LibWeb: Teach HTMLObjectElement to negotiate natural size with SVGs

We do this by generalizing the code previously used for SVGSVGBox into
something that can be used for NavigableViewportContainer as well.

Libraries/LibWeb/HTML/Navigable.cpp

@@ -1931,6 +1931,12 @@ void finalize_a_cross_document_navigation(GC::Ref<Navigable> navigable, HistoryH
 
     // 10. Apply the push/replace history step targetStep to traversable.
     traversable->apply_the_push_or_replace_history_step(target_step, history_handling, TraversableNavigable::SynchronousNavigation::No);
+
+    // AD-HOC: If we're inside a navigable container, let's trigger a relayout in the container document.
+    //         This allows size negotiation between the containing document and SVG documents to happen.
+    if (auto container = navigable->container()) {
+        container->document().set_needs_layout();
+    }
 }
 
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#url-and-history-update-steps

Libraries/LibWeb/Layout/NavigableContainerViewport.cpp

@@ -4,10 +4,12 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Layout/NavigableContainerViewport.h>
 #include <LibWeb/Layout/Viewport.h>
 #include <LibWeb/Painting/NavigableContainerViewportPaintable.h>
+#include <LibWeb/SVG/SVGSVGElement.h>
 
 namespace Web::Layout {
 
@@ -22,6 +24,15 @@ NavigableContainerViewport::~NavigableContainerViewport() = default;
 
 void NavigableContainerViewport::prepare_for_replaced_layout()
 {
+    if (auto const* content_document = dom_node().content_document_without_origin_check()) {
+        if (auto const* root_element = content_document->document_element(); root_element && root_element->is_svg_svg_element()) {
+            auto natural_metrics = SVG::SVGSVGElement::negotiate_natural_metrics(static_cast<SVG::SVGSVGElement const&>(*root_element));
+            set_natural_width(natural_metrics.width);
+            set_natural_height(natural_metrics.height);
+            set_natural_aspect_ratio(natural_metrics.aspect_ratio);
+            return;
+        }
+    }
     // FIXME: Do proper error checking, etc.
     set_natural_width(dom_node().get_attribute_value(HTML::AttributeNames::width).to_number<int>().value_or(300));
     set_natural_height(dom_node().get_attribute_value(HTML::AttributeNames::height).to_number<int>().value_or(150));

Libraries/LibWeb/Layout/SVGSVGBox.cpp

@@ -27,58 +27,10 @@ GC::Ptr<Painting::Paintable> SVGSVGBox::create_paintable() const
 
 void SVGSVGBox::prepare_for_replaced_layout()
 {
-    // https://www.w3.org/TR/SVG2/coords.html#SizingSVGInCSS
-
-    // The intrinsic dimensions must also be determined from the width and height sizing properties.
-    // If either width or height are not specified, the used value is the initial value 'auto'.
-    // 'auto' and percentage lengths must not be used to determine an intrinsic width or intrinsic height.
-
-    Optional<CSSPixels> natural_width;
-    if (auto width = dom_node().width_style_value_from_attribute(); width && width->is_length() && width->as_length().length().is_absolute()) {
-        natural_width = width->as_length().length().absolute_length_to_px();
-    }
-
-    Optional<CSSPixels> natural_height;
-    if (auto height = dom_node().height_style_value_from_attribute(); height && height->is_length() && height->as_length().length().is_absolute()) {
-        natural_height = height->as_length().length().absolute_length_to_px();
-    }
-
-    // The intrinsic aspect ratio must be calculated using the following algorithm. If the algorithm returns null, then there is no intrinsic aspect ratio.
-    auto natural_aspect_ratio = [&]() -> Optional<CSSPixelFraction> {
-        // 1. If the width and height sizing properties on the ‘svg’ element are both absolute values:
-        if (natural_width.has_value() && natural_height.has_value()) {
-            if (natural_width != 0 && natural_height != 0) {
-                // 1. return width / height
-                return *natural_width / *natural_height;
-            }
-            return {};
-        }
-
-        // FIXME: 2. If an SVG View is active:
-        // FIXME:    1. let viewbox be the viewbox defined by the active SVG View
-        // FIXME:    2. return viewbox.width / viewbox.height
-
-        // 3. If the ‘viewBox’ on the ‘svg’ element is correctly specified:
-        if (dom_node().view_box().has_value()) {
-            // 1. let viewbox be the viewbox defined by the ‘viewBox’ attribute on the ‘svg’ element
-            auto const& viewbox = dom_node().view_box().value();
-
-            // 2. return viewbox.width / viewbox.height
-            auto viewbox_width = CSSPixels::nearest_value_for(viewbox.width);
-            auto viewbox_height = CSSPixels::nearest_value_for(viewbox.height);
-            if (viewbox_width != 0 && viewbox_height != 0)
-                return viewbox_width / viewbox_height;
-
-            return {};
-        }
-
-        // 4. return null
-        return {};
-    }();
-
-    set_natural_width(natural_width);
-    set_natural_height(natural_height);
-    set_natural_aspect_ratio(natural_aspect_ratio);
+    auto natural_metrics = SVG::SVGSVGElement::negotiate_natural_metrics(dom_node());
+    set_natural_width(natural_metrics.width);
+    set_natural_height(natural_metrics.height);
+    set_natural_aspect_ratio(natural_metrics.aspect_ratio);
 }
 
