Bug 1292618: Support basic pseudo-element restyling. r=heycam

:before and :after only, for now.

MozReview-Commit-ID: 9hLFvVhqIrN
Signed-off-by: Emilio Cobos Álvarez <ecoal95@gmail.com>

layout/base/ServoRestyleManager.cpp

@@ -6,6 +6,9 @@
 
 #include "mozilla/ServoRestyleManager.h"
 #include "mozilla/ServoStyleSet.h"
+#include "mozilla/dom/ChildIterator.h"
+#include "nsContentUtils.h"
+#include "nsStyleChangeList.h"
 
 using namespace mozilla::dom;
 
@@ -79,10 +82,10 @@ ServoRestyleManager::RecreateStyleContexts(nsIContent* aContent,
       Servo_GetComputedValues(aContent).Consume();
     MOZ_ASSERT(computedValues);
 
+    nsChangeHint changeHint = nsChangeHint(0);
     // NB: Change hint processing only applies to elements, at least until we
     // support display: contents.
     if (aContent->IsElement()) {
-      nsChangeHint changeHint = nsChangeHint(0);
       Element* element = aContent->AsElement();
 
       // Add an explicit change hint if appropriate.
@@ -140,6 +143,36 @@ ServoRestyleManager::RecreateStyleContexts(nsIContent* aContent,
       f->SetStyleContext(newContext);
     }
 
+    // Update pseudo-elements state if appropriate.
+    if (aContent->IsElement()) {
+      Element* aElement = aContent->AsElement();
+      const static CSSPseudoElementType pseudosToRestyle[] = {
+        CSSPseudoElementType::before, CSSPseudoElementType::after,
+      };
+
+      for (CSSPseudoElementType pseudoType : pseudosToRestyle) {
+        nsIAtom* pseudoTag =
+          nsCSSPseudoElements::GetPseudoAtom(pseudoType);
+        if (nsIFrame* pseudoFrame =
+              FrameForPseudoElement(aElement, pseudoTag)) {
+          // TODO: we could maybe make this more performant via calling into
+          // Servo just once to know which pseudo-elements we've got to restyle?
+          RefPtr<nsStyleContext> pseudoContext =
+            aStyleSet->ProbePseudoElementStyle(aElement, pseudoType,
+                                               newContext);
+
+          // If pseudoContext is null here, it means the frame is going away, so
+          // our change hint computation should have already indicated we need
+          // to reframe.
+          MOZ_ASSERT_IF(!pseudoContext,
+                        changeHint & nsChangeHint_ReconstructFrame);
+          if (pseudoContext) {
+            pseudoFrame->SetStyleContext(pseudoContext);
+          }
+        }
+      }
+    }
+
     // TODO: There are other continuations we still haven't restyled, mostly
     // pseudo-elements. We have to deal with those, and with anonymous boxes.
     aContent->UnsetFlags(NODE_IS_DIRTY_FOR_SERVO);
@@ -187,7 +220,37 @@ MarkChildrenAsDirtyForServo(nsIContent* aContent)
   }
 }
 
-void
+/* static */ nsIFrame*
+ServoRestyleManager::FrameForPseudoElement(nsIContent* aContent,
+                                           nsIAtom* aPseudoTagOrNull)
+{
+  MOZ_ASSERT_IF(aPseudoTagOrNull, aContent->IsElement());
+  nsIFrame* primaryFrame = aContent->GetPrimaryFrame();
+
+  if (!aPseudoTagOrNull) {
+    return primaryFrame;
+  }
+
+  if (!primaryFrame) {
+    return nullptr;
+  }
+
+  // NOTE: we probably need to special-case display: contents here. Gecko's
+  // RestyleManager passes the primary frame of the parent instead.
+  if (aPseudoTagOrNull == nsCSSPseudoElements::before) {
+    return nsLayoutUtils::GetBeforeFrameForContent(primaryFrame, aContent);
+  }
+
+  if (aPseudoTagOrNull == nsCSSPseudoElements::after) {
+    return nsLayoutUtils::GetAfterFrameForContent(primaryFrame, aContent);
+  }
+
+  MOZ_CRASH("Unkown pseudo-element given to "
+            "ServoRestyleManager::FrameForPseudoElement");
+  return nullptr;
+}
+
+/* static */ void
 ServoRestyleManager::NoteRestyleHint(Element* aElement, nsRestyleHint aHint)
 {
   const nsRestyleHint HANDLED_RESTYLE_HINTS = eRestyle_Self |

layout/base/ServoRestyleManager.h

@@ -77,6 +77,15 @@ public:
 
   bool HasPendingRestyles() { return !mModifiedElements.IsEmpty(); }
 
+  /**
+   * Gets the appropriate frame given a content and a pseudo-element tag.
+   *
+   * Right now only supports a null tag, before or after. If the pseudo-element
+   * is not null, the content needs to be an element.
+   */
+  static nsIFrame* FrameForPseudoElement(nsIContent* aContent,
+                                         nsIAtom* aPseudoTagOrNull);
+
 protected:
   ~ServoRestyleManager() {}
 

layout/style/ServoBindings.cpp

@@ -14,6 +14,7 @@
 #include "nsDOMTokenList.h"
 #include "nsIDOMNode.h"
 #include "nsIDocument.h"
+#include "nsIFrame.h"
 #include "nsINode.h"
 #include "nsIPrincipal.h"
 #include "nsNameSpaceManager.h"
@@ -24,8 +25,11 @@
 
