Bug 1422230 - part 2: ContentCacheInParent should allow to query content relative to composition string even after sending eCompositionCommit(AsIs) event but not yet handled in the remote process r=m_kato

Currently, ContentCacheInParent uses selection when it handles query content
event whose input offset is relative one after sending eCompositionCommit(AsIs)
event but it's not yet handled by the remote process.  However, in this case,
selection may not be modified with committed string.

So, when mPendingCommitCount is not 0, ContentCacheInParent should compute
absolute offset with the latest composition string information.  For doing
this, it needs to keep storing mCompositionStart until eCompositionCommit(AsIs)
is handled in the remote process actually.

MozReview-Commit-ID: 2Dc69HNIbvh

--HG--
extra : rebase_source : 4be432ad363022e4b3f2e3c82c8d229dc9af889d

widget/ContentCache.cpp

@@ -548,12 +548,12 @@ ContentCacheInParent::AssignContent(const ContentCache& aOther,
     IMEStateManager::MaybeStartOffsetUpdatedInChild(aWidget, mCompositionStart);
   }
 
-  // When the widget has composition, we should set mCompositionStart to
-  // *current* composition start offset.  Note that, in strictly speaking,
-  // widget should not use WidgetQueryContentEvent if there are some pending
-  // compositions (i.e., when mPendingCompositionCount is 2 or more).
+  // When this instance allows to query content relative to composition string,
+  // we should modify mCompositionStart with the latest information in the
+  // remote process because now we have the information around the composition
+  // string.
   mCompositionStartInChild = aOther.mCompositionStart;
-  if (mWidgetHasComposition) {
+  if (mWidgetHasComposition || mPendingCommitCount) {
     if (aOther.mCompositionStart != UINT32_MAX) {
       if (mCompositionStart != aOther.mCompositionStart) {
         mCompositionStart = aOther.mCompositionStart;
@@ -566,9 +566,6 @@ ContentCacheInParent::AssignContent(const ContentCache& aOther,
                            "mCompositionStart shouldn't be invalid offset when "
                            "the widget has composition");
     }
-  } else if (mCompositionStart != UINT32_MAX) {
-    mCompositionStart = UINT32_MAX;
-    mPendingCommitLength = 0;
   }
 
   MOZ_LOG(sContentCacheLog, LogLevel::Info,
@@ -640,7 +637,7 @@ ContentCacheInParent::HandleQueryContentEvent(WidgetQueryContentEvent& aEvent,
            aEvent.mInput.mLength));
         return false;
       }
-    } else if (mWidgetHasComposition) {
+    } else if (mWidgetHasComposition || mPendingCommitCount) {
       if (NS_WARN_IF(!aEvent.mInput.MakeOffsetAbsolute(
                                       mCompositionStart +
                                         mPendingCommitLength))) {
@@ -1142,7 +1139,8 @@ ContentCacheInParent::OnCompositionEvent(const WidgetCompositionEvent& aEvent)
   mWidgetHasComposition = !aEvent.CausesDOMCompositionEndEvent();
 
   if (!mWidgetHasComposition) {
-    mCompositionStart = UINT32_MAX;
+    // mCompositionStart will be reset when commit event is completely handled
+    // in the remote process.
     if (mPendingCompositionCount == 1) {
       mPendingCommitLength = aEvent.mData.Length();
     }
@@ -1217,11 +1215,11 @@ ContentCacheInParent::OnEventNeedingAckHandled(nsIWidget* aWidget,
   MOZ_LOG(sContentCacheLog, LogLevel::Info,
     ("0x%p OnEventNeedingAckHandled(aWidget=0x%p, "
      "aMessage=%s), mPendingEventsNeedingAck=%u, "
-     "mPendingCompositionCount=%" PRIu8 ", mPendingCommitCount=%" PRIu8 ", "
-     "mIsChildIgnoringCompositionEvents=%s",
+     "mWidgetHasComposition=%s, mPendingCompositionCount=%" PRIu8 ", "
+     "mPendingCommitCount=%" PRIu8 ", mIsChildIgnoringCompositionEvents=%s",
      this, aWidget, ToChar(aMessage), mPendingEventsNeedingAck,
-     mPendingCompositionCount, mPendingCommitCount,
-     GetBoolName(mIsChildIgnoringCompositionEvents)));
+     GetBoolName(mWidgetHasComposition), mPendingCompositionCount,
+     mPendingCommitCount, GetBoolName(mIsChildIgnoringCompositionEvents)));
 
 #if MOZ_DIAGNOSTIC_ASSERT_ENABLED
   mReceivedEventMessages.AppendElement(aMessage);
@@ -1302,6 +1300,13 @@ ContentCacheInParent::OnEventNeedingAckHandled(nsIWidget* aWidget,
     mIsChildIgnoringCompositionEvents = true;
   }
 
+  // If neither widget (i.e., IME) nor the remote process has composition,
+  // now, we can forget composition string informations.
+  if (!mWidgetHasComposition &&
+      !mPendingCompositionCount && !mPendingCommitCount) {
+    mCompositionStart = UINT32_MAX;
+  }
+
   if (NS_WARN_IF(!mPendingEventsNeedingAck)) {
 #if MOZ_DIAGNOSTIC_ASSERT_ENABLED
     nsPrintfCString info("\nThere is no pending events but received %s "