Bug 1487659 - Make Selection treat SelectionChangeListener as a concrete class rather than nsISelectionListener r=smaug

SelectionChangeListener is an nsISelectionListener class.  This is added only
to Selection for "normal" and added by nsFrameSelection::Init() after
AccessibleCaretEventHub.  So, we can make Selection directly treat
SelectionChangeListener.

Differential Revision: https://phabricator.services.mozilla.com/D4757

--HG--
extra : moz-landing-system : lando

dom/base/Selection.cpp

@@ -60,7 +60,6 @@
 #include "nsINamed.h"
 
 #include "nsISelectionController.h" //for the enums
-#include "SelectionChangeListener.h"
 #include "nsCopySupport.h"
 #include "nsIClipboard.h"
 #include "nsIFrameInlines.h"
@@ -738,6 +737,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Selection)
   // in JS!).
   tmp->mNotifyAutoCopy = false;
   tmp->StopNotifyingAccessibleCaretEventHub();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSelectionChangeListener)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mSelectionListeners)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mCachedRange)
   tmp->RemoveAllRanges(IgnoreErrors());
@@ -754,6 +754,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Selection)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAnchorFocusRange)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCachedRange)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFrameSelection)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSelectionChangeListener)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSelectionListeners)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(Selection)
@@ -3490,7 +3491,7 @@ Selection::NotifySelectionListeners()
   // We've notified all selection listeners even when some of them are removed
   // (and may be destroyed) during notifying one of them.  Therefore, we should
   // copy all listeners to the local variable first.
-  AutoTArray<nsCOMPtr<nsISelectionListener>, 8>
+  AutoTArray<nsCOMPtr<nsISelectionListener>, 5>
     selectionListeners(mSelectionListeners);
 
   int16_t reason = frameSelection->PopReason();
@@ -3504,6 +3505,10 @@ Selection::NotifySelectionListeners()
     hub->OnSelectionChange(doc, this, reason);
   }
 
+  if (mSelectionChangeListener) {
+    RefPtr<SelectionChangeListener> listener(mSelectionChangeListener);
+    listener->OnSelectionChange(doc, this, reason);
+  }
   for (auto& listener : selectionListeners) {
     listener->NotifySelectionChanged(doc, this, reason);
   }

dom/base/Selection.h

@@ -12,6 +12,7 @@
 #include "mozilla/AccessibleCaretEventHub.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/RangeBoundary.h"
+#include "mozilla/SelectionChangeListener.h"
 #include "mozilla/TextRange.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"
@@ -115,6 +116,18 @@ public:
     mAccessibleCaretEventHub = nullptr;
   }
 
+  /**
+   * EnableSelectionChangeEvent() starts to notify SelectionChangeListener of
+   * selection change to dispatch a selectionchange event at every selection
+   * change.
+   */
+  void EnableSelectionChangeEvent()
+  {
+    if (!mSelectionChangeListener) {
+      mSelectionChangeListener = new SelectionChangeListener();
+    }
+  }
+
   nsIDocument* GetParentObject() const;
   DocGroup* GetDocGroup() const;
 
@@ -718,6 +731,7 @@ private:
   RefPtr<nsRange> mCachedRange;
   RefPtr<nsFrameSelection> mFrameSelection;
   RefPtr<AccessibleCaretEventHub> mAccessibleCaretEventHub;
+  RefPtr<SelectionChangeListener> mSelectionChangeListener;
   RefPtr<nsAutoScrollTimer> mAutoScrollTimer;
   nsTArray<nsCOMPtr<nsISelectionListener>> mSelectionListeners;
   nsRevocableEventPtr<ScrollSelectionIntoViewEvent> mScrollEvent;

dom/base/SelectionChangeListener.cpp

@@ -71,22 +71,18 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(SelectionChangeListener)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOldRanges);
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SelectionChangeListener)
-  NS_INTERFACE_MAP_ENTRY(nsISupports)
-  NS_INTERFACE_MAP_ENTRY(nsISelectionListener)
-NS_INTERFACE_MAP_END
+NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(SelectionChangeListener, AddRef)
+NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(SelectionChangeListener, Release)
 
-NS_IMPL_CYCLE_COLLECTING_ADDREF(SelectionChangeListener)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(SelectionChangeListener)
-
-NS_IMETHODIMP
-SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
-                                                Selection* aSel, int16_t aReason)
+void
+SelectionChangeListener::OnSelectionChange(nsIDocument* aDoc,
+                                           Selection* aSel,
+                                           int16_t aReason)
 {
   nsIDocument* doc = aSel->GetParentObject();
   if (!(doc && nsContentUtils::IsSystemPrincipal(doc->NodePrincipal())) &&
       !nsFrameSelection::sSelectionEventsEnabled) {
-    return NS_OK;
+    return;
   }
 
   // Check if the ranges have actually changed
@@ -103,7 +99,7 @@ SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
     }
 
     if (!changed) {
-      return NS_OK;
+      return;
     }
   }
 
@@ -116,7 +112,7 @@ SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
   if (doc) {
     nsPIDOMWindowInner* inner = doc->GetInnerWindow();
     if (inner && !inner->HasSelectionChangeEventListeners()) {
-      return NS_OK;
+      return;
     }
   }
 
@@ -124,7 +120,7 @@ SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
   // update mOldRanges so that changes after the changes stop being hidden don't
   // incorrectly trigger a change, even though they didn't change anything
   if (aSel->IsBlockingSelectionChangeEvents()) {
-    return NS_OK;
+    return;
   }
 
   // The spec currently doesn't say that we should dispatch this event on text
@@ -163,7 +159,7 @@ SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
     if (const nsFrameSelection* fs = aSel->GetFrameSelection()) {
       if (nsCOMPtr<nsIContent> root = fs->GetLimiter()) {
         if (root->IsInNativeAnonymousSubtree()) {
-          return NS_OK;
+          return;
         }
       }
     }
@@ -174,6 +170,4 @@ SelectionChangeListener::NotifySelectionChanged(nsIDocument* aDoc,
       asyncDispatcher->PostDOMEvent();
     }
   }
-
-  return NS_OK;
 }

dom/base/SelectionChangeListener.h

@@ -7,7 +7,6 @@
 #ifndef mozilla_SelectionChangeListener_h_
 #define mozilla_SelectionChangeListener_h_
 
-#include "nsISelectionListener.h"
 #include "mozilla/Attributes.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsTArray.h"
@@ -19,14 +18,21 @@ class nsINode;
 namespace mozilla {
 namespace dom {
 
-class SelectionChangeListener final : public nsISelectionListener
+// XXX This class name is too generic.  Perhaps, SelectionChangeEventDispatcher?
+//     And also it's odd that this is in |dom| namespace since this is not
+//     an implementation of any DOM object.
+class SelectionChangeListener final
 {
 public:
   // SelectionChangeListener has to participate in cycle collection because
   // it holds strong references to nsINodes in its mOldRanges array.
-  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-  NS_DECL_CYCLE_COLLECTION_CLASS(SelectionChangeListener)
-  NS_DECL_NSISELECTIONLISTENER
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(SelectionChangeListener)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(SelectionChangeListener)
+
+  MOZ_CAN_RUN_SCRIPT
+  void OnSelectionChange(nsIDocument* aDocument,
+                         Selection* aSelection,
+                         int16_t aReason);
 
   // This field is used to keep track of the ranges which were present in the
   // selection when the selectionchange event was previously fired. This allows

dom/base/moz.build

@@ -132,6 +132,7 @@ EXPORTS.mozilla += [
     'FeedWriterEnabled.h',
     'FlushType.h',
     'RangeBoundary.h',
+    'SelectionChangeListener.h',
     'TextInputProcessor.h',
     'UseCounter.h',
 ]

layout/generic/nsFrameSelection.cpp

@@ -60,7 +60,6 @@ static NS_DEFINE_CID(kFrameTraversalCID, NS_FRAMETRAVERSAL_CID);
 #include "nsIDocument.h"
 
 #include "nsISelectionController.h" //for the enums
-#include "SelectionChangeListener.h"
 #include "nsCopySupport.h"
 #include "nsIClipboard.h"
 #include "nsIFrameInlines.h"
@@ -667,10 +666,7 @@ nsFrameSelection::Init(nsIPresShell *aShell, nsIContent *aLimiter,
       (doc && nsContentUtils::IsSystemPrincipal(doc->NodePrincipal()))) {
     int8_t index = GetIndexFromSelectionType(SelectionType::eNormal);
     if (mDomSelections[index]) {
-      // The Selection instance will hold a strong reference to its selectionchangelistener
-      // so we don't have to worry about that!
-      RefPtr<SelectionChangeListener> listener = new SelectionChangeListener;
-      mDomSelections[index]->AddSelectionListener(listener);
+      mDomSelections[index]->EnableSelectionChangeEvent();
     }
   }
 }