--- a/widget/cocoa/TextInputHandler.mm
+++ b/widget/cocoa/TextInputHandler.mm
@@ -1513,16 +1513,18 @@ TextInputHandler::HandleKeyDownEvent(NSE
 
   if (Destroyed()) {
     MOZ_LOG(gLog, LogLevel::Info,
       ("%p TextInputHandler::HandleKeyDownEvent, "
        "widget has been already destroyed", this));
     return false;
   }
 
+  // Insert empty line to the log for easier to read.
+  MOZ_LOG(gLog, LogLevel::Info, (""));
   MOZ_LOG(gLog, LogLevel::Info,
     ("%p TextInputHandler::HandleKeyDownEvent, aNativeEvent=%p, "
      "type=%s, keyCode=%lld (0x%X), modifierFlags=0x%X, characters=\"%s\", "
      "charactersIgnoringModifiers=\"%s\"",
      this, aNativeEvent, GetNativeKeyEventType(aNativeEvent),
      [aNativeEvent keyCode], [aNativeEvent keyCode],
      [aNativeEvent modifierFlags], GetCharacters([aNativeEvent characters]),
      GetCharacters([aNativeEvent charactersIgnoringModifiers])));
@@ -1681,16 +1683,18 @@ TextInputHandler::HandleKeyDownEvent(NSE
   // Note: mWidget might have become null here. Don't count on it from here on.
 
   MOZ_LOG(gLog, LogLevel::Info,
     ("%p TextInputHandler::HandleKeyDownEvent, "
      "keydown handled=%s, keypress handled=%s, causedOtherKeyEvents=%s",
      this, TrueOrFalse(currentKeyEvent->mKeyDownHandled),
      TrueOrFalse(currentKeyEvent->mKeyPressHandled),
      TrueOrFalse(currentKeyEvent->mCausedOtherKeyEvents)));
+  // Insert empty line to the log for easier to read.
+  MOZ_LOG(gLog, LogLevel::Info, (""));
   return currentKeyEvent->IsDefaultPrevented();
 
   NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(false);
 }
 
 void
 TextInputHandler::HandleKeyUpEvent(NSEvent* aNativeEvent)
 {
@@ -2183,39 +2187,41 @@ TextInputHandler::InsertText(NSAttribute
     WidgetContentCommandEvent deleteCommandEvent(true, eContentCommandDelete,
                                                  mWidget);
     DispatchEvent(deleteCommandEvent);
     NS_ENSURE_TRUE_VOID(deleteCommandEvent.mSucceeded);
     // Be aware! The widget might be destroyed here.
     return;
   }
 
-  // If this is not caused by pressing a key or there is a composition, let's
+  bool isReplacingSpecifiedRange =
+    isEditable && aReplacementRange &&
+    aReplacementRange->location != NSNotFound &&
+    !NSEqualRanges(selectedRange, *aReplacementRange);
+
+  // If this is not caused by pressing a key, there is a composition or
+  // replacing a range which is different from current selection, let's
   // insert the text as committing a composition.
-  if (!currentKeyEvent || IsIMEComposing()) {
+  if (!currentKeyEvent || IsIMEComposing() || isReplacingSpecifiedRange) {
     InsertTextAsCommittingComposition(aAttrString, aReplacementRange);
+    if (currentKeyEvent) {
+      currentKeyEvent->mKeyPressHandled = true;
+      currentKeyEvent->mKeyPressDispatched = true;
+    }
     return;
   }
 
   // Don't let the same event be fired twice when hitting
   // enter/return! (Bug 420502)
   if (currentKeyEvent && !currentKeyEvent->CanDispatchKeyPressEvent()) {
     return;
   }
 
+  // XXX Shouldn't we hold mDispatcher instead of mWidget?
   RefPtr<nsChildView> widget(mWidget);
-
-  // If the replacement range is specified, select the range.  Then, the
-  // selection will be replaced by the later keypress event.
-  if (isEditable &&
-      aReplacementRange && aReplacementRange->location != NSNotFound &&
-      !NSEqualRanges(selectedRange, *aReplacementRange)) {
-    NS_ENSURE_TRUE_VOID(SetSelection(*aReplacementRange));
-  }
-
   nsresult rv = mDispatcher->BeginNativeInputTransaction();
   if (NS_WARN_IF(NS_FAILED(rv))) {
       MOZ_LOG(gLog, LogLevel::Error,
         ("%p IMEInputHandler::HandleKeyUpEvent, "
          "FAILED, due to BeginNativeInputTransaction() failure", this));
     return;
   }
 
@@ -3138,29 +3144,47 @@ IMEInputHandler::InsertTextAsCommittingC
 
 void
 IMEInputHandler::SetMarkedText(NSAttributedString* aAttrString,
                                NSRange& aSelectedRange,
                                NSRange* aReplacementRange)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
+  KeyEventState* currentKeyEvent = GetCurrentKeyEvent();
+
   MOZ_LOG(gLog, LogLevel::Info,
     ("%p IMEInputHandler::SetMarkedText, "
      "aAttrString=\"%s\", aSelectedRange={ location=%llu, length=%llu }, "
      "aReplacementRange=%p { location=%llu, length=%llu }, "
      "Destroyed()=%s, IgnoreIMEComposition()=%s, IsIMEComposing()=%s, "
-     "mMarkedRange={ location=%llu, length=%llu }",
+     "mMarkedRange={ location=%llu, length=%llu }, keyevent=%p, "
+     "keydownHandled=%s, keypressDispatched=%s, causedOtherKeyEvents=%s",
      this, GetCharacters([aAttrString string]),
      aSelectedRange.location, aSelectedRange.length, aReplacementRange,
      aReplacementRange ? aReplacementRange->location : 0,
      aReplacementRange ? aReplacementRange->length : 0,
      TrueOrFalse(Destroyed()), TrueOrFalse(IgnoreIMEComposition()),
      TrueOrFalse(IsIMEComposing()),
-     mMarkedRange.location, mMarkedRange.length));
+     mMarkedRange.location, mMarkedRange.length,
+     currentKeyEvent ? currentKeyEvent->mKeyEvent : nullptr,
+     currentKeyEvent ?
+       TrueOrFalse(currentKeyEvent->mKeyDownHandled) : "N/A",
+     currentKeyEvent ?
+       TrueOrFalse(currentKeyEvent->mKeyPressDispatched) : "N/A",
+     currentKeyEvent ?
+       TrueOrFalse(currentKeyEvent->mCausedOtherKeyEvents) : "N/A"));
+
+  // If SetMarkedText() is called during composition, that means that
+  // the key event caused this composition.  So, keypress event shouldn't
+  // be dispatched later, let's consume it here.
+  if (currentKeyEvent) {
+    currentKeyEvent->mKeyPressHandled = true;
+    currentKeyEvent->mKeyPressDispatched = true;
+  }
 
   if (Destroyed() || IgnoreIMEComposition()) {
     return;
   }
 
   RefPtr<IMEInputHandler> kungFuDeathGrip(this);
 
   // First, commit current composition with the latest composition string if the