LibWeb: Make IFC aware that its parent is always a BFC

This simplifies some code and allows us to use tighter types for the
parent context everywhere.

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -384,7 +384,7 @@ void BlockFormattingContext::compute_position(Box& box)
 
 void BlockFormattingContext::layout_inline_children(BlockContainer& block_container, LayoutMode layout_mode)
 {
-    InlineFormattingContext context(block_container, this);
+    InlineFormattingContext context(block_container, *this);
     context.run(block_container, layout_mode);
 }
 

Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp

@@ -455,7 +455,7 @@ float FlexFormattingContext::layout_for_maximum_main_size(Box& box)
         auto& block_container = verify_cast<BlockContainer>(box);
         BlockFormattingContext bfc(block_container, this);
         bfc.run(box, LayoutMode::Default);
-        InlineFormattingContext ifc(block_container, &bfc);
+        InlineFormattingContext ifc(block_container, bfc);
 
         if (is_row_layout()) {
             ifc.run(box, LayoutMode::OnlyRequiredLineBreaks);
@@ -805,7 +805,7 @@ float FlexFormattingContext::determine_hypothetical_cross_size_of_item(Box& box)
         auto& block_container = verify_cast<BlockContainer>(box);
         BlockFormattingContext bfc(block_container, this);
         bfc.run(box, LayoutMode::Default);
-        InlineFormattingContext ifc(block_container, &bfc);
+        InlineFormattingContext ifc(block_container, bfc);
         ifc.run(box, LayoutMode::OnlyRequiredLineBreaks);
 
         return is_row_layout() ? box.height() : box.width();

Userland/Libraries/LibWeb/Layout/FormattingContext.cpp

@@ -95,7 +95,7 @@ OwnPtr<FormattingContext> FormattingContext::create_independent_formatting_conte
 
     VERIFY(is_block_formatting_context());
     if (child_box.children_are_inline())
-        return make<InlineFormattingContext>(verify_cast<BlockContainer>(child_box), this);
+        return make<InlineFormattingContext>(verify_cast<BlockContainer>(child_box), static_cast<BlockFormattingContext&>(*this));
 
     // The child box is a block container that doesn't create its own BFC.
     // It will be formatted by this BFC.

Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp

@@ -17,8 +17,8 @@
 
 namespace Web::Layout {
 
-InlineFormattingContext::InlineFormattingContext(BlockContainer& containing_block, FormattingContext* parent)
-    : FormattingContext(Type::Inline, containing_block, parent)
+InlineFormattingContext::InlineFormattingContext(BlockContainer& containing_block, BlockFormattingContext& parent)
+    : FormattingContext(Type::Inline, containing_block, &parent)
 {
 }
 
@@ -26,14 +26,21 @@ InlineFormattingContext::~InlineFormattingContext()
 {
 }
 
-InlineFormattingContext::AvailableSpaceForLineInfo InlineFormattingContext::available_space_for_line(float y) const
+BlockFormattingContext& InlineFormattingContext::parent()
 {
-    if (!parent()->is_block_formatting_context())
-        return { 0, context_box().width() };
+    return static_cast<BlockFormattingContext&>(*FormattingContext::parent());
+}
 
+BlockFormattingContext const& InlineFormattingContext::parent() const
+{
+    return static_cast<BlockFormattingContext const&>(*FormattingContext::parent());
+}
+
+InlineFormattingContext::AvailableSpaceForLineInfo InlineFormattingContext::available_space_for_line(float y) const
+{
     AvailableSpaceForLineInfo info;
 
-    auto const& bfc = static_cast<BlockFormattingContext const&>(*parent());
+    auto const& bfc = parent();
 
     for (ssize_t i = bfc.left_side_floats().boxes.size() - 1; i >= 0; --i) {
         auto const& floating_box = bfc.left_side_floats().boxes.at(i);

Userland/Libraries/LibWeb/Layout/InlineFormattingContext.h

@@ -15,9 +15,12 @@ namespace Web::Layout {
 
 class InlineFormattingContext final : public FormattingContext {
 public:
-    InlineFormattingContext(BlockContainer& containing_block, FormattingContext* parent);
+    InlineFormattingContext(BlockContainer& containing_block, BlockFormattingContext& parent);
     ~InlineFormattingContext();
 
+    BlockFormattingContext& parent();
+    BlockFormattingContext const& parent() const;
+
     BlockContainer& containing_block() { return static_cast<BlockContainer&>(context_box()); }
     BlockContainer const& containing_block() const { return static_cast<BlockContainer const&>(context_box()); }