| /* |
| * 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 "FloatingContext.h" |
| |
| #if ENABLE(LAYOUT_FORMATTING_CONTEXT) |
| |
| #include "DisplayBox.h" |
| #include "FloatAvoider.h" |
| #include "FloatBox.h" |
| #include "LayoutBox.h" |
| #include "LayoutContainer.h" |
| #include "LayoutState.h" |
| #include <wtf/IsoMallocInlines.h> |
| |
| namespace WebCore { |
| namespace Layout { |
| |
| WTF_MAKE_ISO_ALLOCATED_IMPL(FloatingContext); |
| |
| // Finding the top/left position for a new floating(F) |
| // ____ ____ _____ _______ |
| // | || L2 || | <-----1---->| | |
| // | ||____|| L3 | | R1 | |
| // | L1 | |_____| | | |
| // |____| <-------------2--------->| | |
| // | | |
| // |_______| |
| // |
| // 1. Compute the initial vertical position for (F) -> (1) |
| // 2. Find the corresponding floating pair (L3-R1) |
| // 3. Align (F) horizontally with (L3-R1) depending whether (F) is left/right positioned |
| // 4. Intersect (F) with (L3-R1) |
| // 5. If (F) does not fit, find the next floating pair (L1-R1) |
| // 6. Repeat until either (F) fits/no more floats. |
| // Note that all coordinates are in the coordinate system of the formatting root. |
| // The formatting root here is always the one that establishes the floating context (see inherited floating context). |
| // (It simply means that the float box's formatting root is not necessarily the same as the FormattingContext's root.) |
| |
| class Iterator; |
| |
| class FloatPair { |
| public: |
| struct LeftRightIndex { |
| bool isEmpty() const { return !left && !right;} |
| |
| Optional<unsigned> left; |
| Optional<unsigned> right; |
| }; |
| |
| bool isEmpty() const { return m_floatPair.isEmpty(); } |
| const FloatingState::FloatItem* left() const; |
| const FloatingState::FloatItem* right() const; |
| bool intersects(const Display::Rect&) const; |
| PositionInContextRoot verticalConstraint() const { return m_verticalPosition; } |
| FloatAvoider::HorizontalConstraints horizontalConstraints() const; |
| PositionInContextRoot bottom() const; |
| LeftRightIndex operator*() const { return m_floatPair; }; |
| bool operator==(const FloatPair&) const; |
| |
| private: |
| friend class Iterator; |
| FloatPair(const FloatingState::FloatList&); |
| |
| const FloatingState::FloatList& m_floats; |
| LeftRightIndex m_floatPair; |
| PositionInContextRoot m_verticalPosition; |
| }; |
| |
| class Iterator { |
| public: |
| Iterator(const FloatingState::FloatList&, Optional<PositionInContextRoot> verticalPosition); |
| |
| const FloatPair& operator*() const { return m_current; } |
| Iterator& operator++(); |
| bool operator==(const Iterator&) const; |
| bool operator!=(const Iterator&) const; |
| |
| private: |
| void set(PositionInContextRoot verticalPosition); |
| |
| const FloatingState::FloatList& m_floats; |
| FloatPair m_current; |
| }; |
| |
| static Iterator begin(const FloatingState::FloatList& floats, PositionInContextRoot initialVerticalPosition) |
| { |
| // Start with the inner-most floating pair for the initial vertical position. |
| return Iterator(floats, initialVerticalPosition); |
| } |
| |
| static Iterator end(const FloatingState::FloatList& floats) |
| { |
| return Iterator(floats, { }); |
| } |
| |
| #ifndef NDEBUG |
| static bool areFloatsHorizontallySorted(const FloatingState& floatingState) |
| { |
| auto& floats = floatingState.floats(); |
| auto rightEdgeOfLeftFloats = LayoutUnit::min(); |
| auto leftEdgeOfRightFloats = LayoutUnit::max(); |
| WTF::Optional<LayoutUnit> leftBottom; |
| WTF::Optional<LayoutUnit> rightBottom; |
| |
| for (auto& floatItem : floats) { |
| if (floatItem.isLeftPositioned()) { |
| auto rightEdge = floatItem.rectWithMargin().right(); |
| if (rightEdge < rightEdgeOfLeftFloats) { |
| if (leftBottom && floatItem.rectWithMargin().top() < *leftBottom) |
| return false; |
| } |
| leftBottom = floatItem.rectWithMargin().bottom(); |
| rightEdgeOfLeftFloats = rightEdge; |
| } else { |
| auto leftEdge = floatItem.rectWithMargin().left(); |
| if (leftEdge > leftEdgeOfRightFloats) { |
| if (rightBottom && floatItem.rectWithMargin().top() < *rightBottom) |
| return false; |
| } |
| rightBottom = floatItem.rectWithMargin().bottom(); |
| leftEdgeOfRightFloats = leftEdge; |
| } |
| } |
| return true; |
| } |
| #endif |
| |
| FloatingContext::FloatingContext(FloatingState& floatingState) |
| : m_floatingState(floatingState) |
| { |
| } |
| |
| Point FloatingContext::positionForFloat(const Box& layoutBox) const |
| { |
| ASSERT(layoutBox.isFloatingPositioned()); |
| ASSERT(areFloatsHorizontallySorted(m_floatingState)); |
| |
| if (m_floatingState.isEmpty()) { |
| auto& displayBox = layoutState().displayBoxForLayoutBox(layoutBox); |
| |
| auto alignWithContainingBlock = [&]() -> Position { |
| // If there is no floating to align with, push the box to the left/right edge of its containing block's content box. |
| auto& containingBlockDisplayBox = layoutState().displayBoxForLayoutBox(*layoutBox.containingBlock()); |
| |
| if (layoutBox.isLeftFloatingPositioned()) |
| return Position { containingBlockDisplayBox.contentBoxLeft() + displayBox.marginStart() }; |
| |
| return Position { containingBlockDisplayBox.contentBoxRight() - displayBox.marginEnd() - displayBox.width() }; |
| }; |
| |
| // No float box on the context yet -> align it with the containing block's left/right edge. |
| return { alignWithContainingBlock(), displayBox.top() }; |
| } |
| |
| // Find the top most position where the float box fits. |
| FloatBox floatBox = { layoutBox, m_floatingState, layoutState() }; |
| findPositionForFloatBox(floatBox); |
| return floatBox.rectInContainingBlock().topLeft(); |
| } |
| |
| Optional<Point> FloatingContext::positionForFormattingContextRoot(const Box& layoutBox) const |
| { |
| ASSERT(layoutBox.establishesBlockFormattingContext()); |
| ASSERT(!layoutBox.isFloatingPositioned()); |
| ASSERT(!layoutBox.hasFloatClear()); |
| ASSERT(areFloatsHorizontallySorted(m_floatingState)); |
| |
| if (m_floatingState.isEmpty()) |
| return { }; |
| |
| FloatAvoider floatAvoider = { layoutBox, m_floatingState, layoutState() }; |
| findPositionForFormattingContextRoot(floatAvoider); |
| return { floatAvoider.rectInContainingBlock().topLeft() }; |
| } |
| |
| FloatingContext::ClearancePosition FloatingContext::verticalPositionWithClearance(const Box& layoutBox) const |
| { |
| ASSERT(layoutBox.hasFloatClear()); |
| ASSERT(layoutBox.isBlockLevelBox()); |
| ASSERT(areFloatsHorizontallySorted(m_floatingState)); |
| |
| if (m_floatingState.isEmpty()) |
| return { }; |
| |
| auto bottom = [&](Optional<PositionInContextRoot> floatBottom) -> ClearancePosition { |
| // 'bottom' is in the formatting root's coordinate system. |
| if (!floatBottom) |
| return { }; |
| |
| // 9.5.2 Controlling flow next to floats: the 'clear' property |
| // Then the amount of clearance is set to the greater of: |
| // |
| // 1. The amount necessary to place the border edge of the block even with the bottom outer edge of the lowest float that is to be cleared. |
| // 2. The amount necessary to place the top border edge of the block at its hypothetical position. |
| auto& layoutState = this->layoutState(); |
| auto rootRelativeTop = FormattingContext::mapTopToAncestor(layoutState, layoutBox, downcast<Container>(m_floatingState.root())); |
| auto clearance = *floatBottom - rootRelativeTop; |
| if (clearance <= 0) |
| return { }; |
| |
| // Clearance inhibits margin collapsing. |
| if (auto* previousInFlowSibling = layoutBox.previousInFlowSibling()) { |
| // Does this box with clearance actually collapse its margin before with the previous inflow box's margin after? |
| auto verticalMargin = layoutState.displayBoxForLayoutBox(layoutBox).verticalMargin(); |
| if (verticalMargin.hasCollapsedValues() && verticalMargin.collapsedValues().before) { |
| auto previousVerticalMargin = layoutState.displayBoxForLayoutBox(*previousInFlowSibling).verticalMargin(); |
| auto collapsedMargin = *verticalMargin.collapsedValues().before; |
| auto nonCollapsedMargin = previousVerticalMargin.after() + verticalMargin.before(); |
| auto marginDifference = nonCollapsedMargin - collapsedMargin; |
| // Move the box to the position where it would be with non-collapsed margins. |
| rootRelativeTop += marginDifference; |
| // Having negative clearance is also normal. It just means that the box with the non-collapsed margins is now lower than it needs to be. |
| clearance -= marginDifference; |
| } |
| } |
| // Now adjust the box's position with the clearance. |
| rootRelativeTop += clearance; |
| ASSERT(*floatBottom == rootRelativeTop); |
| |
| // The return vertical position is in the containing block's coordinate system. Convert it to the formatting root's coordinate system if needed. |
| if (layoutBox.containingBlock() == &m_floatingState.root()) |
| return { Position { rootRelativeTop }, clearance }; |
| |
| auto containingBlockRootRelativeTop = FormattingContext::mapTopToAncestor(layoutState, *layoutBox.containingBlock(), downcast<Container>(m_floatingState.root())); |
| return { Position { rootRelativeTop - containingBlockRootRelativeTop }, clearance }; |
| }; |
| |
| auto clear = layoutBox.style().clear(); |
| auto& formattingContextRoot = layoutBox.formattingContextRoot(); |
| |
| if (clear == Clear::Left) |
| return bottom(m_floatingState.leftBottom(formattingContextRoot)); |
| |
| if (clear == Clear::Right) |
| return bottom(m_floatingState.rightBottom(formattingContextRoot)); |
| |
| if (clear == Clear::Both) |
| return bottom(m_floatingState.bottom(formattingContextRoot)); |
| |
| ASSERT_NOT_REACHED(); |
| return { }; |
| } |
| |
| static FloatPair::LeftRightIndex findAvailablePosition(FloatAvoider& floatAvoider, const FloatingState::FloatList& floats) |
| { |
| Optional<PositionInContextRoot> bottomMost; |
| Optional<FloatPair::LeftRightIndex> innerMostLeftAndRight; |
| auto end = Layout::end(floats); |
| for (auto iterator = begin(floats, { floatAvoider.rect().top() }); iterator != end; ++iterator) { |
| ASSERT(!(*iterator).isEmpty()); |
| auto leftRightFloatPair = *iterator; |
| innerMostLeftAndRight = innerMostLeftAndRight.valueOr(*leftRightFloatPair); |
| |
| // Move the box horizontally so that it either |
| // 1. aligns with the current floating pair |
| // 2. or with the containing block's content box if there's no float to align with at this vertical position. |
| floatAvoider.setHorizontalConstraints(leftRightFloatPair.horizontalConstraints()); |
| floatAvoider.setVerticalConstraint(leftRightFloatPair.verticalConstraint()); |
| |
| // Ensure that the float avoider |
| // 1. does not "overflow" its containing block with the current horiztonal constraints. It simply means that the float avoider's |
| // containing block could push the candidate position beyond the current float horizontally (too far to the left/right) |
| // 2. avoids floats on both sides. |
| if (!floatAvoider.overflowsContainingBlock() && !leftRightFloatPair.intersects(floatAvoider.rect())) |
| return *innerMostLeftAndRight; |
| |
| bottomMost = leftRightFloatPair.bottom(); |
| // Move to the next floating pair. |
| } |
| |
| // The candidate box is already below of all the floats. |
| if (!bottomMost) |
| return { }; |
| |
| // Passed all the floats and still does not fit? Push it below the last float. |
| floatAvoider.setVerticalConstraint(*bottomMost); |
| floatAvoider.setHorizontalConstraints({ }); |
| ASSERT(innerMostLeftAndRight); |
| return *innerMostLeftAndRight; |
| } |
| |
| void FloatingContext::findPositionForFloatBox(FloatBox& floatBox) const |
| { |
| findAvailablePosition(floatBox, m_floatingState.floats()); |
| } |
| |
| void FloatingContext::findPositionForFormattingContextRoot(FloatAvoider& floatAvoider) const |
| { |
| // A non-floating formatting root's initial vertical position is its static position. |
| // It means that such boxes can end up vertically placed in-between existing floats (which is |
| // never the case for floats, since they cannot be placed above existing floats). |
| // ____ ____ |
| // | || F1 | |
| // | L1 | ---- |
| // | | ________ |
| // ---- | R1 | |
| // -------- |
| // Document order: 1. float: left (L1) 2. float: right (R1) 3. formatting root (F1) |
| // |
| // 1. Probe for available placement at initial position (note it runs a backward probing algorithm at a specific vertical position) |
| // 2. Check if there's any intersecing float below (forward seaching) |
| // 3. Align the box with the intersected float and probe for placement again (#1). |
| auto& floats = m_floatingState.floats(); |
| while (true) { |
| auto innerMostLeftAndRight = findAvailablePosition(floatAvoider, floats); |
| if (innerMostLeftAndRight.isEmpty()) |
| return; |
| |
| auto overlappingFloatBox = [&floats](auto startFloatIndex, auto floatAvoiderRect) -> const FloatingState::FloatItem* { |
| for (auto i = startFloatIndex; i < floats.size(); ++i) { |
| auto& floatBox = floats[i]; |
| if (floatBox.rectWithMargin().intersects(floatAvoiderRect)) |
| return &floatBox; |
| } |
| return nullptr; |
| }; |
| |
| auto startIndex = std::max(innerMostLeftAndRight.left.valueOr(0), innerMostLeftAndRight.right.valueOr(0)) + 1; |
| auto* intersectedFloatBox = overlappingFloatBox(startIndex, floatAvoider.rect()); |
| if (!intersectedFloatBox) |
| return; |
| floatAvoider.setVerticalConstraint({ intersectedFloatBox->rectWithMargin().top() }); |
| } |
| } |
| |
| FloatPair::FloatPair(const FloatingState::FloatList& floats) |
| : m_floats(floats) |
| { |
| } |
| |
| const FloatingState::FloatItem* FloatPair::left() const |
| { |
| if (!m_floatPair.left) |
| return nullptr; |
| |
| ASSERT(m_floats[*m_floatPair.left].isLeftPositioned()); |
| return &m_floats[*m_floatPair.left]; |
| } |
| |
| const FloatingState::FloatItem* FloatPair::right() const |
| { |
| if (!m_floatPair.right) |
| return nullptr; |
| |
| ASSERT(!m_floats[*m_floatPair.right].isLeftPositioned()); |
| return &m_floats[*m_floatPair.right]; |
| } |
| |
| bool FloatPair::intersects(const Display::Rect& floatAvoiderRect) const |
| { |
| auto intersects = [&](auto* floating) { |
| return floating && floating->rectWithMargin().intersects(floatAvoiderRect); |
| }; |
| |
| ASSERT(!m_floatPair.isEmpty()); |
| return intersects(left()) || intersects(right()); |
| } |
| |
| bool FloatPair::operator ==(const FloatPair& other) const |
| { |
| return m_floatPair.left == other.m_floatPair.left && m_floatPair.right == other.m_floatPair.right; |
| } |
| |
| FloatAvoider::HorizontalConstraints FloatPair::horizontalConstraints() const |
| { |
| Optional<PositionInContextRoot> leftEdge; |
| Optional<PositionInContextRoot> rightEdge; |
| |
| if (left()) |
| leftEdge = PositionInContextRoot { left()->rectWithMargin().right() }; |
| |
| if (right()) |
| rightEdge = PositionInContextRoot { right()->rectWithMargin().left() }; |
| |
| return { leftEdge, rightEdge }; |
| } |
| |
| PositionInContextRoot FloatPair::bottom() const |
| { |
| auto* left = this->left(); |
| auto* right = this->right(); |
| ASSERT(left || right); |
| |
| auto leftBottom = left ? Optional<PositionInContextRoot>(PositionInContextRoot { left->rectWithMargin().bottom() }) : WTF::nullopt; |
| auto rightBottom = right ? Optional<PositionInContextRoot>(PositionInContextRoot { right->rectWithMargin().bottom() }) : WTF::nullopt; |
| |
| if (leftBottom && rightBottom) |
| return std::max(*leftBottom, *rightBottom); |
| |
| if (leftBottom) |
| return *leftBottom; |
| |
| return *rightBottom; |
| } |
| |
| Iterator::Iterator(const FloatingState::FloatList& floats, Optional<PositionInContextRoot> verticalPosition) |
| : m_floats(floats) |
| , m_current(floats) |
| { |
| if (verticalPosition) |
| set(*verticalPosition); |
| } |
| |
| inline static Optional<unsigned> previousFloatingIndex(Float floatingType, const FloatingState::FloatList& floats, unsigned currentIndex) |
| { |
| RELEASE_ASSERT(currentIndex <= floats.size()); |
| |
| while (currentIndex) { |
| auto& floating = floats[--currentIndex]; |
| if ((floatingType == Float::Left && floating.isLeftPositioned()) || (floatingType == Float::Right && !floating.isLeftPositioned())) |
| return currentIndex; |
| } |
| |
| return { }; |
| } |
| |
| Iterator& Iterator::operator++() |
| { |
| if (m_current.isEmpty()) { |
| ASSERT_NOT_REACHED(); |
| return *this; |
| } |
| |
| auto findPreviousFloatingWithLowerBottom = [&](Float floatingType, unsigned currentIndex) -> Optional<unsigned> { |
| |
| RELEASE_ASSERT(currentIndex < m_floats.size()); |
| |
| // Last floating? There's certainly no previous floating at this point. |
| if (!currentIndex) |
| return { }; |
| |
| auto currentBottom = m_floats[currentIndex].rectWithMargin().bottom(); |
| |
| Optional<unsigned> index = currentIndex; |
| while (true) { |
| index = previousFloatingIndex(floatingType, m_floats, *index); |
| if (!index) |
| return { }; |
| |
| if (m_floats[*index].rectWithMargin().bottom() > currentBottom) |
| return index; |
| } |
| |
| ASSERT_NOT_REACHED(); |
| return { }; |
| }; |
| |
| // 1. Take the current floating from left and right and check which one's bottom edge is positioned higher (they could be on the same vertical position too). |
| // The current floats from left and right are considered the inner-most pair for the current vertical position. |
| // 2. Move away from inner-most pair by picking one of the previous floats in the list(#1) |
| // Ensure that the new floating's bottom edge is positioned lower than the current one -which essentially means skipping in-between floats that are positioned higher). |
| // 3. Reset the vertical position and align it with the new left-right pair. These floats are now the inner-most boxes for the current vertical position. |
| // As the result we have more horizontal space on the current vertical position. |
| auto leftBottom = m_current.left() ? Optional<PositionInContextRoot>(m_current.left()->bottom()) : WTF::nullopt; |
| auto rightBottom = m_current.right() ? Optional<PositionInContextRoot>(m_current.right()->bottom()) : WTF::nullopt; |
| |
| auto updateLeft = (leftBottom == rightBottom) || (!rightBottom || (leftBottom && leftBottom < rightBottom)); |
| auto updateRight = (leftBottom == rightBottom) || (!leftBottom || (rightBottom && leftBottom > rightBottom)); |
| |
| if (updateLeft) { |
| ASSERT(m_current.m_floatPair.left); |
| m_current.m_verticalPosition = *leftBottom; |
| m_current.m_floatPair.left = findPreviousFloatingWithLowerBottom(Float::Left, *m_current.m_floatPair.left); |
| } |
| |
| if (updateRight) { |
| ASSERT(m_current.m_floatPair.right); |
| m_current.m_verticalPosition = *rightBottom; |
| m_current.m_floatPair.right = findPreviousFloatingWithLowerBottom(Float::Right, *m_current.m_floatPair.right); |
| } |
| |
| return *this; |
| } |
| |
| void Iterator::set(PositionInContextRoot verticalPosition) |
| { |
| // Move the iterator to the initial vertical position by starting at the inner-most floating pair (last floats on left/right). |
| // 1. Check if the inner-most pair covers the vertical position. |
| // 2. Move outwards from the inner-most pair until the vertical postion intersects. |
| m_current.m_verticalPosition = verticalPosition; |
| // No floats at all? |
| if (m_floats.isEmpty()) { |
| ASSERT_NOT_REACHED(); |
| m_current.m_floatPair = { }; |
| return; |
| } |
| |
| auto findFloatingBelow = [&](Float floatingType) -> Optional<unsigned> { |
| |
| ASSERT(!m_floats.isEmpty()); |
| |
| auto index = floatingType == Float::Left ? m_current.m_floatPair.left : m_current.m_floatPair.right; |
| // Start from the end if we don't have current yet. |
| index = index.valueOr(m_floats.size()); |
| while (true) { |
| index = previousFloatingIndex(floatingType, m_floats, *index); |
| if (!index) |
| return { }; |
| |
| // Is this floating intrusive on this position? |
| auto rect = m_floats[*index].rectWithMargin(); |
| if (rect.top() <= verticalPosition && rect.bottom() > verticalPosition) |
| return index; |
| } |
| |
| return { }; |
| }; |
| |
| m_current.m_floatPair.left = findFloatingBelow(Float::Left); |
| m_current.m_floatPair.right = findFloatingBelow(Float::Right); |
| |
| ASSERT(!m_current.m_floatPair.left || (*m_current.m_floatPair.left < m_floats.size() && m_floats[*m_current.m_floatPair.left].isLeftPositioned())); |
| ASSERT(!m_current.m_floatPair.right || (*m_current.m_floatPair.right < m_floats.size() && !m_floats[*m_current.m_floatPair.right].isLeftPositioned())); |
| } |
| |
| bool Iterator::operator==(const Iterator& other) const |
| { |
| return m_current == other.m_current; |
| } |
| |
| bool Iterator::operator!=(const Iterator& other) const |
| { |
| return !(*this == other); |
| } |
| |
| } |
| } |
| #endif |
