LibWeb: Use BFC root relative coordinates when flowing around floats

While IFC flows text into a block container, floating objects are
anchored at the BFC root, not necessarily the local block container.

Because of this, we have to use root-relative coordinates when checking
how much space is available in between left and right floated objects.

2 files changed, 7 insertions, 3 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/Box.h b/Userland/Libraries/LibWeb/Layout/Box.h
index 231ac863e1..bd29c18aef 100644
--- a/Userland/Libraries/LibWeb/Layout/Box.h
+++ b/Userland/Libraries/LibWeb/Layout/Box.h
@@ -164,7 +164,7 @@ public:
     virtual void before_children_paint(PaintContext&, PaintPhase) override;
     virtual void after_children_paint(PaintContext&, PaintPhase) override;
 
-    Gfx::FloatRect margin_box_rect_in_ancestor_coordinate_space(Box const& ancestor_box)
+    Gfx::FloatRect margin_box_rect_in_ancestor_coordinate_space(Box const& ancestor_box) const
     {
         auto rect = margin_box_as_relative_rect();
         for (auto const* current = parent(); current; current = current->parent()) {
diff --git a/Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp
index 9bad45c3cc..a672b44997 100644
--- a/Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp
+++ b/Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp
@@ -38,6 +38,10 @@ BlockFormattingContext const& InlineFormattingContext::parent() const
 
 InlineFormattingContext::AvailableSpaceForLineInfo InlineFormattingContext::available_space_for_line(float y) const
 {
+    // NOTE: Floats are relative to the BFC root box, not necessarily the containing block of this IFC.
+    auto box_in_root_rect = containing_block().margin_box_rect_in_ancestor_coordinate_space(parent().root());
+    float y_in_root = box_in_root_rect.y() + y;
+
     AvailableSpaceForLineInfo info;
 
     auto const& bfc = parent();
@@ -45,7 +49,7 @@ InlineFormattingContext::AvailableSpaceForLineInfo InlineFormattingContext::avai
     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);
         auto rect = floating_box.margin_box_as_relative_rect();
-        if (rect.contains_vertically(y)) {
+        if (rect.contains_vertically(y_in_root)) {
             info.left = rect.right() + 1;
             break;
         }
@@ -56,7 +60,7 @@ InlineFormattingContext::AvailableSpaceForLineInfo InlineFormattingContext::avai
     for (ssize_t i = bfc.right_side_floats().boxes.size() - 1; i >= 0; --i) {
         auto const& floating_box = bfc.right_side_floats().boxes.at(i);
         auto rect = floating_box.margin_box_as_relative_rect();
-        if (rect.contains_vertically(y)) {
+        if (rect.contains_vertically(y_in_root)) {
             info.right = rect.left() - 1;
             break;
         }