Enhance tabbing support to include links and highlights

This CL adds ability to tab across links and highlights (along with
already supported widgets) behind a newly added feature flag
kTabAcrossPDFAnnotations. This is done by calling the newly added
PDFium API FPDFAnnot_SetFocusableSubtypes().
A unit test has also been added to validate the added support.
Here is the related CL:
https://pdfium-review.googlesource.com/c/pdfium/+/60011/

Bug: 994500
Change-Id: I00312c00f3e6373949a4723cc65778fdb32ab963
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1783695Reviewed-by: Ian Prest <iapres@microsoft.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Neha Gupta <negupta@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#759380}

pdf/pdf_features.cc

@@ -32,5 +32,8 @@ const base::Feature kSaveEditedPDFForm = {"SaveEditedPDFForm",
 #endif  // defined(OS_CHROMEOS)
 };
 
+const base::Feature kTabAcrossPDFAnnotations = {
+    "TabAcrossPDFAnnotations", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features
 }  // namespace chrome_pdf

pdf/pdf_features.h

@@ -18,6 +18,7 @@ extern const base::Feature kAccessiblePDFHighlight;
 extern const base::Feature kPDFAnnotations;
 extern const base::Feature kPDFTwoUpView;
 extern const base::Feature kSaveEditedPDFForm;
+extern const base::Feature kTabAcrossPDFAnnotations;
 
 }  // namespace features
 }  // namespace chrome_pdf

pdf/pdfium/pdfium_engine.cc

@@ -16,6 +16,7 @@
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
+#include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
@@ -29,6 +30,7 @@
 #include "pdf/document_loader_impl.h"
 #include "pdf/draw_utils/coordinates.h"
 #include "pdf/draw_utils/shadow.h"
+#include "pdf/pdf_features.h"
 #include "pdf/pdf_transform.h"
 #include "pdf/pdfium/pdfium_api_string_buffer_adapter.h"
 #include "pdf/pdfium/pdfium_document.h"
@@ -2709,6 +2711,14 @@ void PDFiumEngine::LoadForm() {
     FPDF_SetFormFieldHighlightColor(form(), FPDF_FORMFIELD_UNKNOWN,
                                     kFormHighlightColor);
     FPDF_SetFormFieldHighlightAlpha(form(), kFormHighlightAlpha);
+
+    if (base::FeatureList::IsEnabled(features::kTabAcrossPDFAnnotations)) {
+      static constexpr FPDF_ANNOTATION_SUBTYPE kFocusableAnnotSubtypes[] = {
+          FPDF_ANNOT_LINK, FPDF_ANNOT_HIGHLIGHT, FPDF_ANNOT_WIDGET};
+      FPDF_BOOL ret = FPDFAnnot_SetFocusableSubtypes(
+          form(), kFocusableAnnotSubtypes, base::size(kFocusableAnnotSubtypes));
+      DCHECK(ret);
+    }
   }
 }
 

pdf/pdfium/pdfium_engine_unittest.cc

@@ -4,9 +4,11 @@
 
 #include "pdf/pdfium/pdfium_engine.h"
 
+#include "base/test/scoped_feature_list.h"
 #include "base/test/task_environment.h"
 #include "pdf/document_layout.h"
 #include "pdf/document_metadata.h"
+#include "pdf/pdf_features.h"
 #include "pdf/pdfium/pdfium_page.h"
 #include "pdf/pdfium/pdfium_test_base.h"
 #include "pdf/test/test_client.h"
@@ -258,6 +260,62 @@ class PDFiumEngineTabbingTest : public PDFiumTestBase {
       base::test::TaskEnvironment::TimeSource::MOCK_TIME};
 };
 
