Make app.alert() actually print its message under pdfium_test.

samples/pdfium_test.cc

 // Copyright (c) 2010 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 <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <wchar.h>
 
 #include <list>
 #include <string>
 #include <utility>
 
 #include "../fpdfsdk/include/fpdf_dataavail.h"
 #include "../fpdfsdk/include/fpdf_ext.h"
 #include "../fpdfsdk/include/fpdfformfill.h"
 #include "../fpdfsdk/include/fpdftext.h"
 #include "../fpdfsdk/include/fpdfview.h"
@@ skipping 109 matching lines @@
   // If a PS_NULL pen is used, the dimensions of the rectangle are 1 pixel less.
   Rectangle(dc, 0, 0, width + 1, height + 1);
 
   FPDF_RenderPage(dc, page, 0, 0, width, height, 0,
                   FPDF_ANNOT | FPDF_PRINTING | FPDF_NO_CATCH);
 
   DeleteEnhMetaFile(CloseEnhMetaFile(dc));
 }
 #endif
 
-int Form_Alert(IPDF_JSPLATFORM*, FPDF_WIDESTRING, FPDF_WIDESTRING, int, int) {
-  printf("Form_Alert called.\n");
+int Form_Alert(IPDF_JSPLATFORM*, FPDF_WIDESTRING msg, FPDF_WIDESTRING,
+               int, int) {
+  // Deal with differences between UTF16LE and wchar_t on this platform.
+  size_t characters = 0;
+  while (msg[characters]) {
+    ++characters;
+  }
+  wchar_t* platform_string =
+      (wchar_t*)malloc((characters + 1) * sizeof(wchar_t));
+  for (size_t i = 0; i < characters + 1; ++i) {
+    unsigned char* ptr = (unsigned char*)&msg[i];
+    platform_string[i] = ptr[0] + 256 * ptr[1];
+  }
+  printf("Alert: %ls\n", platform_string);
+  free(platform_string);
   return 0;
 }
 
 void Unsupported_Handler(UNSUPPORT_INFO*, int type) {
   std::string feature = "Unknown";
   switch (type) {
     case FPDF_UNSP_DOC_XFAFORM:
       feature = "XFA";
       break;
     case FPDF_UNSP_DOC_PORTABLECOLLECTION:
@@ skipping 259 matching lines @@
     } else {
       RenderPdf(filename, pBuf, len, format);
     }
     free(pBuf);
   }
 
   FPDF_DestroyLibrary();
 
   return 0;
 }