Expose marked content IDs for images and alt text.

 - Adds two new public bits of API:
    - StructElement_GetMCID(STRUCTELEMENT) to return the marked content
      ID of the struct element.
    - IMAGEOBJ_METADATA.mcid to contain the marked content ID of the
      image.
 - Restores ContentMark::GetMCID, which was removed with other dead
   code in https://pdfium-review.googlesource.com/c/pdfium/+/19170.
 - Adds a couple calls to tests, including a simple new PDF to test
   the struct tree marked content ID.

Bug:pdfium:957
Change-Id: I92856e43d741df989e53a575a08258da19a39f22
Reviewed-on: https://pdfium-review.googlesource.com/20632
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/fpdfsdk/fpdf_structtree_embeddertest.cpp b/fpdfsdk/fpdf_structtree_embeddertest.cpp
index 05b77fc0f7..7ca81f7b2e 100644
--- a/fpdfsdk/fpdf_structtree_embeddertest.cpp
+++ b/fpdfsdk/fpdf_structtree_embeddertest.cpp
@@ -6,6 +6,7 @@
 #include "public/fpdf_structtree.h"
 #include "testing/embedder_test.h"
 #include "testing/test_support.h"
+#include "third_party/base/optional.h"
 
 class FPDFStructTreeEmbeddertest : public EmbedderTest {};
 
@@ -24,6 +25,7 @@ TEST_F(FPDFStructTreeEmbeddertest, GetAltText) {
   EXPECT_EQ(nullptr, element);
   element = FPDF_StructTree_GetChildAtIndex(struct_tree, 0);
   ASSERT_NE(nullptr, element);
+  EXPECT_EQ(-1, FPDF_StructElement_GetMarkedContentID(element));
   EXPECT_EQ(0U, FPDF_StructElement_GetAltText(element, nullptr, 0));
 
   ASSERT_EQ(1, FPDF_StructElement_CountChildren(element));
@@ -34,6 +36,7 @@ TEST_F(FPDFStructTreeEmbeddertest, GetAltText) {
   EXPECT_EQ(nullptr, child_element);
   child_element = FPDF_StructElement_GetChildAtIndex(element, 0);
   ASSERT_NE(nullptr, child_element);
+  EXPECT_EQ(-1, FPDF_StructElement_GetMarkedContentID(child_element));
   EXPECT_EQ(0U, FPDF_StructElement_GetAltText(child_element, nullptr, 0));
 
   ASSERT_EQ(1, FPDF_StructElement_CountChildren(child_element));
@@ -44,6 +47,7 @@ TEST_F(FPDFStructTreeEmbeddertest, GetAltText) {
   EXPECT_EQ(nullptr, gchild_element);
   gchild_element = FPDF_StructElement_GetChildAtIndex(child_element, 0);
   ASSERT_NE(nullptr, gchild_element);
+  EXPECT_EQ(-1, FPDF_StructElement_GetMarkedContentID(gchild_element));
   ASSERT_EQ(24U, FPDF_StructElement_GetAltText(gchild_element, nullptr, 0));
 
   unsigned short buffer[12];
@@ -54,6 +58,7 @@ TEST_F(FPDFStructTreeEmbeddertest, GetAltText) {
   for (size_t i = 0; i < FX_ArraySize(buffer); ++i)
     EXPECT_EQ(0U, buffer[i]);
 
+  EXPECT_EQ(-1, FPDF_StructElement_GetMarkedContentID(gchild_element));
   ASSERT_EQ(24U, FPDF_StructElement_GetAltText(gchild_element, buffer,
                                                sizeof(buffer)));
   const wchar_t kExpected[] = L"Black Image";
@@ -69,6 +74,22 @@ TEST_F(FPDFStructTreeEmbeddertest, GetAltText) {
   FPDF_ClosePage(page);
 }
 
+TEST_F(FPDFStructTreeEmbeddertest, GetMarkedContentID) {
+  ASSERT_TRUE(OpenDocument("marked_content_id.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  FPDF_STRUCTTREE struct_tree = FPDF_StructTree_GetForPage(page);
+  ASSERT_TRUE(struct_tree);
+  ASSERT_EQ(1, FPDF_StructTree_CountChildren(struct_tree));
+
+  FPDF_STRUCTELEMENT element = FPDF_StructTree_GetChildAtIndex(struct_tree, 0);
+  EXPECT_EQ(0, FPDF_StructElement_GetMarkedContentID(element));
+
+  FPDF_StructTree_Close(struct_tree);
+  FPDF_ClosePage(page);
+}
+
 TEST_F(FPDFStructTreeEmbeddertest, GetType) {
   ASSERT_TRUE(OpenDocument("tagged_alt_text.pdf"));
   FPDF_PAGE page = LoadPage(0);