/* * Copyright (c) 2020, Andreas Kling * 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT HOLDER OR 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 #include #include #include #include #include #include #include #include #include namespace Web::Layout { BlockFormattingContext::BlockFormattingContext(Box& context_box, FormattingContext* parent) : FormattingContext(context_box, parent) { } BlockFormattingContext::~BlockFormattingContext() { } bool BlockFormattingContext::is_initial() const { return is(context_box()); } void BlockFormattingContext::run(Box& box, LayoutMode layout_mode) { if (is_initial()) { layout_initial_containing_block(layout_mode); return; } // FIXME: BFC currently computes the width+height of the target box. // This is necessary to be able to place absolutely positioned descendants. // The same work is also done by the parent BFC for each of its blocks.. if (layout_mode == LayoutMode::Default) compute_width(box); if (box.children_are_inline()) { layout_inline_children(box, layout_mode); } else { layout_block_level_children(box, layout_mode); } if (layout_mode == LayoutMode::Default) { compute_height(box); box.for_each_child_of_type([&](auto& child_box) { if (child_box.is_absolutely_positioned()) { layout_absolutely_positioned_element(child_box); } return IterationDecision::Continue; }); } } void BlockFormattingContext::compute_width(Box& box) { if (box.is_absolutely_positioned()) { compute_width_for_absolutely_positioned_element(box); return; } if (is(box)) { // FIXME: This should not be done *by* ReplacedBox auto& replaced = downcast(box); replaced.prepare_for_replaced_layout(); compute_width_for_block_level_replaced_element_in_normal_flow(replaced); return; } if (box.is_floating()) { compute_width_for_floating_box(box); return; } auto& computed_values = box.computed_values(); float width_of_containing_block = box.width_of_logical_containing_block(); auto zero_value = CSS::Length::make_px(0); auto margin_left = CSS::Length::make_auto(); auto margin_right = CSS::Length::make_auto(); const auto padding_left = computed_values.padding().left.resolved_or_zero(box, width_of_containing_block); const auto padding_right = computed_values.padding().right.resolved_or_zero(box, width_of_containing_block); auto try_compute_width = [&](const auto& a_width) { CSS::Length width = a_width; margin_left = computed_values.margin().left.resolved_or_zero(box, width_of_containing_block); margin_right = computed_values.margin().right.resolved_or_zero(box, width_of_containing_block); float total_px = computed_values.border_left().width + computed_values.border_right().width; for (auto& value : { margin_left, padding_left, width, padding_right, margin_right }) { total_px += value.to_px(box); } if (!box.is_inline()) { // 10.3.3 Block-level, non-replaced elements in normal flow // If 'width' is not 'auto' and 'border-left-width' + 'padding-left' + 'width' + 'padding-right' + 'border-right-width' (plus any of 'margin-left' or 'margin-right' that are not 'auto') is larger than the width of the containing block, then any 'auto' values for 'margin-left' or 'margin-right' are, for the following rules, treated as zero. if (width.is_auto() && total_px > width_of_containing_block) { if (margin_left.is_auto()) margin_left = zero_value; if (margin_right.is_auto()) margin_right = zero_value; } // 10.3.3 cont'd. auto underflow_px = width_of_containing_block - total_px; if (width.is_auto()) { if (margin_left.is_auto()) margin_left = zero_value; if (margin_right.is_auto()) margin_right = zero_value; if (underflow_px >= 0) { width = CSS::Length(underflow_px, CSS::Length::Type::Px); } else { width = zero_value; margin_right = CSS::Length(margin_right.to_px(box) + underflow_px, CSS::Length::Type::Px); } } else { if (!margin_left.is_auto() && !margin_right.is_auto()) { margin_right = CSS::Length(margin_right.to_px(box) + underflow_px, CSS::Length::Type::Px); } else if (!margin_left.is_auto() && margin_right.is_auto()) { margin_right = CSS::Length(underflow_px, CSS::Length::Type::Px); } else if (margin_left.is_auto() && !margin_right.is_auto()) { margin_left = CSS::Length(underflow_px, CSS::Length::Type::Px); } else { // margin_left.is_auto() && margin_right.is_auto() auto half_of_the_underflow = CSS::Length(underflow_px / 2, CSS::Length::Type::Px); margin_left = half_of_the_underflow; margin_right = half_of_the_underflow; } } } else if (box.is_inline_block()) { // 10.3.9 'Inline-block', non-replaced elements in normal flow // A computed value of 'auto' for 'margin-left' or 'margin-right' becomes a used value of '0'. if (margin_left.is_auto()) margin_left = zero_value; if (margin_right.is_auto()) margin_right = zero_value; // If 'width' is 'auto', the used value is the shrink-to-fit width as for floating elements. if (width.is_auto()) { // Find the available width: in this case, this is the width of the containing // block minus the used values of 'margin-left', 'border-left-width', 'padding-left', // 'padding-right', 'border-right-width', 'margin-right', and the widths of any relevant scroll bars. float available_width = width_of_containing_block - margin_left.to_px(box) - computed_values.border_left().width - padding_left.to_px(box) - padding_right.to_px(box) - computed_values.border_right().width - margin_right.to_px(box); auto result = calculate_shrink_to_fit_widths(box); // Then the shrink-to-fit width is: min(max(preferred minimum width, available width), preferred width). width = CSS::Length(min(max(result.preferred_minimum_width, available_width), result.preferred_width), CSS::Length::Type::Px); } } return width; }; auto specified_width = computed_values.width().resolved_or_auto(box, width_of_containing_block); // 1. The tentative used width is calculated (without 'min-width' and 'max-width') auto used_width = try_compute_width(specified_width); // 2. The tentative used width is greater than 'max-width', the rules above are applied again, // but this time using the computed value of 'max-width' as the computed value for 'width'. auto specified_max_width = computed_values.max_width().resolved_or_auto(box, width_of_containing_block); if (!specified_max_width.is_auto()) { if (used_width.to_px(box) > specified_max_width.to_px(box)) { used_width = try_compute_width(specified_max_width); } } // 3. If the resulting width is smaller than 'min-width', the rules above are applied again, // but this time using the value of 'min-width' as the computed value for 'width'. auto specified_min_width = computed_values.min_width().resolved_or_auto(box, width_of_containing_block); if (!specified_min_width.is_auto()) { if (used_width.to_px(box) < specified_min_width.to_px(box)) { used_width = try_compute_width(specified_min_width); } } box.set_width(used_width.to_px(box)); box.box_model().margin.left = margin_left.to_px(box); box.box_model().margin.right = margin_right.to_px(box); box.box_model().border.left = computed_values.border_left().width; box.box_model().border.right = computed_values.border_right().width; box.box_model().padding.left = padding_left.to_px(box); box.box_model().padding.right = padding_right.to_px(box); } void BlockFormattingContext::compute_width_for_floating_box(Box& box) { // 10.3.5 Floating, non-replaced elements auto& computed_values = box.computed_values(); float width_of_containing_block = box.width_of_logical_containing_block(); auto zero_value = CSS::Length::make_px(0); auto margin_left = CSS::Length::make_auto(); auto margin_right = CSS::Length::make_auto(); const auto padding_left = computed_values.padding().left.resolved_or_zero(box, width_of_containing_block); const auto padding_right = computed_values.padding().right.resolved_or_zero(box, width_of_containing_block); // If 'margin-left', or 'margin-right' are computed as 'auto', their used value is '0'. if (margin_left.is_auto()) margin_left = zero_value; if (margin_right.is_auto()) margin_right = zero_value; auto width = computed_values.width().resolved_or_auto(box, width_of_containing_block); // If 'width' is computed as 'auto', the used value is the "shrink-to-fit" width. if (width.is_auto()) { // Find the available width: in this case, this is the width of the containing // block minus the used values of 'margin-left', 'border-left-width', 'padding-left', // 'padding-right', 'border-right-width', 