1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731
|
/*
* Copyright (C) 2018 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "BlockFormattingContext.h"
#include "BlockFormattingGeometry.h"
#include "BlockFormattingState.h"
#include "BlockMarginCollapse.h"
#include "FloatingContext.h"
#include "LayoutBox.h"
#include "LayoutChildIterator.h"
#include "LayoutContainingBlockChainIterator.h"
#include "LayoutContext.h"
#include "LayoutDescendantIterator.h"
#include "LayoutElementBox.h"
#include "LayoutInitialContainingBlock.h"
#include "LayoutState.h"
#include "Logging.h"
#include "PlacedFloats.h"
#include "RenderStyleInlines.h"
#include "TableWrapperBlockFormattingContext.h"
#include <wtf/TZoneMallocInlines.h>
#include <wtf/text/TextStream.h>
namespace WebCore {
namespace Layout {
WTF_MAKE_TZONE_OR_ISO_ALLOCATED_IMPL(BlockFormattingContext);
BlockFormattingContext::BlockFormattingContext(const ElementBox& formattingContextRoot, BlockFormattingState& blockFormattingState)
: FormattingContext(formattingContextRoot, blockFormattingState.layoutState())
, m_blockFormattingState(blockFormattingState)
, m_blockFormattingGeometry(*this)
, m_blockFormattingQuirks(*this)
{
}
void BlockFormattingContext::layoutInFlowContent(const ConstraintsForInFlowContent& constraints)
{
// 9.4.1 Block formatting contexts
// In a block formatting context, boxes are laid out one after the other, vertically, beginning at the top of a containing block.
// The vertical distance between two sibling boxes is determined by the 'margin' properties.
// Vertical margins between adjacent block-level boxes in a block formatting context collapse.
LOG_WITH_STREAM(FormattingContextLayout, stream << "[Start] -> block formatting context -> formatting root(" << &root() << ")");
auto& formattingRoot = root();
ASSERT(formattingRoot.hasInFlowOrFloatingChild());
auto& placedFloats = formattingState().placedFloats();
auto floatingContext = FloatingContext { root(), layoutState(), placedFloats };
Vector<const ElementBox*> layoutQueue;
enum class LayoutDirection { Child, Sibling };
auto appendNextToLayoutQueue = [&] (const auto& layoutBox, auto direction) {
if (direction == LayoutDirection::Child) {
for (auto* child = layoutBox.firstInFlowOrFloatingChild(); child; child = child->nextInFlowOrFloatingSibling()) {
layoutQueue.append(downcast<ElementBox>(child));
return true;
}
return false;
}
if (direction == LayoutDirection::Sibling) {
for (auto* nextSibling = layoutBox.nextInFlowOrFloatingSibling(); nextSibling; nextSibling = nextSibling->nextInFlowOrFloatingSibling()) {
layoutQueue.append(downcast<ElementBox>(nextSibling));
return true;
}
return false;
}
ASSERT_NOT_REACHED();
return false;
};
auto constraintsForLayoutBox = [&] (const auto& layoutBox) {
auto& containingBlock = this->containingBlock(layoutBox);
return &containingBlock == &formattingRoot ? constraints : formattingGeometry().constraintsForInFlowContent(containingBlock);
};
// This is a post-order tree traversal layout.
// The root container layout is done in the formatting context it lives in, not that one it creates, so let's start with the first child.
appendNextToLayoutQueue(formattingRoot, LayoutDirection::Child);
// 1. Go all the way down to the leaf node
// 2. Compute static position and width as we traverse down
// 3. As we climb back on the tree, compute height and finialize position
// (Any subtrees with new formatting contexts need to layout synchronously)
while (!layoutQueue.isEmpty()) {
// Traverse down on the descendants and compute width/static position until we find a leaf node.
while (true) {
auto& layoutBox = *layoutQueue.last();
auto containingBlockConstraints = constraintsForLayoutBox(layoutBox);
computeBorderAndPadding(layoutBox, containingBlockConstraints.horizontal());
computeStaticVerticalPosition(layoutBox, containingBlockConstraints.logicalTop());
computeWidthAndMargin(floatingContext, layoutBox, { constraints, containingBlockConstraints });
computeStaticHorizontalPosition(layoutBox, containingBlockConstraints.horizontal());
computePositionToAvoidFloats(floatingContext, layoutBox, { constraints, containingBlockConstraints });
if (layoutBox.establishesFormattingContext()) {
if (layoutBox.hasInFlowOrFloatingChild()) {
if (layoutBox.establishesInlineFormattingContext()) {
// IFCs inherit floats from parent FCs. We need final vertical position to find intruding floats.
precomputeVerticalPositionForBoxAndAncestors(layoutBox, { constraints, containingBlockConstraints });
}
// Layout the inflow descendants of this formatting context root.
auto formattingContext = LayoutContext::createFormattingContext(layoutBox, layoutState());
if (layoutBox.isTableWrapperBox())
downcast<TableWrapperBlockFormattingContext>(*formattingContext).setHorizontalConstraintsIgnoringFloats(containingBlockConstraints.horizontal());
formattingContext->layoutInFlowContent(formattingGeometry().constraintsForInFlowContent(layoutBox));
}
break;
}
if (!appendNextToLayoutQueue(layoutBox, LayoutDirection::Child))
break;
}
// Climb back on the ancestors and compute height/final position.
while (!layoutQueue.isEmpty()) {
auto& layoutBox = *layoutQueue.takeLast();
auto containingBlockConstraints = constraintsForLayoutBox(layoutBox);
// All inflow descendants (if there are any) are laid out by now. Let's compute the box's height and vertical margin.
computeHeightAndMargin(layoutBox, containingBlockConstraints);
if (layoutBox.isFloatingPositioned())
placedFloats.append(floatingContext.makeFloatItem(layoutBox, geometryForBox(layoutBox)));
else {
// Adjust the vertical position now that we've got final margin values for non-float avoider boxes.
// Float avoiders have pre-computed vertical positions when floats are present.
if (!layoutBox.isFloatAvoider() || floatingContext.isEmpty()) {
auto& formattingState = this->formattingState();
auto& boxGeometry = formattingState.boxGeometry(layoutBox);
boxGeometry.setTop(verticalPositionWithMargin(layoutBox, formattingState.usedVerticalMargin(layoutBox), containingBlockConstraints.logicalTop()));
}
}
auto establishesBlockFormattingContext = layoutBox.establishesBlockFormattingContext();
if (establishesBlockFormattingContext) {
// Now that we computed the box's height, we can layout the out-of-flow descendants.
if (layoutBox.hasChild()) {
downcast<BlockFormattingContext>(*LayoutContext::createFormattingContext(layoutBox, layoutState())).layoutOutOfFlowContent(formattingGeometry().constraintsForOutOfFlowContent(layoutBox));
}
}
if (!layoutBox.establishesFormattingContext())
placeInFlowPositionedChildren(layoutBox, containingBlockConstraints.horizontal());
if (appendNextToLayoutQueue(layoutBox, LayoutDirection::Sibling))
break;
}
}
// Place the inflow positioned children.
placeInFlowPositionedChildren(formattingRoot, constraints.horizontal());
LOG_WITH_STREAM(FormattingContextLayout, stream << "[End] -> block formatting context -> formatting root(" << &root() << ")");
}
void BlockFormattingContext::layoutOutOfFlowContent(const ConstraintsForOutOfFlowContent& constraints)
{
LOG_WITH_STREAM(FormattingContextLayout, stream << "Start: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());
collectOutOfFlowDescendantsIfNeeded();
auto constraintsForLayoutBox = [&] (const auto& outOfFlowBox) {
auto& containingBlock = this->containingBlock(outOfFlowBox);
return &containingBlock == &root() ? constraints : formattingGeometry().constraintsForOutOfFlowContent(containingBlock);
};
for (auto& outOfFlowBox : formattingState().outOfFlowBoxes()) {
ASSERT(outOfFlowBox->establishesFormattingContext());
auto containingBlockConstraints = constraintsForLayoutBox(outOfFlowBox);
auto horizontalConstraintsForBorderAndPadding = HorizontalConstraints { containingBlockConstraints.horizontal.logicalLeft, containingBlockConstraints.borderAndPaddingConstraints };
computeBorderAndPadding(outOfFlowBox, horizontalConstraintsForBorderAndPadding);
computeOutOfFlowHorizontalGeometry(outOfFlowBox, containingBlockConstraints);
auto* elementBox = dynamicDowncast<ElementBox>(outOfFlowBox.get());
if (elementBox && elementBox->hasChild()) {
auto formattingContext = LayoutContext::createFormattingContext(*elementBox, layoutState());
if (elementBox->hasInFlowOrFloatingChild())
formattingContext->layoutInFlowContent(formattingGeometry().constraintsForInFlowContent(*elementBox));
computeOutOfFlowVerticalGeometry(*elementBox, containingBlockConstraints);
} else
computeOutOfFlowVerticalGeometry(outOfFlowBox, containingBlockConstraints);
}
LOG_WITH_STREAM(FormattingContextLayout, stream << "End: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());
}
void BlockFormattingContext::computeOutOfFlowHorizontalGeometry(const Box& layoutBox, const ConstraintsForOutOfFlowContent& constraints)
{
ASSERT(layoutBox.isOutOfFlowPositioned());
auto compute = [&](std::optional<LayoutUnit> usedWidth) {
return formattingGeometry().outOfFlowHorizontalGeometry(layoutBox, constraints.horizontal, constraints.vertical, { usedWidth, { } });
};
auto containingBlockWidth = constraints.horizontal.logicalWidth;
auto horizontalGeometry = compute({ });
if (auto maxWidth = formattingGeometry().computedMaxWidth(layoutBox, containingBlockWidth)) {
auto maxHorizontalGeometry = compute(maxWidth);
if (horizontalGeometry.contentWidthAndMargin.contentWidth > maxHorizontalGeometry.contentWidthAndMargin.contentWidth)
horizontalGeometry = maxHorizontalGeometry;
}
if (auto minWidth = formattingGeometry().computedMinWidth(layoutBox, containingBlockWidth)) {
auto minHorizontalGeometry = compute(minWidth);
if (horizontalGeometry.contentWidthAndMargin.contentWidth < minHorizontalGeometry.contentWidthAndMargin.contentWidth)
horizontalGeometry = minHorizontalGeometry;
}
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
boxGeometry.setLeft(horizontalGeometry.left + horizontalGeometry.contentWidthAndMargin.usedMargin.start);
boxGeometry.setContentBoxWidth(horizontalGeometry.contentWidthAndMargin.contentWidth);
auto& usedHorizontalMargin = horizontalGeometry.contentWidthAndMargin.usedMargin;
boxGeometry.setHorizontalMargin({ usedHorizontalMargin.start, usedHorizontalMargin.end });
}
void BlockFormattingContext::computeOutOfFlowVerticalGeometry(const Box& layoutBox, const ConstraintsForOutOfFlowContent& constraints)
{
ASSERT(layoutBox.isOutOfFlowPositioned());
auto compute = [&](std::optional<LayoutUnit> usedHeight) {
return formattingGeometry().outOfFlowVerticalGeometry(layoutBox, constraints.horizontal, constraints.vertical, { usedHeight });
};
auto containingBlockHeight = constraints.vertical.logicalHeight;
auto verticalGeometry = compute({ });
if (auto maxHeight = formattingGeometry().computedMaxHeight(layoutBox, containingBlockHeight)) {
auto maxVerticalGeometry = compute(maxHeight);
if (verticalGeometry.contentHeightAndMargin.contentHeight > maxVerticalGeometry.contentHeightAndMargin.contentHeight)
verticalGeometry = maxVerticalGeometry;
}
if (auto minHeight = formattingGeometry().computedMinHeight(layoutBox, containingBlockHeight)) {
auto minVerticalGeometry = compute(minHeight);
if (verticalGeometry.contentHeightAndMargin.contentHeight < minVerticalGeometry.contentHeightAndMargin.contentHeight)
verticalGeometry = minVerticalGeometry;
}
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
auto nonCollapsedVerticalMargin = verticalGeometry.contentHeightAndMargin.nonCollapsedMargin;
boxGeometry.setTop(verticalGeometry.top + nonCollapsedVerticalMargin.before);
boxGeometry.setContentBoxHeight(verticalGeometry.contentHeightAndMargin.contentHeight);
// Margins of absolutely positioned boxes do not collapse.
boxGeometry.setVerticalMargin({ nonCollapsedVerticalMargin.before, nonCollapsedVerticalMargin.after });
}
void BlockFormattingContext::collectOutOfFlowDescendantsIfNeeded()
{
if (!formattingState().outOfFlowBoxes().isEmpty())
return;
auto& root = this->root();
if (!root.hasChild())
return;
if (!root.isPositioned() && !is<InitialContainingBlock>(root))
return;
// Collect the out-of-flow descendants at the formatting root level (as opposed to at the containing block level, though they might be the same).
// FIXME: Turn this into a register-self as boxes are being inserted.
for (auto& descendant : descendantsOfType<Box>(root)) {
if (!descendant.isOutOfFlowPositioned())
continue;
auto nearestFormattingContextRoot = [&] () -> const ElementBox* {
for (auto& containingBlock : containingBlockChain(descendant)) {
if (containingBlock.establishesBlockFormattingContext())
return &containingBlock;
}
ASSERT_NOT_REACHED();
return nullptr;
};
if (nearestFormattingContextRoot() != &root)
continue;
formattingState().addOutOfFlowBox(descendant);
}
}
LayoutUnit BlockFormattingContext::usedContentHeight() const
{
// 10.6.7 'Auto' heights for block formatting context roots
// If it has block-level children, the height is the distance between the top margin-edge of the topmost block-level
// child box and the bottom margin-edge of the bottommost block-level child box.
// In addition, if the element has any floating descendants whose bottom margin edge is below the element's bottom content edge,
// then the height is increased to include those edges. Only floats that participate in this block formatting context are taken
// into account, e.g., floats inside absolutely positioned descendants or other floats are not.
auto top = std::optional<LayoutUnit> { };
auto bottom = std::optional<LayoutUnit> { };
if (root().hasInFlowChild()) {
top = BoxGeometry::marginBoxRect(geometryForBox(*root().firstInFlowChild())).top();
bottom = BoxGeometry::marginBoxRect(geometryForBox(*root().lastInFlowChild())).bottom();
}
auto floatingContext = FloatingContext { root(), layoutState(), formattingState().placedFloats() };
if (auto floatTop = floatingContext.placedFloats().highestPositionOnBlockAxis()) {
top = std::min(*floatTop, top.value_or(*floatTop));
auto floatBottom = *floatingContext.placedFloats().lowestPositionOnBlockAxis();
bottom = std::max(floatBottom, bottom.value_or(floatBottom));
}
return *bottom - *top;
}
std::optional<LayoutUnit> BlockFormattingContext::usedAvailableWidthForFloatAvoider(const FloatingContext& floatingContext, const ElementBox& layoutBox, const ConstraintsPair& constraintsPair)
{
// Normally the available width for an in-flow block level box is the width of the containing block's content box.
// However (and can't find it anywhere in the spec) non-floating positioned float avoider block level boxes are constrained by existing floats.
ASSERT(layoutBox.isFloatAvoider());
if (floatingContext.isEmpty())
return { };
// Float clear pushes the block level box either below the floats, or just one side below but the other side could overlap.
// What it means is that the used available width always matches the containing block's constraint.
if (layoutBox.hasFloatClear())
return { };
ASSERT(layoutBox.establishesFormattingContext());
// Vertical static position is not computed yet for this formatting context root, so let's just pre-compute it for now.
precomputeVerticalPositionForBoxAndAncestors(layoutBox, constraintsPair);
auto logicalTopInFormattingContextRootCoordinate = [&] (auto& floatAvoider) {
auto top = BoxGeometry::borderBoxTop(geometryForBox(floatAvoider));
for (auto& ancestor : containingBlockChainWithinFormattingContext(floatAvoider, root()))
top += BoxGeometry::borderBoxTop(geometryForBox(ancestor));
return top;
};
auto floatConstraintsInContainingBlockCoordinate = [&] (auto floatConstraints) {
if (!floatConstraints.start && !floatConstraints.end)
return FloatingContext::Constraints { };
auto offset = LayoutSize { };
for (auto& ancestor : containingBlockChainWithinFormattingContext(layoutBox, root()))
offset += toLayoutSize(BoxGeometry::borderBoxTopLeft(geometryForBox(ancestor)));
if (floatConstraints.start)
floatConstraints.start = PointInContextRoot { *floatConstraints.start - offset };
if (floatConstraints.end)
floatConstraints.end = PointInContextRoot { *floatConstraints.end - offset };
return floatConstraints;
};
// FIXME: Check if the non-yet-computed height affects this computation - and whether we have to resolve it at a later point.
auto logicalTop = logicalTopInFormattingContextRootCoordinate(layoutBox);
auto constraints = floatConstraintsInContainingBlockCoordinate(floatingContext.constraints(logicalTop, logicalTop, FloatingContext::MayBeAboveLastFloat::No));
if (!constraints.start && !constraints.end)
return { };
// Shrink the available space if the floats are actually intruding at this vertical position.
auto availableWidth = constraintsPair.containingBlock.horizontal().logicalWidth;
if (constraints.start)
availableWidth -= constraints.start->x;
if (constraints.end)
availableWidth -= std::max(0_lu, constraintsPair.containingBlock.horizontal().logicalRight() - constraints.end->x);
return availableWidth;
}
void BlockFormattingContext::placeInFlowPositionedChildren(const ElementBox& elementBox, const HorizontalConstraints& horizontalConstraints)
{
LOG_WITH_STREAM(FormattingContextLayout, stream << "Start: move in-flow positioned children -> parent: " << &elementBox);
for (auto& childBox : childrenOfType<ElementBox>(elementBox)) {
if (!childBox.isInFlowPositioned())
continue;
auto positionOffset = formattingGeometry().inFlowPositionedPositionOffset(childBox, horizontalConstraints);
formattingState().boxGeometry(childBox).move(positionOffset);
}
LOG_WITH_STREAM(FormattingContextLayout, stream << "End: move in-flow positioned children -> parent: " << &elementBox);
}
void BlockFormattingContext::computeStaticVerticalPosition(const ElementBox& layoutBox, LayoutUnit containingBlockContentBoxTop)
{
formattingState().boxGeometry(layoutBox).setTop(formattingGeometry().staticVerticalPosition(layoutBox, containingBlockContentBoxTop));
}
void BlockFormattingContext::computeStaticHorizontalPosition(const ElementBox& layoutBox, const HorizontalConstraints& horizontalConstraints)
{
formattingState().boxGeometry(layoutBox).setLeft(formattingGeometry().staticHorizontalPosition(layoutBox, horizontalConstraints));
}
void BlockFormattingContext::precomputeVerticalPositionForBoxAndAncestors(const ElementBox& layoutBox, const ConstraintsPair& constraintsPair)
{
// In order to figure out whether a box should avoid a float, we need to know the final positions of both (ignore relative positioning for now).
// In block formatting context the final position for a normal flow box includes
// 1. the static position and
// 2. the corresponding (non)collapsed margins.
// Now the vertical margins are computed when all the descendants are finalized, because the margin values might be depending on the height of the box
// (and the height might be based on the content).
// So when we get to the point where we intersect the box with the float to decide if the box needs to move, we don't yet have the final vertical position.
//
// The idea here is that as long as we don't cross the block formatting context boundary, we should be able to pre-compute the final top position.
// FIXME: we currently don't account for the "clear" property when computing the final position for an ancestor.
auto& formattingGeometry = this->formattingGeometry();
for (auto* ancestor = &layoutBox; ancestor && ancestor != &root(); ancestor = &containingBlock(*ancestor)) {
auto constraintsForAncestor = [&] {
auto& containingBlock = this->containingBlock(*ancestor);
return &containingBlock == &root() ? constraintsPair.formattingContextRoot : formattingGeometry.constraintsForInFlowContent(containingBlock);
}();
auto computedVerticalMargin = formattingGeometry.computedVerticalMargin(*ancestor, constraintsForAncestor.horizontal());
auto usedNonCollapsedMargin = UsedVerticalMargin::NonCollapsedValues { computedVerticalMargin.before.value_or(0), computedVerticalMargin.after.value_or(0) };
auto precomputedMarginBefore = marginCollapse().precomputedMarginBefore(*ancestor, usedNonCollapsedMargin, formattingGeometry);
auto& boxGeometry = formattingState().boxGeometry(*ancestor);
auto nonCollapsedValues = UsedVerticalMargin::NonCollapsedValues { precomputedMarginBefore.nonCollapsedValue, { } };
auto collapsedValues = UsedVerticalMargin::CollapsedValues { precomputedMarginBefore.collapsedValue, { }, false };
auto verticalMargin = UsedVerticalMargin { nonCollapsedValues, collapsedValues, { precomputedMarginBefore.positiveAndNegativeMarginBefore, { } } };
formattingState().setUsedVerticalMargin(*ancestor, verticalMargin);
boxGeometry.setVerticalMargin({ marginBefore(verticalMargin), marginAfter(verticalMargin) });
boxGeometry.setTop(verticalPositionWithMargin(*ancestor, verticalMargin, constraintsForAncestor.logicalTop()));
#if ASSERT_ENABLED
setPrecomputedMarginBefore(*ancestor, precomputedMarginBefore);
boxGeometry.setHasPrecomputedMarginBefore();
#endif
}
}
void BlockFormattingContext::computePositionToAvoidFloats(const FloatingContext& floatingContext, const ElementBox& layoutBox, const ConstraintsPair& constraintsPair)
{
if (!layoutBox.isFloatAvoider())
return;
// In order to position a float avoider we need to know its vertical position relative to its formatting context root (and not just its containing block),
// because all the already-placed floats (floats that we are trying to avoid here) in this BFC might belong
// to a different set of containing blocks (but they all descendants of the BFC root).
// However according to the BFC rules, at this point of the layout flow we don't yet have computed vertical positions for the ancestors.
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
if (layoutBox.isFloatingPositioned()) {
precomputeVerticalPositionForBoxAndAncestors(layoutBox, constraintsPair);
auto borderBoxTopLeft = floatingContext.positionForFloat(layoutBox, boxGeometry, constraintsPair.containingBlock.horizontal());
boxGeometry.setTopLeft(borderBoxTopLeft);
return;
}
// Non-float positioned float avoiders (formatting context roots and clear boxes) should be fine unless there are floats in this context.
if (floatingContext.isEmpty())
return;
precomputeVerticalPositionForBoxAndAncestors(layoutBox, constraintsPair);
if (layoutBox.hasFloatClear())
return computeVerticalPositionForFloatClear(floatingContext, layoutBox);
ASSERT(layoutBox.establishesFormattingContext());
auto borderBoxTopLeft = floatingContext.positionForNonFloatingFloatAvoider(layoutBox, boxGeometry);
boxGeometry.setTopLeft(borderBoxTopLeft);
}
void BlockFormattingContext::computeVerticalPositionForFloatClear(const FloatingContext& floatingContext, const ElementBox& layoutBox)
{
ASSERT(layoutBox.hasFloatClear());
if (floatingContext.isEmpty())
return;
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
auto verticalPositionAndClearance = floatingContext.blockAxisPositionWithClearance(layoutBox, boxGeometry);
if (!verticalPositionAndClearance)
return;
ASSERT(verticalPositionAndClearance->position >= BoxGeometry::borderBoxTop(boxGeometry));
boxGeometry.setTop(verticalPositionAndClearance->position);
if (verticalPositionAndClearance->clearance)
formattingState().setHasClearance(layoutBox);
// FIXME: Reset the margin values on the ancestors/previous siblings now that the float avoider with clearance does not margin collapse anymore.
}
void BlockFormattingContext::computeWidthAndMargin(const FloatingContext& floatingContext, const ElementBox& layoutBox, const ConstraintsPair& constraintsPair)
{
auto availableWidthFloatAvoider = std::optional<LayoutUnit> { };
if (layoutBox.isFloatAvoider()) {
// Float avoiders' available width might be shrunk by existing floats in the context.
availableWidthFloatAvoider = usedAvailableWidthForFloatAvoider(floatingContext, layoutBox, constraintsPair);
}
auto contentWidthAndMargin = formattingGeometry().computedContentWidthAndMargin(layoutBox, constraintsPair.containingBlock.horizontal(), availableWidthFloatAvoider);
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
boxGeometry.setContentBoxWidth(contentWidthAndMargin.contentWidth);
boxGeometry.setHorizontalMargin({ contentWidthAndMargin.usedMargin.start, contentWidthAndMargin.usedMargin.end });
}
void BlockFormattingContext::computeHeightAndMargin(const ElementBox& layoutBox, const ConstraintsForInFlowContent& constraints)
{
auto compute = [&](std::optional<LayoutUnit> usedHeight) -> ContentHeightAndMargin {
if (layoutBox.isInFlow())
return formattingGeometry().inFlowContentHeightAndMargin(layoutBox, constraints.horizontal(), { usedHeight });
if (layoutBox.isFloatingPositioned())
return formattingGeometry().floatingContentHeightAndMargin(layoutBox, constraints.horizontal(), { usedHeight });
ASSERT_NOT_REACHED();
return { };
};
auto contentHeightAndMargin = compute({ });
if (auto maxHeight = formattingGeometry().computedMaxHeight(layoutBox)) {
if (contentHeightAndMargin.contentHeight > *maxHeight) {
auto maxHeightAndMargin = compute(maxHeight);
// Used height should remain the same.
ASSERT((layoutState().inQuirksMode() && (layoutBox.isBodyBox() || layoutBox.isDocumentBox())) || maxHeightAndMargin.contentHeight == *maxHeight);
contentHeightAndMargin = { *maxHeight, maxHeightAndMargin.nonCollapsedMargin };
}
}
if (auto minHeight = formattingGeometry().computedMinHeight(layoutBox)) {
if (contentHeightAndMargin.contentHeight < *minHeight) {
auto minHeightAndMargin = compute(minHeight);
// Used height should remain the same.
ASSERT((layoutState().inQuirksMode() && (layoutBox.isBodyBox() || layoutBox.isDocumentBox())) || minHeightAndMargin.contentHeight == *minHeight);
contentHeightAndMargin = { *minHeight, minHeightAndMargin.nonCollapsedMargin };
}
}
// 1. Compute collapsed margins.
// 2. Adjust vertical position using the collapsed values.
// 3. Adjust previous in-flow sibling margin after using this margin.
auto marginCollapse = this->marginCollapse();
auto verticalMargin = marginCollapse.collapsedVerticalValues(layoutBox, contentHeightAndMargin.nonCollapsedMargin);
// Cache the computed positive and negative margin value pair.
formattingState().setUsedVerticalMargin(layoutBox, verticalMargin);
#if ASSERT_ENABLED
if (hasPrecomputedMarginBefore(layoutBox) && precomputedMarginBefore(layoutBox).usedValue() != marginBefore(verticalMargin)) {
// When the pre-computed margin turns out to be incorrect, we need to re-layout this subtree with the correct margin values.
// <div style="float: left"></div>
// <div>
// <div style="margin-bottom: 200px"></div>
// </div>
// The float box triggers margin before computation on the ancestor chain to be able to intersect with other floats in the same floating context.
// However in some cases the parent margin-top collapses with some next siblings (nephews) and there's no way to be able to properly
// account for that without laying out every node in the FC (in the example, the margin-bottom pushes down the float).
ASSERT_NOT_IMPLEMENTED_YET();
}
#endif
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
boxGeometry.setContentBoxHeight(contentHeightAndMargin.contentHeight);
boxGeometry.setVerticalMargin({ marginBefore(verticalMargin), marginAfter(verticalMargin) });
// Adjust the previous sibling's margin bottom now that this box's vertical margin is computed.
updateMarginAfterForPreviousSibling(layoutBox);
}
IntrinsicWidthConstraints BlockFormattingContext::computedIntrinsicWidthConstraints()
{
auto& formattingState = this->formattingState();
ASSERT(!formattingState.intrinsicWidthConstraints());
// Visit the in-flow descendants and compute their min/max intrinsic width if needed.
// 1. Go all the way down to the leaf node
// 2. Check if actually need to visit all the boxes as we traverse down (already computed, container's min/max does not depend on descendants etc)
// 3. As we climb back on the tree, compute min/max intrinsic width
// (Any subtrees with new formatting contexts need to layout synchronously)
Vector<const ElementBox*> queue;
if (root().hasInFlowOrFloatingChild())
queue.append(downcast<ElementBox>(root().firstInFlowOrFloatingChild()));
IntrinsicWidthConstraints constraints;
auto maximumHorizontalStackingWidth = LayoutUnit { };
auto currentHorizontalStackingWidth = LayoutUnit { };
while (!queue.isEmpty()) {
while (true) {
// Check if we have to deal with descendant content.
auto& layoutBox = *queue.last();
// Float avoiders are all establish a new formatting context. No need to look inside them.
if (layoutBox.isFloatAvoider() && !layoutBox.hasFloatClear())
break;
// Non-floating block level boxes reset the current horizontal float stacking.
// SPEC: This is a bit odd as floating positioning is a formatting context level concept:
// e.g.
// <div style="float: left; width: 10px;"></div>
// <div></div>
// <div style="float: left; width: 40px;"></div>
// ...will produce a max width of 40px which makes the floats vertically stacked.
// Vertically stacked floats makes me think we haven't managed to provide the maximum preferred width for the content.
maximumHorizontalStackingWidth = std::max(currentHorizontalStackingWidth, maximumHorizontalStackingWidth);
currentHorizontalStackingWidth = { };
// Already has computed intrinsic constraints.
if (formattingState.intrinsicWidthConstraintsForBox(layoutBox))
break;
// Box with fixed width defines their descendant content intrinsic width.
if (layoutBox.style().width().isFixed())
break;
// Non-float avoider formatting context roots are opaque to intrinsic width computation.
if (layoutBox.establishesFormattingContext())
break;
// No relevant child content.
if (!layoutBox.hasInFlowOrFloatingChild())
break;
queue.append(downcast<ElementBox>(layoutBox.firstInFlowOrFloatingChild()));
}
// Compute min/max intrinsic width bottom up if needed.
while (!queue.isEmpty()) {
auto& layoutBox = *queue.takeLast();
auto desdendantConstraints = formattingState.intrinsicWidthConstraintsForBox(layoutBox);
if (!desdendantConstraints) {
desdendantConstraints = formattingGeometry().intrinsicWidthConstraints(layoutBox);
formattingState.setIntrinsicWidthConstraintsForBox(layoutBox, *desdendantConstraints);
}
constraints.minimum = std::max(constraints.minimum, desdendantConstraints->minimum);
auto willStackHorizontally = layoutBox.isFloatAvoider() && !layoutBox.hasFloatClear();
if (willStackHorizontally)
currentHorizontalStackingWidth += desdendantConstraints->maximum;
else
constraints.maximum = std::max(constraints.maximum, desdendantConstraints->maximum);
// Move over to the next sibling or take the next box in the queue.
if (auto* nextSibling = downcast<ElementBox>(layoutBox.nextInFlowOrFloatingSibling())) {
queue.append(nextSibling);
break;
}
}
}
maximumHorizontalStackingWidth = std::max(currentHorizontalStackingWidth, maximumHorizontalStackingWidth);
constraints.maximum = std::max(constraints.maximum, maximumHorizontalStackingWidth);
formattingState.setIntrinsicWidthConstraints(constraints);
return constraints;
}
LayoutUnit BlockFormattingContext::verticalPositionWithMargin(const ElementBox& layoutBox, const UsedVerticalMargin& verticalMargin, LayoutUnit containingBlockContentBoxTop) const
{
ASSERT(!layoutBox.isOutOfFlowPositioned());
// Now that we've computed the final margin before, let's shift the box's vertical position if needed.
// 1. Check if the box has clearance. If so, we've already precomputed/finalized the top value and vertical margin does not impact it anymore.
// 2. Check if the margin before collapses with the previous box's margin after. if not -> return previous box's bottom including margin after + marginBefore
// 3. Check if the previous box's margins collapse through. If not -> return previous box' bottom excluding margin after + marginBefore (they are supposed to be equal)
// 4. Go to previous box and start from step #1 until we hit the parent box.
auto& boxGeometry = geometryForBox(layoutBox);
if (formattingState().hasClearance(layoutBox))
return BoxGeometry::borderBoxTop(boxGeometry);
auto* currentLayoutBox = &layoutBox;
while (currentLayoutBox) {
if (!currentLayoutBox->previousInFlowSibling())
break;
auto& previousInFlowSibling = downcast<ElementBox>(*currentLayoutBox->previousInFlowSibling());
if (!marginCollapse().marginBeforeCollapsesWithPreviousSiblingMarginAfter(*currentLayoutBox)) {
auto& previousBoxGeometry = geometryForBox(previousInFlowSibling);
return BoxGeometry::marginBoxRect(previousBoxGeometry).bottom() + marginBefore(verticalMargin);
}
if (!marginCollapse().marginsCollapseThrough(previousInFlowSibling)) {
auto& previousBoxGeometry = geometryForBox(previousInFlowSibling);
return BoxGeometry::borderBoxRect(previousBoxGeometry).bottom() + marginBefore(verticalMargin);
}
currentLayoutBox = &previousInFlowSibling;
}
// Adjust vertical position depending whether this box directly or indirectly adjoins with its parent.
auto directlyAdjoinsParent = !layoutBox.previousInFlowSibling();
if (directlyAdjoinsParent) {
// If the top and bottom margins of a box are adjoining, then it is possible for margins to collapse through it.
// In this case, the position of the element depends on its relationship with the other elements whose margins are being collapsed.
if (verticalMargin.collapsedValues.isCollapsedThrough) {
// If the element's margins are collapsed with its parent's top margin, the top border edge of the box is defined to be the same as the parent's.
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(layoutBox))
return containingBlockContentBoxTop;
// Otherwise, either the element's parent is not taking part in the margin collapsing, or only the parent's bottom margin is involved.
// The position of the element's top border edge is the same as it would have been if the element had a non-zero bottom border.
auto beforeMarginWithBottomBorder = marginCollapse().marginBeforeIgnoringCollapsingThrough(layoutBox, verticalMargin.nonCollapsedValues);
return containingBlockContentBoxTop + beforeMarginWithBottomBorder;
}
// Non-collapsed through box vertical position depending whether the margin collapses.
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(layoutBox))
return containingBlockContentBoxTop;
return containingBlockContentBoxTop + marginBefore(verticalMargin);
}
// At this point this box indirectly (via collapsed through previous in-flow siblings) adjoins the parent. Let's check if it margin collapses with the parent.
auto& containingBlock = this->containingBlock(layoutBox);
ASSERT(containingBlock.firstInFlowChild());
ASSERT(containingBlock.firstInFlowChild() != &layoutBox);
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(downcast<ElementBox>(*containingBlock.firstInFlowChild())))
return containingBlockContentBoxTop;
return containingBlockContentBoxTop + marginBefore(verticalMargin);
}
void BlockFormattingContext::updateMarginAfterForPreviousSibling(const ElementBox& layoutBox)
{
auto marginCollapse = this->marginCollapse();
auto& formattingState = this->formattingState();
// 1. Get the margin before value from the next in-flow sibling. This is the same as this box's margin after value now since they are collapsed.
// 2. Update the collapsed margin after value as well as the positive/negative cache.
// 3. Check if the box's margins collapse through.
// 4. If so, update the positive/negative cache.
// 5. In case of collapsed through margins check if the before margin collapes with the previous inflow sibling's after margin.
// 6. If so, jump to #2.
// 7. No need to propagate to parent because its margin is not computed yet (pre-computed at most).
auto* currentBox = &layoutBox;
while (marginCollapse.marginBeforeCollapsesWithPreviousSiblingMarginAfter(*currentBox)) {
auto& previousSibling = *downcast<ElementBox>(currentBox->previousInFlowSibling());
auto previousSiblingVerticalMargin = formattingState.usedVerticalMargin(previousSibling);
auto collapsedVerticalMarginBefore = previousSiblingVerticalMargin.collapsedValues.before;
auto collapsedVerticalMarginAfter = geometryForBox(*currentBox).marginBefore();
auto marginsCollapseThrough = marginCollapse.marginsCollapseThrough(previousSibling);
if (marginsCollapseThrough)
collapsedVerticalMarginBefore = collapsedVerticalMarginAfter;
// Update positive/negative cache.
auto previousSiblingPositiveNegativeMargin = formattingState.usedVerticalMargin(previousSibling).positiveAndNegativeValues;
auto positiveNegativeMarginBefore = formattingState.usedVerticalMargin(*currentBox).positiveAndNegativeValues.before;
auto adjustedPreviousSiblingVerticalMargin = previousSiblingVerticalMargin;
adjustedPreviousSiblingVerticalMargin.positiveAndNegativeValues.after = marginCollapse.computedPositiveAndNegativeMargin(positiveNegativeMarginBefore, previousSiblingPositiveNegativeMargin.after);
if (marginsCollapseThrough) {
adjustedPreviousSiblingVerticalMargin.positiveAndNegativeValues.before = marginCollapse.computedPositiveAndNegativeMargin(previousSiblingPositiveNegativeMargin.before, adjustedPreviousSiblingVerticalMargin.positiveAndNegativeValues.after);
adjustedPreviousSiblingVerticalMargin.positiveAndNegativeValues.after = adjustedPreviousSiblingVerticalMargin.positiveAndNegativeValues.before;
}
formattingState.setUsedVerticalMargin(previousSibling, adjustedPreviousSiblingVerticalMargin);
if (!marginsCollapseThrough)
break;
currentBox = &previousSibling;
}
}
void BlockFormattingContext::computeBorderAndPadding(const Box& layoutBox, const HorizontalConstraints& horizontalConstraint)
{
auto& boxGeometry = formattingState().boxGeometry(layoutBox);
boxGeometry.setBorder(formattingGeometry().computedBorder(layoutBox));
boxGeometry.setPadding(formattingGeometry().computedPadding(layoutBox, horizontalConstraint.logicalWidth));
}
BlockMarginCollapse BlockFormattingContext::marginCollapse() const
{
return BlockMarginCollapse { layoutState(), formattingState() };
}
}
}
|