 #include "mozilla/EventStates.h"
 #include "mozilla/ServoElementSnapshot.h"
+#include "mozilla/ServoRestyleManager.h"
 #include "mozilla/dom/Element.h"
 
+using namespace mozilla;
+
 #define IMPL_STRONG_REF_TYPE(name, T)           \
   already_AddRefed<T> name::Consume() {         \
     RefPtr<T> result = dont_AddRef(mPtr);       \
@@ -196,15 +200,17 @@ Gecko_UnsetNodeFlags(RawGeckoNode* aNode, uint32_t aFlags)
 }
 
 nsStyleContext*
-Gecko_GetStyleContext(RawGeckoNode* aNode)
+Gecko_GetStyleContext(RawGeckoNode* aNode, nsIAtom* aPseudoTagOrNull)
 {
   MOZ_ASSERT(aNode->IsContent());
-  nsIFrame* primaryFrame = aNode->AsContent()->GetPrimaryFrame();
-  if (!primaryFrame) {
+  nsIFrame* relevantFrame =
+    ServoRestyleManager::FrameForPseudoElement(aNode->AsContent(),
+                                               aPseudoTagOrNull);
+  if (!relevantFrame) {
     return nullptr;
   }
 
-  return primaryFrame->StyleContext();
+  return relevantFrame->StyleContext();
 }
 
 nsChangeHint
@@ -727,6 +733,12 @@ Gecko_ClearPODTArray(void* aArray, size_t aElementSize, size_t aElementAlign)
                                                         aElementSize, aElementAlign);
 }
 
+void
+Gecko_ClearStyleContents(nsStyleContent* aContent)
+{
+  aContent->AllocateContents(0);
+}
+
 void
 Gecko_EnsureImageLayersLength(nsStyleImageLayers* aLayers, size_t aLen)
 {
@@ -819,7 +831,7 @@ Servo_DropNodeData(ServoNodeData* data)
 
 RawServoStyleSheetStrong
 Servo_StylesheetFromUTF8Bytes(const uint8_t* bytes, uint32_t length,
-                              mozilla::css::SheetParsingMode mode,
+                              css::SheetParsingMode mode,
                               const uint8_t* base_bytes, uint32_t base_length,
                               ThreadSafeURIHolder* base,
                               ThreadSafeURIHolder* referrer,

layout/style/ServoBindings.h

@@ -215,7 +215,8 @@ void Gecko_UnsetNodeFlags(RawGeckoNode* node, uint32_t flags);
 //
 // Also, we might want a ComputedValues to ComputedValues API for animations?
 // Not if we do them in Gecko...
-nsStyleContext* Gecko_GetStyleContext(RawGeckoNode* node);
+nsStyleContext* Gecko_GetStyleContext(RawGeckoNode* node,
+                                      nsIAtom* aPseudoTagOrNull);
 nsChangeHint Gecko_CalcStyleDifference(nsStyleContext* oldstyle,
                                        ServoComputedValuesBorrowed newstyle);
 void Gecko_StoreStyleDifference(RawGeckoNode* node, nsChangeHint change);
@@ -231,6 +232,10 @@ void Gecko_EnsureTArrayCapacity(void* array, size_t capacity, size_t elem_size);
 // otherwise. This is ensured with rust traits for the relevant structs.
 void Gecko_ClearPODTArray(void* array, size_t elem_size, size_t elem_align);
 
+// Clear the mContents field in nsStyleContent. This is needed to run the
+// destructors, otherwise we'd leak the images (though we still don't support
+// those), strings, and whatnot.
+void Gecko_ClearStyleContents(nsStyleContent* content);
 void Gecko_EnsureImageLayersLength(nsStyleImageLayers* layers, size_t len);
 
 void Gecko_InitializeImageLayer(nsStyleImageLayers::Layer* layer,

layout/style/ServoStyleSet.cpp

@@ -114,8 +114,7 @@ ServoStyleSet::GetContext(already_AddRefed<ServoComputedValues> aComputedValues,
   bool skipFixup = false;
 
   return NS_NewStyleContext(aParentContext, mPresContext, aPseudoTag,
-                            aPseudoType,
-                            Move(aComputedValues), skipFixup);
+                            aPseudoType, Move(aComputedValues), skipFixup);
 }
 
 already_AddRefed<nsStyleContext>