From faf4f2c23f7f165fae58ee93217e2559d89c2317 Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Sun, 4 May 2025 14:39:03 +0200
Subject: [PATCH] Issue #2736 - Part 10: Re-work <source> `srcset` attribute.

Use subject principal as triggering principal in <source> "srcset"
attribute for <picture>.
---
 dom/html/HTMLImageElement.cpp       |  4 ++++
 dom/html/HTMLSourceElement.cpp      |  5 +++++
 dom/html/HTMLSourceElement.h        | 14 +++++++++++---
 dom/webidl/HTMLSourceElement.webidl |  2 +-
 4 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/dom/html/HTMLImageElement.cpp b/dom/html/HTMLImageElement.cpp
index 6945174954..4dd46f5a0e 100644
--- a/dom/html/HTMLImageElement.cpp
+++ b/dom/html/HTMLImageElement.cpp
@@ -1060,6 +1060,8 @@ HTMLImageElement::PictureSourceSrcsetChanged(nsIContent *aSourceNode,
     nsCOMPtr<nsIPrincipal> principal;
     if (aSourceNode == this) {
       principal = mSrcsetTriggeringPrincipal;
+    } else if (auto* source = HTMLSourceElement::FromContent(aSourceNode)) {
+      principal = source->GetSrcsetTriggeringPrincipal();
     }
     mResponsiveSelector->SetCandidatesFromSourceSet(aNewValue, principal);
   }
@@ -1254,6 +1256,8 @@ HTMLImageElement::TryCreateResponsiveSelector(nsIContent *aSourceNode)
     if (!SourceElementMatches(aSourceNode)) {
       return false;
     }
+    auto* source = HTMLSourceElement::FromContent(aSourceNode);
+    principal = source->GetSrcsetTriggeringPrincipal();
   } else if (aSourceNode->IsHTMLElement(nsGkAtoms::img)) {
     // Otherwise this is the <img> tag itself
     MOZ_ASSERT(aSourceNode == this);
diff --git a/dom/html/HTMLSourceElement.cpp b/dom/html/HTMLSourceElement.cpp
index afe481dfd7..2a5ad4b908 100644
--- a/dom/html/HTMLSourceElement.cpp
+++ b/dom/html/HTMLSourceElement.cpp
@@ -102,6 +102,11 @@ HTMLSourceElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                 nsIPrincipal* aMaybeScriptedPrincipal,
                                 bool aNotify)
 {
+  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::srcset) {
+    mSrcsetTriggeringPrincipal = nsContentUtils::GetAttrTriggeringPrincipal(
+        this, aValue ? aValue->GetStringValue() : EmptyString(),
+        aMaybeScriptedPrincipal);
+  }
   // If we are associated with a <picture> with a valid <img>, notify it of
   // responsive parameter changes
   Element *parent = nsINode::GetParentElement();
diff --git a/dom/html/HTMLSourceElement.h b/dom/html/HTMLSourceElement.h
index aeaf884c81..7d5fb4de31 100644
--- a/dom/html/HTMLSourceElement.h
+++ b/dom/html/HTMLSourceElement.h
@@ -69,6 +69,11 @@ public:
     return mSrcTriggeringPrincipal;
   }
 
+  nsIPrincipal* GetSrcsetTriggeringPrincipal() const
+  {
+    return mSrcsetTriggeringPrincipal;
+  }
+
   void GetType(DOMString& aType)
   {
     GetHTMLAttr(nsGkAtoms::type, aType);
@@ -78,13 +83,13 @@ public:
     SetHTMLAttr(nsGkAtoms::type, aType, rv);
   }
 
-  void GetSrcset(DOMString& aSrcset)
+  void GetSrcset(DOMString& aSrcset, nsIPrincipal&)
   {
     GetHTMLAttr(nsGkAtoms::srcset, aSrcset);
   }
-  void SetSrcset(const nsAString& aSrcset, mozilla::ErrorResult& rv)
+  void SetSrcset(const nsAString& aSrcset, nsIPrincipal& aTriggeringPrincipal, mozilla::ErrorResult& rv)
   {
-    SetHTMLAttr(nsGkAtoms::srcset, aSrcset, rv);
+    SetHTMLAttr(nsGkAtoms::srcset, aSrcset, aTriggeringPrincipal, rv);
   }
 
   void GetSizes(DOMString& aSizes)
@@ -124,6 +129,9 @@ private:
   // The triggering principal for the src attribute.
   nsCOMPtr<nsIPrincipal> mSrcTriggeringPrincipal;
 
+  // The triggering principal for the srcset attribute.
+  nsCOMPtr<nsIPrincipal> mSrcsetTriggeringPrincipal;
+
   // Generates a new nsMediaList using the given input
   void UpdateMediaList(const nsAttrValue* aValue);
 };
diff --git a/dom/webidl/HTMLSourceElement.webidl b/dom/webidl/HTMLSourceElement.webidl
index 78570b8579..17f5ef7997 100644
--- a/dom/webidl/HTMLSourceElement.webidl
+++ b/dom/webidl/HTMLSourceElement.webidl
@@ -20,7 +20,7 @@ interface HTMLSourceElement : HTMLElement {
 };
 
 partial interface HTMLSourceElement {
-           [CEReactions, SetterThrows]
+           [CEReactions, NeedsSubjectPrincipal, SetterThrows]
            attribute DOMString srcset;
            [CEReactions, SetterThrows]
            attribute DOMString sizes;