From 6b8adb522c640ce8daedb053ee86accfa2444cc1 Mon Sep 17 00:00:00 2001
From: Sam Atkins <sam@ladybird.org>
Date: Fri, 14 Mar 2025 16:58:10 +0000
Subject: [PATCH] LibWeb: Set iframe border to 0px when frameborder attribute
 is invalid

Corresponds to https://github.com/whatwg/html/commit/6e19cef90ed53a3a5afaf170075956dd53834674
---
 Libraries/LibWeb/CSS/Default.css            |  2 --
 Libraries/LibWeb/HTML/HTMLIFrameElement.cpp | 33 +++++++++++++++++++--
 Libraries/LibWeb/HTML/HTMLIFrameElement.h   |  2 ++
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/Libraries/LibWeb/CSS/Default.css b/Libraries/LibWeb/CSS/Default.css
index aeb47669a13..62864d65f52 100644
--- a/Libraries/LibWeb/CSS/Default.css
+++ b/Libraries/LibWeb/CSS/Default.css
@@ -758,8 +758,6 @@ video {
  * https://html.spec.whatwg.org/multipage/rendering.html#attributes-for-embedded-content-and-images
  */
 
-iframe[frameborder='0'], iframe[frameborder=no i] { border: none; }
-
 embed[align=left i], iframe[align=left i], img[align=left i],
 input[type=image i][align=left i], object[align=left i] {
     float: left;
diff --git a/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp b/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp
index 1d819e25f6d..185594cad35 100644
--- a/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp
@@ -1,20 +1,21 @@
 /*
  * Copyright (c) 2020-2021, Andreas Kling <andreas@ladybird.org>
- * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2023-2025, Sam Atkins <sam@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibURL/Origin.h>
 #include <LibWeb/Bindings/HTMLIFrameElementPrototype.h>
 #include <LibWeb/CSS/ComputedProperties.h>
 #include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
+#include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
 #include <LibWeb/DOM/DOMTokenList.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Event.h>
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/HTMLIFrameElement.h>
 #include <LibWeb/HTML/Navigable.h>
+#include <LibWeb/HTML/Numbers.h>
 #include <LibWeb/HTML/Parser/HTMLParser.h>
 #include <LibWeb/HTML/TraversableNavigable.h>
 #include <LibWeb/Layout/NavigableContainerViewport.h>
@@ -226,6 +227,34 @@ i32 HTMLIFrameElement::default_tab_index_value() const
     return 0;
 }
 
+bool HTMLIFrameElement::is_presentational_hint(FlyString const& name) const
+{
+    if (Base::is_presentational_hint(name))
+        return true;
+
+    return name == HTML::AttributeNames::frameborder;
+}
+
+void HTMLIFrameElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
+{
+    Base::apply_presentational_hints(cascaded_properties);
+
+    // https://html.spec.whatwg.org/multipage/rendering.html#attributes-for-embedded-content-and-images:attr-iframe-frameborder
+    // When an iframe element has a frameborder attribute whose value, when parsed using the rules for parsing integers,
+    // is zero or an error, the user agent is expected to have presentational hints setting the element's
+    // 'border-top-width', 'border-right-width', 'border-bottom-width', and 'border-left-width' properties to zero.
+    if (auto frameborder_attribute = get_attribute(HTML::AttributeNames::frameborder); frameborder_attribute.has_value()) {
+        auto frameborder = parse_integer(*frameborder_attribute);
+        if (!frameborder.has_value() || frameborder == 0) {
+            auto zero = CSS::LengthStyleValue::create(CSS::Length::make_px(0));
+            cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::BorderTopWidth, zero);
+            cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::BorderRightWidth, zero);
+            cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::BorderBottomWidth, zero);
+            cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::BorderLeftWidth, zero);
+        }
+    }
+}
+
 // https://html.spec.whatwg.org/multipage/iframe-embed-object.html#dom-iframe-sandbox
 GC::Ref<DOM::DOMTokenList> HTMLIFrameElement::sandbox()
 {
diff --git a/Libraries/LibWeb/HTML/HTMLIFrameElement.h b/Libraries/LibWeb/HTML/HTMLIFrameElement.h
index d13cc854366..0bf82bd79be 100644
--- a/Libraries/LibWeb/HTML/HTMLIFrameElement.h
+++ b/Libraries/LibWeb/HTML/HTMLIFrameElement.h
@@ -48,6 +48,8 @@ private:
     virtual void removed_from(Node* old_parent, Node& old_root) override;
     virtual void attribute_changed(FlyString const& name, Optional<String> const& old_value, Optional<String> const& value, Optional<FlyString> const& namespace_) override;
     virtual i32 default_tab_index_value() const override;
+    virtual bool is_presentational_hint(FlyString const&) const override;
+    virtual void apply_presentational_hints(GC::Ref<CSS::CascadedProperties>) const override;
 
     // https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-iframe-element:dimension-attributes
     virtual bool supports_dimension_attributes() const override { return true; }