Fix crashing in CPDFXFA_Document::GetPage()

fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp

Index: fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
diff --git a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
index 16f3209af3dac8357a6062eb2316924c69809891..109a0946ba2dd6557d811cf74441f78255ff0284 100644
--- a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
+++ b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
@@ -145,29 +145,23 @@ int CPDFXFA_Document::GetPageCount() {
 }
 
 CPDFXFA_Page* CPDFXFA_Document::GetPage(int page_index) {

[Lei Zhang, 2015/12/21 17:47:59]

What happen if |page_index| is negative?

[jun_fang, 2016/01/04 09:30:23]

It shouldn't be less than 0. Will add a test to make sure |page_index| >= 0.

-  if (!m_pPDFDoc && !m_pXFADoc)

[Lei Zhang, 2015/12/21 17:47:58]

Do you still care about these being nullptrs?

-    return NULL;
-
-  CPDFXFA_Page* pPage = NULL;
-  if (m_XFAPageList.GetSize()) {
+  CPDFXFA_Page* pPage = nullptr;
+  int nCount = m_XFAPageList.GetSize();
+  if (nCount > 0 && page_index < nCount) {
     pPage = m_XFAPageList.GetAt(page_index);
     if (pPage)
       pPage->AddRef();
   } else {
     m_XFAPageList.SetSize(GetPageCount());
   }
-
-  if (!pPage) {
-    pPage = new CPDFXFA_Page(this, page_index);
-    FX_BOOL bRet = pPage->LoadPage();
-    if (!bRet) {
-      delete pPage;
-      return NULL;
-    }
-
-    m_XFAPageList.SetAt(page_index, pPage);
+  if (pPage)
+    return pPage;
+  pPage = new CPDFXFA_Page(this, page_index);
+  if (!pPage->LoadPage()) {
+    delete pPage;
+    return nullptr;
   }
-
+  m_XFAPageList.SetAt(page_index, pPage);
   return pPage;
 }
 
@@ -491,6 +485,22 @@ FX_BOOL CPDFXFA_Document::PopupMenu(IXFA_Widget* hWidget,
 
 void CPDFXFA_Document::PageViewEvent(IXFA_PageView* pPageView,
                                      FX_DWORD dwFlags) {

[Lei Zhang, 2015/12/21 17:47:58]

Is |dwFlags| always just a single value, or can it be something like
(XFA_PAGEVIEWEVENT_PostAdded | XFA_PAGEVIEWEVENT_PostRemoved) ?

[jun_fang, 2016/01/04 09:30:23]

It's just a single value.

+  if (!pPageView || (FXFA_PAGEVIEWEVENT_POSTADDED != dwFlags &&

[jun_fang, 2015/12/21 07:19:59]

SDK needs to handle changes on page view.
The events include FXFA_PAGEVIEWEVENT_POSTADDED and
FXFA_PAGEVIEWEVENT_POSTREMOVED.

[Lei Zhang, 2015/12/21 17:47:59]

The posted value is XFA_PAGEVIEWEVENT_PostRemoved, but the checked value is
FXFA_PAGEVIEWEVENT_POSTREMOVED. Can we use one of the two consistently?

[jun_fang, 2016/01/04 09:30:23]

Acknowledged.

+                     FXFA_PAGEVIEWEVENT_POSTREMOVED != dwFlags)) {
+    return;
+  }
+  CPDFXFA_Page* pPage = nullptr;
+  if (FXFA_PAGEVIEWEVENT_POSTADDED == dwFlags) {

[Lei Zhang, 2015/12/21 17:47:58]

nit: Prefer to just write: var == value

I believe Clang at least, will warn if one accidentally writes: var = value

[jun_fang, 2016/01/04 09:30:23]

Acknowledged.

+    pPage = GetPage(pPageView->GetPageViewIndex());
+    if (pPage)
+      pPage->SetXFAPageView(pPageView);
+    return;
+  }
+  pPage = GetPage(pPageView);
+  if (!pPage)
+    return;
+  pPage->SetXFAPageView(nullptr);
+  m_pSDKDoc->GetPageView(pPage)->ClearFXAnnots();
 }
 
 void CPDFXFA_Document::WidgetEvent(IXFA_Widget* hWidget,