Bug 1315874 - Pass a base style context to nsSMILCSSProperty; r=heycam

We will use this in the next patch in this series to fetch the base style.

(I tried simply passing this as a parameter to GetBaseStyle but it proved to be
more complicated since all the overrides of GetBaseStyle would need to be
updated to take a parameter that would be irrelevant to most of them.)

MozReview-Commit-ID: Fdr4rFUlE9V

--HG--
extra : rebase_source : 26978951302b4764938959a065402f05220b6093

dom/smil/nsSMILCSSProperty.cpp

@@ -53,8 +53,11 @@ GetCSSComputedValue(Element* aElem,
 
 // Class Methods
 nsSMILCSSProperty::nsSMILCSSProperty(nsCSSPropertyID aPropID,
-                                     Element* aElement)
-  : mPropID(aPropID), mElement(aElement)
+                                     Element* aElement,
+                                     nsStyleContext* aBaseStyleContext)
+  : mPropID(aPropID)
+  , mElement(aElement)
+  , mBaseStyleContext(aBaseStyleContext)
 {
   MOZ_ASSERT(IsPropertyAnimatable(mPropID),
              "Creating a nsSMILCSSProperty for a property "

dom/smil/nsSMILCSSProperty.h

@@ -15,6 +15,8 @@
 #include "nsCSSPropertyID.h"
 #include "nsCSSValue.h"
 
+class nsStyleContext;
+
 namespace mozilla {
 namespace dom {
 class Element;
@@ -33,8 +35,14 @@ public:
    * Constructs a new nsSMILCSSProperty.
    * @param  aPropID   The CSS property we're interested in animating.
    * @param  aElement  The element whose CSS property is being animated.
+   * @param  aBaseStyleContext  The style context to use when getting the base
+   *                            value. If this is nullptr and GetBaseValue is
+   *                            called, an empty nsSMILValue initialized with
+   *                            the nsSMILCSSValueType will be returned.
    */
-  nsSMILCSSProperty(nsCSSPropertyID aPropID, mozilla::dom::Element* aElement);
+  nsSMILCSSProperty(nsCSSPropertyID aPropID,
+                    mozilla::dom::Element* aElement,
+                    nsStyleContext* aBaseStyleContext);
 
   // nsISMILAttr methods
   virtual nsresult ValueFromString(const nsAString& aStr,
@@ -62,6 +70,12 @@ protected:
   // as the Compositing step, and DOM elements don't get a chance to die during
   // that time.
   mozilla::dom::Element*   mElement;
+
+  // The style context to use when fetching base styles.
+  // As with mElement, since an nsISMILAttr only lives as long as the
+  // compositing step and since ComposeAttribute holds an owning reference to
+  // the base style context, we can use a non-owning reference here.
+  nsStyleContext* mBaseStyleContext;
 };
 
 #endif // NS_SMILCSSPROPERTY_H_

dom/smil/nsSMILCompositor.cpp

@@ -6,6 +6,7 @@
 
 #include "nsSMILCompositor.h"
 
+#include "nsComputedDOMStyle.h"
 #include "nsCSSProps.h"
 #include "nsHashKeys.h"
 #include "nsSMILCSSProperty.h"
@@ -54,9 +55,18 @@ nsSMILCompositor::ComposeAttribute(bool& aMightHavePendingStyleUpdates)
   if (!mKey.mElement)
     return;
 
+  // If we might need to resolve base styles, grab a suitable style context
+  // for initializing our nsISMILAttr with.
+  RefPtr<nsStyleContext> baseStyleContext;
+  if (MightNeedBaseStyle()) {
+    baseStyleContext =
+      nsComputedDOMStyle::GetUnanimatedStyleContextNoFlush(mKey.mElement,
+                                                           nullptr, nullptr);
+  }
+
   // FIRST: Get the nsISMILAttr (to grab base value from, and to eventually
   // give animated value to)
-  UniquePtr<nsISMILAttr> smilAttr = CreateSMILAttr();
+  UniquePtr<nsISMILAttr> smilAttr = CreateSMILAttr(baseStyleContext);
   if (!smilAttr) {
     // Target attribute not found (or, out of memory)
     return;
@@ -115,7 +125,7 @@ nsSMILCompositor::ClearAnimationEffects()
   if (!mKey.mElement || !mKey.mAttributeName)
     return;
 
-  UniquePtr<nsISMILAttr> smilAttr = CreateSMILAttr();
+  UniquePtr<nsISMILAttr> smilAttr = CreateSMILAttr(nullptr);
   if (!smilAttr) {
     // Target attribute not found (or, out of memory)
     return;
@@ -126,12 +136,13 @@ nsSMILCompositor::ClearAnimationEffects()
 // Protected Helper Functions
 // --------------------------
 UniquePtr<nsISMILAttr>
-nsSMILCompositor::CreateSMILAttr()
+nsSMILCompositor::CreateSMILAttr(nsStyleContext* aBaseStyleContext)
 {
   nsCSSPropertyID propID = GetCSSPropertyToAnimate();
 
   if (propID != eCSSProperty_UNKNOWN) {
-    return MakeUnique<nsSMILCSSProperty>(propID, mKey.mElement.get());
+    return MakeUnique<nsSMILCSSProperty>(propID, mKey.mElement.get(),
+                                         aBaseStyleContext);
   }
 
   return mKey.mElement->GetAnimatedAttr(mKey.mAttributeNamespaceID,

dom/smil/nsSMILCompositor.h

@@ -74,7 +74,11 @@ public:
 
  private:
   // Create a nsISMILAttr for my target, on the heap.
-  mozilla::UniquePtr<nsISMILAttr> CreateSMILAttr();
+  //
+  // @param aBaseStyleContext  An optional style context which, if set, will be
+  //                           used when fetching the base style.
+  mozilla::UniquePtr<nsISMILAttr>
+  CreateSMILAttr(nsStyleContext* aBaseStyleContext);
 
   // Returns the CSS property this compositor should animate, or
   // eCSSProperty_UNKNOWN if this compositor does not animate a CSS property.