[unseasoned-pdf] Fixed issue that the link area doesn't match the text.

On a display with device scale larger than 1.0, a link's clickable
area does not match where it is displayed in the Pepper-free PDF viewer
due to the wrong scale level is applied to the input event.

The Pepper implementation has the correct behavior, which applies the
viewport-to-DIP scale to the input event in
PepperPluginInstanceImpl::HandleInputEvent(), then applies the device
scale to the input event in PdfViewPluginBase::HandleInputEvent().

However, the Pepper-free implementation applies device scale to the
input event twice, in both PdfViewWebPlugin::HandleInputEvent() and
PdfViewPluginBase::HandleInputEvent().

This CL corrects the scale level applied to the input event in
PdfViewWebPlugin::HandleInputEvent() and adds unit tests for this issue.

Bug: 1240395
Change-Id: Ic0dc20d9c989896325edbae07e5b7ace3b76d2db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3101860
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Commit-Queue: Hui Yingst <nigi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#915298}

pdf/BUILD.gn

@@ -413,8 +413,10 @@ if (enable_pdf) {
       "//base",
       "//ppapi/cpp:objects",
       "//testing/gtest",
+      "//third_party/blink/public/common:headers",
       "//ui/gfx:geometry_skia",
       "//ui/gfx/range",
+      "//ui/latency:latency",
     ]
   }
 
@@ -500,6 +502,7 @@ if (enable_pdf) {
       "//third_party/blink/public/common:headers",
       "//third_party/pdfium",
       "//ui/base",
+      "//ui/events/blink:blink",
       "//ui/gfx:test_support",
       "//ui/gfx/geometry",
       "//ui/gfx/range",

pdf/DEPS

@@ -20,5 +20,6 @@ include_rules = [
 specific_include_rules = {
   ".*_unittest.*\.cc": [
     "+cc/test",
+    "+ui/latency/latency_info.h",
   ],
 }

pdf/pdf_view_web_plugin.cc

@@ -429,11 +429,11 @@ blink::WebInputEventResult PdfViewWebPlugin::HandleInputEvent(
     const blink::WebCoalescedInputEvent& event,
     ui::Cursor* cursor) {
   // TODO(crbug.com/702993): The input events received by the Pepper plugin
-  // already have the device scale applied. The scaling done here should be
-  // moved into `PdfViewPluginBase::HandleInputEvent()` once the Pepper plugin
-  // is removed.
+  // already have the viewport-to-DIP scale applied. The scaling done here
+  // should be moved into `PdfViewPluginBase::HandleInputEvent()` once the
+  // Pepper plugin is removed.
   std::unique_ptr<blink::WebInputEvent> scaled_event =
-      ui::ScaleWebInputEvent(event.Event(), device_scale());
+      ui::ScaleWebInputEvent(event.Event(), viewport_to_dip_scale_);
 
   const blink::WebInputEvent& event_to_handle =
       scaled_event ? *scaled_event : event.Event();

pdf/pdf_view_web_plugin_unittest.cc

@@ -16,6 +16,9 @@
 #include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/blink/public/common/input/web_coalesced_input_event.h"
+#include "third_party/blink/public/common/input/web_input_event.h"
+#include "third_party/blink/public/common/input/web_pointer_properties.h"
 #include "third_party/blink/public/platform/web_string.h"
 #include "third_party/blink/public/platform/web_text_input_type.h"
 #include "third_party/blink/public/platform/web_vector.h"
@@ -23,10 +26,14 @@
 #include "third_party/blink/public/web/web_plugin_params.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "ui/base/cursor/cursor.h"
+#include "ui/events/blink/blink_event_util.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/skia_util.h"
+#include "ui/latency/latency_info.h"
 
 namespace chrome_pdf {
 
@@ -43,6 +50,9 @@ using ::testing::Return;
 // testing.
 constexpr gfx::Size kCanvasSize(100, 100);
 
+// A common device scale for high DPI displays.
+constexpr float kDeviceScale = 2.0f;
+
 // Note: Make sure `kDefaultColor` is different from `kPaintColor` and the
 // plugin's background color. This will help identify bitmap changes after
 // painting.
@@ -86,6 +96,18 @@ SkBitmap GenerateExpectedBitmapForPaint(float device_scale,
   return expected_bitmap;
 }
 
+blink::WebMouseEvent CreateDefaultMouseDownEvent() {
+  blink::WebMouseEvent web_event(
+      blink::WebInputEvent::Type::kMouseDown,
+      /*position=*/gfx::PointF(),
+      /*global_position=*/gfx::PointF(),
+      blink::WebPointerProperties::Button::kLeft,
+      /*click_count_param=*/1, blink::WebInputEvent::Modifiers::kLeftButtonDown,
+      blink::WebInputEvent::GetStaticTimeStampForTests());
+  web_event.SetFrameScale(1);
+  return web_event;
+}
+
 class FakeContainerWrapper final : public PdfViewWebPlugin::ContainerWrapper {
  public:
   explicit FakeContainerWrapper(PdfViewWebPlugin* web_plugin)
@@ -386,6 +408,42 @@ TEST_F(PdfViewWebPluginTest, PaintSnapshots) {
   }
 }
 
