Add FPDFFormObj_GetObject() API

To be used together with the existing FPDFFormObj_CountObjects()
function.

Change-Id: I8ed69624e967708c8db7e8f135e28fbe6a52752f
Reviewed-on: https://pdfium-review.googlesource.com/37890
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>

4 files changed, 60 insertions, 12 deletions

diff --git a/fpdfsdk/fpdf_edit_embeddertest.cpp b/fpdfsdk/fpdf_edit_embeddertest.cpp
index 0c0776f9d7..227e5c9ef5 100644
--- a/fpdfsdk/fpdf_edit_embeddertest.cpp
+++ b/fpdfsdk/fpdf_edit_embeddertest.cpp
@@ -1769,6 +1769,26 @@ TEST_F(FPDFEditEmbeddertest, TestFormGetObjects) {
   ASSERT_EQ(-1, FPDFFormObj_CountObjects(nullptr));
   ASSERT_EQ(2, FPDFFormObj_CountObjects(form));
 
+  // FPDFFormObj_GetObject() positive testing.
+  FPDF_PAGEOBJECT text1 = FPDFFormObj_GetObject(form, 0);
+  ASSERT_TRUE(text1);
+  float left = 0;
+  float bottom = 0;
+  float right = 0;
+  float top = 0;
+  ASSERT_TRUE(FPDFPageObj_GetBounds(text1, &left, &bottom, &right, &top));
+  ASSERT_EQ(271, static_cast<int>(top));
+
+  FPDF_PAGEOBJECT text2 = FPDFFormObj_GetObject(form, 1);
+  ASSERT_TRUE(text2);
+  ASSERT_TRUE(FPDFPageObj_GetBounds(text2, &left, &bottom, &right, &top));
+  ASSERT_EQ(221, static_cast<int>(top));
+
+  // FPDFFormObj_GetObject() negative testing.
+  ASSERT_EQ(nullptr, FPDFFormObj_GetObject(nullptr, 0));
+  ASSERT_EQ(nullptr, FPDFFormObj_GetObject(form, -1));
+  ASSERT_EQ(nullptr, FPDFFormObj_GetObject(form, 2));
+
   UnloadPage(page);
 }
 
diff --git a/fpdfsdk/fpdf_editpage.cpp b/fpdfsdk/fpdf_editpage.cpp
index ded55b9bef..f1dbf70192 100644
--- a/fpdfsdk/fpdf_editpage.cpp
+++ b/fpdfsdk/fpdf_editpage.cpp
@@ -140,6 +140,23 @@ unsigned int GetUnsignedAlpha(float alpha) {
   return static_cast<unsigned int>(alpha * 255.f + 0.5f);
 }
 
+const CPDF_PageObjectList* CPDFPageObjListFromFPDFFormObject(
+    FPDF_PAGEOBJECT page_object) {
+  auto* pPageObj = CPDFPageObjectFromFPDFPageObject(page_object);
+  if (!pPageObj)
+    return nullptr;
+
+  CPDF_FormObject* pFormObject = pPageObj->AsForm();
+  if (!pFormObject)
+    return nullptr;
+
+  const CPDF_Form* pForm = pFormObject->form();
+  if (!pForm)
+    return nullptr;
+
+  return pForm->GetPageObjectList();
+}
+
 }  // namespace
 
 FPDF_EXPORT FPDF_DOCUMENT FPDF_CALLCONV FPDF_CreateNewDocument() {
@@ -812,21 +829,21 @@ FPDFPageObj_SetLineCap(FPDF_PAGEOBJECT page_object, int line_cap) {
 
 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)
+  const CPDF_PageObjectList* pObjectList =
+      CPDFPageObjListFromFPDFFormObject(page_object);
+  if (!pObjectList)
     return -1;
 
-  const CPDF_Form* pForm = pFormObject->form();
-  if (!pForm)
-    return -1;
+  return pObjectList->size();
+}
 
-  const CPDF_PageObjectList* pObjectList = pForm->GetPageObjectList();
+FPDF_EXPORT FPDF_PAGEOBJECT FPDF_CALLCONV
+FPDFFormObj_GetObject(FPDF_PAGEOBJECT form_object, unsigned long index) {
+  const CPDF_PageObjectList* pObjectList =
+      CPDFPageObjListFromFPDFFormObject(form_object);
   if (!pObjectList)
-    return -1;
+    return nullptr;
 
-  return pObjectList->size();
+  return FPDFPageObjectFromCPDFPageObject(
+      pObjectList->GetPageObjectByIndex(index));
 }
diff --git a/fpdfsdk/fpdf_view_c_api_test.c b/fpdfsdk/fpdf_view_c_api_test.c
index d4c812f7a5..114a6b0024 100644
--- a/fpdfsdk/fpdf_view_c_api_test.c
+++ b/fpdfsdk/fpdf_view_c_api_test.c
@@ -127,6 +127,7 @@ int CheckPDFiumCApi() {
     // fpdf_edit.h
     CHK(FPDFFont_Close);
     CHK(FPDFFormObj_CountObjects);
+    CHK(FPDFFormObj_GetObject);
     CHK(FPDFImageObj_GetBitmap);
     CHK(FPDFImageObj_GetImageDataDecoded);
     CHK(FPDFImageObj_GetImageDataRaw);
diff --git a/public/fpdf_edit.h b/public/fpdf_edit.h
index fdd8c97d05..b97a7adbd9 100644
--- a/public/fpdf_edit.h
+++ b/public/fpdf_edit.h
@@ -1265,6 +1265,16 @@ FPDF_EXPORT int FPDF_CALLCONV FPDFText_GetTextRenderMode(FPDF_PAGEOBJECT text);
 FPDF_EXPORT int FPDF_CALLCONV
 FPDFFormObj_CountObjects(FPDF_PAGEOBJECT form_object);
 
+// Experimental API.
+// Get page object in |form_object| at |index|.
+//
+//   form_object - handle to a form object.
+//   index       - the 0-based index of a page object.
+//
+// Returns the handle to the page object, or NULL on error.
+FPDF_EXPORT FPDF_PAGEOBJECT FPDF_CALLCONV
+FPDFFormObj_GetObject(FPDF_PAGEOBJECT form_object, unsigned long index);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus