FormattingContext.cpp 48 KB

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  1. /*
  2. * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
  3. *
  4. * SPDX-License-Identifier: BSD-2-Clause
  5. */
  6. #include <LibWeb/Dump.h>
  7. #include <LibWeb/Layout/BlockFormattingContext.h>
  8. #include <LibWeb/Layout/Box.h>
  9. #include <LibWeb/Layout/FlexFormattingContext.h>
  10. #include <LibWeb/Layout/FormattingContext.h>
  11. #include <LibWeb/Layout/ReplacedBox.h>
  12. #include <LibWeb/Layout/SVGFormattingContext.h>
  13. #include <LibWeb/Layout/SVGSVGBox.h>
  14. #include <LibWeb/Layout/TableBox.h>
  15. #include <LibWeb/Layout/TableCellBox.h>
  16. #include <LibWeb/Layout/TableFormattingContext.h>
  17. namespace Web::Layout {
  18. FormattingContext::FormattingContext(Type type, FormattingState& state, Box const& context_box, FormattingContext* parent)
  19. : m_type(type)
  20. , m_parent(parent)
  21. , m_context_box(context_box)
  22. , m_state(state)
  23. {
  24. }
  25. FormattingContext::~FormattingContext() = default;
  26. void FormattingContext::run_intrinsic_size_determination(Box const& box)
  27. {
  28. run(box, LayoutMode::IntrinsicSizeDetermination);
  29. }
  30. bool FormattingContext::creates_block_formatting_context(Box const& box)
  31. {
  32. if (box.is_root_element())
  33. return true;
  34. if (box.is_floating())
  35. return true;
  36. if (box.is_absolutely_positioned())
  37. return true;
  38. if (box.is_inline_block())
  39. return true;
  40. if (is<TableCellBox>(box))
  41. return true;
  42. CSS::Overflow overflow_x = box.computed_values().overflow_x();
  43. if ((overflow_x != CSS::Overflow::Visible) && (overflow_x != CSS::Overflow::Clip))
  44. return true;
  45. CSS::Overflow overflow_y = box.computed_values().overflow_y();
  46. if ((overflow_y != CSS::Overflow::Visible) && (overflow_y != CSS::Overflow::Clip))
  47. return true;
  48. auto display = box.computed_values().display();
  49. if (display.is_flow_root_inside())
  50. return true;
  51. if (box.parent()) {
  52. auto parent_display = box.parent()->computed_values().display();
  53. if (parent_display.is_flex_inside()) {
  54. // FIXME: Flex items (direct children of the element with display: flex or inline-flex) if they are neither flex nor grid nor table containers themselves.
  55. if (!display.is_flex_inside())
  56. return true;
  57. }
  58. }
  59. // FIXME: table-caption
  60. // FIXME: anonymous table cells
  61. // FIXME: Elements with contain: layout, content, or paint.
  62. // FIXME: grid
  63. // FIXME: multicol
  64. // FIXME: column-span: all
  65. return false;
  66. }
  67. OwnPtr<FormattingContext> FormattingContext::create_independent_formatting_context_if_needed(FormattingState& state, Box const& child_box)
  68. {
  69. if (child_box.is_replaced_box() && !child_box.can_have_children()) {
  70. // NOTE: This is a bit strange.
  71. // Basically, we create a pretend formatting context for replaced elements that does nothing.
  72. // This allows other formatting contexts to treat them like elements that actually need inside layout
  73. // without having separate code to handle replaced elements.
  74. // FIXME: Find a better abstraction for this.
  75. struct ReplacedFormattingContext : public FormattingContext {
  76. ReplacedFormattingContext(FormattingState& state, Box const& box)
  77. : FormattingContext(Type::Block, state, box)
  78. {
  79. }
  80. virtual void run(Box const&, LayoutMode) override { }
  81. };
  82. return make<ReplacedFormattingContext>(state, child_box);
  83. }
  84. if (!child_box.can_have_children())
  85. return {};
  86. auto child_display = child_box.computed_values().display();
  87. if (is<SVGSVGBox>(child_box))
  88. return make<SVGFormattingContext>(state, child_box, this);
  89. if (child_display.is_flex_inside())
  90. return make<FlexFormattingContext>(state, child_box, this);
  91. if (creates_block_formatting_context(child_box))
  92. return make<BlockFormattingContext>(state, verify_cast<BlockContainer>(child_box), this);
  93. if (child_display.is_table_inside())
  94. return make<TableFormattingContext>(state, verify_cast<TableBox>(child_box), this);
  95. VERIFY(is_block_formatting_context());
  96. VERIFY(!child_box.children_are_inline());
  97. // The child box is a block container that doesn't create its own BFC.
  98. // It will be formatted by this BFC.
  99. if (!child_display.is_flow_inside()) {
  100. dbgln("FIXME: Child box doesn't create BFC, but inside is also not flow! display={}", child_display.to_string());
  101. // HACK: Instead of crashing, create a dummy formatting context that does nothing.
  102. // FIXME: Remove this once it's no longer needed. It currently swallows problem with standalone
  103. // table-related boxes that don't get fixed up by CSS anonymous table box generation.
  104. struct DummyFormattingContext : public FormattingContext {
  105. DummyFormattingContext(FormattingState& state, Box const& box)
  106. : FormattingContext(Type::Block, state, box)
  107. {
  108. }
  109. virtual void run(Box const&, LayoutMode) override { }
  110. };
  111. return make<DummyFormattingContext>(state, child_box);
  112. }
  113. VERIFY(child_box.is_block_container());
  114. VERIFY(child_display.is_flow_inside());
  115. return {};
  116. }
  117. OwnPtr<FormattingContext> FormattingContext::layout_inside(Box const& child_box, LayoutMode layout_mode)
  118. {
  119. if (!child_box.can_have_children())
  120. return {};
  121. auto independent_formatting_context = create_independent_formatting_context_if_needed(m_state, child_box);
  122. if (independent_formatting_context)
  123. independent_formatting_context->run(child_box, layout_mode);
  124. else
  125. run(child_box, layout_mode);
  126. return independent_formatting_context;
  127. }
  128. float FormattingContext::greatest_child_width(Box const& box)
  129. {
  130. float max_width = 0;
  131. if (box.children_are_inline()) {
  132. for (auto& line_box : m_state.get(verify_cast<BlockContainer>(box)).line_boxes) {
  133. max_width = max(max_width, line_box.width());
  134. }
  135. } else {
  136. box.for_each_child_of_type<Box>([&](auto& child) {
  137. max_width = max(max_width, m_state.get(child).border_box_width());
  138. });
  139. }
  140. return max_width;
  141. }
  142. FormattingContext::ShrinkToFitResult FormattingContext::calculate_shrink_to_fit_widths(Box const& box)
  143. {
  144. return {
  145. .preferred_width = calculate_max_content_width(box),
  146. .preferred_minimum_width = calculate_min_content_width(box),
  147. };
  148. }
  149. static Gfx::FloatSize solve_replaced_size_constraint(FormattingState const& state, float w, float h, ReplacedBox const& box)
  150. {
  151. // 10.4 Minimum and maximum widths: 'min-width' and 'max-width'
  152. auto const& containing_block = *box.containing_block();
  153. auto const& containing_block_state = state.get(containing_block);
  154. auto width_of_containing_block = CSS::Length::make_px(containing_block_state.content_width);
  155. auto height_of_containing_block = CSS::Length::make_px(containing_block_state.content_height);
  156. auto specified_min_width = box.computed_values().min_width().is_auto() ? 0 : box.computed_values().min_width().resolved(box, width_of_containing_block).to_px(box);
  157. auto specified_max_width = box.computed_values().max_width().is_auto() ? w : box.computed_values().max_width().resolved(box, width_of_containing_block).to_px(box);
  158. auto specified_min_height = box.computed_values().min_height().is_auto() ? 0 : box.computed_values().min_height().resolved(box, height_of_containing_block).to_px(box);
  159. auto specified_max_height = box.computed_values().max_height().is_auto() ? h : box.computed_values().max_height().resolved(box, height_of_containing_block).to_px(box);
  160. auto min_width = min(specified_min_width, specified_max_width);
  161. auto max_width = max(specified_min_width, specified_max_width);
  162. auto min_height = min(specified_min_height, specified_max_height);
  163. auto max_height = max(specified_min_height, specified_max_height);
  164. if (w > max_width)
  165. return { w, max(max_width * h / w, min_height) };
  166. if (w < min_width)
  167. return { max_width, min(min_width * h / w, max_height) };
  168. if (h > max_height)
  169. return { max(max_height * w / h, min_width), max_height };
  170. if (h < min_height)
  171. return { min(min_height * w / h, max_width), min_height };
  172. if ((w > max_width && h > max_height) && (max_width / w < max_height / h))
  173. return { max_width, max(min_height, max_width * h / w) };
  174. if ((w > max_width && h > max_height) && (max_width / w > max_height / h))
  175. return { max(min_width, max_height * w / h), max_height };
  176. if ((w < min_width && h < min_height) && (min_width / w < min_height / h))
  177. return { min(max_width, min_height * w / h), min_height };
  178. if ((w < min_width && h < min_height) && (min_width / w > min_height / h))
  179. return { min_width, min(max_height, min_width * h / w) };
  180. if (w < min_width && h > max_height)
  181. return { min_width, max_height };
  182. if (w > max_width && h < min_height)
  183. return { max_width, min_height };
  184. return { w, h };
  185. }
  186. float FormattingContext::compute_auto_height_for_block_level_element(FormattingState const& state, Box const& box)
  187. {
  188. if (creates_block_formatting_context(box))
  189. return compute_auto_height_for_block_formatting_context_root(state, verify_cast<BlockContainer>(box));
  190. auto const& box_state = state.get(box);
  191. auto display = box.computed_values().display();
  192. if (display.is_flex_inside())
  193. return box_state.content_height;
  194. // https://www.w3.org/TR/CSS22/visudet.html#normal-block
  195. // 10.6.3 Block-level non-replaced elements in normal flow when 'overflow' computes to 'visible'
  196. // The element's height is the distance from its top content edge to the first applicable of the following:
  197. // 1. the bottom edge of the last line box, if the box establishes a inline formatting context with one or more lines
  198. if (box.children_are_inline() && !box_state.line_boxes.is_empty())
  199. return box_state.line_boxes.last().bottom();
  200. // 2. the bottom edge of the bottom (possibly collapsed) margin of its last in-flow child, if the child's bottom margin does not collapse with the element's bottom margin
  201. // FIXME: 3. the bottom border edge of the last in-flow child whose top margin doesn't collapse with the element's bottom margin
  202. if (!box.children_are_inline()) {
  203. for (auto* child_box = box.last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
  204. if (child_box->is_absolutely_positioned() || child_box->is_floating())
  205. continue;
  206. // FIXME: This is hack. If the last child is a list-item marker box, we ignore it for purposes of height calculation.
  207. // Perhaps markers should not be considered in-flow(?) Perhaps they should always be the first child of the list-item
  208. // box instead of the last child.
  209. if (child_box->is_list_item_marker_box())
  210. continue;
  211. auto const& child_box_state = state.get(*child_box);
  212. // Ignore anonymous block containers with no lines. These don't count as in-flow block boxes.
  213. if (child_box->is_anonymous() && child_box->is_block_container() && child_box_state.line_boxes.is_empty())
  214. continue;
  215. // FIXME: Handle margin collapsing.
  216. return max(0, child_box_state.offset.y() + child_box_state.content_height + child_box_state.margin_box_bottom());
  217. }
  218. }
  219. // 4. zero, otherwise
  220. return 0;
  221. }
  222. // https://www.w3.org/TR/CSS22/visudet.html#root-height
  223. float FormattingContext::compute_auto_height_for_block_formatting_context_root(FormattingState const& state, BlockContainer const& root)
  224. {
  225. // 10.6.7 'Auto' heights for block formatting context roots
  226. Optional<float> top;
  227. Optional<float> bottom;
  228. if (root.children_are_inline()) {
  229. // If it only has inline-level children, the height is the distance between
  230. // the top content edge and the bottom of the bottommost line box.
  231. auto const& line_boxes = state.get(root).line_boxes;
  232. top = 0;
  233. if (!line_boxes.is_empty())
  234. bottom = line_boxes.last().bottom();
  235. } else {
  236. // If it has block-level children, the height is the distance between
  237. // the top margin-edge of the topmost block-level child box
  238. // and the bottom margin-edge of the bottommost block-level child box.
  239. root.for_each_child_of_type<Box>([&](Layout::Box& child_box) {
  240. // Absolutely positioned children are ignored,
  241. // and relatively positioned boxes are considered without their offset.
  242. // Note that the child box may be an anonymous block box.
  243. if (child_box.is_absolutely_positioned())
  244. return IterationDecision::Continue;
  245. // FIXME: This doesn't look right.
  246. if ((root.computed_values().overflow_y() == CSS::Overflow::Visible) && child_box.is_floating())
  247. return IterationDecision::Continue;
  248. auto const& child_box_state = state.get(child_box);
  249. float child_box_top = child_box_state.offset.y() - child_box_state.margin_box_top();
  250. float child_box_bottom = child_box_state.offset.y() + child_box_state.content_height + child_box_state.margin_box_bottom();
  251. if (!top.has_value() || child_box_top < top.value())
  252. top = child_box_top;
  253. if (!bottom.has_value() || child_box_bottom > bottom.value())
  254. bottom = child_box_bottom;
  255. return IterationDecision::Continue;
  256. });
  257. }
  258. // In addition, if the element has any floating descendants
  259. // whose bottom margin edge is below the element's bottom content edge,
  260. // then the height is increased to include those edges.
  261. root.for_each_child_of_type<Box>([&](Layout::Box& child_box) {
  262. if (!child_box.is_floating())
  263. return IterationDecision::Continue;
  264. auto const& child_box_state = state.get(child_box);
  265. float child_box_bottom = child_box_state.offset.y() + child_box_state.content_height + child_box_state.margin_box_bottom();
  266. if (!bottom.has_value() || child_box_bottom > bottom.value())
  267. bottom = child_box_bottom;
  268. return IterationDecision::Continue;
  269. });
  270. return max(0, bottom.value_or(0) - top.value_or(0));
  271. }
  272. // 10.3.2 Inline, replaced elements, https://www.w3.org/TR/CSS22/visudet.html#inline-replaced-width
  273. float FormattingContext::tentative_width_for_replaced_element(FormattingState const& state, ReplacedBox const& box, CSS::Length const& computed_width)
  274. {
  275. auto const& containing_block = *box.containing_block();
  276. auto height_of_containing_block = CSS::Length::make_px(state.get(containing_block).content_height);
  277. auto computed_height = box.computed_values().height().resolved(box, height_of_containing_block).resolved(box);
  278. float used_width = computed_width.to_px(box);
  279. // If 'height' and 'width' both have computed values of 'auto' and the element also has an intrinsic width,
  280. // then that intrinsic width is the used value of 'width'.
  281. if (computed_height.is_auto() && computed_width.is_auto() && box.has_intrinsic_width())
  282. return box.intrinsic_width().value();
  283. // If 'height' and 'width' both have computed values of 'auto' and the element has no intrinsic width,
  284. // but does have an intrinsic height and intrinsic ratio;
  285. // or if 'width' has a computed value of 'auto',
  286. // 'height' has some other computed value, and the element does have an intrinsic ratio; then the used value of 'width' is:
  287. //
  288. // (used height) * (intrinsic ratio)
  289. if ((computed_height.is_auto() && computed_width.is_auto() && !box.has_intrinsic_width() && box.has_intrinsic_height() && box.has_intrinsic_aspect_ratio())
  290. || (computed_width.is_auto() && box.has_intrinsic_aspect_ratio())) {
  291. return compute_height_for_replaced_element(state, box) * box.intrinsic_aspect_ratio().value();
  292. }
  293. // If 'height' and 'width' both have computed values of 'auto' and the element has an intrinsic ratio but no intrinsic height or width,
  294. // then the used value of 'width' is undefined in CSS 2.2. However, it is suggested that, if the containing block's width does not itself
  295. // depend on the replaced element's width, then the used value of 'width' is calculated from the constraint equation used for block-level,
  296. // non-replaced elements in normal flow.
  297. // Otherwise, if 'width' has a computed value of 'auto', and the element has an intrinsic width, then that intrinsic width is the used value of 'width'.
  298. if (computed_width.is_auto() && box.has_intrinsic_width())
  299. return box.intrinsic_width().value();
  300. // Otherwise, if 'width' has a computed value of 'auto', but none of the conditions above are met, then the used value of 'width' becomes 300px.
  301. // If 300px is too wide to fit the device, UAs should use the width of the largest rectangle that has a 2:1 ratio and fits the device instead.
  302. if (computed_width.is_auto())
  303. return 300;
  304. return used_width;
  305. }
  306. void FormattingContext::compute_width_for_absolutely_positioned_element(Box const& box)
  307. {
  308. if (is<ReplacedBox>(box))
  309. compute_width_for_absolutely_positioned_replaced_element(verify_cast<ReplacedBox>(box));
  310. else
  311. compute_width_for_absolutely_positioned_non_replaced_element(box);
  312. }
  313. void FormattingContext::compute_height_for_absolutely_positioned_element(Box const& box)
  314. {
  315. if (is<ReplacedBox>(box))
  316. compute_height_for_absolutely_positioned_replaced_element(verify_cast<ReplacedBox>(box));
  317. else
  318. compute_height_for_absolutely_positioned_non_replaced_element(box);
  319. }
  320. float FormattingContext::compute_width_for_replaced_element(FormattingState const& state, ReplacedBox const& box)
  321. {
  322. // 10.3.4 Block-level, replaced elements in normal flow...
  323. // 10.3.2 Inline, replaced elements
  324. auto zero_value = CSS::Length::make_px(0);
  325. auto width_of_containing_block_as_length = CSS::Length::make_px(containing_block_width_for(box, state));
  326. auto margin_left = box.computed_values().margin().left.resolved(box, width_of_containing_block_as_length).resolved(box);
  327. auto margin_right = box.computed_values().margin().right.resolved(box, width_of_containing_block_as_length).resolved(box);
  328. // A computed value of 'auto' for 'margin-left' or 'margin-right' becomes a used value of '0'.
  329. if (margin_left.is_auto())
  330. margin_left = zero_value;
  331. if (margin_right.is_auto())
  332. margin_right = zero_value;
  333. auto specified_width = box.computed_values().width().resolved(box, width_of_containing_block_as_length).resolved(box);
  334. // 1. The tentative used width is calculated (without 'min-width' and 'max-width')
  335. auto used_width = tentative_width_for_replaced_element(state, box, specified_width);
  336. // 2. The tentative used width is greater than 'max-width', the rules above are applied again,
  337. // but this time using the computed value of 'max-width' as the computed value for 'width'.
  338. auto specified_max_width = box.computed_values().max_width().resolved(box, width_of_containing_block_as_length).resolved(box);
  339. if (!specified_max_width.is_auto()) {
  340. if (used_width > specified_max_width.to_px(box)) {
  341. used_width = tentative_width_for_replaced_element(state, box, specified_max_width);
  342. }
  343. }
  344. // 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
  345. // but this time using the value of 'min-width' as the computed value for 'width'.
  346. auto specified_min_width = box.computed_values().min_width().resolved(box, width_of_containing_block_as_length).resolved(box);
  347. if (!specified_min_width.is_auto()) {
  348. if (used_width < specified_min_width.to_px(box)) {
  349. used_width = tentative_width_for_replaced_element(state, box, specified_min_width);
  350. }
  351. }
  352. return used_width;
  353. }
  354. // 10.6.2 Inline replaced elements, block-level replaced elements in normal flow, 'inline-block' replaced elements in normal flow and floating replaced elements
  355. // https://www.w3.org/TR/CSS22/visudet.html#inline-replaced-height
  356. float FormattingContext::tentative_height_for_replaced_element(FormattingState const& state, ReplacedBox const& box, CSS::Length const& computed_height)
  357. {
  358. auto width_of_containing_block_as_length = CSS::Length::make_px(containing_block_width_for(box, state));
  359. auto computed_width = box.computed_values().width().resolved(box, width_of_containing_block_as_length).resolved(box);
  360. // If 'height' and 'width' both have computed values of 'auto' and the element also has
  361. // an intrinsic height, then that intrinsic height is the used value of 'height'.
  362. if (computed_width.is_auto() && computed_height.is_auto() && box.has_intrinsic_height())
  363. return box.intrinsic_height().value();
  364. // Otherwise, if 'height' has a computed value of 'auto', and the element has an intrinsic ratio then the used value of 'height' is:
  365. //
  366. // (used width) / (intrinsic ratio)
  367. if (computed_height.is_auto() && box.has_intrinsic_aspect_ratio())
  368. return compute_width_for_replaced_element(state, box) / box.intrinsic_aspect_ratio().value();
  369. // Otherwise, if 'height' has a computed value of 'auto', and the element has an intrinsic height, then that intrinsic height is the used value of 'height'.
  370. if (computed_height.is_auto() && box.has_intrinsic_height())
  371. return box.intrinsic_height().value();
  372. // Otherwise, if 'height' has a computed value of 'auto', but none of the conditions above are met,
  373. // then the used value of 'height' must be set to the height of the largest rectangle that has a 2:1 ratio, has a height not greater than 150px,
  374. // and has a width not greater than the device width.
  375. if (computed_height.is_auto())
  376. return 150;
  377. return computed_height.to_px(box);
  378. }
  379. float FormattingContext::compute_height_for_replaced_element(FormattingState const& state, ReplacedBox const& box)
  380. {
  381. // 10.6.2 Inline replaced elements, block-level replaced elements in normal flow,
  382. // 'inline-block' replaced elements in normal flow and floating replaced elements
  383. auto width_of_containing_block_as_length = CSS::Length::make_px(containing_block_width_for(box, state));
  384. auto height_of_containing_block_as_length = CSS::Length::make_px(containing_block_height_for(box, state));
  385. auto specified_width = box.computed_values().width().resolved(box, width_of_containing_block_as_length).resolved(box);
  386. auto specified_height = box.computed_values().height().resolved(box, height_of_containing_block_as_length).resolved(box);
  387. float used_height = tentative_height_for_replaced_element(state, box, specified_height);
  388. if (specified_width.is_auto() && specified_height.is_auto() && box.has_intrinsic_aspect_ratio()) {
  389. float w = tentative_width_for_replaced_element(state, box, specified_width);
  390. float h = used_height;
  391. used_height = solve_replaced_size_constraint(state, w, h, box).height();
  392. }
  393. return used_height;
  394. }
  395. void FormattingContext::compute_width_for_absolutely_positioned_non_replaced_element(Box const& box)
  396. {
  397. auto width_of_containing_block = containing_block_width_for(box);
  398. auto width_of_containing_block_as_length = CSS::Length::make_px(width_of_containing_block);
  399. auto& computed_values = box.computed_values();
  400. auto zero_value = CSS::Length::make_px(0);
  401. auto margin_left = CSS::Length::make_auto();
  402. auto margin_right = CSS::Length::make_auto();
  403. auto const border_left = computed_values.border_left().width;
  404. auto const border_right = computed_values.border_right().width;
  405. auto const padding_left = computed_values.padding().left.resolved(box, width_of_containing_block_as_length).to_px(box);
  406. auto const padding_right = computed_values.padding().right.resolved(box, width_of_containing_block_as_length).to_px(box);
  407. auto try_compute_width = [&](auto const& a_width) {
  408. margin_left = computed_values.margin().left.resolved(box, width_of_containing_block_as_length).resolved(box);
  409. margin_right = computed_values.margin().right.resolved(box, width_of_containing_block_as_length).resolved(box);
  410. auto left = computed_values.inset().left.resolved(box, width_of_containing_block_as_length).resolved(box);
  411. auto right = computed_values.inset().right.resolved(box, width_of_containing_block_as_length).resolved(box);
  412. auto width = a_width;
  413. auto solve_for_left = [&] {
  414. return CSS::Length(width_of_containing_block - margin_left.to_px(box) - border_left - padding_left - width.to_px(box) - padding_right - border_right - margin_right.to_px(box) - right.to_px(box), CSS::Length::Type::Px);
  415. };
  416. auto solve_for_width = [&] {
  417. return CSS::Length(width_of_containing_block - left.to_px(box) - margin_left.to_px(box) - border_left - padding_left - padding_right - border_right - margin_right.to_px(box) - right.to_px(box), CSS::Length::Type::Px);
  418. };
  419. auto solve_for_right = [&] {
  420. return CSS::Length(width_of_containing_block - left.to_px(box) - margin_left.to_px(box) - border_left - padding_left - width.to_px(box) - padding_right - border_right - margin_right.to_px(box), CSS::Length::Type::Px);
  421. };
  422. // If all three of 'left', 'width', and 'right' are 'auto':
  423. if (left.is_auto() && width.is_auto() && right.is_auto()) {
  424. // First set any 'auto' values for 'margin-left' and 'margin-right' to 0.
  425. if (margin_left.is_auto())
  426. margin_left = CSS::Length::make_px(0);
  427. if (margin_right.is_auto())
  428. margin_right = CSS::Length::make_px(0);
  429. // Then, if the 'direction' property of the element establishing the static-position containing block
  430. // is 'ltr' set 'left' to the static position and apply rule number three below;
  431. // otherwise, set 'right' to the static position and apply rule number one below.
  432. // FIXME: This is very hackish.
  433. left = CSS::Length::make_px(0);
  434. goto Rule3;
  435. }
  436. if (!left.is_auto() && !width.is_auto() && !right.is_auto()) {
  437. // FIXME: This should be solved in a more complicated way.
  438. return width;
  439. }
  440. if (margin_left.is_auto())
  441. margin_left = CSS::Length::make_px(0);
  442. if (margin_right.is_auto())
  443. margin_right = CSS::Length::make_px(0);
  444. // 1. 'left' and 'width' are 'auto' and 'right' is not 'auto',
  445. // then the width is shrink-to-fit. Then solve for 'left'
  446. if (left.is_auto() && width.is_auto() && !right.is_auto()) {
  447. auto result = calculate_shrink_to_fit_widths(box);
  448. solve_for_left();
  449. auto available_width = solve_for_width();
  450. width = CSS::Length(min(max(result.preferred_minimum_width, available_width.to_px(box)), result.preferred_width), CSS::Length::Type::Px);
  451. }
  452. // 2. 'left' and 'right' are 'auto' and 'width' is not 'auto',
  453. // then if the 'direction' property of the element establishing
  454. // the static-position containing block is 'ltr' set 'left'
  455. // to the static position, otherwise set 'right' to the static position.
  456. // Then solve for 'left' (if 'direction is 'rtl') or 'right' (if 'direction' is 'ltr').
  457. else if (left.is_auto() && right.is_auto() && !width.is_auto()) {
  458. // FIXME: Check direction
  459. // FIXME: Use the static-position containing block
  460. left = zero_value;
  461. right = solve_for_right();
  462. }
  463. // 3. 'width' and 'right' are 'auto' and 'left' is not 'auto',
  464. // then the width is shrink-to-fit. Then solve for 'right'
  465. else if (width.is_auto() && right.is_auto() && !left.is_auto()) {
  466. Rule3:
  467. auto result = calculate_shrink_to_fit_widths(box);
  468. auto available_width = solve_for_width();
  469. width = CSS::Length(min(max(result.preferred_minimum_width, available_width.to_px(box)), result.preferred_width), CSS::Length::Type::Px);
  470. right = solve_for_right();
  471. }
  472. // 4. 'left' is 'auto', 'width' and 'right' are not 'auto', then solve for 'left'
  473. else if (left.is_auto() && !width.is_auto() && !right.is_auto()) {
  474. left = solve_for_left();
  475. }
  476. // 5. 'width' is 'auto', 'left' and 'right' are not 'auto', then solve for 'width'
  477. else if (width.is_auto() && !left.is_auto() && !right.is_auto()) {
  478. width = solve_for_width();
  479. }
  480. // 6. 'right' is 'auto', 'left' and 'width' are not 'auto', then solve for 'right'
  481. else if (right.is_auto() && !left.is_auto() && !width.is_auto()) {
  482. right = solve_for_right();
  483. }
  484. return width;
  485. };
  486. auto specified_width = computed_values.width().resolved(box, width_of_containing_block_as_length).resolved(box);
  487. // 1. The tentative used width is calculated (without 'min-width' and 'max-width')
  488. auto used_width = try_compute_width(specified_width);
  489. // 2. The tentative used width is greater than 'max-width', the rules above are applied again,
  490. // but this time using the computed value of 'max-width' as the computed value for 'width'.
  491. auto specified_max_width = computed_values.max_width().resolved(box, width_of_containing_block_as_length).resolved(box);
  492. if (!specified_max_width.is_auto()) {
  493. if (used_width.to_px(box) > specified_max_width.to_px(box)) {
  494. used_width = try_compute_width(specified_max_width);
  495. }
  496. }
  497. // 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
  498. // but this time using the value of 'min-width' as the computed value for 'width'.
  499. auto specified_min_width = computed_values.min_width().resolved(box, width_of_containing_block_as_length).resolved(box);
  500. if (!specified_min_width.is_auto()) {
  501. if (used_width.to_px(box) < specified_min_width.to_px(box)) {
  502. used_width = try_compute_width(specified_min_width);
  503. }
  504. }
  505. auto& box_state = m_state.get_mutable(box);
  506. box_state.content_width = used_width.to_px(box);
  507. box_state.margin_left = margin_left.to_px(box);
  508. box_state.margin_right = margin_right.to_px(box);
  509. box_state.border_left = border_left;
  510. box_state.border_right = border_right;
  511. box_state.padding_left = padding_left;
  512. box_state.padding_right = padding_right;
  513. }
  514. void FormattingContext::compute_width_for_absolutely_positioned_replaced_element(ReplacedBox const& box)
  515. {
  516. // 10.3.8 Absolutely positioned, replaced elements
  517. // The used value of 'width' is determined as for inline replaced elements.
  518. // FIXME: This const_cast is gross.
  519. const_cast<ReplacedBox&>(box).prepare_for_replaced_layout();
  520. m_state.get_mutable(box).content_width = compute_width_for_replaced_element(m_state, box);
  521. }
  522. // https://www.w3.org/TR/CSS22/visudet.html#abs-non-replaced-height
  523. void FormattingContext::compute_height_for_absolutely_positioned_non_replaced_element(Box const& box)
  524. {
  525. // 10.6.4 Absolutely positioned, non-replaced elements
  526. // FIXME: The section below is partly on-spec, partly ad-hoc.
  527. auto& computed_values = box.computed_values();
  528. auto const& containing_block = *box.containing_block();
  529. auto& box_state = m_state.get_mutable(box);
  530. auto width_of_containing_block = containing_block_width_for(box);
  531. auto height_of_containing_block = containing_block_height_for(box);
  532. auto width_of_containing_block_as_length = CSS::Length::make_px(width_of_containing_block);
  533. auto height_of_containing_block_as_length = CSS::Length::make_px(height_of_containing_block);
  534. CSS::Length specified_top = computed_values.inset().top.resolved(box, height_of_containing_block_as_length).resolved(box);
  535. CSS::Length specified_bottom = computed_values.inset().bottom.resolved(box, height_of_containing_block_as_length).resolved(box);
  536. CSS::Length specified_height = CSS::Length::make_auto();
  537. if (computed_values.height().is_percentage()
  538. && !(containing_block.computed_values().height().is_length() && containing_block.computed_values().height().length().is_absolute())) {
  539. // specified_height is already auto
  540. } else {
  541. specified_height = computed_values.height().resolved(box, height_of_containing_block_as_length).resolved(box);
  542. }
  543. auto specified_max_height = computed_values.max_height().resolved(box, height_of_containing_block_as_length).resolved(box);
  544. auto specified_min_height = computed_values.min_height().resolved(box, height_of_containing_block_as_length).resolved(box);
  545. box_state.margin_top = computed_values.margin().top.resolved(box, width_of_containing_block_as_length).to_px(box);
  546. box_state.margin_bottom = computed_values.margin().bottom.resolved(box, width_of_containing_block_as_length).to_px(box);
  547. box_state.border_top = computed_values.border_top().width;
  548. box_state.border_bottom = computed_values.border_bottom().width;
  549. box_state.padding_top = computed_values.padding().top.resolved(box, width_of_containing_block_as_length).to_px(box);
  550. box_state.padding_bottom = computed_values.padding().bottom.resolved(box, width_of_containing_block_as_length).to_px(box);
  551. if (specified_height.is_auto() && specified_top.is_auto() && specified_bottom.is_auto()) {
  552. specified_height = CSS::Length(compute_auto_height_for_block_level_element(m_state, box), CSS::Length::Type::Px);
  553. }
  554. else if (specified_height.is_auto() && !specified_top.is_auto() && specified_bottom.is_auto()) {
  555. specified_height = CSS::Length(compute_auto_height_for_block_level_element(m_state, box), CSS::Length::Type::Px);
  556. box_state.inset_bottom = height_of_containing_block - specified_height.to_px(box) - specified_top.to_px(box) - box_state.margin_top - box_state.padding_top - box_state.border_top - box_state.margin_bottom - box_state.padding_bottom - box_state.border_bottom;
  557. }
  558. else if (specified_height.is_auto() && !specified_top.is_auto() && !specified_bottom.is_auto()) {
  559. specified_height = CSS::Length(height_of_containing_block - specified_top.to_px(box) - box_state.margin_top - box_state.padding_top - box_state.border_top - specified_bottom.to_px(box) - box_state.margin_bottom - box_state.padding_bottom - box_state.border_bottom, CSS::Length::Type::Px);
  560. }
  561. if (!specified_height.is_auto()) {
  562. float used_height = specified_height.to_px(box);
  563. if (!specified_max_height.is_auto())
  564. used_height = min(used_height, specified_max_height.to_px(box));
  565. if (!specified_min_height.is_auto())
  566. used_height = max(used_height, specified_min_height.to_px(box));
  567. box_state.content_height = used_height;
  568. }
  569. }
  570. void FormattingContext::layout_absolutely_positioned_element(Box const& box)
  571. {
  572. auto width_of_containing_block = containing_block_width_for(box);
  573. auto height_of_containing_block = containing_block_height_for(box);
  574. auto width_of_containing_block_as_length = CSS::Length::make_px(width_of_containing_block);
  575. auto height_of_containing_block_as_length = CSS::Length::make_px(height_of_containing_block);
  576. auto specified_width = box.computed_values().width().resolved(box, width_of_containing_block_as_length).resolved(box);
  577. compute_width_for_absolutely_positioned_element(box);
  578. auto independent_formatting_context = layout_inside(box, LayoutMode::Normal);
  579. compute_height_for_absolutely_positioned_element(box);
  580. auto& box_state = m_state.get_mutable(box);
  581. box_state.margin_left = box.computed_values().margin().left.resolved(box, width_of_containing_block_as_length).to_px(box);
  582. box_state.margin_top = box.computed_values().margin().top.resolved(box, height_of_containing_block_as_length).to_px(box);
  583. box_state.margin_right = box.computed_values().margin().right.resolved(box, width_of_containing_block_as_length).to_px(box);
  584. box_state.margin_bottom = box.computed_values().margin().bottom.resolved(box, height_of_containing_block_as_length).to_px(box);
  585. box_state.border_left = box.computed_values().border_left().width;
  586. box_state.border_right = box.computed_values().border_right().width;
  587. box_state.border_top = box.computed_values().border_top().width;
  588. box_state.border_bottom = box.computed_values().border_bottom().width;