+TEST_F(PdfViewWebPluginTest, HandleInputEventWithUseZoomForDSFEnabled) {
+  // Test when using zoom for DSF is enabled.
+  EXPECT_CALL(*client_ptr_, IsUseZoomForDSFEnabled)
+      .WillRepeatedly(Return(true));
+  wrapper_ptr_->set_device_scale(kDeviceScale);
+  UpdatePluginGeometry(kDeviceScale, gfx::Rect(20, 20));
+
+  ui::Cursor dummy_cursor;
+  plugin_->HandleInputEvent(
+      blink::WebCoalescedInputEvent(CreateDefaultMouseDownEvent(),
+                                    ui::LatencyInfo()),
+      &dummy_cursor);
+
+  ASSERT_TRUE(engine_ptr_->GetScaledMouseEvent());
+  EXPECT_EQ(gfx::PointF(-10.0f, 0.0f),
+            engine_ptr_->GetScaledMouseEvent()->PositionInWidget());
+}
+
+TEST_F(PdfViewWebPluginTest, HandleInputEventWithUseZoomForDSFDisabled) {
+  // Test when using zoom for DSF is disabled.
+  EXPECT_CALL(*client_ptr_, IsUseZoomForDSFEnabled)
+      .WillRepeatedly(Return(false));
+  wrapper_ptr_->set_device_scale(kDeviceScale);
+  UpdatePluginGeometry(kDeviceScale, gfx::Rect(20, 20));
+
+  ui::Cursor dummy_cursor;
+  plugin_->HandleInputEvent(
+      blink::WebCoalescedInputEvent(CreateDefaultMouseDownEvent(),
+                                    ui::LatencyInfo()),
+      &dummy_cursor);
+
+  ASSERT_TRUE(engine_ptr_->GetScaledMouseEvent());
+  EXPECT_EQ(gfx::PointF(-20.0f, 0.0f),
+            engine_ptr_->GetScaledMouseEvent()->PositionInWidget());
+}
+
 TEST_F(PdfViewWebPluginTest, ChangeTextSelection) {
   ASSERT_FALSE(plugin_->HasSelection());
   ASSERT_TRUE(plugin_->SelectionAsText().IsEmpty());

pdf/test/test_pdfium_engine.cc

@@ -5,6 +5,8 @@
 #include "pdf/test/test_pdfium_engine.h"
 
 #include <string.h>
+
+#include <memory>
 #include <vector>
 
 #include "base/check_op.h"
@@ -16,6 +18,8 @@
 #include "pdf/pdf_engine.h"
 #include "pdf/pdfium/pdfium_engine.h"
 #include "pdf/pdfium/pdfium_form_filler.h"
+#include "third_party/blink/public/common/input/web_input_event.h"
+#include "third_party/blink/public/common/input/web_mouse_event.h"
 
 namespace chrome_pdf {
 
@@ -30,6 +34,20 @@ TestPDFiumEngine::TestPDFiumEngine(PDFEngine::Client* client)
 
 TestPDFiumEngine::~TestPDFiumEngine() = default;
 
+bool TestPDFiumEngine::HandleInputEvent(
+    const blink::WebInputEvent& scaled_event) {
+  // Since blink::WebInputEvent is an abstract class, we cannot use equal
+  // matcher to verify its value. Here we test with blink::WebMouseEvent
+  // specifically.
+  if (!blink::WebInputEvent::IsMouseEventType(scaled_event.GetType()))
+    return false;
+
+  blink::WebMouseEvent* mouse_event = new blink::WebMouseEvent;
+  scaled_mouse_event_.reset(mouse_event);
+  *mouse_event = static_cast<const blink::WebMouseEvent&>(scaled_event);
+  return true;
+}
+
 bool TestPDFiumEngine::HasPermission(DocumentPermission permission) const {
   return base::Contains(permissions_, permission);
 }
@@ -65,6 +83,10 @@ std::vector<uint8_t> TestPDFiumEngine::GetSaveData() {
   return std::vector<uint8_t>(std::begin(kSaveData), std::end(kSaveData));
 }
 
+const blink::WebMouseEvent* TestPDFiumEngine::GetScaledMouseEvent() const {
+  return scaled_mouse_event_ ? scaled_mouse_event_.get() : nullptr;
+}
+
 void TestPDFiumEngine::SetPermissions(
     const std::vector<DocumentPermission>& permissions) {
   permissions_.clear();

pdf/test/test_pdfium_engine.h

@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <memory>
 #include <vector>
 
 #include "base/containers/flat_set.h"
@@ -15,6 +16,11 @@
 #include "pdf/document_metadata.h"
 #include "pdf/pdf_engine.h"
 #include "pdf/pdfium/pdfium_engine.h"
+#include "third_party/blink/public/common/input/web_mouse_event.h"
+
+namespace blink {
+class WebInputEvent;
+}  // namespace blink
 
 namespace chrome_pdf {
 
@@ -34,6 +40,9 @@ class TestPDFiumEngine : public PDFiumEngine {
 
   ~TestPDFiumEngine() override;
 
+  // Sets a scaled mouse event for testing.
+  bool HandleInputEvent(const blink::WebInputEvent& scaled_event) override;
+
   bool HasPermission(DocumentPermission permission) const override;
 
   const std::vector<DocumentAttachmentInfo>& GetDocumentAttachmentInfoList()
@@ -52,6 +61,8 @@ class TestPDFiumEngine : public PDFiumEngine {
 
   std::vector<uint8_t> GetSaveData() override;
 
+  const blink::WebMouseEvent* GetScaledMouseEvent() const;
+
   void SetPermissions(const std::vector<DocumentPermission>& permissions);
 
  protected:
@@ -66,6 +77,8 @@ class TestPDFiumEngine : public PDFiumEngine {
 
   DocumentMetadata metadata_;
 
+  std::unique_ptr<blink::WebMouseEvent> scaled_mouse_event_;
+
   base::flat_set<DocumentPermission> permissions_;
 };