LibWeb: Rename the LayoutMode enum values and explain them

The old mode names, while mechanically accurate, didn't really reflect
their relationship to the CSS specifications.

This patch renames them as follows:

    Default => Normal
    AllPossibleLineBreaks => MinContent
    OnlyRequiredLineBreaks => MaxContent

There's also now an explainer comment with the LayoutMode enum about the
specific implications of layout in each mode.

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -577,7 +577,7 @@ void Document::update_layout()
     icb.set_has_definite_width(true);
     icb.set_has_definite_height(true);
 
-    root_formatting_context.run(*m_layout_root, Layout::LayoutMode::Default);
+    root_formatting_context.run(*m_layout_root, Layout::LayoutMode::Normal);
     formatting_state.commit();
 
     m_layout_root->build_stacking_context_tree();

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -224,13 +224,13 @@ void BlockFormattingContext::compute_width_for_floating_box(Box const& box, Layo
     float width_of_containing_block = 0;
 
     switch (layout_mode) {
-    case LayoutMode::Default:
+    case LayoutMode::Normal:
         width_of_containing_block = m_state.get(containing_block).content_width;
         break;
-    case LayoutMode::AllPossibleLineBreaks:
+    case LayoutMode::MinContent:
         width_of_containing_block = 0;
         break;
-    case LayoutMode::OnlyRequiredLineBreaks:
+    case LayoutMode::MaxContent:
         width_of_containing_block = INFINITY;
         break;
     }
@@ -408,7 +408,7 @@ void BlockFormattingContext::layout_block_level_children(BlockContainer const& b
         return IterationDecision::Continue;
     });
 
-    if (layout_mode != LayoutMode::Default) {
+    if (layout_mode != LayoutMode::Normal) {
         auto& width = block_container.computed_values().width();
         if (!width.has_value() || (width->is_length() && width->length().is_auto())) {
             auto& block_container_state = m_state.get_mutable(block_container);
@@ -559,13 +559,13 @@ void BlockFormattingContext::layout_floating_box(Box const& box, BlockContainer
     float width_of_containing_block = 0;
 
     switch (layout_mode) {
-    case LayoutMode::Default:
+    case LayoutMode::Normal:
         width_of_containing_block = m_state.get(containing_block).content_width;
         break;
-    case LayoutMode::AllPossibleLineBreaks:
+    case LayoutMode::MinContent:
         width_of_containing_block = 0;
         break;
-    case LayoutMode::OnlyRequiredLineBreaks:
+    case LayoutMode::MaxContent:
         width_of_containing_block = INFINITY;
         break;
     }

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.h

@@ -27,7 +27,7 @@ public:
     auto const& right_side_floats() const { return m_right_floats; }
 
     static float compute_theoretical_height(FormattingState const&, Box const&);
-    void compute_width(Box const&, LayoutMode = LayoutMode::Default);
+    void compute_width(Box const&, LayoutMode = LayoutMode::Normal);
 
     // https://www.w3.org/TR/css-display/#block-formatting-context-root
     BlockContainer const& root() const { return static_cast<BlockContainer const&>(context_box()); }

Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp

@@ -112,7 +112,7 @@ void FlexFormattingContext::run(Box const& run_box, LayoutMode)
     // AD-HOC: Layout the inside of all flex items.
     copy_dimensions_from_flex_items_to_boxes();
     for (auto& flex_item : m_flex_items) {
-        auto independent_formatting_context = layout_inside(flex_item.box, LayoutMode::Default);
+        auto independent_formatting_context = layout_inside(flex_item.box, LayoutMode::Normal);
         independent_formatting_context->parent_context_did_dimension_child_root_box();
     }
 
@@ -451,7 +451,7 @@ float FlexFormattingContext::calculate_indefinite_main_size(FlexItem const& item
         } else {
             box_state.content_width = resolved_definite_cross_size(item.box);
         }
-        independent_formatting_context->run(item.box, LayoutMode::Default);
+        independent_formatting_context->run(item.box, LayoutMode::Normal);
 
         if (is_row_layout())
             return box_state.content_width;
@@ -477,7 +477,7 @@ float FlexFormattingContext::calculate_indefinite_main_size(FlexItem const& item
     VERIFY(independent_formatting_context);
 
     box_state.content_width = fit_content_cross_size;
-    independent_formatting_context->run(item.box, LayoutMode::Default);
+    independent_formatting_context->run(item.box, LayoutMode::Normal);
 
     return BlockFormattingContext::compute_theoretical_height(throwaway_state, item.box);
 }
@@ -825,7 +825,7 @@ void FlexFormattingContext::determine_hypothetical_cross_size_of_item(FlexItem&
         } else {
             box_state.content_height = resolved_definite_main_size(item.box);
         }
-        independent_formatting_context->run(item.box, LayoutMode::Default);
+        independent_formatting_context->run(item.box, LayoutMode::Normal);
 
         if (is_row_layout())
             item.hypothetical_cross_size = BlockFormattingContext::compute_theoretical_height(throwaway_state, item.box);
@@ -854,7 +854,7 @@ void FlexFormattingContext::determine_hypothetical_cross_size_of_item(FlexItem&
         VERIFY(independent_formatting_context);
 
         box_state.content_width = fit_content_main_size;
-        independent_formatting_context->run(item.box, LayoutMode::Default);
+        independent_formatting_context->run(item.box, LayoutMode::Normal);
 
         item.hypothetical_cross_size = BlockFormattingContext::compute_theoretical_height(throwaway_state, item.box);
     }

Userland/Libraries/LibWeb/Layout/FormattingContext.cpp

@@ -692,7 +692,7 @@ void FormattingContext::layout_absolutely_positioned_element(Box const& box)
     auto specified_width = box.computed_values().width().has_value() ? box.computed_values().width()->resolved(box, width_of_containing_block).resolved(box) : CSS::Length::make_auto();
 
     compute_width_for_absolutely_positioned_element(box);
-    auto independent_formatting_context = layout_inside(box, LayoutMode::Default);
+    auto independent_formatting_context = layout_inside(box, LayoutMode::Normal);
     compute_height_for_absolutely_positioned_element(box);
 
     box_state.margin_left = box.computed_values().margin().left.resolved(box, width_of_containing_block).to_px(box);
@@ -824,7 +824,7 @@ FormattingState::IntrinsicSizes FormattingContext::calculate_intrinsic_sizes(Lay
         auto independent_formatting_context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
         VERIFY(independent_formatting_context);
 
-        independent_formatting_context->run(box, LayoutMode::OnlyRequiredLineBreaks);
+        independent_formatting_context->run(box, LayoutMode::MaxContent);
         cached_box_sizes.max_content_size.set_width(independent_formatting_context->greatest_child_width(box));
         cached_box_sizes.max_content_size.set_height(BlockFormattingContext::compute_theoretical_height(throwaway_state, box));
     }
@@ -836,7 +836,7 @@ FormattingState::IntrinsicSizes FormattingContext::calculate_intrinsic_sizes(Lay
         containing_block_state.content_height = 0;
         auto independent_formatting_context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, box);
         VERIFY(independent_formatting_context);
-        independent_formatting_context->run(box, LayoutMode::AllPossibleLineBreaks);
+        independent_formatting_context->run(box, LayoutMode::MinContent);
         cached_box_sizes.min_content_size.set_width(independent_formatting_context->greatest_child_width(box));
         cached_box_sizes.min_content_size.set_height(BlockFormattingContext::compute_theoretical_height(throwaway_state, box));
     }

Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp

@@ -84,7 +84,7 @@ void InlineFormattingContext::run(Box const&, LayoutMode layout_mode)
 
     auto& containing_block_state = m_state.get_mutable(containing_block());
 
-    if (layout_mode != LayoutMode::Default) {
+    if (layout_mode != LayoutMode::Normal) {
         containing_block_state.content_width = max_line_width;
     }
 

Userland/Libraries/LibWeb/Layout/LineBuilder.cpp

@@ -37,13 +37,13 @@ void LineBuilder::begin_new_line(bool increment_y)
         m_current_y += max(m_max_height_on_current_line, m_context.containing_block().line_height());
 
     switch (m_layout_mode) {
-    case LayoutMode::Default:
+    case LayoutMode::Normal:
         m_available_width_for_current_line = m_context.available_space_for_line(m_current_y);
         break;
-    case LayoutMode::AllPossibleLineBreaks:
+    case LayoutMode::MinContent:
         m_available_width_for_current_line = 0;
         break;
-    case LayoutMode::OnlyRequiredLineBreaks:
+    case LayoutMode::MaxContent:
         m_available_width_for_current_line = INFINITY;
         break;
     }
@@ -81,11 +81,11 @@ void LineBuilder::append_text_chunk(TextNode const& text_node, size_t offset_in_
 
 bool LineBuilder::should_break(LayoutMode layout_mode, float next_item_width, bool should_force_break)
 {
-    if (layout_mode == LayoutMode::AllPossibleLineBreaks)
+    if (layout_mode == LayoutMode::MinContent)
         return true;
     if (should_force_break)
         return true;
-    if (layout_mode == LayoutMode::OnlyRequiredLineBreaks)
+    if (layout_mode == LayoutMode::MaxContent)
         return false;
     auto const& line_boxes = m_containing_block_state.line_boxes;
     if (line_boxes.is_empty() || line_boxes.last().is_empty())

Userland/Libraries/LibWeb/Layout/Node.h

@@ -21,9 +21,20 @@
 namespace Web::Layout {
 
 enum class LayoutMode {
-    Default,
-    AllPossibleLineBreaks,
-    OnlyRequiredLineBreaks,
+    // Normal layout.
+    // - We use the containing block's used width.
+    // - Content flows into the available space, line breaks inserted where necessary.
+    Normal,
+
+    // MinContent layout is used for discovering the min-content intrinsic size of a box.
+    // - We act as if the containing block has 0 used width.
+    // - Every line-breaking opportunity is taken.
+    MinContent,
+
+    // MaxContent layout is used for discovering the max-content intrinsic size of a box.
+    // - We act as if the containing block has infinite used width.
+    // - Only forced line-breaking opportunities are taken.
+    MaxContent,
 };
 
 class Node : public TreeNode<Node> {

Userland/Libraries/LibWeb/Layout/TableFormattingContext.cpp

@@ -81,9 +81,9 @@ void TableFormattingContext::calculate_column_widths(Box const& row, Vector<floa
         auto& cell_state = m_state.get_mutable(cell);
         compute_width(cell);
         if (use_auto_layout) {
-            (void)layout_inside(cell, LayoutMode::OnlyRequiredLineBreaks);
+            (void)layout_inside(cell, LayoutMode::MaxContent);
         } else {
-            (void)layout_inside(cell, LayoutMode::Default);
+            (void)layout_inside(cell, LayoutMode::Normal);
         }
         column_widths[column_index] = max(column_widths[column_index], cell_state.content_width);
         column_index += cell.colspan();
@@ -105,9 +105,9 @@ void TableFormattingContext::layout_row(Box const& row, Vector<float>& column_wi
 
         // Layout the cell contents a second time, now that we know its final width.
         if (use_auto_layout) {
-            (void)layout_inside(cell, LayoutMode::OnlyRequiredLineBreaks);
+            (void)layout_inside(cell, LayoutMode::MaxContent);
         } else {
-            (void)layout_inside(cell, LayoutMode::Default);
+            (void)layout_inside(cell, LayoutMode::Normal);
         }
 
         BlockFormattingContext::compute_height(cell, m_state);

Userland/Libraries/LibWeb/Layout/TextNode.cpp

@@ -141,7 +141,7 @@ Optional<TextNode::Chunk> TextNode::ChunkIterator::next()
             }
         }
 
-        if (m_wrap_lines || m_layout_mode == LayoutMode::AllPossibleLineBreaks) {
+        if (m_wrap_lines || m_layout_mode == LayoutMode::MinContent) {
             bool is_space = is_ascii_space(*m_iterator);
             if (is_space != m_last_was_space) {
                 m_last_was_space = is_space;
@@ -163,7 +163,7 @@ Optional<TextNode::Chunk> TextNode::ChunkIterator::next()
 
 Optional<TextNode::Chunk> TextNode::ChunkIterator::try_commit_chunk(Utf8View::Iterator const& start, Utf8View::Iterator const& end, bool has_breaking_newline, bool must_commit) const
 {
-    if (m_layout_mode == LayoutMode::OnlyRequiredLineBreaks && !must_commit)
+    if (m_layout_mode == LayoutMode::MaxContent && !must_commit)
         return {};
 
     auto byte_offset = m_utf8_view.byte_offset_of(start);