Reduce signed/unsigned comparison warnings

fpdfsdk/fxedit/fxet_edit.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "fpdfsdk/include/fxedit/fxet_edit.h"
 
 #include <algorithm>
 
@@ skipping 92 matching lines @@
                                         uint16_t word,
                                         int32_t nWordStyle) {
   if (CPDF_Font* pPDFFont = m_pFontMap->GetPDFFont(nFontIndex)) {
     uint32_t charcode = word;
 
     if (pPDFFont->IsUnicodeCompatible())
       charcode = pPDFFont->CharCodeFromUnicode(word);
     else
       charcode = m_pFontMap->CharCodeFromUnicode(nFontIndex, word);
 
-    if (charcode != -1)
+    if (charcode != CPDF_Font::kInvalidCharCode)
       return pPDFFont->GetCharWidthF(charcode);
   }
 
   return 0;
 }
 
 int32_t CFX_Edit_Provider::GetTypeAscent(int32_t nFontIndex) {
   if (CPDF_Font* pPDFFont = m_pFontMap->GetPDFFont(nFontIndex))
     return pPDFFont->GetTypeAscent();
 
@@ skipping 2901 matching lines @@
     if (m_bOprNotify && m_pOprNotify)
       m_pOprNotify->OnAddUndo(pEditUndoItem);
   }
 }
 
 void CFX_Edit::AddUndoItem(IFX_Edit_UndoItem* pUndoItem) {
   m_Undo.AddItem(pUndoItem);
   if (m_bOprNotify && m_pOprNotify)
     m_pOprNotify->OnAddUndo(pUndoItem);
 }