Bug 1525107 - Implement <meta name=color-scheme>. r=dholbert

There are still tests failing because
https://bugzilla.mozilla.org/show_bug.cgi?id=1736034 hasn't been synced
yet.

Once that lands, they will still fail because we don't change
Canvas/CanvasText based on color-scheme, but that I'm attaching
patches for after this one.

Differential Revision: https://phabricator.services.mozilla.com/D129743

dom/base/Document.cpp

@@ -220,7 +220,6 @@
 #include "mozilla/dom/TimeoutManager.h"
 #include "mozilla/dom/Touch.h"
 #include "mozilla/dom/TouchEvent.h"
-#include "mozilla/dom/TreeOrderedArray.h"
 #include "mozilla/dom/TreeOrderedArrayInlines.h"
 #include "mozilla/dom/TreeWalker.h"
 #include "mozilla/dom/URL.h"
@@ -10768,6 +10767,45 @@ void Document::GetXMLDeclaration(nsAString& aVersion, nsAString& aEncoding,
   }
 }
 
+void Document::AddColorSchemeMeta(HTMLMetaElement& aMeta) {
+  mColorSchemeMetaTags.Insert(aMeta);
+  RecomputeColorScheme();
+}
+
+void Document::RemoveColorSchemeMeta(HTMLMetaElement& aMeta) {
+  mColorSchemeMetaTags.RemoveElement(aMeta);
+  RecomputeColorScheme();
+}
+
+void Document::RecomputeColorScheme() {
+  if (!StaticPrefs::layout_css_color_scheme_enabled()) {
+    return;
+  }
+  auto oldColorScheme = mColorSchemeBits;
+  mColorSchemeBits = 0;
+  const nsTArray<HTMLMetaElement*>& elements = mColorSchemeMetaTags;
+  for (const HTMLMetaElement* el : elements) {
+    nsAutoString content;
+    if (!el->GetAttr(nsGkAtoms::content, content)) {
+      continue;
+    }
+
+    NS_ConvertUTF16toUTF8 contentU8(content);
+    if (Servo_ColorScheme_Parse(&contentU8, &mColorSchemeBits)) {
+      break;
+    }
+  }
+
+  if (mColorSchemeBits == oldColorScheme) {
+    return;
+  }
+
+  if (nsPresContext* pc = GetPresContext()) {
+    // This affects system colors, which are inherited, so we need to recascade.
+    pc->RebuildAllStyleData(nsChangeHint(0), RestyleHint::RecascadeSubtree());
+  }
+}
+
 bool Document::IsScriptEnabled() {
   // If this document is sandboxed without 'allow-scripts'
   // script is not enabled

dom/base/Document.h

@@ -50,6 +50,7 @@
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/EventTarget.h"
 #include "mozilla/dom/Nullable.h"
+#include "mozilla/dom/TreeOrderedArray.h"
 #include "mozilla/dom/ViewportMetaData.h"
 #include "nsAtom.h"
 #include "nsCOMArray.h"
@@ -2179,11 +2180,17 @@ class Document : public nsINode,
   /**
    * Returns the bits for the color-scheme specified by the
    * <meta name="color-scheme">.
-   *
-   * TODO(emilio): Actually process the meta tag.
    */
   uint8_t GetColorSchemeBits() const { return mColorSchemeBits; }
 
+  /**
+   * Traverses the DOM and computes the supported color schemes as per
+   * https://html.spec.whatwg.org/#meta-color-scheme
+   */
+  void RecomputeColorScheme();
+  void AddColorSchemeMeta(HTMLMetaElement&);
+  void RemoveColorSchemeMeta(HTMLMetaElement&);
+
   /**
    * Returns true if this is what HTML 5 calls an "HTML document" (for example
    * regular HTML document with Content-Type "text/html", image documents and
@@ -5188,6 +5195,13 @@ class Document : public nsINode,
   // element.
   UniquePtr<ViewportMetaData> mLastModifiedViewportMetaData;
 
+  // A tree ordered list of all color-scheme meta tags in this document.
+  //
+  // TODO(emilio): There are other meta tags in the spec that have a similar
+  // processing model to color-scheme. We could store all in-document meta tags
+  // here to get sane and fast <meta> element processing.
+  TreeOrderedArray<HTMLMetaElement> mColorSchemeMetaTags;
+
   // These member variables cache information about the viewport so we don't
   // have to recalculate it each time.
   LayoutDeviceToScreenScale mScaleMinFloat;

dom/html/HTMLMetaElement.cpp

@@ -43,15 +43,15 @@ nsresult HTMLMetaElement::AfterSetAttr(int32_t aNameSpaceID, nsAtom* aName,
     if (Document* document = GetUncomposedDoc()) {
       if (aName == nsGkAtoms::content) {
         if (const nsAttrValue* name = GetParsedAttr(nsGkAtoms::name)) {
-          MetaAddedOrChanged(*document, *name, FromChange::Yes);
+          MetaAddedOrChanged(*document, *name, ChangeKind::ContentChange);
         }
         CreateAndDispatchEvent(*document, u"DOMMetaChanged"_ns);
       } else if (aName == nsGkAtoms::name) {
         if (aOldValue) {
-          MetaRemoved(*document, *aOldValue, FromChange::Yes);
+          MetaRemoved(*document, *aOldValue, ChangeKind::NameChange);
         }
         if (aValue) {
-          MetaAddedOrChanged(*document, *aValue, FromChange::Yes);
+          MetaAddedOrChanged(*document, *aValue, ChangeKind::NameChange);
         }
         CreateAndDispatchEvent(*document, u"DOMMetaChanged"_ns);
       }
@@ -113,7 +113,7 @@ nsresult HTMLMetaElement::BindToTree(BindContext& aContext, nsINode& aParent) {
   }
 
   if (const nsAttrValue* name = GetParsedAttr(nsGkAtoms::name)) {
-    MetaAddedOrChanged(doc, *name, FromChange::No);
+    MetaAddedOrChanged(doc, *name, ChangeKind::TreeChange);
   }
   CreateAndDispatchEvent(doc, u"DOMMetaAdded"_ns);
   return rv;
@@ -122,7 +122,7 @@ nsresult HTMLMetaElement::BindToTree(BindContext& aContext, nsINode& aParent) {
 void HTMLMetaElement::UnbindFromTree(bool aNullParent) {
   if (Document* oldDoc = GetUncomposedDoc()) {
     if (const nsAttrValue* name = GetParsedAttr(nsGkAtoms::name)) {
-      MetaRemoved(*oldDoc, *name, FromChange::No);
+      MetaRemoved(*oldDoc, *name, ChangeKind::TreeChange);
     }
     CreateAndDispatchEvent(*oldDoc, u"DOMMetaRemoved"_ns);
   }
@@ -143,7 +143,7 @@ JSObject* HTMLMetaElement::WrapNode(JSContext* aCx,
 
 void HTMLMetaElement::MetaAddedOrChanged(Document& aDoc,
                                          const nsAttrValue& aName,
-                                         FromChange aFromChange) {
+                                         ChangeKind aChangeKind) {
   nsAutoString content;
   const bool hasContent = GetAttr(nsGkAtoms::content, content);
   if (aName.Equals(nsGkAtoms::viewport, eIgnoreCase)) {
@@ -159,12 +159,21 @@ void HTMLMetaElement::MetaAddedOrChanged(Document& aDoc,
     return aDoc.UpdateReferrerInfoFromMeta(content,
                                            /* aPreload = */ false);
   }
+  if (aName.Equals(nsGkAtoms::color_scheme, eIgnoreCase)) {
+    if (aChangeKind != ChangeKind::ContentChange) {
+      return aDoc.AddColorSchemeMeta(*this);
+    }
+    return aDoc.RecomputeColorScheme();
+  }
 }
 
 void HTMLMetaElement::MetaRemoved(Document& aDoc, const nsAttrValue& aName,
-                                  FromChange aFromChange) {
-  // TODO(emilio): We probably want to deal with <meta name=color-scheme> and co
-  // here.
+                                  ChangeKind aChangeKind) {
+  MOZ_ASSERT(aChangeKind != ChangeKind::ContentChange,
+             "Content change can't trigger removal");
+  if (aName.Equals(nsGkAtoms::color_scheme, eIgnoreCase)) {
+    return aDoc.RemoveColorSchemeMeta(*this);
+  }
 }
 
 }  // namespace mozilla::dom

dom/html/HTMLMetaElement.h

@@ -62,11 +62,11 @@ class HTMLMetaElement final : public nsGenericHTMLElement {
   virtual ~HTMLMetaElement();
 
  private:
-  enum class FromChange : bool { No, Yes };
+  enum class ChangeKind : uint8_t { TreeChange, NameChange, ContentChange };
   void MetaRemoved(Document& aDoc, const nsAttrValue& aName,
-                   FromChange aFromChange);
+                   ChangeKind aChangeKind);
   void MetaAddedOrChanged(Document& aDoc, const nsAttrValue& aName,
-                          FromChange aFromChange);
+                          ChangeKind aChangeKind);
 };
 
