Fix partial information printed with blank window covering the center

fpdfsdk/src/fpdfview.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/fpdfview.h"
 
 #include <memory>
 
@@ skipping 318 matching lines @@
                                        int rotate,
                                        int flags) {
   CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return;
 
   CRenderContext* pContext = new CRenderContext;
   pPage->SetPrivateData((void*)1, pContext, DropContext);
 
 #ifndef _WIN32_WCE
-  CFX_DIBitmap* pBitmap = NULL;
-  FX_BOOL bBackgroundAlphaNeeded = FALSE;
-  bBackgroundAlphaNeeded = pPage->BackgroundAlphaNeeded();
-  if (bBackgroundAlphaNeeded) {
+  CFX_DIBitmap* pBitmap = nullptr;
+  FX_BOOL bBackgroundAlphaNeeded = pPage->BackgroundAlphaNeeded();
+  FX_BOOL bHasImageMask = pPage->HasImageMask();
+  if (bBackgroundAlphaNeeded || bHasImageMask) {
     pBitmap = new CFX_DIBitmap;
     pBitmap->Create(size_x, size_y, FXDIB_Argb);
     pBitmap->Clear(0x00ffffff);
 #ifdef _SKIA_SUPPORT_
     pContext->m_pDevice = new CFX_SkiaDevice;
     ((CFX_SkiaDevice*)pContext->m_pDevice)->Attach((CFX_DIBitmap*)pBitmap);
 #else
     pContext->m_pDevice = new CFX_FxgeDevice;
     ((CFX_FxgeDevice*)pContext->m_pDevice)->Attach((CFX_DIBitmap*)pBitmap);
 #endif
-  } else
+  } else {
     pContext->m_pDevice = new CFX_WindowsDevice(dc);
+  }
 
   FPDF_RenderPage_Retail(pContext, page, start_x, start_y, size_x, size_y,
                          rotate, flags, TRUE, NULL);
 
-  if (bBackgroundAlphaNeeded) {
+  if (bBackgroundAlphaNeeded || bHasImageMask) {
     if (pBitmap) {
       CFX_WindowsDevice WinDC(dc);
 
       if (WinDC.GetDeviceCaps(FXDC_DEVICE_CLASS) == FXDC_PRINTER) {
         CFX_DIBitmap* pDst = new CFX_DIBitmap;
         int pitch = pBitmap->GetPitch();
         pDst->Create(size_x, size_y, FXDIB_Rgb32);
         FXSYS_memset(pDst->GetBuffer(), -1, pitch * size_y);
         pDst->CompositeBitmap(0, 0, size_x, size_y, pBitmap, 0, 0,
                               FXDIB_BLEND_NORMAL, NULL, FALSE, NULL);
         WinDC.StretchDIBits(pDst, 0, 0, size_x, size_y);
         delete pDst;
-      } else
+      } else {
         WinDC.SetDIBits(pBitmap, 0, 0);
+      }
     }
   }
 #else
   // get clip region
   RECT rect, cliprect;
   rect.left = start_x;
   rect.top = start_y;
   rect.right = start_x + size_x;
   rect.bottom = start_y + size_y;
   GetClipBox(dc, &cliprect);
@@ skipping 80 matching lines @@
 
   BitBlt(dc, rect.left, rect.top, width, height, hMemDC, 0, 0, SRCCOPY);
   SelectObject(hMemDC, hOldBitmap);
   DeleteDC(hMemDC);
 
 #ifdef DEBUG_TRACE
   CPDF_ModuleMgr::Get()->ReportError(999, "Finished screen rendering");
 #endif
 
 #endif
-  if (bBackgroundAlphaNeeded) {
+  if (bBackgroundAlphaNeeded || bHasImageMask)
     delete pBitmap;
-    pBitmap = NULL;
-  }
+
   delete pContext;
   pPage->RemovePrivateData((void*)1);
 }
 #endif
 
 DLLEXPORT void STDCALL FPDF_RenderPageBitmap(FPDF_BITMAP bitmap,
                                              FPDF_PAGE page,
                                              int start_x,
                                              int start_y,
                                              int size_x,
@@ skipping 416 matching lines @@
   if (!buffer) {
     *buflen = len;
   } else if (*buflen >= len) {
     memcpy(buffer, utf16Name.c_str(), len);
     *buflen = len;
   } else {
     *buflen = -1;
   }
   return (FPDF_DEST)pDestObj;
 }