417 | } |
| 418 | |
| 419 | #[test] |
| 420 | fn a_height_request_of_four_rows_gets_four_rows() { |
| 421 | let mut tree = Tree::new(); |
| 422 | let root = tree.root(); |
| 423 | let id = label(&mut tree, root, "hi"); |
| 424 | tree.set(id, "height-request", Value::Num(4.0)); |
| 425 | assert_eq!(height_for_width(&tree, id, 10), 4); |
| 426 | } |
| 427 | |
| 428 | #[test] |
| 429 | fn a_horizontal_box_gives_the_surplus_to_whoever_expands() { |
| 430 | let mut tree = Tree::new(); |
| 431 | let row = tree.new_node("hbox"); |
| 432 | tree.set(row, "orientation", Value::Str("horizontal".into())); |
| 433 | let root = tree.root(); |
| 434 | tree.append(root, row); |
| 435 | let a = label(&mut tree, row, "aa"); |
| 436 | let b = label(&mut tree, row, "bb"); |
| 437 | tree.set(b, "hexpand", Value::Bool(true)); |
| 438 | assert_eq!(share(&tree, row, 20, true), vec![2, 18]); |
| 439 | let _ = a; |
| 440 | } |
| 441 | |
| 442 | #[test] |
| 443 | fn a_short_box_shrinks_toward_the_minimums_rather_than_clipping_the_first_child() { |
| 444 | let mut tree = Tree::new(); |
| 445 | let row = tree.new_node("hbox"); |
| 446 | tree.set(row, "orientation", Value::Str("horizontal".into())); |
| 447 | let root = tree.root(); |
| 448 | tree.append(root, row); |
| 449 | label(&mut tree, row, "one two"); |
| 450 | label(&mut tree, row, "three four"); |
| 451 | // 17 natural, 10 offered: both give up some, neither goes under its |
| 452 | // longest word. |
| 453 | let shares = share(&tree, row, 10, true); |
| 454 | assert_eq!(shares.iter().sum::<u16>(), 10); |
| 455 | assert!(shares[0] >= 3 && shares[1] >= 5, "{shares:?}"); |
| 456 | } |
| 457 | |
| 458 | #[test] |
| 459 | fn spacing_comes_off_the_room_before_it_is_shared() { |
| 460 | let mut tree = Tree::new(); |
| 461 | let row = tree.new_node("hbox"); |
| 462 | tree.set(row, "orientation", Value::Str("horizontal".into())); |
| 463 | tree.set(row, "spacing", Value::Num(2.0)); |
| 464 | let root = tree.root(); |
| 465 | tree.append(root, row); |
| 466 | let a = label(&mut tree, row, "aa"); |
| 467 | let b = label(&mut tree, row, "bb"); |
| 468 | tree.set(a, "hexpand", Value::Bool(true)); |
| 469 | tree.set(b, "hexpand", Value::Bool(true)); |
| 470 | assert_eq!(share(&tree, row, 12, true), vec![5, 5]); |
| 471 | } |
| 472 | |
| 473 | #[test] |
| 474 | fn a_centred_child_sits_in_the_middle_of_its_row() { |
| 475 | assert_eq!(place(Align::Center, 4, 10), (3, 4)); |
| 476 | assert_eq!(place(Align::End, 4, 10), (6, 4)); |
| 477 | assert_eq!(place(Align::Fill, 4, 10), (0, 10)); |
| 478 | } |
| 479 | |
| 480 | #[test] |
| 481 | fn a_frame_spends_a_cell_a_side_on_its_border() { |
| 482 | let mut tree = Tree::new(); |
| 483 | let frame = tree.new_node("frame"); |
| 484 | let root = tree.root(); |
| 485 | tree.append(root, frame); |
| 486 | label(&mut tree, frame, "hi"); |
| 487 | assert_eq!(width(&tree, frame, false), 4); |
| 488 | assert_eq!(height_for_width(&tree, frame, 4), 3); |
| 489 | } |
| 490 | } |