Bug 285974 Crash when we use ATOK on the other of editor[@ nsWindow::OnIMEQueryCharPosition]

patch by masayuki@d-toybox.com r=timeless sr=roc

editor/libeditor/base/nsEditor.cpp

@@ -2211,7 +2211,8 @@ nsEditor::GetQueryCaretRect(nsQueryCaretRectEventReply* aReply)
   PRBool cursorIsCollapsed;
   rv = caretP->GetCaretCoordinates(nsICaret::eIMECoordinates, selection,
                                    &aReply->mCaretRect, &cursorIsCollapsed, nsnull);
-
+  if (NS_SUCCEEDED(rv))
+    aReply->mRectIsValid = PR_TRUE;
   return rv;
 }
 

widget/public/nsGUIEvent.h

@@ -735,9 +735,11 @@ struct nsReconversionEvent : public nsInputEvent
 
 struct nsQueryCaretRectEventReply {
   nsQueryCaretRectEventReply()
+    : mRectIsValid(PR_FALSE)
   {
   }
 
+  PRBool mRectIsValid;
   nsRect mCaretRect;
 };
 

widget/src/windows/nsWindow.cpp

@@ -6963,6 +6963,11 @@ PRBool nsWindow::OnIMEQueryCharPosition(LPARAM aData, LRESULT *oResult, PRBool a
     nsQueryCaretRectEvent event(NS_QUERYCARETRECT, this);
     InitEvent(event, &point);
     DispatchWindowEvent(&event);
+    // The active widget doesn't support this event.
+    if (!event.theReply.mRectIsValid) {
+      *oResult = FALSE;
+      return PR_FALSE;
+    }
     NS_RELEASE(event.widget);
 
     nsRect screenRect, widgetRect(event.theReply.mCaretRect);
@@ -6978,6 +6983,13 @@ PRBool nsWindow::OnIMEQueryCharPosition(LPARAM aData, LRESULT *oResult, PRBool a
     return PR_TRUE;
   }
 
+  // If the char positions are not cached, we should not return the values by LPARAM.
+  // Because in this case, the active widget is not editor.
+  if (!sIMECompCharPos) {
+    *oResult = FALSE;
+    return PR_FALSE;
+  }
+
   long charPosition;
   if (aUseUnicode || pCharPosition->dwCharPos == 0) {
     if (pCharPosition->dwCharPos > sIMECompUnicode->Length()) {