'margin-right', and the widths of any relevant scroll bars. float available_width = width_of_containing_block - margin_left.to_px(box) - computed_values.border_left().width - padding_left.to_px(box) - padding_right.to_px(box) - computed_values.border_right().width - margin_right.to_px(box); auto result = calculate_shrink_to_fit_widths(box); // Then the shrink-to-fit width is: min(max(preferred minimum width, available width), preferred width). width = CSS::Length(min(max(result.preferred_minimum_width, available_width), result.preferred_width), CSS::Length::Type::Px); } float final_width = width.resolved_or_zero(box, width_of_containing_block).to_px(box); box.set_width(final_width); } void BlockFormattingContext::compute_width_for_block_level_replaced_element_in_normal_flow(ReplacedBox& box) { box.set_width(compute_width_for_replaced_element(box)); } void BlockFormattingContext::compute_height_for_block_level_replaced_element_in_normal_flow(ReplacedBox& box) { box.set_height(compute_height_for_replaced_element(box)); } void BlockFormattingContext::compute_height(Box& box) { if (is(box)) { compute_height_for_block_level_replaced_element_in_normal_flow(downcast(box)); return; } auto& computed_values = box.computed_values(); auto& containing_block = *box.containing_block(); CSS::Length specified_height; if (computed_values.height().is_percentage() && !containing_block.computed_values().height().is_absolute()) { specified_height = CSS::Length::make_auto(); } else { specified_height = computed_values.height().resolved_or_auto(box, containing_block.height()); } auto specified_max_height = computed_values.max_height().resolved_or_auto(box, containing_block.height()); box.box_model().margin.top = computed_values.margin().top.resolved_or_zero(box, containing_block.width()).to_px(box); box.box_model().margin.bottom = computed_values.margin().bottom.resolved_or_zero(box, containing_block.width()).to_px(box); box.box_model().border.top = computed_values.border_top().width; box.box_model().border.bottom = computed_values.border_bottom().width; box.box_model().padding.top = computed_values.padding().top.resolved_or_zero(box, containing_block.width()).to_px(box); box.box_model().padding.bottom = computed_values.padding().bottom.resolved_or_zero(box, containing_block.width()).to_px(box); if (!specified_height.is_auto()) { float used_height = specified_height.to_px(box); if (!specified_max_height.is_auto()) used_height = min(used_height, specified_max_height.to_px(box)); box.set_height(used_height); } } void BlockFormattingContext::layout_inline_children(Box& box, LayoutMode layout_mode) { InlineFormattingContext context(box, this); context.run(box, layout_mode); } void BlockFormattingContext::layout_block_level_children(Box& box, LayoutMode layout_mode) { float content_height = 0; float content_width = 0; box.for_each_child_of_type([&](auto& child_box) { if (child_box.is_absolutely_positioned()) return IterationDecision::Continue; if (child_box.is_floating()) { layout_floating_child(child_box, box); return IterationDecision::Continue; } compute_width(child_box); layout_inside(child_box, layout_mode); compute_height(child_box); if (is(child_box)) place_block_level_replaced_element_in_normal_flow(child_box, box); else if (is(child_box)) place_block_level_non_replaced_element_in_normal_flow(child_box, box); // FIXME: This should be factored differently. It's uncool that we mutate the tree *during* layout! // Instead, we should generate the marker box during the tree build. if (is(child_box)) downcast(child_box).layout_marker(); content_height = max(content_height, child_box.effective_offset().y() + child_box.height() + child_box.box_model().margin_box().bottom); content_width = max(content_width, downcast(child_box).width()); return IterationDecision::Continue; }); if (layout_mode != LayoutMode::Default) { if (box.computed_values().width().is_undefined() || box.computed_values().width().is_auto()) box.set_width(content_width); } if (box.computed_values().height().is_undefined_or_auto()) box.set_height(content_height); else box.set_height(box.computed_values().height().resolved_or_zero(box, context_box().height()).to_px(box)); } void BlockFormattingContext::place_block_level_replaced_element_in_normal_flow(Box& child_box, Box& containing_block) { VERIFY(!containing_block.is_absolutely_positioned()); auto& replaced_element_box_model = child_box.box_model(); replaced_element_box_model.margin.top = child_box.computed_values().margin().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); replaced_element_box_model.margin.bottom = child_box.computed_values().margin().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); replaced_element_box_model.border.top = child_box.computed_values().border_top().width; replaced_element_box_model.border.bottom = child_box.computed_values().border_bottom().width; replaced_element_box_model.padding.top = child_box.computed_values().padding().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); replaced_element_box_model.padding.bottom = child_box.computed_values().padding().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); float x = replaced_element_box_model.margin.left + replaced_element_box_model.border.left + replaced_element_box_model.padding.left + replaced_element_box_model.offset.left; float y = replaced_element_box_model.margin_box().top + containing_block.box_model().offset.top; child_box.set_offset(x, y); } void BlockFormattingContext::place_block_level_non_replaced_element_in_normal_flow(Box& child_box, Box& containing_block) { auto& box_model = child_box.box_model(); auto& computed_values = child_box.computed_values(); box_model.margin.top = computed_values.margin().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); box_model.margin.bottom = computed_values.margin().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); box_model.border.top = computed_values.border_top().width; box_model.border.bottom = computed_values.border_bottom().width; box_model.padding.top = computed_values.padding().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); box_model.padding.bottom = computed_values.padding().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box); float x = box_model.margin.left + box_model.border.left + box_model.padding.left + box_model.offset.left; if (containing_block.computed_values().text_align() == CSS::TextAlign::LibwebCenter) { x = (containing_block.width() / 2) - child_box.width() / 2; } float y = box_model.margin_box().top + box_model.offset.top; // NOTE: Empty (0-height) preceding siblings have their margins collapsed with *their* preceding sibling, etc. float collapsed_bottom_margin_of_preceding_siblings = 0; auto* relevant_sibling = child_box.previous_sibling_of_type(); while (relevant_sibling != nullptr) { if (!relevant_sibling->is_absolutely_positioned() && !relevant_sibling->is_floating()) { collapsed_bottom_margin_of_preceding_siblings = max(collapsed_bottom_margin_of_preceding_siblings, relevant_sibling->box_model().margin.bottom); if (relevant_sibling->border_box_height() > 0) break; } relevant_sibling = relevant_sibling->previous_sibling(); } if (relevant_sibling) { y += relevant_sibling->effective_offset().y() + relevant_sibling->height() + relevant_sibling->box_model().border_box().bottom; // Collapse top margin with bottom margin of preceding siblings if needed float my_margin_top = box_model.margin.top; if (my_margin_top < 0 || collapsed_bottom_margin_of_preceding_siblings < 0) { // Negative margins present. float largest_negative_margin = -min(my_margin_top, collapsed_bottom_margin_of_preceding_siblings); float largest_positive_margin = (my_margin_top < 0 && collapsed_bottom_margin_of_preceding_siblings < 0) ? 0 : max(my_margin_top, collapsed_bottom_margin_of_preceding_siblings); float final_margin = largest_positive_margin - largest_negative_margin; y += final_margin - my_margin_top; } else if (collapsed_bottom_margin_of_preceding_siblings > my_margin_top) { // Sibling's margin is larger than mine, adjust so we use sibling's. y += collapsed_bottom_margin_of_preceding_siblings - my_margin_top; } } if (child_box.computed_values().clear() == CSS::Clear::Left || child_box.computed_values().clear() == CSS::Clear::Both) { if (!m_left_floating_boxes.is_empty()) { float clearance_y = 0; for (auto* floating_box : m_left_floating_boxes) { clearance_y = max(clearance_y, floating_box->effective_offset().y() + floating_box->box_model().margin_box().bottom); } y = max(y, clearance_y); m_left_floating_boxes.clear(); } } if (child_box.computed_values().clear() == CSS::Clear::Right || child_box.computed_values().clear() == CSS::Clear::Both) { if (!m_right_floating_boxes.is_empty()) { float clearance_y = 0; for (auto* floating_box : m_right_floating_boxes) { clearance_y = max(clearance_y, floating_box->effective_offset().y() + floating_box->box_model().margin_box().bottom); } y = max(y, clearance_y); m_right_floating_boxes.clear(); } } child_box.set_offset(x, y); } void BlockFormattingContext::layout_initial_containing_block(LayoutMode layout_mode) { auto viewport_rect = context_box().frame().viewport_rect(); auto& icb = downcast(context_box()); icb.build_stacking_context_tree(); icb.set_width(viewport_rect.width()); layout_block_level_children(context_box(), layout_mode); VERIFY(!icb.children_are_inline()); // FIXME: The ICB should have the height of the viewport. // Instead of auto-sizing the ICB, we should spill into overflow. float lowest_bottom = 0; icb.for_each_child_of_type([&](auto& child) { lowest_bottom = max(lowest_bottom, child.absolute_rect().bottom()); }); // FIXME: This is a hack and should be managed by an overflow mechanism. icb.set_height(max(static_cast(viewport_rect.height()), lowest_bottom)); } static Gfx::FloatRect rect_in_coordinate_space(const Box& box, const Box& context_box) { Gfx::FloatRect rect { box.effective_offset(), box.size() }; for (auto* ancestor = box.parent(); ancestor; ancestor = ancestor->parent()) { if (is(*ancestor)) { auto offset = downcast(*ancestor).effective_offset(); rect.move_by(offset); } if (ancestor == &context_box) break; } return rect; } void BlockFormattingContext::layout_floating_child(Box& box, Box& containing_block) { VERIFY(box.is_floating()); compute_width(box); layout_inside(box, LayoutMode::Default); compute_height(box); // First we place the box normally (to get the right y coordinate.) place_block_level_non_replaced_element_in_normal_flow(box, containing_block); // Then we float it to the left or right. float x = box.effective_offset().x(); auto box_in_context_rect = rect_in_coordinate_space(box, context_box()); float y_in_context_box = box_in_context_rect.y(); // Next, float to the left and/or right if (box.computed_values().float_() == CSS::Float::Left) { if (!m_left_floating_boxes.is_empty()) { auto& previous_floating_box = *m_left_floating_boxes.last(); auto previous_rect = rect_in_coordinate_space(previous_floating_box, context_box()); if (previous_rect.contains_vertically(y_in_context_box)) { // This box touches another already floating box. Stack to the right. x = previous_floating_box.effective_offset().x() + previous_floating_box.width(); } else { // This box does not touch another floating box, go all the way to the left. x = 0; // Also, forget all previous left-floating boxes while we're here since they're no longer relevant. m_left_floating_boxes.clear(); } } else { // This is the first left-floating box. Go all the way to the left. x = 0; } m_left_floating_boxes.append(&box); } else if (box.computed_values().float_() == CSS::Float::Right) { if (!m_right_floating_boxes.is_empty()) { auto& previous_floating_box = *m_right_floating_boxes.last(); auto previous_rect = rect_in_coordinate_space(previous_floating_box, context_box()); if (previous_rect.contains_vertically(y_in_context_box)) { // This box touches another already floating box. Stack to the left. x = previous_floating_box.effective_offset().x() - box.width(); } else { // This box does not touch another floating box, go all the way to the right. x = containing_block.width() - box.width(); // Also, forget all previous right-floating boxes while we're here since they're no longer relevant. m_right_floating_boxes.clear(); } } else { // This is the first right-floating box. Go all the way to the right. x = containing_block.width() - box.width(); } m_right_floating_boxes.append(&box); } box.set_offset(x, box.effective_offset().y()); } }