Introduce CPDF_Document::FromFPDFDocument().

fpdfsdk/src/fpdfformfill.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 "../../public/fpdf_formfill.h"
 #include "../../public/fpdfview.h"
 #include "../../third_party/base/nonstd_unique_ptr.h"
 #include "../include/fsdk_define.h"
@@ skipping 61 matching lines @@
   CPDF_InterForm interform(pPage->m_pDocument, FALSE);
   int z_order = -1;
   (void)interform.GetControlAtPoint(pPage, (FX_FLOAT)page_x, (FX_FLOAT)page_y,
                                     &z_order);
   return z_order;
 }
 
 DLLEXPORT FPDF_FORMHANDLE STDCALL
 FPDFDOC_InitFormFillEnvironment(FPDF_DOCUMENT document,
                                 FPDF_FORMFILLINFO* formInfo) {
-  if (!document || !formInfo || formInfo->version != 1)
+  if (!formInfo || formInfo->version != 1)
     return nullptr;
 
-  CPDF_Document* pDocument = (CPDF_Document*)document;
+  CPDF_Document* pDocument = CPDF_Document::FromFPDFDocument(document);
+  if (!pDocument)
+    return nullptr;
   CPDFDoc_Environment* pEnv = new CPDFDoc_Environment(pDocument, formInfo);
   pEnv->SetSDKDocument(new CPDFSDK_Document(pDocument, pEnv));
   return pEnv;
 }
 
 DLLEXPORT void STDCALL
 FPDFDOC_ExitFormFillEnvironment(FPDF_FORMHANDLE hHandle) {
   if (!hHandle)
     return;
 
@@ skipping 239 matching lines @@
       }
     } else {
       bExistCAAction = aa.ActionExist(CPDF_AAction::ClosePage);
       if (bExistCAAction) {
         CPDF_Action action = aa.GetAction(CPDF_AAction::ClosePage);
         pActionHandler->DoAction_Page(action, CPDF_AAction::ClosePage, pSDKDoc);
       }
     }
   }
 }