Introduce CPDFPageFromFPFDPage()

Abstracts the way that pages are passed to the embedder
between XFA and master.

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1406543004 .

9 files changed, 95 insertions, 90 deletions

diff --git a/fpdfsdk/src/fpdf_flatten.cpp b/fpdfsdk/src/fpdf_flatten.cpp
index 210df63d3e..b2303f36aa 100644
--- a/fpdfsdk/src/fpdf_flatten.cpp
+++ b/fpdfsdk/src/fpdf_flatten.cpp
@@ -310,11 +310,11 @@ void GetOffset(FX_FLOAT& fa,
 }
 
 DLLEXPORT int STDCALL FPDFPage_Flatten(FPDF_PAGE page, int nFlag) {
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!page) {
     return FLATTEN_FAIL;
   }
 
-  CPDF_Page* pPage = (CPDF_Page*)(page);
   CPDF_Document* pDocument = pPage->m_pDocument;
   CPDF_Dictionary* pPageDict = pPage->m_pFormDict;
 
diff --git a/fpdfsdk/src/fpdf_progressive.cpp b/fpdfsdk/src/fpdf_progressive.cpp
index aaa55a18f6..b13eb553cc 100644
--- a/fpdfsdk/src/fpdf_progressive.cpp
+++ b/fpdfsdk/src/fpdf_progressive.cpp
@@ -18,16 +18,13 @@ DLLEXPORT int STDCALL FPDF_RenderPageBitmap_Start(FPDF_BITMAP bitmap,
                                                   int rotate,
                                                   int flags,
                                                   IFSDK_PAUSE* pause) {
-  if (bitmap == NULL || page == NULL)
+  if (!bitmap || !pause || pause->version != 1)
     return FPDF_RENDER_FAILED;
 
-  if (!pause)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return FPDF_RENDER_FAILED;
 
-  if (pause->version != 1)
-    return FPDF_RENDER_FAILED;
-
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CRenderContext* pContext = new CRenderContext;
   pPage->SetPrivateData((void*)1, pContext, DropContext);
 #ifdef _SKIA_SUPPORT_
@@ -59,16 +56,13 @@ DLLEXPORT int STDCALL FPDF_RenderPageBitmap_Start(FPDF_BITMAP bitmap,
 
 DLLEXPORT int STDCALL FPDF_RenderPage_Continue(FPDF_PAGE page,
                                                IFSDK_PAUSE* pause) {
-  if (page == NULL)
-    return FPDF_RENDER_FAILED;
-
-  if (!pause)
+  if (!pause || pause->version != 1)
     return FPDF_RENDER_FAILED;
 
-  if (pause->version != 1)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return FPDF_RENDER_FAILED;
 
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CRenderContext* pContext = (CRenderContext*)pPage->GetPrivateData((void*)1);
   if (pContext && pContext->m_pRenderer) {
     IFSDK_PAUSE_Adapter IPauseAdapter(pause);
@@ -80,10 +74,10 @@ DLLEXPORT int STDCALL FPDF_RenderPage_Continue(FPDF_PAGE page,
 }
 
 DLLEXPORT void STDCALL FPDF_RenderPage_Close(FPDF_PAGE page) {
-  if (!page)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
 
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CRenderContext* pContext = (CRenderContext*)pPage->GetPrivateData((void*)1);
   if (!pContext)
     return;
diff --git a/fpdfsdk/src/fpdf_transformpage.cpp b/fpdfsdk/src/fpdf_transformpage.cpp
index 4a892f1320..cdc646ae7e 100644
--- a/fpdfsdk/src/fpdf_transformpage.cpp
+++ b/fpdfsdk/src/fpdf_transformpage.cpp
@@ -9,10 +9,6 @@
 
 namespace {
 
-CPDF_Page* GetPageFromFPDFPage(FPDF_PAGE page) {
-  return static_cast<CPDF_Page*>(page);
-}
-
 void SetBoundingBox(CPDF_Page* page,
                     const CFX_ByteStringC& key,
                     float left,
@@ -53,7 +49,7 @@ DLLEXPORT void STDCALL FPDFPage_SetMediaBox(FPDF_PAGE page,
                                             float bottom,
                                             float right,
                                             float top) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return;
 
@@ -65,7 +61,7 @@ DLLEXPORT void STDCALL FPDFPage_SetCropBox(FPDF_PAGE page,
                                            float bottom,
                                            float right,
                                            float top) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return;
 
@@ -77,7 +73,7 @@ DLLEXPORT FPDF_BOOL STDCALL FPDFPage_GetMediaBox(FPDF_PAGE page,
                                                  float* bottom,
                                                  float* right,
                                                  float* top) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   return pPage && GetBoundingBox(pPage, "MediaBox", left, bottom, right, top);
 }
 
@@ -86,14 +82,14 @@ DLLEXPORT FPDF_BOOL STDCALL FPDFPage_GetCropBox(FPDF_PAGE page,
                                                 float* bottom,
                                                 float* right,
                                                 float* top) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   return pPage && GetBoundingBox(pPage, "CropBox", left, bottom, right, top);
 }
 
 DLLEXPORT FPDF_BOOL STDCALL FPDFPage_TransFormWithClip(FPDF_PAGE page,
                                                        FS_MATRIX* matrix,
                                                        FS_RECTF* clipRect) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return FALSE;
 
@@ -266,7 +262,7 @@ void OutputPath(CFX_ByteTextBuf& buf, CPDF_Path path) {
 
 DLLEXPORT void STDCALL FPDFPage_InsertClipPath(FPDF_PAGE page,
                                                FPDF_CLIPPATH clipPath) {
-  CPDF_Page* pPage = GetPageFromFPDFPage(page);
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return;
 
diff --git a/fpdfsdk/src/fpdfdoc.cpp b/fpdfsdk/src/fpdfdoc.cpp
index 05b151e0a7..b770295604 100644
--- a/fpdfsdk/src/fpdfdoc.cpp
+++ b/fpdfsdk/src/fpdfdoc.cpp
@@ -201,7 +201,10 @@ DLLEXPORT unsigned long STDCALL FPDFDest_GetPageIndex(FPDF_DOCUMENT document,
 
 DLLEXPORT FPDF_LINK STDCALL
 FPDFLink_GetLinkAtPoint(FPDF_PAGE page, double x, double y) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
+    return nullptr;
+
   CPDF_LinkList* pLinkList = GetLinkList(pPage);
   if (!pLinkList)
     return nullptr;
@@ -212,7 +215,10 @@ FPDFLink_GetLinkAtPoint(FPDF_PAGE page, double x, double y) {
 
 DLLEXPORT int STDCALL
 FPDFLink_GetLinkZOrderAtPoint(FPDF_PAGE page, double x, double y) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
+    return -1;
+
   CPDF_LinkList* pLinkList = GetLinkList(pPage);
   if (!pLinkList)
     return -1;
@@ -251,10 +257,10 @@ DLLEXPORT FPDF_ACTION STDCALL FPDFLink_GetAction(FPDF_LINK pDict) {
 DLLEXPORT FPDF_BOOL STDCALL FPDFLink_Enumerate(FPDF_PAGE page,
                                                int* startPos,
                                                FPDF_LINK* linkAnnot) {
-  if (!page || !startPos || !linkAnnot)
+  if (!startPos || !linkAnnot)
     return FALSE;
-  CPDF_Page* pPage = (CPDF_Page*)page;
-  if (!pPage->m_pFormDict)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage || !pPage->m_pFormDict)
     return FALSE;
   CPDF_Array* pAnnots = pPage->m_pFormDict->GetArray("Annots");
   if (!pAnnots)
diff --git a/fpdfsdk/src/fpdfeditimg.cpp b/fpdfsdk/src/fpdfeditimg.cpp
index 0c8ea1627a..73fc251195 100644
--- a/fpdfsdk/src/fpdfeditimg.cpp
+++ b/fpdfsdk/src/fpdfeditimg.cpp
@@ -30,7 +30,9 @@ FPDFImageObj_LoadJpegFile(FPDF_PAGE* pages,
   CPDF_ImageObject* pImgObj = (CPDF_ImageObject*)image_object;
   pImgObj->m_GeneralState.GetModify();
   for (int index = 0; index < nCount; index++) {
-    CPDF_Page* pPage = (CPDF_Page*)pages[index];
+    CPDF_Page* pPage = CPDFPageFromFPDFPage(pages[index]);
+    if (!pPage)
+      continue;
     pImgObj->m_pImage->ResetCache(pPage, NULL);
   }
   pImgObj->m_pImage->SetJpegImage(pFile);
@@ -69,7 +71,9 @@ DLLEXPORT FPDF_BOOL STDCALL FPDFImageObj_SetBitmap(FPDF_PAGE* pages,
   CPDF_ImageObject* pImgObj = (CPDF_ImageObject*)image_object;
   pImgObj->m_GeneralState.GetModify();
   for (int index = 0; index < nCount; index++) {
-    CPDF_Page* pPage = (CPDF_Page*)pages[index];
+    CPDF_Page* pPage = CPDFPageFromFPDFPage(pages[index]);
+    if (!pPage)
+      continue;
     pImgObj->m_pImage->ResetCache(pPage, NULL);
   }
   pImgObj->m_pImage->SetImage(pBmp, FALSE);
diff --git a/fpdfsdk/src/fpdfeditpage.cpp b/fpdfsdk/src/fpdfeditpage.cpp
index 6e1b852a47..f2d13d6ba1 100644
--- a/fpdfsdk/src/fpdfeditpage.cpp
+++ b/fpdfsdk/src/fpdfeditpage.cpp
@@ -85,7 +85,7 @@ DLLEXPORT FPDF_PAGE STDCALL FPDFPage_New(FPDF_DOCUMENT document,
 }
 
 DLLEXPORT int STDCALL FPDFPage_GetRotation(FPDF_PAGE page) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       !pPage->m_pFormDict->GetElement("Type")->GetDirect() ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
@@ -129,7 +129,7 @@ DLLEXPORT int STDCALL FPDFPage_GetRotation(FPDF_PAGE page) {
 
 DLLEXPORT void STDCALL FPDFPage_InsertObject(FPDF_PAGE page,
                                              FPDF_PAGEOBJECT page_obj) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       !pPage->m_pFormDict->GetElement("Type")->GetDirect() ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
@@ -171,13 +171,10 @@ DLLEXPORT void STDCALL FPDFPage_InsertObject(FPDF_PAGE page,
     default:
       break;
   }
-
-  //	pPage->ParseContent();
-  // pPage->GenerateContent();
 }
 
 DLLEXPORT int STDCALL FPDFPage_CountObject(FPDF_PAGE page) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       !pPage->m_pFormDict->GetElement("Type")->GetDirect() ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
@@ -185,27 +182,22 @@ DLLEXPORT int STDCALL FPDFPage_CountObject(FPDF_PAGE page) {
     return -1;
   }
   return pPage->CountObjects();
-  //	return 0;
 }
 
 DLLEXPORT FPDF_PAGEOBJECT STDCALL FPDFPage_GetObject(FPDF_PAGE page,
                                                      int index) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
           "Page")) {
     return NULL;
   }
   return pPage->GetObjectByIndex(index);
-  //	return NULL;
 }
 
 DLLEXPORT FPDF_BOOL STDCALL FPDFPage_HasTransparency(FPDF_PAGE page) {
-  if (!page)
-    return FALSE;
-  CPDF_Page* pPage = (CPDF_Page*)page;
-
-  return pPage->BackgroundAlphaNeeded();
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  return pPage && pPage->BackgroundAlphaNeeded();
 }
 
 DLLEXPORT FPDF_BOOL STDCALL
@@ -247,7 +239,7 @@ FPDFPageObj_HasTransparency(FPDF_PAGEOBJECT pageObject) {
 }
 
 DLLEXPORT FPDF_BOOL STDCALL FPDFPage_GenerateContent(FPDF_PAGE page) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       !pPage->m_pFormDict->GetElement("Type")->GetDirect() ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
@@ -282,9 +274,9 @@ DLLEXPORT void STDCALL FPDFPage_TransformAnnots(FPDF_PAGE page,
                                                 double d,
                                                 double e,
                                                 double f) {
-  if (page == NULL)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CPDF_AnnotList AnnotList(pPage);
   for (int i = 0; i < AnnotList.Count(); i++) {
     CPDF_Annot* pAnnot = AnnotList.GetAt(i);
@@ -310,7 +302,7 @@ DLLEXPORT void STDCALL FPDFPage_TransformAnnots(FPDF_PAGE page,
 }
 
 DLLEXPORT void STDCALL FPDFPage_SetRotation(FPDF_PAGE page, int rotate) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage || !pPage->m_pFormDict || !pPage->m_pFormDict->KeyExist("Type") ||
       !pPage->m_pFormDict->GetElement("Type")->GetDirect() ||
       pPage->m_pFormDict->GetElement("Type")->GetDirect()->GetString().Compare(
diff --git a/fpdfsdk/src/fpdfformfill.cpp b/fpdfsdk/src/fpdfformfill.cpp
index 02f906f513..7c2c350501 100644
--- a/fpdfsdk/src/fpdfformfill.cpp
+++ b/fpdfsdk/src/fpdfformfill.cpp
@@ -24,11 +24,12 @@ CPDFSDK_InterForm* FormHandleToInterForm(FPDF_FORMHANDLE hHandle) {
 
 CPDFSDK_PageView* FormHandleToPageView(FPDF_FORMHANDLE hHandle,
                                        FPDF_PAGE page) {
-  if (!page)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return nullptr;
 
   CPDFSDK_Document* pSDKDoc = FormHandleToSDKDoc(hHandle);
-  return pSDKDoc ? pSDKDoc->GetPageView((CPDF_Page*)page, TRUE) : nullptr;
+  return pSDKDoc ? pSDKDoc->GetPageView(pPage, TRUE) : nullptr;
 }
 
 }  // namespace
@@ -37,10 +38,11 @@ DLLEXPORT int STDCALL FPDFPage_HasFormFieldAtPoint(FPDF_FORMHANDLE hHandle,
                                                    FPDF_PAGE page,
                                                    double page_x,
                                                    double page_y) {
-  if (!page || !hHandle)
+  if (!hHandle)
+    return -1;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return -1;
-
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CPDF_InterForm interform(pPage->m_pDocument, FALSE);
   CPDF_FormControl* pFormCtrl = interform.GetControlAtPoint(
       pPage, (FX_FLOAT)page_x, (FX_FLOAT)page_y, nullptr);
@@ -48,10 +50,7 @@ DLLEXPORT int STDCALL FPDFPage_HasFormFieldAtPoint(FPDF_FORMHANDLE hHandle,
     return -1;
 
   CPDF_FormField* pFormField = pFormCtrl->GetField();
-  if (!pFormField)
-    return -1;
-
-  return pFormField->GetFieldType();
+  return pFormField ? pFormField->GetFieldType() : -1;
 }
 
 DLLEXPORT int STDCALL FPDPage_HasFormFieldAtPoint(FPDF_FORMHANDLE hHandle,
@@ -65,10 +64,11 @@ DLLEXPORT int STDCALL FPDFPage_FormFieldZOrderAtPoint(FPDF_FORMHANDLE hHandle,
                                                       FPDF_PAGE page,
                                                       double page_x,
                                                       double page_y) {
-  if (!page || !hHandle)
+  if (!hHandle)
+    return -1;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return -1;
-
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CPDF_InterForm interform(pPage->m_pDocument, FALSE);
   int z_order = -1;
   (void)interform.GetControlAtPoint(pPage, (FX_FLOAT)page_x, (FX_FLOAT)page_y,
@@ -192,10 +192,13 @@ DLLEXPORT void STDCALL FPDF_FFLDraw(FPDF_FORMHANDLE hHandle,
                                     int size_y,
                                     int rotate,
                                     int flags) {
-  if (!hHandle || !page)
+  if (!hHandle)
+    return;
+
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
 
-  CPDF_Page* pPage = (CPDF_Page*)page;
   CPDF_RenderOptions options;
   if (flags & FPDF_LCD_TEXT)
     options.m_Flags |= RENDER_CLEARTYPE;
@@ -263,14 +266,17 @@ DLLEXPORT void STDCALL FORM_OnAfterLoadPage(FPDF_PAGE page,
 
 DLLEXPORT void STDCALL FORM_OnBeforeClosePage(FPDF_PAGE page,
                                               FPDF_FORMHANDLE hHandle) {
-  if (!hHandle || !page)
+  if (!hHandle)
     return;
 
   CPDFSDK_Document* pSDKDoc = ((CPDFDoc_Environment*)hHandle)->GetSDKDocument();
   if (!pSDKDoc)
     return;
 
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
+    return;
+
   CPDFSDK_PageView* pPageView = pSDKDoc->GetPageView(pPage, FALSE);
   if (pPageView) {
     pPageView->SetValid(FALSE);
@@ -316,10 +322,12 @@ DLLEXPORT void STDCALL FORM_DoDocumentAAction(FPDF_FORMHANDLE hHandle,
 DLLEXPORT void STDCALL FORM_DoPageAAction(FPDF_PAGE page,
                                           FPDF_FORMHANDLE hHandle,
                                           int aaType) {
-  if (!hHandle || !page)
+  if (!hHandle)
     return;
   CPDFSDK_Document* pSDKDoc = ((CPDFDoc_Environment*)hHandle)->GetSDKDocument();
-  CPDF_Page* pPage = (CPDF_Page*)page;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
+    return;
   CPDFSDK_PageView* pPageView = pSDKDoc->GetPageView(pPage, FALSE);
   if (pPageView) {
     CPDFDoc_Environment* pEnv = pSDKDoc->GetEnv();
diff --git a/fpdfsdk/src/fpdftext.cpp b/fpdfsdk/src/fpdftext.cpp
index 43edd525e8..800c138f3f 100644
--- a/fpdfsdk/src/fpdftext.cpp
+++ b/fpdfsdk/src/fpdftext.cpp
@@ -7,18 +7,19 @@
 #include "../../core/include/fpdfdoc/fpdf_doc.h"
 #include "../../core/include/fpdftext/fpdf_text.h"
 #include "../../public/fpdf_text.h"
+#include "../include/fsdk_define.h"
 
 #ifdef _WIN32
 #include <tchar.h>
 #endif
 
 DLLEXPORT FPDF_TEXTPAGE STDCALL FPDFText_LoadPage(FPDF_PAGE page) {
-  if (!page)
-    return NULL;
-  IPDF_TextPage* textpage = NULL;
-  CPDF_ViewerPreferences viewRef(((CPDF_Page*)page)->m_pDocument);
-  textpage =
-      IPDF_TextPage::CreateTextPage((CPDF_Page*)page, viewRef.IsDirectionR2L());
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
+    return nullptr;
+  CPDF_ViewerPreferences viewRef(pPage->m_pDocument);
+  IPDF_TextPage* textpage =
+      IPDF_TextPage::CreateTextPage(pPage, viewRef.IsDirectionR2L());
   textpage->ParseTextPage();
   return textpage;
 }
diff --git a/fpdfsdk/src/fpdfview.cpp b/fpdfsdk/src/fpdfview.cpp
index 17f52ec263..b2c5618a52 100644
--- a/fpdfsdk/src/fpdfview.cpp
+++ b/fpdfsdk/src/fpdfview.cpp
@@ -20,6 +20,10 @@ CPDF_Document* CPDFDocumentFromFPDFDocument(FPDF_DOCUMENT doc) {
   return static_cast<CPDF_Document*>(doc);
 }
 
+CPDF_Page* CPDFPageFromFPDFPage(FPDF_PAGE page) {
+  return static_cast<CPDF_Page*>(page);
+}
+
 CPDF_CustomAccess::CPDF_CustomAccess(FPDF_FILEACCESS* pFileAccess) {
   if (pFileAccess)
     m_FileAccess = *pFileAccess;
@@ -284,15 +288,13 @@ DLLEXPORT FPDF_PAGE STDCALL FPDF_LoadPage(FPDF_DOCUMENT document,
 }
 
 DLLEXPORT double STDCALL FPDF_GetPageWidth(FPDF_PAGE page) {
-  if (!page)
-    return 0.0;
-  return ((CPDF_Page*)page)->GetPageWidth();
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  return pPage ? pPage->GetPageWidth() : 0.0;
 }
 
 DLLEXPORT double STDCALL FPDF_GetPageHeight(FPDF_PAGE page) {
-  if (!page)
-    return 0.0;
-  return ((CPDF_Page*)page)->GetPageHeight();
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  return pPage ? pPage->GetPageHeight() : 0.0;
 }
 
 void DropContext(void* data) {
@@ -312,9 +314,9 @@ DLLEXPORT void STDCALL FPDF_RenderPage(HDC dc,
                                        int size_y,
                                        int rotate,
                                        int flags) {
-  if (page == NULL)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
-  CPDF_Page* pPage = (CPDF_Page*)page;
 
   CRenderContext* pContext = new CRenderContext;
   pPage->SetPrivateData((void*)1, pContext, DropContext);
@@ -472,10 +474,11 @@ DLLEXPORT void STDCALL FPDF_RenderPageBitmap(FPDF_BITMAP bitmap,
                                              int size_y,
                                              int rotate,
                                              int flags) {
-  if (bitmap == NULL || page == NULL)
+  if (!bitmap)
+    return;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
-  CPDF_Page* pPage = (CPDF_Page*)page;
-
   CRenderContext* pContext = new CRenderContext;
   pPage->SetPrivateData((void*)1, pContext, DropContext);
 #ifdef _SKIA_SUPPORT_
@@ -570,10 +573,11 @@ DLLEXPORT void STDCALL FPDF_PageToDevice(FPDF_PAGE page,
                                          double page_y,
                                          int* device_x,
                                          int* device_y) {
-  if (page == NULL || device_x == NULL || device_y == NULL)
+  if (!device_x || !device_y)
+    return;
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
-  CPDF_Page* pPage = (CPDF_Page*)page;
-
   CPDF_Matrix page2device;
   pPage->GetDisplayMatrix(page2device, start_x, start_y, size_x, size_y,
                           rotate);
@@ -681,8 +685,8 @@ void FPDF_RenderPage_Retail(CRenderContext* pContext,
                             int flags,
                             FX_BOOL bNeedToRestore,
                             IFSDK_PAUSE_Adapter* pause) {
-  CPDF_Page* pPage = (CPDF_Page*)page;
-  if (pPage == NULL)
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!pPage)
     return;
 
   if (!pContext->m_pOptions)