Bug 1275914 part.2 Modify TextComposition::mCompositionStartOffset after every composition event dispatch r=smaug

When composition string hasn't been non-empty, insertion point of the composition string can be changed by a DOM event handler.  E.g., compositionstart, first compositionupdate and first text.  Therefore, TextComposition should update the composition start offset cache after every event dispatch.

MozReview-Commit-ID: FOPewPTRuCn

--HG--
extra : rebase_source : 95fbba8130a1d21e957cee305b3b2a433bfae56a

dom/events/TextComposition.cpp

@@ -69,6 +69,7 @@ TextComposition::TextComposition(nsPresContext* aPresContext,
   , mAllowControlCharacters(
       Preferences::GetBool("dom.compositionevent.allow_control_characters",
                            false))
+  , mWasCompositionStringEmpty(true)
 {
   MOZ_ASSERT(aCompositionEvent->mNativeIMEContext.IsValid());
 }
@@ -152,6 +153,8 @@ TextComposition::DispatchEvent(WidgetCompositionEvent* aDispatchEvent,
 
   EventDispatcher::Dispatch(mNode, mPresContext,
                             aDispatchEvent, nullptr, aStatus, aCallBack);
+
+  OnCompositionEventDispatched(aDispatchEvent);
 }
 
 void
@@ -241,6 +244,8 @@ TextComposition::DispatchCompositionEvent(
                    EventDispatchingCallback* aCallBack,
                    bool aIsSynthesized)
 {
+  mWasCompositionStringEmpty = mString.IsEmpty();
+
   // If the content is a container of TabParent, composition should be in the
   // remote process.
   if (mTabParent) {
@@ -402,7 +407,7 @@ TextComposition::DispatchCompositionEvent(
     MOZ_ASSERT(!HasEditor(), "Why does the editor still keep to hold this?");
   }
 
-  OnCompositionEventHandled(aCompositionEvent);
+  MaybeNotifyIMEOfCompositionEventHandled(aCompositionEvent);
 }
 
 // static
@@ -430,32 +435,57 @@ TextComposition::HandleSelectionEvent(nsPresContext* aPresContext,
 }
 
 void
-TextComposition::OnCompositionEventHandled(
+TextComposition::OnCompositionEventDispatched(
                    const WidgetCompositionEvent* aCompositionEvent)
 {
   MOZ_RELEASE_ASSERT(!mTabParent);
 
-  nsEventStatus status;
+  if (!IsValidStateForComposition(aCompositionEvent->mWidget)) {
+    return;
+  }
 
-  // When compositon start, notify the rect of first offset character.
-  // When not compositon start, notify the rect of selected composition
-  // string if compositionchange event.
-  if (aCompositionEvent->mMessage == eCompositionStart) {
+  // Every composition event may cause changing composition start offset,
+  // especially when there is no composition string.  Therefore, we need to
+  // update mCompositionStartOffset with the latest offset.
+
+  MOZ_ASSERT(aCompositionEvent->mMessage != eCompositionStart ||
+               mWasCompositionStringEmpty,
+             "mWasCompositionStringEmpty should be true if the dispatched "
+             "event is eCompositionStart");
+
+  if (mWasCompositionStringEmpty &&
+      !aCompositionEvent->CausesDOMCompositionEndEvent()) {
+    // If there was no composition string, current selection start may be the
+    // offset for inserting composition string.
     nsCOMPtr<nsIWidget> widget = mPresContext->GetRootWidget();
-    // Update composition start offset
     WidgetQueryContentEvent selectedTextEvent(true, eQuerySelectedText, widget);
-    widget->DispatchEvent(&selectedTextEvent, status);
-    if (selectedTextEvent.mSucceeded) {
-      mCompositionStartOffset = selectedTextEvent.mReply.mOffset;
+    nsEventStatus status = nsEventStatus_eIgnore;
+    if (mString.IsEmpty()) {
+      widget->DispatchEvent(&selectedTextEvent, status);
     } else {
-      // Unknown offset
-      NS_WARNING("Cannot get start offset of IME composition");
+      MOZ_ASSERT(aCompositionEvent->mMessage == eCompositionChange);
+      // TODO: Update mCompositionStartOffset with first IME selection
+    }
+    if (NS_WARN_IF(!selectedTextEvent.mSucceeded)) {
+      // XXX Is this okay?
       mCompositionStartOffset = 0;
+    } else {
+      mCompositionStartOffset = selectedTextEvent.mReply.mOffset;
     }
     mTargetClauseOffsetInComposition = 0;
-  } else if (aCompositionEvent->CausesDOMTextEvent()) {
+  }
+
+  if (aCompositionEvent->CausesDOMTextEvent()) {
     mTargetClauseOffsetInComposition = aCompositionEvent->TargetClauseOffset();
-  } else {
+  }
+}
+
+void
+TextComposition::MaybeNotifyIMEOfCompositionEventHandled(
+                   const WidgetCompositionEvent* aCompositionEvent)
+{
+  if (aCompositionEvent->mMessage != eCompositionStart &&
+      !aCompositionEvent->CausesDOMTextEvent()) {
     return;
   }
 

dom/events/TextComposition.h

@@ -258,6 +258,10 @@ private:
   // and compositionend events.
   bool mAllowControlCharacters;
 
+  // mWasCompositionStringEmpty is true if the composition string was empty
+  // when DispatchCompositionEvent() is called.
+  bool mWasCompositionStringEmpty;
+
   // Hide the default constructor and copy constructor.
   TextComposition()
     : mPresContext(nullptr)
@@ -272,6 +276,7 @@ private:
     , mRequestedToCommitOrCancel(false)
     , mWasNativeCompositionEndEventDiscarded(false)
     , mAllowControlCharacters(false)
+    , mWasCompositionStringEmpty(true)
   {}
   TextComposition(const TextComposition& aOther);
 
@@ -375,9 +380,18 @@ private:
   void OnCompositionEventDiscarded(WidgetCompositionEvent* aCompositionEvent);
 
   /**
-   * Calculate composition offset then notify composition update to widget
+   * OnCompositionEventDispatched() is called after a composition event is
+   * dispatched.
    */
-  void OnCompositionEventHandled(
+  void OnCompositionEventDispatched(
+         const WidgetCompositionEvent* aDispatchEvent);
+
+  /**
+   * MaybeNotifyIMEOfCompositionEventHandled() notifies IME of composition
+   * event handled.  This should be called after dispatching a composition
+   * event which came from widget.
+   */
+  void MaybeNotifyIMEOfCompositionEventHandled(
          const WidgetCompositionEvent* aCompositionEvent);
 
   /**