  589. box_state.inset_left = box.computed_values().inset().left.resolved(box, width_of_containing_block_as_length).to_px(box);
  590. box_state.inset_top = box.computed_values().inset().top.resolved(box, height_of_containing_block_as_length).to_px(box);
  591. box_state.inset_right = box.computed_values().inset().right.resolved(box, width_of_containing_block_as_length).to_px(box);
  592. box_state.inset_bottom = box.computed_values().inset().bottom.resolved(box, height_of_containing_block_as_length).to_px(box);
  593. auto is_auto = [](auto const& length_percentage) {
  594. return length_percentage.is_length() && length_percentage.length().is_auto();
  595. };
  596. if (is_auto(box.computed_values().inset().left) && specified_width.is_auto() && is_auto(box.computed_values().inset().right)) {
  597. if (is_auto(box.computed_values().margin().left))
  598. box_state.margin_left = 0;
  599. if (is_auto(box.computed_values().margin().right))
  600. box_state.margin_right = 0;
  601. }
  602. Gfx::FloatPoint used_offset;
  603. if (!is_auto(box.computed_values().inset().left)) {
  604. float x_offset = box_state.inset_left
  605. + box_state.border_box_left();
  606. used_offset.set_x(x_offset + box_state.margin_left);
  607. } else if (!is_auto(box.computed_values().inset().right)) {
  608. float x_offset = 0
  609. - box_state.inset_right
  610. - box_state.border_box_right();
  611. used_offset.set_x(width_of_containing_block + x_offset - box_state.content_width - box_state.margin_right);
  612. } else {
  613. float x_offset = box_state.margin_box_left();
  614. used_offset.set_x(x_offset);
  615. }
  616. if (!is_auto(box.computed_values().inset().top)) {
  617. float y_offset = box_state.inset_top
  618. + box_state.border_box_top();
  619. used_offset.set_y(y_offset + box_state.margin_top);
  620. } else if (!is_auto(box.computed_values().inset().bottom)) {
  621. float y_offset = 0
  622. - box_state.inset_bottom
  623. - box_state.border_box_bottom();
  624. used_offset.set_y(height_of_containing_block + y_offset - box_state.content_height - box_state.margin_bottom);
  625. } else {
  626. float y_offset = box_state.margin_box_top();
  627. used_offset.set_y(y_offset);
  628. }
  629. box_state.offset = used_offset;
  630. if (independent_formatting_context)
  631. independent_formatting_context->parent_context_did_dimension_child_root_box();
  632. }
  633. void FormattingContext::compute_height_for_absolutely_positioned_replaced_element(ReplacedBox const& box)
  634. {
  635. // 10.6.5 Absolutely positioned, replaced elements
  636. // The used value of 'height' is determined as for inline replaced elements.
  637. m_state.get_mutable(box).content_height = compute_height_for_replaced_element(m_state, box);
  638. }
  639. // https://www.w3.org/TR/css-position-3/#relpos-insets
  640. void FormattingContext::compute_inset(Box const& box)
  641. {
  642. if (box.computed_values().position() != CSS::Position::Relative)
  643. return;
  644. auto resolve_two_opposing_insets = [&](CSS::LengthPercentage const& computed_start, CSS::LengthPercentage const& computed_end, float& used_start, float& used_end, float reference_for_percentage) {
  645. auto resolved_first = computed_start.resolved(box, CSS::Length::make_px(reference_for_percentage)).resolved(box);
  646. auto resolved_second = computed_end.resolved(box, CSS::Length::make_px(reference_for_percentage)).resolved(box);
  647. if (resolved_first.is_auto() && resolved_second.is_auto()) {
  648. // If opposing inset properties in an axis both compute to auto (their initial values),
  649. // their used values are zero (i.e., the boxes stay in their original position in that axis).
  650. used_start = 0;
  651. used_end = 0;
  652. } else if (resolved_first.is_auto() || resolved_second.is_auto()) {
  653. // If only one is auto, its used value becomes the negation of the other, and the box is shifted by the specified amount.
  654. if (resolved_first.is_auto()) {
  655. used_end = resolved_second.to_px(box);
  656. used_start = 0 - used_end;
  657. } else {
  658. used_start = resolved_first.to_px(box);
  659. used_end = 0 - used_start;
  660. }
  661. } else {
  662. // If neither is auto, the position is over-constrained; (with respect to the writing mode of its containing block)
  663. // the computed end side value is ignored, and its used value becomes the negation of the start side.
  664. used_start = resolved_first.to_px(box);
  665. used_end = 0 - used_start;
  666. }
  667. };
  668. auto& box_state = m_state.get_mutable(box);
  669. auto const& computed_values = box.computed_values();
  670. // FIXME: Respect the containing block's writing-mode.
  671. resolve_two_opposing_insets(computed_values.inset().left, computed_values.inset().right, box_state.inset_left, box_state.inset_right, containing_block_width_for(box));
  672. resolve_two_opposing_insets(computed_values.inset().top, computed_values.inset().bottom, box_state.inset_top, box_state.inset_bottom, containing_block_height_for(box));
  673. }
  674. float FormattingContext::calculate_fit_content_size(float min_content_size, float max_content_size, Optional<float> available_space) const
  675. {
  676. // If the available space in a given axis is definite, equal to clamp(min-content size, stretch-fit size, max-content size)
  677. // (i.e. max(min-content size, min(max-content size, stretch-fit size))).
  678. if (available_space.has_value()) {
  679. // FIXME: Compute the real stretch-fit size.
  680. auto stretch_fit_size = *available_space;
  681. auto s = max(min_content_size, min(max_content_size, stretch_fit_size));
  682. return s;
  683. }
  684. // FIXME: When sizing under a min-content constraint, equal to the min-content size.
  685. // Otherwise, equal to the max-content size in that axis.