 }

Libraries/LibWeb/SVG/SVGSVGElement.cpp

@@ -266,4 +266,58 @@ GC::Ref<SVGTransform> SVGSVGElement::create_svg_transform() const
     return SVGTransform::create(realm());
 }
 
+SVGSVGElement::NaturalMetrics SVGSVGElement::negotiate_natural_metrics(SVG::SVGSVGElement const& svg_root)
+{
+    // https://www.w3.org/TR/SVG2/coords.html#SizingSVGInCSS
+
+    NaturalMetrics natural_metrics;
+
+    // The intrinsic dimensions must also be determined from the width and height sizing properties.
+    // If either width or height are not specified, the used value is the initial value 'auto'.
+    // 'auto' and percentage lengths must not be used to determine an intrinsic width or intrinsic height.
+
+    if (auto width = svg_root.width_style_value_from_attribute(); width && width->is_length() && width->as_length().length().is_absolute()) {
+        natural_metrics.width = width->as_length().length().absolute_length_to_px();
+    }
+
+    if (auto height = svg_root.height_style_value_from_attribute(); height && height->is_length() && height->as_length().length().is_absolute()) {
+        natural_metrics.height = height->as_length().length().absolute_length_to_px();
+    }
+
+    // The intrinsic aspect ratio must be calculated using the following algorithm. If the algorithm returns null, then there is no intrinsic aspect ratio.
+    natural_metrics.aspect_ratio = [&]() -> Optional<CSSPixelFraction> {
+        // 1. If the width and height sizing properties on the ‘svg’ element are both absolute values:
+        if (natural_metrics.width.has_value() && natural_metrics.height.has_value()) {
+            if (natural_metrics.width != 0 && natural_metrics.height != 0) {
+                // 1. return width / height
+                return *natural_metrics.width / *natural_metrics.height;
+            }
+            return {};
+        }
+
+        // FIXME: 2. If an SVG View is active:
+        // FIXME:    1. let viewbox be the viewbox defined by the active SVG View
+        // FIXME:    2. return viewbox.width / viewbox.height
+
+        // 3. If the ‘viewBox’ on the ‘svg’ element is correctly specified:
+        if (svg_root.view_box().has_value()) {
+            // 1. let viewbox be the viewbox defined by the ‘viewBox’ attribute on the ‘svg’ element
+            auto const& viewbox = svg_root.view_box().value();
+
+            // 2. return viewbox.width / viewbox.height
+            auto viewbox_width = CSSPixels::nearest_value_for(viewbox.width);
+            auto viewbox_height = CSSPixels::nearest_value_for(viewbox.height);
+            if (viewbox_width != 0 && viewbox_height != 0)
+                return viewbox_width / viewbox_height;
+
+            return {};
+        }
+
+        // 4. return null
+        return {};
+    }();
+
+    return natural_metrics;
+}
+
 }

Libraries/LibWeb/SVG/SVGSVGElement.h

@@ -83,6 +83,14 @@ class SVGSVGElement final : public SVGGraphicsElement
     [[nodiscard]] RefPtr<CSS::CSSStyleValue> width_style_value_from_attribute() const;
     [[nodiscard]] RefPtr<CSS::CSSStyleValue> height_style_value_from_attribute() const;
 
+    struct NaturalMetrics {
+        Optional<CSSPixels> width;
+        Optional<CSSPixels> height;
+        Optional<CSSPixelFraction> aspect_ratio;
+    };
+
+    static NaturalMetrics negotiate_natural_metrics(SVGSVGElement const&);
+
 private:
     SVGSVGElement(DOM::Document&, DOM::QualifiedName);