From 7953bd839175696cc55a56969f0bff9598e08fcf Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 22 Jun 2022 18:05:28 +0200
Subject: [PATCH] LibWeb: Implement "transferred size suggestion" for flex
 items

---
 .../LibWeb/Layout/FlexFormattingContext.cpp   | 25 +++++++++++++++++--
 .../LibWeb/Layout/FlexFormattingContext.h     |  1 +
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp
index 5f5afa99b0..eb80adeee4 100644
--- a/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp
+++ b/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp
@@ -654,6 +654,22 @@ float FlexFormattingContext::content_size_suggestion(FlexItem const& item) const
     return calculate_min_and_max_content_height(item.box).min_content_size;
 }
 
+// https://drafts.csswg.org/css-flexbox-1/#transferred-size-suggestion
+Optional<float> FlexFormattingContext::transferred_size_suggestion(FlexItem const& item) const
+{
+    // If the item has a preferred aspect ratio and its preferred cross size is definite,
+    // then the transferred size suggestion is that size
+    // (clamped by its minimum and maximum cross sizes if they are definite), converted through the aspect ratio.
+    if (item.box.has_intrinsic_aspect_ratio() && has_definite_cross_size(item.box)) {
+        auto aspect_ratio = item.box.intrinsic_aspect_ratio().value();
+        // FIXME: Clamp cross size to min/max cross size before this conversion.
+        return resolved_definite_cross_size(item.box) * aspect_ratio;
+    }
+
+    // It is otherwise undefined.
+    return {};
+}
+
 // https://drafts.csswg.org/css-flexbox-1/#content-based-minimum-size
 float FlexFormattingContext::content_based_minimum_size(FlexItem const& item) const
 {
@@ -664,8 +680,13 @@ float FlexFormattingContext::content_based_minimum_size(FlexItem const& item) co
             return min(specified_size_suggestion.value(), content_size_suggestion(item));
         }
 
-        // FIXME: otherwise, the smaller of its transferred size suggestion and its content size suggestion
-        //        if the element is replaced and its transferred size suggestion exists;
+        // otherwise, the smaller of its transferred size suggestion and its content size suggestion
+        // if the element is replaced and its transferred size suggestion exists;
+        if (item.box.is_replaced_box()) {
+            if (auto transferred_size_suggestion = this->transferred_size_suggestion(item); transferred_size_suggestion.has_value()) {
+                return min(transferred_size_suggestion.value(), content_size_suggestion(item));
+            }
+        }
 
         // otherwise its content size suggestion.
         return content_size_suggestion(item);
diff --git a/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.h b/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.h
index d997bdd973..0797d95460 100644
--- a/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.h
+++ b/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.h
@@ -82,6 +82,7 @@ private:
     float automatic_minimum_size(FlexItem const&) const;
     float content_based_minimum_size(FlexItem const&) const;
     Optional<float> specified_size_suggestion(FlexItem const&) const;
+    Optional<float> transferred_size_suggestion(FlexItem const&) const;
     float content_size_suggestion(FlexItem const&) const;
 
     void set_main_size(Box const&, float size);