Added FPDFAnnot_GetAnnotIndex()

Added FPDFAnnot_GetAnnotIndex() to get the index of an annotation. This
is useful if linked annotations are renedered together - then we need to
know which ones in the annotation list we need to skip.

Bug=pdfium:863,pdfium:737

Change-Id: I53482a15e0fd9a896b348b64d68e99f9c21da9f9
Reviewed-on: https://pdfium-review.googlesource.com/11970
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/fpdfsdk/fpdfannot.cpp b/fpdfsdk/fpdfannot.cpp
index ec748e66ec..8c62ecf311 100644
--- a/fpdfsdk/fpdfannot.cpp
+++ b/fpdfsdk/fpdfannot.cpp
@@ -241,6 +241,30 @@ FPDF_EXPORT FPDF_ANNOTATION FPDF_CALLCONV FPDFPage_GetAnnot(FPDF_PAGE page,
   return pNewAnnot.release();
 }
 
+FPDF_EXPORT int FPDF_CALLCONV FPDFPage_GetAnnotIndex(FPDF_PAGE page,
+                                                     FPDF_ANNOTATION annot) {
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  CPDF_AnnotContext* pAnnot = CPDFAnnotContextFromFPDFAnnotation(annot);
+  if (!pPage || !pPage->m_pFormDict || !pAnnot || !pAnnot->GetAnnotDict())
+    return -1;
+
+  CPDF_Array* pAnnots = pPage->m_pFormDict->GetArrayFor("Annots");
+  if (!pAnnots)
+    return -1;
+
+  CPDF_Dictionary* pDict = pAnnot->GetAnnotDict();
+  auto it =
+      std::find_if(pAnnots->begin(), pAnnots->end(),
+                   [pDict](const std::unique_ptr<CPDF_Object>& candidate) {
+                     return candidate->GetDirect() == pDict;
+                   });
+
+  if (it == pAnnots->end())
+    return -1;
+
+  return it - pAnnots->begin();
+}
+
 FPDF_EXPORT void FPDF_CALLCONV FPDFPage_CloseAnnot(FPDF_ANNOTATION annot) {
   delete CPDFAnnotContextFromFPDFAnnotation(annot);
 }