Add FPDFAnnot_GetFormFieldAtPoint() and embedder tests.

Given a point on a page, this method returns the interactive form
annotation whose rectangle contains that point. If there is no such
annotation, nullptr is returned. FPDFPage_CloseAnnot() must be called
after the annotation this method returns is no longer needed.

The tests for this method use the returned annotation to check its
interactive form annotation flags via
FPDFAnnot_GetFormFieldFlags().

BUG=chromium:59266

Change-Id: I8728792bea5367c172e08fdb6bae83eafb70eb68
Reviewed-on: https://pdfium-review.googlesource.com/7970
Commit-Queue: Diana Gage <drgage@google.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>

4 files changed, 126 insertions, 0 deletions

diff --git a/fpdfsdk/fpdfannot.cpp b/fpdfsdk/fpdfannot.cpp
index f3a9ea1b72..fcbed5c2ce 100644
--- a/fpdfsdk/fpdfannot.cpp
+++ b/fpdfsdk/fpdfannot.cpp
@@ -804,3 +804,22 @@ DLLEXPORT int STDCALL FPDFAnnot_GetFormFieldFlags(FPDF_PAGE page,
   CPDF_FormField* pFormField = interform.GetFieldByDict(pAnnotDict);
   return pFormField ? pFormField->GetFieldFlags() : FPDF_FORMFLAG_NONE;
 }
+
+DLLEXPORT FPDF_ANNOTATION STDCALL
+FPDFAnnot_GetFormFieldAtPoint(FPDF_FORMHANDLE hHandle,
+                              FPDF_PAGE page,
+                              double page_x,
+                              double page_y) {
+  CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
+  if (!hHandle || !pPage)
+    return nullptr;
+
+  CPDF_InterForm interform(pPage->m_pDocument.Get());
+  int annot_index = -1;
+  CPDF_FormControl* pFormCtrl = interform.GetControlAtPoint(
+      pPage, CFX_PointF(static_cast<float>(page_x), static_cast<float>(page_y)),
+      &annot_index);
+  if (!pFormCtrl || annot_index == -1)
+    return nullptr;
+  return FPDFPage_GetAnnot(page, annot_index);
+}
diff --git a/fpdfsdk/fpdfannot_embeddertest.cpp b/fpdfsdk/fpdfannot_embeddertest.cpp
index b50f73f3ab..58a00067a7 100644
--- a/fpdfsdk/fpdfannot_embeddertest.cpp
+++ b/fpdfsdk/fpdfannot_embeddertest.cpp
@@ -956,3 +956,88 @@ TEST_F(FPDFAnnotEmbeddertest, GetFormFieldFlagsComboBox) {
 
   UnloadPage(page);
 }
+
+TEST_F(FPDFAnnotEmbeddertest, GetFormAnnotNull) {
+  // Open file with form text fields.
+  EXPECT_TRUE(OpenDocument("text_form.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  // Attempt to get an annotation where no annotation exists on page.
+  FPDF_ANNOTATION annot =
+      FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 0, 0);
+  EXPECT_FALSE(annot);
+
+  UnloadPage(page);
+}
+
+TEST_F(FPDFAnnotEmbeddertest, GetFormAnnotAndCheckFlagsTextField) {
+  // Open file with form text fields.
+  EXPECT_TRUE(OpenDocument("text_form_multiple.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  // Retrieve user-editable text field annotation.
+  FPDF_ANNOTATION annot =
+      FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 105, 118);
+  ASSERT_TRUE(annot);
+
+  // Check that interactive form annotation flag values are as expected.
+  int flags = FPDFAnnot_GetFormFieldFlags(page, annot);
+  EXPECT_FALSE(flags & FPDF_FORMFLAG_READONLY);
+  FPDFPage_CloseAnnot(annot);
+
+  // Retrieve read-only text field annotation.
+  annot = FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 105, 202);
+  ASSERT_TRUE(annot);
+
+  // Check that interactive form annotation flag values are as expected.
+  flags = FPDFAnnot_GetFormFieldFlags(page, annot);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_READONLY);
+  FPDFPage_CloseAnnot(annot);
+
+  UnloadPage(page);
+}
+
+TEST_F(FPDFAnnotEmbeddertest, GetFormAnnotAndCheckFlagsComboBox) {
+  // Open file with form comboboxes.
+  EXPECT_TRUE(OpenDocument("combobox_form.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  // Retrieve user-editable combobox annotation.
+  FPDF_ANNOTATION annot =
+      FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 102, 63);
+  ASSERT_TRUE(annot);
+
+  // Check that interactive form annotation flag values are as expected.
+  int flags = FPDFAnnot_GetFormFieldFlags(page, annot);
+  EXPECT_FALSE(flags & FPDF_FORMFLAG_READONLY);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_CHOICE_COMBO);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_CHOICE_EDIT);
+  FPDFPage_CloseAnnot(annot);
+
+  // Retrieve regular combobox annotation.
+  annot = FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 102, 113);
+  ASSERT_TRUE(annot);
+
+  // Check that interactive form annotation flag values are as expected.
+  flags = FPDFAnnot_GetFormFieldFlags(page, annot);
+  EXPECT_FALSE(flags & FPDF_FORMFLAG_READONLY);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_CHOICE_COMBO);
+  EXPECT_FALSE(flags & FPDF_FORMFLAG_CHOICE_EDIT);
+  FPDFPage_CloseAnnot(annot);
+
+  // Retrieve read-only combobox annotation.
+  annot = FPDFAnnot_GetFormFieldAtPoint(form_handle(), page, 102, 213);
+  ASSERT_TRUE(annot);
+
+  // Check that interactive form annotation flag values are as expected.
+  flags = FPDFAnnot_GetFormFieldFlags(page, annot);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_READONLY);
+  EXPECT_TRUE(flags & FPDF_FORMFLAG_CHOICE_COMBO);
+  EXPECT_FALSE(flags & FPDF_FORMFLAG_CHOICE_EDIT);
+  FPDFPage_CloseAnnot(annot);
+
+  UnloadPage(page);
+}
diff --git a/fpdfsdk/fpdfview_c_api_test.c b/fpdfsdk/fpdfview_c_api_test.c
index 1405b40ce8..546ae47512 100644
--- a/fpdfsdk/fpdfview_c_api_test.c
+++ b/fpdfsdk/fpdfview_c_api_test.c
@@ -62,6 +62,7 @@ int CheckPDFiumCApi() {
     CHK(FPDFAnnot_GetFlags);
     CHK(FPDFAnnot_SetFlags);
     CHK(FPDFAnnot_GetFormFieldFlags);
+    CHK(FPDFAnnot_GetFormFieldAtPoint);
 
     // fpdf_attachment.h
     CHK(FPDFDoc_GetAttachmentCount);
diff --git a/public/fpdf_annot.h b/public/fpdf_annot.h
index 2a44e45bc8..c0f9a6e4c6 100644
--- a/public/fpdf_annot.h
+++ b/public/fpdf_annot.h
@@ -9,6 +9,7 @@
 #include "fpdfview.h"
 
 #include "fpdf_doc.h"
+#include "fpdf_formfill.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -404,6 +405,26 @@ DLLEXPORT FPDF_BOOL STDCALL FPDFAnnot_SetFlags(FPDF_ANNOTATION annot,
 DLLEXPORT int STDCALL FPDFAnnot_GetFormFieldFlags(FPDF_PAGE page,
                                                   FPDF_ANNOTATION annot);
 
+// Experimental API.
+// Retrieves an interactive form annotation whose rectangle contains a given
+// point on a page. Must call FPDFPage_CloseAnnot() when the annotation returned
+// is no longer needed.
+//
+//
+//    hHandle     -   handle to the form fill module, returned by
+//                    FPDFDOC_InitFormFillEnvironment.
+//    page        -   handle to the page, returned by FPDF_LoadPage function.
+//    page_x      -   X position in PDF "user space".
+//    page_y      -   Y position in PDF "user space".
+//
+// Returns the interactive form annotation whose rectangle contains the given
+// coordinates on the page. If there is no such annotation, return NULL.
+DLLEXPORT FPDF_ANNOTATION STDCALL
+FPDFAnnot_GetFormFieldAtPoint(FPDF_FORMHANDLE hHandle,
+                              FPDF_PAGE page,
+                              double page_x,
+                              double page_y);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus