| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "core/layout/ng/ng_block_layout_algorithm.h" |
| |
| #include "core/layout/ng/ng_constraint_space.h" |
| #include "core/layout/ng/ng_fragment_builder.h" |
| #include "core/layout/ng/ng_fragment.h" |
| #include "core/layout/ng/ng_length_utils.h" |
| #include "core/layout/ng/ng_units.h" |
| #include "core/style/ComputedStyle.h" |
| #include "platform/LengthFunctions.h" |
| |
| namespace blink { |
| namespace { |
| |
| LayoutUnit ComputeCollapsedMarginBlockStart( |
| const NGMarginStrut& prev_margin_strut, |
| const NGMarginStrut& curr_margin_strut) { |
| return std::max(prev_margin_strut.margin_block_end, |
| curr_margin_strut.margin_block_start) - |
| std::max(prev_margin_strut.negative_margin_block_end.abs(), |
| curr_margin_strut.negative_margin_block_start.abs()); |
| } |
| |
| // Whether an in-flow block-level child creates a new formatting context. |
| // |
| // This will *NOT* check the following cases: |
| // - The child is out-of-flow, e.g. floating or abs-pos. |
| // - The child is a inline-level, e.g. "display: inline-block". |
| // - The child establishes a new formatting context, but should be a child of |
| // another layout algorithm, e.g. "display: table-caption" or flex-item. |
| bool IsNewFormattingContextForInFlowBlockLevelChild( |
| const NGConstraintSpace& space, |
| const ComputedStyle& style) { |
| // TODO(layout-dev): This doesn't capture a few cases which can't be computed |
| // directly from style yet: |
| // - The child is a <fieldset>. |
| // - "column-span: all" is set on the child (requires knowledge that we are |
| // in a multi-col formatting context). |
| // (https://drafts.csswg.org/css-multicol-1/#valdef-column-span-all) |
| |
| if (style.specifiesColumns() || style.containsPaint() || |
| style.containsLayout()) |
| return true; |
| |
| if (!style.isOverflowVisible()) |
| return true; |
| |
| EDisplay display = style.display(); |
| if (display == EDisplay::Grid || display == EDisplay::Flex || |
| display == EDisplay::Box) |
| return true; |
| |
| if (space.WritingMode() != FromPlatformWritingMode(style.getWritingMode())) |
| return true; |
| |
| return false; |
| } |
| |
| } // namespace |
| |
| NGBlockLayoutAlgorithm::NGBlockLayoutAlgorithm( |
| PassRefPtr<const ComputedStyle> style, |
| NGBox* first_child) |
| : style_(style), |
| first_child_(first_child), |
| state_(kStateInit), |
| is_fragment_margin_strut_block_start_updated_(false) { |
| DCHECK(style_); |
| } |
| |
| bool NGBlockLayoutAlgorithm::Layout(const NGConstraintSpace* constraint_space, |
| NGPhysicalFragment** out) { |
| switch (state_) { |
| case kStateInit: { |
| border_and_padding_ = |
| ComputeBorders(*style_) + ComputePadding(*constraint_space, *style_); |
| |
| LayoutUnit inline_size = |
| ComputeInlineSizeForFragment(*constraint_space, *style_); |
| LayoutUnit adjusted_inline_size = |
| inline_size - border_and_padding_.InlineSum(); |
| // TODO(layout-ng): For quirks mode, should we pass blockSize instead of |
| // -1? |
| LayoutUnit block_size = ComputeBlockSizeForFragment( |
| *constraint_space, *style_, NGSizeIndefinite); |
| LayoutUnit adjusted_block_size(block_size); |
| // Our calculated block-axis size may be indefinite at this point. |
| // If so, just leave the size as NGSizeIndefinite instead of subtracting |
| // borders and padding. |
| if (adjusted_block_size != NGSizeIndefinite) |
| adjusted_block_size -= border_and_padding_.BlockSum(); |
| constraint_space_for_children_ = new NGConstraintSpace( |
| FromPlatformWritingMode(style_->getWritingMode()), |
| FromPlatformDirection(style_->direction()), *constraint_space, |
| NGLogicalSize(adjusted_inline_size, adjusted_block_size)); |
| content_size_ = border_and_padding_.block_start; |
| |
| builder_ = new NGFragmentBuilder(NGPhysicalFragmentBase::FragmentBox); |
| builder_->SetDirection(constraint_space->Direction()); |
| builder_->SetWritingMode(constraint_space->WritingMode()); |
| builder_->SetInlineSize(inline_size).SetBlockSize(block_size); |
| current_child_ = first_child_; |
| state_ = kStateChildLayout; |
| return false; |
| } |
| case kStateChildLayout: { |
| if (current_child_) { |
| constraint_space_for_children_->SetIsNewFormattingContext( |
| IsNewFormattingContextForInFlowBlockLevelChild( |
| *constraint_space, *current_child_->Style())); |
| |
| NGFragment* fragment; |
| if (!current_child_->Layout(constraint_space_for_children_, &fragment)) |
| return false; |
| NGBoxStrut child_margins = ComputeMargins( |
| *constraint_space_for_children_, *current_child_->Style(), |
| constraint_space_for_children_->WritingMode(), |
| constraint_space_for_children_->Direction()); |
| ApplyAutoMargins(*constraint_space_for_children_, |
| *current_child_->Style(), *fragment, child_margins); |
| |
| const NGBoxStrut margins = |
| CollapseMargins(*constraint_space, child_margins, *fragment); |
| |
| // TODO(layout-ng): Support auto margins |
| builder_->AddChild( |
| fragment, NGLogicalOffset(border_and_padding_.inline_start + |
| child_margins.inline_start, |
| content_size_ + margins.block_start)); |
| |
| content_size_ += fragment->BlockSize() + margins.BlockSum(); |
| max_inline_size_ = |
| std::max(max_inline_size_, fragment->InlineSize() + |
| child_margins.InlineSum() + |
| border_and_padding_.InlineSum()); |
| current_child_ = current_child_->NextSibling(); |
| if (current_child_) |
| return false; |
| } |
| state_ = kStateFinalize; |
| return false; |
| } |
| case kStateFinalize: { |
| content_size_ += border_and_padding_.block_end; |
| |
| // Recompute the block-axis size now that we know our content size. |
| LayoutUnit block_size = ComputeBlockSizeForFragment( |
| *constraint_space, *style_, content_size_); |
| |
| builder_->SetBlockSize(block_size) |
| .SetInlineOverflow(max_inline_size_) |
| .SetBlockOverflow(content_size_); |
| *out = builder_->ToFragment(); |
| state_ = kStateInit; |
| return true; |
| } |
| }; |
| NOTREACHED(); |
| *out = nullptr; |
| return true; |
| } |
| |
| NGBoxStrut NGBlockLayoutAlgorithm::CollapseMargins( |
| const NGConstraintSpace& space, |
| const NGBoxStrut& margins, |
| const NGFragment& fragment) { |
| bool is_zero_height_box = !fragment.BlockSize() && margins.IsEmpty() && |
| fragment.MarginStrut().IsEmpty(); |
| // Create the current child's margin strut from its children's margin strut or |
| // use margin strut from the the last non-empty child. |
| NGMarginStrut curr_margin_strut = |
| is_zero_height_box ? prev_child_margin_strut_ : fragment.MarginStrut(); |
| |
| // Calculate borders and padding for the current child. |
| NGBoxStrut border_and_padding = |
| ComputeBorders(*current_child_->Style()) + |
| ComputePadding(space, *current_child_->Style()); |
| |
| // Collapse BLOCK-START margins if there is no padding or border between |
| // parent (current child) and its first in-flow child. |
| if (border_and_padding.block_start) { |
| curr_margin_strut.SetMarginBlockStart(margins.block_start); |
| } else { |
| curr_margin_strut.AppendMarginBlockStart(margins.block_start); |
| } |
| |
| // Collapse BLOCK-END margins if |
| // 1) there is no padding or border between parent (current child) and its |
| // first/last in-flow child |
| // 2) parent's logical height is auto. |
| if (current_child_->Style()->logicalHeight().isAuto() && |
| !border_and_padding.block_end) { |
| curr_margin_strut.AppendMarginBlockEnd(margins.block_end); |
| } else { |
| curr_margin_strut.SetMarginBlockEnd(margins.block_end); |
| } |
| |
| NGBoxStrut result_margins; |
| // Margins of the newly established formatting context do not participate |
| // in Collapsing Margins: |
| // - Compute margins block start for adjoining blocks *including* 1st block. |
| // - Compute margins block end for the last block. |
| // - Do not set the computed margins to the parent fragment. |
| if (space.IsNewFormattingContext()) { |
| result_margins.block_start = ComputeCollapsedMarginBlockStart( |
| prev_child_margin_strut_, curr_margin_strut); |
| bool is_last_child = !current_child_->NextSibling(); |
| if (is_last_child) |
| result_margins.block_end = curr_margin_strut.BlockEndSum(); |
| return result_margins; |
| } |
| |
| // Zero-height boxes are ignored and do not participate in margin collapsing. |
| if (is_zero_height_box) |
| return result_margins; |
| |
| // Compute the margin block start for adjoining blocks *excluding* 1st block |
| if (is_fragment_margin_strut_block_start_updated_) { |
| result_margins.block_start = ComputeCollapsedMarginBlockStart( |
| prev_child_margin_strut_, curr_margin_strut); |
| } |
| |
| // Update the parent fragment's margin strut |
| UpdateMarginStrut(curr_margin_strut); |
| |
| prev_child_margin_strut_ = curr_margin_strut; |
| return result_margins; |
| } |
| |
| void NGBlockLayoutAlgorithm::UpdateMarginStrut(const NGMarginStrut& from) { |
| if (!is_fragment_margin_strut_block_start_updated_) { |
| builder_->SetMarginStrutBlockStart(from); |
| is_fragment_margin_strut_block_start_updated_ = true; |
| } |
| builder_->SetMarginStrutBlockEnd(from); |
| } |
| |
| } // namespace blink |