Issue #1629 - Uplift implementation of <link disabled> behavior for stylesheets.

4 files changed, 66 insertions, 20 deletions

diff --git a/dom/html/HTMLLinkElement.cpp b/dom/html/HTMLLinkElement.cpp
index 8afe767bd..1b78cbd69 100644
--- a/dom/html/HTMLLinkElement.cpp
+++ b/dom/html/HTMLLinkElement.cpp
@@ -33,6 +33,8 @@
 #define LINK_ELEMENT_FLAG_BIT(n_) \
   NODE_FLAG_BIT(ELEMENT_TYPE_SPECIFIC_BITS_OFFSET + (n_))
 
+#define LINK_DISABLED Preferences::GetBool("dom.link.disabled_attribute.enabled", true)
+
 // Link element specific bits
 enum {
   // Indicates that a DNS Prefetch has been requested from this Link element.
@@ -92,9 +94,14 @@ NS_INTERFACE_TABLE_TAIL_INHERITING(nsGenericHTMLElement)
 
 NS_IMPL_ELEMENT_CLONE(HTMLLinkElement)
 
+
 bool
-HTMLLinkElement::Disabled()
+HTMLLinkElement::Disabled() const
 {
+  if (LINK_DISABLED) {
+    return GetBoolAttr(nsGkAtoms::disabled);
+  }
+
   StyleSheet* ss = GetSheet();
   return ss && ss->Disabled();
 }
@@ -107,8 +114,12 @@ HTMLLinkElement::GetMozDisabled(bool* aDisabled)
 }
 
 void
-HTMLLinkElement::SetDisabled(bool aDisabled)
-{
+HTMLLinkElement::SetDisabled(bool aDisabled, ErrorResult& aRv)
+{ 
+  if (LINK_DISABLED) {
+  return SetHTMLBoolAttr(nsGkAtoms::disabled, aDisabled, aRv);
+  }
+
   if (StyleSheet* ss = GetSheet()) {
     ss->SetDisabled(aDisabled);
   }
@@ -117,11 +128,11 @@ HTMLLinkElement::SetDisabled(bool aDisabled)
 NS_IMETHODIMP
 HTMLLinkElement::SetMozDisabled(bool aDisabled)
 {
-  SetDisabled(aDisabled);
-  return NS_OK;
+  ErrorResult rv;
+  SetDisabled(aDisabled, rv);
+  return rv.StealNSResult(); 
 }
 
-
 NS_IMPL_STRING_ATTR(HTMLLinkElement, Charset, charset)
 NS_IMPL_URI_ATTR(HTMLLinkElement, Href, href)
 NS_IMPL_STRING_ATTR(HTMLLinkElement, Hreflang, hreflang)
@@ -369,7 +380,8 @@ HTMLLinkElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
          aName == nsGkAtoms::rel ||
          aName == nsGkAtoms::title ||
          aName == nsGkAtoms::media ||
-         aName == nsGkAtoms::type)) {
+         aName == nsGkAtoms::type ||
+         (LINK_DISABLED && aName == nsGkAtoms::disabled))) {
       bool dropSheet = false;
       if (aName == nsGkAtoms::rel) {
         nsAutoString value;
@@ -396,17 +408,24 @@ HTMLLinkElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                dropSheet ||
                                (aName == nsGkAtoms::title ||
                                 aName == nsGkAtoms::media ||
-                                aName == nsGkAtoms::type));
+                                aName == nsGkAtoms::type ||
+                                (LINK_DISABLED && aName == nsGkAtoms::disabled)));
     }
   } else {
-    // Since removing href or rel makes us no longer link to a
-    // stylesheet, force updates for those too.
+    // If the disabled attribute is removed from a link element, the 
+    // stylesheet may be explicitly enabled.
     if (aNameSpaceID == kNameSpaceID_None) {
+      if (aName == nsGkAtoms::disabled && LINK_DISABLED) {
+        mExplicitlyEnabled = true;
+      }
+      // Since removing href or rel makes us no longer link to a
+      // stylesheet, force updates for those too.
       if (aName == nsGkAtoms::href ||
           aName == nsGkAtoms::rel ||
           aName == nsGkAtoms::title ||
           aName == nsGkAtoms::media ||
-          aName == nsGkAtoms::type) {
+          aName == nsGkAtoms::type ||
+          (LINK_DISABLED && aName == nsGkAtoms::disabled)) {
         UpdateStyleSheetInternal(nullptr, nullptr, true);
       }
       if (aName == nsGkAtoms::href ||
@@ -499,13 +518,15 @@ HTMLLinkElement::GetStyleSheetInfo(nsAString& aTitle,
                                    nsAString& aType,
                                    nsAString& aMedia,
                                    bool* aIsScoped,
-                                   bool* aIsAlternate)
+                                   bool* aIsAlternate,
+                                   bool* aIsExplicitlyEnabled)
 {
   aTitle.Truncate();
   aType.Truncate();
   aMedia.Truncate();
   *aIsScoped = false;
   *aIsAlternate = false;
+  *aIsExplicitlyEnabled = false;
 
   nsAutoString rel;
   GetAttr(kNameSpaceID_None, nsGkAtoms::rel, rel);
@@ -515,6 +536,20 @@ HTMLLinkElement::GetStyleSheetInfo(nsAString& aTitle,
     return;
   }
 
