Disable PDF content interaction in read-only mode

Since Presentation mode is read-only, ignore all input events to
disable form editing and tabbing across PDF contents.

When entering read-only mode:
- Unselect any selected text.
- Kill any form focus.
- Remove all form highlights, so they don't appear interactable.

Bug: 1157120
Change-Id: Idf0b5669b9d0f55ccd68198aa941fdeb1097910e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596857
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838492}

chrome/test/data/pdf/BUILD.gn

@@ -133,6 +133,7 @@ js_library("fullscreen_test") {
     ":test_util",
     "../webui:test_util.m",
     "//chrome/browser/resources/pdf:constants",
+    "//chrome/browser/resources/pdf:pdf_scripting_api",
     "//chrome/browser/resources/pdf:pdf_viewer",
     "//third_party/polymer/v3_0/components-chromium/iron-test-helpers:mock-interactions",
     "//ui/webui/resources/js:cr.m",

chrome/test/data/pdf/fullscreen_test.js

@@ -4,6 +4,7 @@
 
 import {eventToPromise} from 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/_test_resources/webui/test_util.m.js';
 import {FittingType} from 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/constants.js';
+import {PDFScriptingAPI} from 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/pdf_scripting_api.js';
 import {PDFViewerElement} from 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/pdf_viewer.js';
 import {isMac} from 'chrome://resources/js/cr.m.js';
 import {keyDownOn} from 'chrome://resources/polymer/v3_0/iron-test-helpers/mock-interactions.js';
@@ -128,6 +129,17 @@ const tests = [
 
     chrome.test.succeed();
   },
+  async function testTextSelectionDisabled() {
+    await ensureFullscreen();
+
+    const client = new PDFScriptingAPI(window, window);
+    client.selectAll();
+    client.getSelectedText(selectedText => {
+      // No text should be selected.
+      chrome.test.assertEq(0, selectedText.length);
+      chrome.test.succeed();
+    });
+  },
 ];
 
 chrome.test.runTests(tests);

pdf/out_of_process_instance.cc

@@ -689,6 +689,12 @@ void OutOfProcessInstance::HandleMessage(const pp::Var& message) {
 }
 
 bool OutOfProcessInstance::HandleInputEvent(const pp::InputEvent& event) {
+  // Ignore user input in read-only mode.
+  // TODO(dhoss): Add a test for ignored input events. It is currently difficult
+  // to unit test certain `OutOfProcessInstance` methods.
+  if (engine()->IsReadOnly())
+    return false;
+
   // To simplify things, convert the event into device coordinates.
   pp::InputEvent event_device_res(event);
   {

pdf/pdfium/pdfium_engine.cc

@@ -976,7 +976,7 @@ void PDFiumEngine::KillFormFocus() {
 
 void PDFiumEngine::UpdateFocus(bool has_focus) {
   base::AutoReset<bool> updating_focus_guard(&updating_focus_, true);
-  if (has_focus) {
+  if (has_focus && !IsReadOnly()) {
     UpdateFocusItemType(last_focused_item_type_);
     if (focus_item_type_ == FocusElementType::kPage &&
         PageIndexInBounds(last_focused_page_) &&
@@ -2064,6 +2064,20 @@ bool PDFiumEngine::IsReadOnly() const {
 
 void PDFiumEngine::SetReadOnly(bool enable) {
   read_only_ = enable;
+
+  // Restore form highlights.
+  if (!read_only_) {
+    FPDF_SetFormFieldHighlightAlpha(form(), kFormHighlightAlpha);
+    return;
+  }
+
+  // Hide form highlights.
+  FPDF_SetFormFieldHighlightAlpha(form(), /*alpha=*/0);
+  KillFormFocus();
+
+  // Unselect text.
+  SelectionChangeInvalidator selection_invalidator(this);
+  selection_.clear();
 }
 
 void PDFiumEngine::SetTwoUpView(bool enable) {
@@ -2222,7 +2236,7 @@ bool PDFiumEngine::HasPermission(DocumentPermission permission) const {
 }
 
 void PDFiumEngine::SelectAll() {
-  if (in_form_text_area_)
+  if (in_form_text_area_ || IsReadOnly())
     return;
 
   SelectionChangeInvalidator selection_invalidator(this);

pdf/pdfium/pdfium_engine_unittest.cc

@@ -36,6 +36,7 @@ using ::testing::InSequence;
 using ::testing::Invoke;
 using ::testing::IsEmpty;
 using ::testing::NiceMock;
+using ::testing::Not;
 using ::testing::Return;
 using ::testing::StrictMock;
 
@@ -1125,4 +1126,56 @@ TEST_F(PDFiumEngineTabbingTest, ScrollFocusedAnnotationIntoView) {
   ScrollFocusedAnnotationIntoView(engine.get());
 }
 
+class ReadOnlyTestClient : public TestClient {
+ public:
+  ReadOnlyTestClient() = default;
+  ~ReadOnlyTestClient() override = default;
+  ReadOnlyTestClient(const ReadOnlyTestClient&) = delete;
+  ReadOnlyTestClient& operator=(const ReadOnlyTestClient&) = delete;
+
+  // Mock PDFEngine::Client methods.
+  MOCK_METHOD(void, FormTextFieldFocusChange, (bool), (override));
+  MOCK_METHOD(void, SetSelectedText, (const std::string&), (override));
+};
+
+using PDFiumEngineReadOnlyTest = PDFiumTestBase;
+
+TEST_F(PDFiumEngineReadOnlyTest, KillFormFocus) {
+  NiceMock<ReadOnlyTestClient> client;
+  std::unique_ptr<PDFiumEngine> engine = InitializeEngine(
+      &client, FILE_PATH_LITERAL("annotation_form_fields.pdf"));
+  ASSERT_TRUE(engine);
+
+  // Setting read-only mode should kill form focus.
+  EXPECT_FALSE(engine->IsReadOnly());
+  EXPECT_CALL(client, FormTextFieldFocusChange(false));
+  engine->SetReadOnly(true);
+
+  // Attempting to focus during read-only mode should once more trigger a
+  // killing of form focus.
+  EXPECT_TRUE(engine->IsReadOnly());
+  EXPECT_CALL(client, FormTextFieldFocusChange(false));
+  engine->UpdateFocus(true);
+}
+
+TEST_F(PDFiumEngineReadOnlyTest, UnselectText) {
+  NiceMock<ReadOnlyTestClient> client;
+  std::unique_ptr<PDFiumEngine> engine =
+      InitializeEngine(&client, FILE_PATH_LITERAL("hello_world2.pdf"));
+  ASSERT_TRUE(engine);
+
+  // Update the plugin size so that all the text is visible by
+  // `SelectionChangeInvalidator`.
+  engine->PluginSizeUpdated({500, 500});
+
+  // Select text before going into read-only mode.
+  EXPECT_FALSE(engine->IsReadOnly());
+  EXPECT_CALL(client, SetSelectedText(Not(IsEmpty())));
+  engine->SelectAll();
+
+  // Setting read-only mode should unselect the text.
+  EXPECT_CALL(client, SetSelectedText(IsEmpty()));
+  engine->SetReadOnly(true);
+}
+
 }  // namespace chrome_pdf