Hit testing Views elements doesn't account for device scale factor

This fix is needed to make touch work in the browser frame
when a screen reader is on. It consists in two main parts:
1. Apply the scale factor to the hit point received after touching
any element in the frame.
2. Add unit tests for the scale factor.

Bug: 990560
Change-Id: I00c3cd4de4ea49e8e8f881eb1db17c6a649b873c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1796888
Commit-Queue: Maria Villarreal <mavill@microsoft.com>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#697399}

ui/accessibility/platform/ax_fragment_root_win_unittest.cc

@@ -5,10 +5,12 @@
 #include "ui/accessibility/platform/ax_fragment_root_win.h"
 #include "ui/accessibility/platform/ax_platform_node_win.h"
 #include "ui/accessibility/platform/ax_platform_node_win_unittest.h"
+#include "ui/accessibility/platform/test_ax_node_wrapper.h"
 
 #include <UIAutomationClient.h>
 #include <UIAutomationCoreApi.h>
 
+#include "base/auto_reset.h"
 #include "base/win/scoped_safearray.h"
 #include "base/win/scoped_variant.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -77,6 +79,13 @@ TEST_F(AXFragmentRootTest, TestUIAElementProviderFromPoint) {
   EXPECT_HRESULT_SUCCEEDED(fragment_root_prov->ElementProviderFromPoint(
       47, 67, &provider_from_point));
   EXPECT_EQ(root_provider.Get(), provider_from_point.Get());
+
+  // This is on node 1 with scale factor of 1.5.
+  std::unique_ptr<base::AutoReset<float>> scale_factor_reset =
+      TestAXNodeWrapper::SetScaleFactor(1.5);
+  EXPECT_HRESULT_SUCCEEDED(fragment_root_prov->ElementProviderFromPoint(
+      60, 60, &provider_from_point));
+  EXPECT_EQ(element1_provider.Get(), provider_from_point.Get());
 }
 
 TEST_F(AXFragmentRootTest, TestUIAGetFocus) {

ui/accessibility/platform/ax_platform_node_win_unittest.cc

@@ -9,6 +9,7 @@
 
 #include <memory>
 
+#include "base/auto_reset.h"
 #include "base/stl_util.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/win/atl.h"
@@ -445,7 +446,7 @@ TEST_F(AXPlatformNodeWinTest, TestIAccessibleDetachedObject) {
 TEST_F(AXPlatformNodeWinTest, TestIAccessibleHitTest) {
   AXNodeData root;
   root.id = 1;
-  root.relative_bounds.bounds = gfx::RectF(0, 0, 30, 30);
+  root.relative_bounds.bounds = gfx::RectF(0, 0, 40, 40);
 
   AXNodeData node1;
   node1.id = 2;
@@ -455,7 +456,7 @@ TEST_F(AXPlatformNodeWinTest, TestIAccessibleHitTest) {
 
   AXNodeData node2;
   node2.id = 3;
-  node2.relative_bounds.bounds = gfx::RectF(20, 20, 10, 10);
+  node2.relative_bounds.bounds = gfx::RectF(20, 20, 20, 20);
   node2.SetName("Name2");
   root.child_ids.push_back(node2.id);
 
@@ -463,17 +464,23 @@ TEST_F(AXPlatformNodeWinTest, TestIAccessibleHitTest) {
 
   ComPtr<IAccessible> root_obj(GetRootIAccessible());
 
-  ScopedVariant obj;
-
-  // This is way outside of the root node
-  EXPECT_EQ(S_FALSE, root_obj->accHitTest(50, 50, obj.Receive()));
-  EXPECT_EQ(VT_EMPTY, obj.type());
-
-  // this is directly on node 1.
-  EXPECT_EQ(S_OK, root_obj->accHitTest(5, 5, obj.Receive()));
-  ASSERT_NE(nullptr, obj.ptr());
-
-  CheckVariantHasName(obj, L"Name1");
+  // This is way outside of the root node.
+  ScopedVariant obj_1;
+  EXPECT_EQ(S_FALSE, root_obj->accHitTest(50, 50, obj_1.Receive()));
+  EXPECT_EQ(VT_EMPTY, obj_1.type());
+
+  // This is directly on node 1.
+  EXPECT_EQ(S_OK, root_obj->accHitTest(5, 5, obj_1.Receive()));
+  ASSERT_NE(nullptr, obj_1.ptr());
+  CheckVariantHasName(obj_1, L"Name1");
+
+  // This is directly on node 2 with a scale factor of 1.5.
+  ScopedVariant obj_2;
+  std::unique_ptr<base::AutoReset<float>> scale_factor_reset =
+      TestAXNodeWrapper::SetScaleFactor(1.5);
+  EXPECT_EQ(S_OK, root_obj->accHitTest(38, 38, obj_2.Receive()));
+  ASSERT_NE(nullptr, obj_2.ptr());
+  CheckVariantHasName(obj_2, L"Name2");
 }
 
 TEST_F(AXPlatformNodeWinTest, TestIAccessibleName) {

ui/accessibility/platform/test_ax_node_wrapper.cc

@@ -26,6 +26,9 @@ std::unordered_map<AXNode*, TestAXNodeWrapper*> g_node_to_wrapper_map;
 // A global coordinate offset.
 gfx::Vector2d g_offset;
 
+// A global scale factor.
+float g_scale_factor = 1.0;
+
 // A global map that stores which node is focused on a determined tree.
 //   - If a tree has no node being focused, there shouldn't be any entry on the
 //     map associated with such tree, i.e. a pair {tree, nullptr} is invalid.
@@ -88,6 +91,12 @@ const AXNode* TestAXNodeWrapper::GetNodeFromLastDefaultAction() {
   return g_node_from_last_default_action;
 }
 
+// static
+std::unique_ptr<base::AutoReset<float>> TestAXNodeWrapper::SetScaleFactor(
+    float value) {
+  return std::make_unique<base::AutoReset<float>>(&g_scale_factor, value);
+}
+
 TestAXNodeWrapper::~TestAXNodeWrapper() {
   platform_node_->Destroy();
 }
@@ -228,7 +237,8 @@ TestAXNodeWrapper* TestAXNodeWrapper::HitTestSyncInternal(int x, int y) {
 }
 
 gfx::NativeViewAccessible TestAXNodeWrapper::HitTestSync(int x, int y) {
-  TestAXNodeWrapper* wrapper = HitTestSyncInternal(x, y);
+  TestAXNodeWrapper* wrapper =
+      HitTestSyncInternal(x / g_scale_factor, y / g_scale_factor);
   return wrapper ? wrapper->ax_platform_node()->GetNativeViewAccessible()
                  : nullptr;
 }

ui/accessibility/platform/test_ax_node_wrapper.h

@@ -9,6 +9,7 @@
 #include <string>
 #include <vector>
 
+#include "base/auto_reset.h"
 #include "build/build_config.h"
 #include "ui/accessibility/ax_node.h"
 #include "ui/accessibility/ax_tree.h"
@@ -40,6 +41,9 @@ class TestAXNodeWrapper : public AXPlatformNodeDelegateBase {
   // called from for testing.
   static const AXNode* GetNodeFromLastDefaultAction();
 
+  // Set a global scale factor for testing.
+  static std::unique_ptr<base::AutoReset<float>> SetScaleFactor(float value);
+
   ~TestAXNodeWrapper() override;
 
   AXPlatformNode* ax_platform_node() const { return platform_node_; }

ui/views/accessibility/view_ax_platform_node_delegate.cc

@@ -16,6 +16,7 @@
 #include "ui/accessibility/platform/ax_platform_node.h"
 #include "ui/accessibility/platform/ax_platform_node_base.h"
 #include "ui/accessibility/platform/ax_unique_id.h"
+#include "ui/base/layout.h"
 #include "ui/events/event_utils.h"
 #include "ui/views/accessibility/view_accessibility_utils.h"
 #include "ui/views/controls/native/native_view_host.h"
@@ -325,6 +326,15 @@ gfx::NativeViewAccessible ViewAXPlatformNodeDelegate::HitTestSync(int x,
   if (IsLeaf())
     return GetNativeObject();
 
+  gfx::NativeView native_view = view()->GetWidget()->GetNativeView();
+  float scale_factor = 1.0;
+  if (native_view) {
+    scale_factor = ui::GetScaleFactorForNativeView(native_view);
+    scale_factor = scale_factor <= 0 ? 1.0 : scale_factor;
+  }
+  x /= scale_factor;
+  y /= scale_factor;
+
   // Search child widgets first, since they're on top in the z-order.
   for (Widget* child_widget : GetChildWidgets().child_widgets) {
     View* child_root_view = child_widget->GetRootView();