+TEST_F(PDFiumEngineTabbingTest, TabbingSupportedAnnots) {
+  /*
+   * Document structure
+   * Document
+   * ++ Page 1
+   * ++++ Widget annotation
+   * ++++ Widget annotation
+   * ++++ Highlight annotation
+   * ++++ Link annotation
+   */
+
+  // Enable feature flag.
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitAndEnableFeature(
+      chrome_pdf::features::kTabAcrossPDFAnnotations);
+
+  TestClient client;
+  std::unique_ptr<PDFiumEngine> engine =
+      InitializeEngine(&client, FILE_PATH_LITERAL("annots.pdf"));
+  ASSERT_TRUE(engine);
+
+  ASSERT_EQ(1, engine->GetNumberOfPages());
+
+  ASSERT_EQ(PDFiumEngine::FocusElementType::kNone,
+            GetFocusedElementType(engine.get()));
+  EXPECT_EQ(-1, GetLastFocusedPage(engine.get()));
+
+  ASSERT_TRUE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kDocument,
+            GetFocusedElementType(engine.get()));
+
+  ASSERT_TRUE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kPage,
+            GetFocusedElementType(engine.get()));
+  EXPECT_EQ(0, GetLastFocusedPage(engine.get()));
+
+  ASSERT_TRUE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kPage,
+            GetFocusedElementType(engine.get()));
+  EXPECT_EQ(0, GetLastFocusedPage(engine.get()));
+
+  ASSERT_TRUE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kPage,
+            GetFocusedElementType(engine.get()));
+  EXPECT_EQ(0, GetLastFocusedPage(engine.get()));
+
+  ASSERT_TRUE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kPage,
+            GetFocusedElementType(engine.get()));
+  EXPECT_EQ(0, GetLastFocusedPage(engine.get()));
+
+  ASSERT_FALSE(HandleTabEvent(engine.get(), 0));
+  EXPECT_EQ(PDFiumEngine::FocusElementType::kNone,
+            GetFocusedElementType(engine.get()));
+}
+
 TEST_F(PDFiumEngineTabbingTest, TabbingForwardTest) {
   /*
    * Document structure

pdf/test/data/annots.in

+{{header}}
+{{object 1 0}} <<
+  /Type /Catalog
+  /Pages 2 0 R
+  /AcroForm [5 0 R 6 0 R]
+>>
+endobj
+{{object 2 0}} <<
+  /Type /Pages
+  /Count 1
+  /Kids [3 0 R]
+>>
+endobj
+{{object 3 0}} <<
+  /Type /Page
+  /Parent 2 0 R
+  /Annots [5 0 R 6 0 R 7 0 R 8 0 R]
+  /Contents 4 0 R
+  /Tabs /R
+>>
+endobj
+{{object 4 0}} <<
+  {{streamlen}}
+>>
+stream
+BT
+70 340 Td
+14 Tf
+(External Link ) Tj
+ET
+endstream
+endobj
+{{object 5 0}} <<
+  /Type /Annot
+  /Subtype /Widget
+  /FT /Tx
+  /Parent 3 0 R
+  /T (TextField)
+  /Rect [69 670 220 690]
+>>
+endobj
+{{object 6 0}} <<
+  /Type /Annot
+  /Subtype /Widget
+  /FT /Btn
+  /Rect [69 360 220 380]
+  /A <<
+    /URI (https://www.google.com)
+    /S /URI
+  >>
+  /F 4
+  /T (button)
+  /Ff 65536
+>>
+endobj
+{{object 7 0}} <<
+  /Type /Annot
+  /Subtype /Link
+  /Rect [69 338 180 358]
+  /A <<
+    /Type /Action
+    /S /URI
+    /URI (https://www.google.com/)
+  >>
+  /F 4
+>>
+endobj
+{{object 8 0}} <<
+  /Type /Annot
+  /Subtype /Highlight
+  /F 4
+  /QuadPoints [120 358 150 358 120 338 150 338]
+  /C [1 0.90196 0]
+  /Rect [120 338 150 358]
+>>
+endobj
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF
\ No newline at end of file