  686. return max_content_size;
  687. }
  688. float FormattingContext::calculate_fit_content_width(Layout::Box const& box, Optional<float> available_space) const
  689. {
  690. return calculate_fit_content_size(calculate_min_content_width(box), calculate_max_content_width(box), available_space);
  691. }
  692. float FormattingContext::calculate_fit_content_height(Layout::Box const& box, Optional<float> available_space) const
  693. {
  694. return calculate_fit_content_size(calculate_min_content_height(box), calculate_max_content_height(box), available_space);
  695. }
  696. float FormattingContext::calculate_auto_height(FormattingState const& state, Box const& box)
  697. {
  698. if (is<ReplacedBox>(box)) {
  699. return compute_height_for_replaced_element(state, verify_cast<ReplacedBox>(box));
  700. }
  701. return compute_auto_height_for_block_level_element(state, box);
  702. }
  703. float FormattingContext::calculate_min_content_width(Layout::Box const& box) const
  704. {
  705. if (box.has_intrinsic_width())
  706. return *box.intrinsic_width();
  707. auto& root_state = m_state.m_root;
  708. auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new FormattingState::IntrinsicSizes); });
  709. if (cache.min_content_width.has_value())
  710. return *cache.min_content_width;
  711. FormattingState throwaway_state(&m_state);
  712. auto const& containing_block = *box.containing_block();
  713. auto& containing_block_state = throwaway_state.get_mutable(containing_block);
  714. containing_block_state.content_width = 0;
  715. auto& box_state = throwaway_state.get_mutable(box);
  716. box_state.width_constraint = SizeConstraint::MinContent;
  717. auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
  718. VERIFY(context);
  719. context->run_intrinsic_size_determination(box);
  720. if (context->type() == FormattingContext::Type::Flex) {
  721. cache.min_content_width = box_state.content_width;
  722. } else {
  723. cache.min_content_width = context->greatest_child_width(box);
  724. }
  725. return *cache.min_content_width;
  726. }
  727. float FormattingContext::calculate_max_content_width(Layout::Box const& box) const
  728. {
  729. if (box.has_intrinsic_width())
  730. return *box.intrinsic_width();
  731. auto& root_state = m_state.m_root;
  732. auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new FormattingState::IntrinsicSizes); });
  733. if (cache.max_content_width.has_value())
  734. return *cache.max_content_width;
  735. FormattingState throwaway_state(&m_state);
  736. auto const& containing_block = *box.containing_block();
  737. auto& containing_block_state = throwaway_state.get_mutable(containing_block);
  738. containing_block_state.content_width = INFINITY;
  739. auto& box_state = throwaway_state.get_mutable(box);
  740. box_state.width_constraint = SizeConstraint::MaxContent;
  741. auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
  742. VERIFY(context);
  743. context->run_intrinsic_size_determination(box);
  744. if (context->type() == FormattingContext::Type::Flex) {
  745. cache.max_content_width = box_state.content_width;
  746. } else {
  747. cache.max_content_width = context->greatest_child_width(box);
  748. }
  749. return *cache.max_content_width;
  750. }
  751. float FormattingContext::calculate_min_content_height(Layout::Box const& box) const
  752. {
  753. if (box.has_intrinsic_height())
  754. return *box.intrinsic_height();
  755. auto& root_state = m_state.m_root;
  756. auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new FormattingState::IntrinsicSizes); });
  757. if (cache.min_content_height.has_value())
  758. return *cache.min_content_height;
  759. FormattingState throwaway_state(&m_state);
  760. auto const& containing_block = *box.containing_block();
  761. auto& containing_block_state = throwaway_state.get_mutable(containing_block);
  762. containing_block_state.content_height = 0;
  763. auto& box_state = throwaway_state.get_mutable(box);
  764. box_state.height_constraint = SizeConstraint::MinContent;
  765. auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
  766. VERIFY(context);
  767. context->run_intrinsic_size_determination(box);
  768. if (context->type() == FormattingContext::Type::Flex) {
  769. cache.min_content_height = box_state.content_height;
  770. } else {
  771. cache.min_content_height = calculate_auto_height(throwaway_state, box);
  772. }
  773. return *cache.min_content_height;
  774. }
  775. float FormattingContext::calculate_max_content_height(Layout::Box const& box) const
  776. {
  777. if (box.has_intrinsic_height())
  778. return *box.intrinsic_height();
  779. auto& root_state = m_state.m_root;
  780. auto& cache = *root_state.intrinsic_sizes.ensure(&box, [] { return adopt_own(*new FormattingState::IntrinsicSizes); });
  781. if (cache.max_content_height.has_value())
  782. return *cache.max_content_height;
  783. FormattingState throwaway_state(&m_state);
  784. auto const& containing_block = *box.containing_block();
  785. auto& containing_block_state = throwaway_state.get_mutable(containing_block);
  786. containing_block_state.content_height = INFINITY;
  787. auto& box_state = throwaway_state.get_mutable(box);
  788. box_state.height_constraint = SizeConstraint::MaxContent;
  789. auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
  790. VERIFY(context);
  791. context->run_intrinsic_size_determination(box);
  792. if (context->type() == FormattingContext::Type::Flex) {
  793. cache.max_content_height = box_state.content_height;
  794. } else {
  795. cache.max_content_height = calculate_auto_height(throwaway_state, box);
  796. }
  797. return *cache.max_content_height;
  798. }
  799. float FormattingContext::containing_block_width_for(Box const& box, FormattingState const& state)
  800. {
  801. auto& containing_block_state = state.get(*box.containing_block());
  802. auto& box_state = state.get(box);
  803. switch (box_state.width_constraint) {
  804. case SizeConstraint::MinContent:
  805. return 0;
  806. case SizeConstraint::MaxContent:
  807. return INFINITY;
  808. case SizeConstraint::None:
  809. return containing_block_state.content_width;
  810. }
  811. VERIFY_NOT_REACHED();
  812. }
  813. float FormattingContext::containing_block_height_for(Box const& box, FormattingState const& state)
  814. {
  815. auto& containing_block_state = state.get(*box.containing_block());
  816. auto& box_state = state.get(box);
  817. switch (box_state.height_constraint) {
  818. case SizeConstraint::MinContent:
  819. return 0;
  820. case SizeConstraint::MaxContent:
  821. return INFINITY;
  822. case SizeConstraint::None:
  823. return containing_block_state.content_height;
  824. }
  825. VERIFY_NOT_REACHED();
  826. }
  827. }