From b2c899af118e40e3786abde0825ba7f00cc5d248 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 20 May 2023 17:44:18 +0200
Subject: [PATCH] LibWeb: Make standalone SVG document roots the size of the
 viewport

We have to special-case these, otherwise our normal CSS layout algorithm
will see that some SVG roots have width/height assigned, and make those
the used width/height.

When used in an SVG-as-image context, the outermost viewport must be the
authoritative root size.
---
 .../LibWeb/Layout/BlockFormattingContext.cpp   | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
index 6da13110ee..c5492a9530 100644
--- a/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
+++ b/Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp
@@ -17,6 +17,7 @@
 #include <LibWeb/Layout/ListItemBox.h>
 #include <LibWeb/Layout/ListItemMarkerBox.h>
 #include <LibWeb/Layout/ReplacedBox.h>
+#include <LibWeb/Layout/SVGSVGBox.h>
 #include <LibWeb/Layout/TableBox.h>
 #include <LibWeb/Layout/TableWrapper.h>
 #include <LibWeb/Layout/Viewport.h>
@@ -794,10 +795,19 @@ void BlockFormattingContext::layout_viewport(LayoutMode layout_mode, AvailableSp
     auto& viewport = verify_cast<Layout::Viewport>(root());
     auto& viewport_state = m_state.get_mutable(viewport);
 
-    if (root().children_are_inline())
-        layout_inline_children(root(), layout_mode, available_space);
-    else
-        layout_block_level_children(root(), layout_mode, available_space);
+    // NOTE: If we are laying out a standalone SVG document, we give it some special treatment:
+    //       The root <svg> container gets the same size as the viewport,
+    //       and we call directly into the SVG layout code from here.
+    if (root().first_child() && root().first_child()->is_svg_svg_box()) {
+        auto const& svg_root = verify_cast<SVGSVGBox>(*root().first_child());
+        auto svg_formatting_context = create_independent_formatting_context_if_needed(m_state, svg_root);
+        svg_formatting_context->run(svg_root, layout_mode, available_space);
+    } else {
+        if (root().children_are_inline())
+            layout_inline_children(root(), layout_mode, available_space);
+        else
+            layout_block_level_children(root(), layout_mode, available_space);
+    }
 
     CSSPixels bottom_edge = 0;
     CSSPixels right_edge = 0;