+  if (LINK_DISABLED) {
+
+  // Is the link disabled?
+  if (Disabled()) {
+    return;
+  }
+
+  // Is it explicitly enabled?
+  if (mExplicitlyEnabled) {
+    *aIsExplicitlyEnabled = true;
+  }
+
+  }
+
   nsAutoString title;
   GetAttr(kNameSpaceID_None, nsGkAtoms::title, title);
   title.CompressWhitespace();
diff --git a/dom/html/HTMLLinkElement.h b/dom/html/HTMLLinkElement.h
index 421b149e9..f9c832c8d 100644
--- a/dom/html/HTMLLinkElement.h
+++ b/dom/html/HTMLLinkElement.h
@@ -84,8 +84,8 @@ public:
   virtual bool HasDeferredDNSPrefetchRequest() override;
 
   // WebIDL
-  bool Disabled();
-  void SetDisabled(bool aDisabled);
+  bool Disabled() const;
+  void SetDisabled(bool aDisabled, ErrorResult& aRv);
   // XPCOM GetHref is fine.
   void SetHref(const nsAString& aHref, ErrorResult& aRv)
   {
@@ -179,10 +179,18 @@ protected:
                                  nsAString& aType,
                                  nsAString& aMedia,
                                  bool* aIsScoped,
-                                 bool* aIsAlternate) override;
-protected:
+                                 bool* aIsAlternate,
+                                 bool* aIsExplicitlyEnabled) override;
+
   RefPtr<nsDOMTokenList> mRelList;
 
+  // The "explicitly enabled" flag. This flag is set whenever the 'disabled'
+  // attribute is explicitly unset, and makes alternate stylesheets not be
+  // disabled by default anymore.
+  //
+  // See https://github.com/whatwg/html/issues/3840#issuecomment-481034206.
+  bool mExplicitlyEnabled = false;
+
 private:
   RefPtr<ImportLoader> mImportLoader;
 };
diff --git a/dom/html/HTMLStyleElement.cpp b/dom/html/HTMLStyleElement.cpp
index 329dda648..87dc68f83 100644
--- a/dom/html/HTMLStyleElement.cpp
+++ b/dom/html/HTMLStyleElement.cpp
@@ -66,7 +66,7 @@ HTMLStyleElement::GetMozDisabled(bool* aDisabled)
 }
 
 bool
-HTMLStyleElement::Disabled()
+HTMLStyleElement::Disabled() const
 {
   StyleSheet* ss = GetSheet();
   return ss && ss->Disabled();
@@ -222,12 +222,14 @@ HTMLStyleElement::GetStyleSheetInfo(nsAString& aTitle,
                                     nsAString& aType,
                                     nsAString& aMedia,
                                     bool* aIsScoped,
-                                    bool* aIsAlternate)
+                                    bool* aIsAlternate,
+                                    bool* aIsExplicitlyEnabled)
 {
   aTitle.Truncate();
   aType.Truncate();
   aMedia.Truncate();
   *aIsAlternate = false;
+  *aIsExplicitlyEnabled = false;
 
   nsAutoString title;
   GetAttr(kNameSpaceID_None, nsGkAtoms::title, title);
diff --git a/dom/html/HTMLStyleElement.h b/dom/html/HTMLStyleElement.h
index 6b2a12b1f..9f82b8e51 100644
--- a/dom/html/HTMLStyleElement.h
+++ b/dom/html/HTMLStyleElement.h
@@ -58,7 +58,7 @@ public:
   NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
   NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
 
-  bool Disabled();
+  bool Disabled() const;
   void SetDisabled(bool aDisabled);
   void SetMedia(const nsAString& aMedia, ErrorResult& aError)
   {
@@ -87,7 +87,8 @@ protected:
                          nsAString& aType,
                          nsAString& aMedia,
                          bool* aIsScoped,
-                         bool* aIsAlternate) override;
+                         bool* aIsAlternate,
+                         bool* aIsExplicitlyEnabled) override;
   /**
    * Common method to call from the various mutation observer methods.
    * aContent is a content node that's either the one that changed or its