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>

4 files changed, 39 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);
 }
diff --git a/fpdfsdk/fpdfannot_embeddertest.cpp b/fpdfsdk/fpdfannot_embeddertest.cpp
index 47b71667b2..6c0cdedab5 100644
--- a/fpdfsdk/fpdfannot_embeddertest.cpp
+++ b/fpdfsdk/fpdfannot_embeddertest.cpp
@@ -919,11 +919,13 @@ TEST_F(FPDFAnnotEmbeddertest, ExtractLinkedAnnotations) {
   ASSERT_TRUE(OpenDocument("annotation_highlight_square_with_ap.pdf"));
   FPDF_PAGE page = FPDF_LoadPage(document(), 0);
   ASSERT_TRUE(page);
+  EXPECT_EQ(-1, FPDFPage_GetAnnotIndex(page, nullptr));
 
   // Retrieve the highlight annotation which has its popup defined.
   FPDF_ANNOTATION annot = FPDFPage_GetAnnot(page, 0);
   ASSERT_TRUE(annot);
   EXPECT_EQ(FPDF_ANNOT_HIGHLIGHT, FPDFAnnot_GetSubtype(annot));
+  EXPECT_EQ(0, FPDFPage_GetAnnotIndex(page, annot));
   std::unique_ptr<unsigned short, pdfium::FreeDeleter> popup_key =
       GetFPDFWideString(L"Popup");
   ASSERT_TRUE(FPDFAnnot_HasKey(annot, popup_key.get()));
@@ -934,6 +936,7 @@ TEST_F(FPDFAnnotEmbeddertest, ExtractLinkedAnnotations) {
   FPDF_ANNOTATION popup = FPDFAnnot_GetLinkedAnnot(annot, popup_key.get());
   ASSERT_TRUE(popup);
   EXPECT_EQ(FPDF_ANNOT_POPUP, FPDFAnnot_GetSubtype(popup));
+  EXPECT_EQ(1, FPDFPage_GetAnnotIndex(page, popup));
   FS_RECTF rect;
   ASSERT_TRUE(FPDFAnnot_GetRect(popup, &rect));
   EXPECT_NEAR(612.0f, rect.left, 0.001f);
diff --git a/fpdfsdk/fpdfview_c_api_test.c b/fpdfsdk/fpdfview_c_api_test.c
index b42dc160da..5bad9c8e7b 100644
--- a/fpdfsdk/fpdfview_c_api_test.c
+++ b/fpdfsdk/fpdfview_c_api_test.c
@@ -40,6 +40,7 @@ int CheckPDFiumCApi() {
     CHK(FPDFPage_CreateAnnot);
     CHK(FPDFPage_GetAnnotCount);
     CHK(FPDFPage_GetAnnot);
+    CHK(FPDFPage_GetAnnotIndex);
     CHK(FPDFPage_CloseAnnot);
     CHK(FPDFPage_RemoveAnnot);
     CHK(FPDFAnnot_GetSubtype);
diff --git a/public/fpdf_annot.h b/public/fpdf_annot.h
index 6a89ff9384..429a3f7541 100644
--- a/public/fpdf_annot.h
+++ b/public/fpdf_annot.h
@@ -134,6 +134,17 @@ FPDF_EXPORT FPDF_ANNOTATION FPDF_CALLCONV FPDFPage_GetAnnot(FPDF_PAGE page,
                                                             int index);
 
 // Experimental API.
+// Get the index of |annot| in |page|. This is the opposite of
+// FPDFPage_GetAnnot().
+//
+//   page  - handle to the page that the annotation is on.
+//   annot - handle to an annotation.
+//
+// Returns the index of |annot|, or -1 on failure.
+FPDF_EXPORT int FPDF_CALLCONV FPDFPage_GetAnnotIndex(FPDF_PAGE page,
+                                                     FPDF_ANNOTATION annot);
+
+// Experimental API.
 // Close an annotation. Must be called when the annotation returned by
 // FPDFPage_CreateAnnot() or FPDFPage_GetAnnot() is no longer needed. This
 // function does not remove the annotation from the document.