Call FPDFAvail_IsFormAvail() before creating form.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 2580 matching lines @@
   }
 
   if (FPDFDoc_GetPageMode(doc_) == PAGEMODE_USEOUTLINES)
     client_->DocumentHasUnsupportedFeature("Bookmarks");
 
   permissions_ = FPDF_GetDocPermissions(doc_);
   permissions_handler_revision_ = FPDF_GetSecurityHandlerRevision(doc_);
 
   if (!form_) {
     // Only returns 0 when data isn't available.  If form data is downloaded, or
-    // if this isn't a form, returns positive values.
-    if (!doc_loader_.IsDocumentComplete() &&
-        !FPDFAvail_IsFormAvail(fpdf_availability_, &download_hints_)) {
+    // if this isn't a form, returns positive values. FPDFAvail_IsFormAvail()
+    // must be called before continuing, so it must come first in the condition.
+    if (!FPDFAvail_IsFormAvail(fpdf_availability_, &download_hints_) &&

[Lei Zhang, 2015/12/30 01:09:21]

How about we call these 2 functions separately, and then compare their results?
It's probably better to do more checking for FPDFAvail_IsFormAvail() since it's
not returning a bool. I think you'd want to make sure it returned
PDF_FORM_AVAIL.

[spelchat, 2015/12/30 17:14:58]

PDF_FORM_NOTEXIST is OK too, it just means there is no form in the PDF.
PDF_FORM_ERROR shouldn't happen.

I've massaged the code a bit to make things clearer, !FPDFAvail_IsFormAvail()
was confusing.

+        !doc_loader_.IsDocumentComplete()) {
       return;
     }
 
     form_ = FPDFDOC_InitFormFillEnvironment(
         doc_, static_cast<FPDF_FORMFILLINFO*>(this));
 #ifdef PDF_USE_XFA
     FPDF_LoadXFA(doc_);
 #endif
 
     FPDF_SetFormFieldHighlightColor(form_, 0, kFormHighlightColor);
@@ skipping 1385 matching lines @@
     double* height) {
   FPDF_DOCUMENT doc = FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, NULL);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf