Add new public APIs to find the z-order for links and widgets.

fpdfsdk/src/fpdfdoc.cpp

Index: fpdfsdk/src/fpdfdoc.cpp
diff --git a/fpdfsdk/src/fpdfdoc.cpp b/fpdfsdk/src/fpdfdoc.cpp
index bcd401b4c48a300338b7821150321fb9e92f9a51..dabb8ca70138a41da5ea426911ef84d5596a0e6a 100644
--- a/fpdfsdk/src/fpdfdoc.cpp
+++ b/fpdfsdk/src/fpdfdoc.cpp
@@ -169,16 +169,37 @@ DLLEXPORT FPDF_LINK STDCALL FPDFLink_GetLinkAtPoint(FPDF_PAGE page,
                                                     double x,
                                                     double y) {
   if (!page)
-    return NULL;
+    return nullptr;
+
+  CPDF_Page* pPage = (CPDF_Page*)page;
+  // Link list is stored with the document
+  CPDF_Document* pDoc = pPage->m_pDocument;
+  CPDF_LinkList* pLinkList = (CPDF_LinkList*)pDoc->GetPrivateData(&THISMODULE);
+  if (!pLinkList) {
+    pLinkList = new CPDF_LinkList;
+    pDoc->SetPrivateData(&THISMODULE, pLinkList, ReleaseLinkList);
+  }
+  return pLinkList->GetLinkAtPoint(pPage, (FX_FLOAT)x, (FX_FLOAT)y, nullptr)
+      .GetDict();
+}
+
+DLLEXPORT int STDCALL FPDFLink_GetLinkZOrderAtPoint(FPDF_PAGE page,
+                                                    double x,
+                                                    double y) {
+  if (!page)
+    return -1;
+
   CPDF_Page* pPage = (CPDF_Page*)page;
   // Link list is stored with the document
   CPDF_Document* pDoc = pPage->m_pDocument;
   CPDF_LinkList* pLinkList = (CPDF_LinkList*)pDoc->GetPrivateData(&THISMODULE);

[Tom Sepez, 2015/08/07 18:14:06]

nit: Is this the only place we do "get or create"? Otherwise consolidate
duplicate code?

[Lei Zhang, 2015/08/07 23:03:41]

I consolidated.

   if (!pLinkList) {
-    pLinkList = new CPDF_LinkList(pDoc);
+    pLinkList = new CPDF_LinkList;
     pDoc->SetPrivateData(&THISMODULE, pLinkList, ReleaseLinkList);
   }
-  return pLinkList->GetLinkAtPoint(pPage, (FX_FLOAT)x, (FX_FLOAT)y).GetDict();
+  int z_order = -1;
+  pLinkList->GetLinkAtPoint(pPage, (FX_FLOAT)x, (FX_FLOAT)y, &z_order);

[Tom Sepez, 2015/08/07 18:14:06]

nit: maybe (void) to indicate result not used?

[Lei Zhang, 2015/08/07 23:03:41]

Done.

+  return z_order;
 }
 
 DLLEXPORT FPDF_DEST STDCALL FPDFLink_GetDest(FPDF_DOCUMENT document,