LibWeb: Assign hypothetical flex item main sizes as temporary main size

This colors a bit outside the lines of the specification, but the spec
doesn't offer a proper explanation for how descendants of a flex item
are supposed to have access to the flex item's main size for purposes
of percentage resolution.

The approach I came up with here was to take the hypothetical main size
of each flex item, and assign it as a temporary main size. This allows
percentage resolution in descendants to work against the pre-flexing
main size of items. This seems to match how other engines behave,
although it feels somewhat dirty. If/when we learn more about this,
we can come up with something nicer.

1 files changed, 5 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/LayoutState.h b/Userland/Libraries/LibWeb/Layout/LayoutState.h
index 9e79c0ce34..a85eae6e5e 100644
--- a/Userland/Libraries/LibWeb/Layout/LayoutState.h
+++ b/Userland/Libraries/LibWeb/Layout/LayoutState.h
@@ -53,6 +53,11 @@ struct LayoutState {
         void set_content_width(float);
         void set_content_height(float);
 
+        // NOTE: These are used by FlexFormattingContext to assign a temporary main size to items
+        //       early on, so that descendants have something to resolve percentages against.
+        void set_temporary_content_width(float);
+        void set_temporary_content_height(float);
+
         bool has_definite_width() const { return m_has_definite_width && width_constraint == SizeConstraint::None; }
         bool has_definite_height() const { return m_has_definite_height && height_constraint == SizeConstraint::None; }