 }  // namespace dom

servo/components/style/values/specified/color.rs

@@ -935,6 +935,11 @@ impl ColorScheme {
             bits: ColorSchemeFlags::empty(),
         }
     }
+
+    /// Returns the raw bitfield.
+    pub fn raw_bits(&self) -> u8 {
+        self.bits.bits
+    }
 }
 
 impl Parse for ColorScheme {

servo/ports/geckolib/glue.rs

@@ -7214,3 +7214,27 @@ pub extern "C" fn Servo_GenericFontFamily_Parse(input: &nsACString) -> GenericFo
     let mut input = Parser::new(&mut input);
     GenericFontFamily::parse(&context, &mut input).unwrap_or(GenericFontFamily::None)
 }
+
+#[no_mangle]
+pub extern "C" fn Servo_ColorScheme_Parse(input: &nsACString, out: &mut u8) -> bool {
+    use style::values::specified::ColorScheme;
+
+    let context = ParserContext::new(
+        Origin::Author,
+        unsafe { dummy_url_data() },
+        Some(CssRuleType::Style),
+        ParsingMode::DEFAULT,
+        QuirksMode::NoQuirks,
+        None,
+        None,
+    );
+    let input = unsafe { input.as_str_unchecked() };
+    let mut input = ParserInput::new(&input);
+    let mut input = Parser::new(&mut input);
+    let scheme = match input.parse_entirely(|i| ColorScheme::parse(&context, i)) {
+        Ok(scheme) => scheme,
+        Err(..) => return false,
+    };
+    *out = scheme.raw_bits();
+    true
+}

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/__dir__.ini

@@ -0,0 +1 @@
+prefs: [layout.css.color-scheme.enabled:true]

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-attribute-changes.html.ini

@@ -1,24 +1,9 @@
 [meta-color-scheme-attribute-changes.html]
-  [Removed name attribute from meta color-scheme.]
-    expected: FAIL
-
-  [Set content attribute of meta color-scheme to empty string.]
-    expected: FAIL
-
   [Set content attribute of meta color-scheme to 'light'.]
     expected: FAIL
 
-  [Removed the content attribute of meta color-scheme.]
-    expected: FAIL
-
   [Set meta name to color-scheme.]
     expected: FAIL
 
   [Meta color-scheme initially 'dark'.]
     expected: FAIL
-
-  [Set content attribute of meta color-scheme to an invalid value.]
-    expected: FAIL
-
-  [Set content attribute of meta color-scheme to 'dark'.]
-    expected: FAIL

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-empty-content-value.html.ini

@@ -1,4 +0,0 @@
-[meta-color-scheme-empty-content-value.html]
-  [Meta color-scheme with empty content attribute has no effect.]
-    expected: FAIL
-

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-insert.html.ini

@@ -4,7 +4,3 @@
 
   [Inserted meta color-scheme before existing in head applies]
     expected: FAIL
-
-  [Initial color-scheme]
-    expected: FAIL
-

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-no-content-value.html.ini

@@ -1,4 +0,0 @@
-[meta-color-scheme-no-content-value.html]
-  [Meta color-scheme without content attribute has no effect.]
-    expected: FAIL
-

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-remove-head.html.ini

@@ -1,7 +1,3 @@
 [meta-color-scheme-remove-head.html]
-  [Initial value after removing head including meta color-scheme.]
-    expected: FAIL
-
   [Meta color-scheme applies.]
     expected: FAIL
-

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-remove.html.ini

@@ -1,10 +1,6 @@
 [meta-color-scheme-remove.html]
-  [Initial color-scheme with both meta elements removed.]
-    expected: FAIL
-
   [Second meta applies after first one is removed.]
     expected: FAIL
 
   [First meta applies.]
     expected: FAIL
-

testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/color-scheme/meta-color-scheme-single-value-in-shadow-tree.html.ini

@@ -1,4 +0,0 @@
-[meta-color-scheme-single-value-in-shadow-tree.html]
-  [Meta color-scheme in shadow tree does not apply.]
-    expected: FAIL
-

xpcom/ds/StaticAtoms.py

@@ -251,8 +251,8 @@ STATIC_ATOMS = [
     Atom("collapse", "collapse"),
     Atom("collapsed", "collapsed"),
     Atom("color", "color"),
-    Atom("colorIndex", "color-index"),
-    Atom("colorScheme", "color-scheme"),
+    Atom("color_index", "color-index"),
+    Atom("color_scheme", "color-scheme"),
     Atom("cols", "cols"),
     Atom("colspan", "colspan"),
     Atom("combobox", "combobox"),