Add FPDFFormObj_CountObjects() API

To find out the number of sub-objects a form object has, similar to how
FPDFPage_CountObjects() does it for page objects.

Change-Id: I7e5775dece42b74fd5b71b1d9622a1aa37bf64ac
Reviewed-on: https://pdfium-review.googlesource.com/37316
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>

3 files changed, 36 insertions, 0 deletions

diff --git a/fpdfsdk/fpdf_edit_embeddertest.cpp b/fpdfsdk/fpdf_edit_embeddertest.cpp
index be872ee186..e169c46b6d 100644
--- a/fpdfsdk/fpdf_edit_embeddertest.cpp
+++ b/fpdfsdk/fpdf_edit_embeddertest.cpp
@@ -1573,6 +1573,20 @@ TEST_F(FPDFEditEmbeddertest, TestGetTextRenderMode) {
   UnloadPage(page);
 }
 
+TEST_F(FPDFEditEmbeddertest, TestFormGetObjects) {
+  EXPECT_TRUE(OpenDocument("form_object.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+  ASSERT_EQ(1, FPDFPage_CountObjects(page));
+
+  FPDF_PAGEOBJECT form = FPDFPage_GetObject(page, 0);
+  EXPECT_EQ(FPDF_PAGEOBJ_FORM, FPDFPageObj_GetType(form));
+  ASSERT_EQ(-1, FPDFFormObj_CountObjects(nullptr));
+  ASSERT_EQ(2, FPDFFormObj_CountObjects(form));
+
+  UnloadPage(page);
+}
+
 // Tests adding text from standard font using FPDFText_LoadStandardFont.
 TEST_F(FPDFEditEmbeddertest, AddStandardFontText2) {
   // Start with a blank page
diff --git a/fpdfsdk/fpdf_editpage.cpp b/fpdfsdk/fpdf_editpage.cpp
index 8a1200885a..4151de5dfd 100644
--- a/fpdfsdk/fpdf_editpage.cpp
+++ b/fpdfsdk/fpdf_editpage.cpp
@@ -751,3 +751,24 @@ FPDFPageObj_SetLineCap(FPDF_PAGEOBJECT page_object, int line_cap) {
   pPageObj->SetDirty(true);
   return true;
 }
+
+FPDF_EXPORT int FPDF_CALLCONV
+FPDFFormObj_CountObjects(FPDF_PAGEOBJECT page_object) {
+  auto* pPageObj = CPDFPageObjectFromFPDFPageObject(page_object);
+  if (!pPageObj)
+    return -1;
+
+  CPDF_FormObject* pFormObject = pPageObj->AsForm();
+  if (!pFormObject)
+    return -1;
+
+  const CPDF_Form* pForm = pFormObject->form();
+  if (!pForm)
+    return -1;
+
+  const CPDF_PageObjectList* pObjectList = pForm->GetPageObjectList();
+  if (!pObjectList)
+    return -1;
+
+  return pObjectList->size();
+}
diff --git a/fpdfsdk/fpdf_view_c_api_test.c b/fpdfsdk/fpdf_view_c_api_test.c
index 53d5a77cfd..c0021fc7c0 100644
--- a/fpdfsdk/fpdf_view_c_api_test.c
+++ b/fpdfsdk/fpdf_view_c_api_test.c
@@ -126,6 +126,7 @@ int CheckPDFiumCApi() {
 
     // fpdf_edit.h
     CHK(FPDFFont_Close);
+    CHK(FPDFFormObj_CountObjects);
     CHK(FPDFImageObj_GetBitmap);
     CHK(FPDFImageObj_GetImageDataDecoded);
     CHK(FPDFImageObj_GetImageDataRaw);