Expose DPI helper functions for Runner apps to use (#16313)

ci/licenses_golden/licenses_flutter

@@ -1116,6 +1116,9 @@ FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flu
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_view_controller.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/plugin_registrar_windows.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/plugin_registrar_windows_unittests.cc
+FILE: ../../../flutter/shell/platform/windows/dpi_utils.cc
+FILE: ../../../flutter/shell/platform/windows/dpi_utils.h
+FILE: ../../../flutter/shell/platform/windows/dpi_utils_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_windows.cc
 FILE: ../../../flutter/shell/platform/windows/key_event_handler.cc
 FILE: ../../../flutter/shell/platform/windows/key_event_handler.h
@@ -1125,10 +1128,9 @@ FILE: ../../../flutter/shell/platform/windows/platform_handler.h
 FILE: ../../../flutter/shell/platform/windows/public/flutter_windows.h
 FILE: ../../../flutter/shell/platform/windows/text_input_plugin.cc
 FILE: ../../../flutter/shell/platform/windows/text_input_plugin.h
-FILE: ../../../flutter/shell/platform/windows/win32_dpi_helper.cc
-FILE: ../../../flutter/shell/platform/windows/win32_dpi_helper.h
 FILE: ../../../flutter/shell/platform/windows/win32_flutter_window.cc
 FILE: ../../../flutter/shell/platform/windows/win32_flutter_window.h
+FILE: ../../../flutter/shell/platform/windows/win32_flutter_window_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/win32_task_runner.cc
 FILE: ../../../flutter/shell/platform/windows/win32_task_runner.h
 FILE: ../../../flutter/shell/platform/windows/win32_window.cc

shell/platform/windows/BUILD.gn

@@ -41,6 +41,8 @@ source_set("flutter_windows_source") {
   sources = [
     "angle_surface_manager.cc",
     "angle_surface_manager.h",
+    "dpi_utils.cc",
+    "dpi_utils.h",
     "flutter_windows.cc",
     "key_event_handler.cc",
     "key_event_handler.h",
@@ -49,8 +51,6 @@ source_set("flutter_windows_source") {
     "platform_handler.h",
     "text_input_plugin.cc",
     "text_input_plugin.h",
-    "win32_dpi_helper.cc",
-    "win32_dpi_helper.h",
     "win32_flutter_window.cc",
     "win32_flutter_window.h",
     "win32_task_runner.cc",
@@ -109,8 +109,12 @@ executable("flutter_windows_unittests") {
   testonly = true
 
   sources = [
+    "dpi_utils_unittests.cc",
     "testing/win32_flutter_window_test.cc",
     "testing/win32_flutter_window_test.h",
+    "testing/win32_window_test.cc",
+    "testing/win32_window_test.h",
+    "win32_flutter_window_unittests.cc",
     "win32_window_unittests.cc",
   ]
 

shell/platform/windows/dpi_utils.cc

+#include "dpi_utils.h"
+
+namespace flutter {
+
+namespace {
+
+constexpr UINT kDefaultDpi = 96;
+
+// This is the MDT_EFFECTIVE_DPI value from MONITOR_DPI_TYPE, an enum declared
+// in ShellScalingApi.h. Replicating here to avoid importing the library
+// directly.
+constexpr UINT kEffectiveDpiMonitorType = 0;
+
+template <typename T>
+
+/// Retrieves a function |name| from a given |comBaseModule| into |outProc|.
+/// Returns a bool indicating whether the function was found.
+bool AssignProcAddress(HMODULE comBaseModule, const char* name, T*& outProc) {
+  outProc = reinterpret_cast<T*>(GetProcAddress(comBaseModule, name));
+  return *outProc != nullptr;
+}
+
+/// A helper class for abstracting various Windows DPI related functions across
+/// Windows OS versions.
+class Win32DpiHelper {
+ public:
+  Win32DpiHelper();
+
+  ~Win32DpiHelper();
+
+  /// Returns the DPI for |hwnd|. Supports all DPI awareness modes, and is
+  /// backward compatible down to Windows Vista. If |hwnd| is nullptr, returns
+  /// the DPI for the primary monitor. If Per-Monitor DPI awareness is not
+  /// available, returns the system's DPI.
+  UINT GetDpiForWindow(HWND);
+
+  /// Returns the DPI of a given monitor. Defaults to 96 if the API is not
+  /// available.
+  UINT GetDpiForMonitor(HMONITOR);
+
+ private:
+  using GetDpiForWindow_ = UINT __stdcall(HWND);
+  using GetDpiForMonitor_ = HRESULT __stdcall(HMONITOR hmonitor,
+                                              UINT dpiType,
+                                              UINT* dpiX,
+                                              UINT* dpiY);
+  using EnableNonClientDpiScaling_ = BOOL __stdcall(HWND hwnd);
+
+  GetDpiForWindow_* get_dpi_for_window_ = nullptr;
+  GetDpiForMonitor_* get_dpi_for_monitor_ = nullptr;
+  EnableNonClientDpiScaling_* enable_non_client_dpi_scaling_ = nullptr;
+
+  HMODULE user32_module_ = nullptr;
+  HMODULE shlib_module_ = nullptr;
+  bool dpi_for_window_supported_ = false;
+  bool dpi_for_monitor_supported_ = false;
+};
+
+Win32DpiHelper::Win32DpiHelper() {
+  if ((user32_module_ = LoadLibraryA("User32.dll")) != nullptr) {
+    dpi_for_window_supported_ = (AssignProcAddress(
+        user32_module_, "GetDpiForWindow", get_dpi_for_window_));
+  }
+  if ((shlib_module_ = LoadLibraryA("Shcore.dll")) != nullptr) {
+    dpi_for_monitor_supported_ = AssignProcAddress(
+        shlib_module_, "GetDpiForMonitor", get_dpi_for_monitor_);
+  }
+}
+
+Win32DpiHelper::~Win32DpiHelper() {
+  if (user32_module_ != nullptr) {
+    FreeLibrary(user32_module_);
+  }
+  if (shlib_module_ != nullptr) {
+    FreeLibrary(shlib_module_);
+  }
+}
+
+UINT Win32DpiHelper::GetDpiForWindow(HWND hwnd) {
+  // GetDpiForWindow returns the DPI for any awareness mode. If not available,
+  // or no |hwnd| is provided, fallback to a per monitor, system, or default
+  // DPI.
+  if (dpi_for_window_supported_ && hwnd != nullptr) {
+    return get_dpi_for_window_(hwnd);
+  }
+
+  if (dpi_for_monitor_supported_) {
+    HMONITOR monitor = nullptr;
+    if (hwnd != nullptr) {
+      monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTOPRIMARY);
+    }
+    return GetDpiForMonitor(monitor);
+  }
+  HDC hdc = GetDC(hwnd);
+  UINT dpi = GetDeviceCaps(hdc, LOGPIXELSX);
+  ReleaseDC(hwnd, hdc);
+  return dpi;
+}
+
+UINT Win32DpiHelper::GetDpiForMonitor(HMONITOR monitor) {
+  if (dpi_for_monitor_supported_) {
+    if (monitor == nullptr) {
+      const POINT target_point = {0, 0};
+      monitor = MonitorFromPoint(target_point, MONITOR_DEFAULTTOPRIMARY);
+    }
+    UINT dpi_x = 0, dpi_y = 0;
+    HRESULT result =
+        get_dpi_for_monitor_(monitor, kEffectiveDpiMonitorType, &dpi_x, &dpi_y);
+    if (SUCCEEDED(result)) {
+      return dpi_x;
+    }
+  }
+  return kDefaultDpi;
+}  // namespace
+
+Win32DpiHelper* GetHelper() {
+  static Win32DpiHelper* dpi_helper = new Win32DpiHelper();
+  return dpi_helper;
+}
+}  // namespace
+
+UINT GetDpiForHWND(HWND hwnd) {
+  return GetHelper()->GetDpiForWindow(hwnd);
+}
+
+UINT GetDpiForMonitor(HMONITOR monitor) {
+  return GetHelper()->GetDpiForMonitor(monitor);
+}
+}  // namespace flutter

shell/platform/windows/dpi_utils.h

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "Windows.h"
+
+#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_UTILS_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_UTILS_H_
+
+namespace flutter {
+
+/// Returns the DPI for |hwnd|. Supports all DPI awareness modes, and is
+/// backward compatible down to Windows Vista. If |hwnd| is nullptr, returns the
+/// DPI for the primary monitor. If Per-Monitor DPI awareness is not available,
+/// returns the system's DPI.
+UINT GetDpiForHWND(HWND hwnd);
+
+/// Returns the DPI of a given monitor. Defaults to 96 if the API is not
+/// available.
+UINT GetDpiForMonitor(HMONITOR monitor);
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_UTILS_H_

shell/platform/windows/dpi_utils_unittests.cc

+#include <windows.h>
+
+#include "flutter/shell/platform/windows/dpi_utils.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+
+TEST(DpiUtilsTest, NonZero) {
+  ASSERT_GT(GetDpiForHWND(nullptr), 0);
+  ASSERT_GT(GetDpiForMonitor(nullptr), 0);
+};
+
+TEST(DpiUtilsTest, NullHwndUsesPrimaryMonitor) {
+  const POINT target_point = {0, 0};
+  HMONITOR monitor = MonitorFromPoint(target_point, MONITOR_DEFAULTTOPRIMARY);
+  ASSERT_EQ(GetDpiForHWND(nullptr), GetDpiForMonitor(monitor));
+};
+
+}  // namespace testing
+}  // namespace flutter

shell/platform/windows/flutter_windows.cc

@@ -15,6 +15,7 @@
 #include "flutter/shell/platform/common/cpp/client_wrapper/include/flutter/plugin_registrar.h"
 #include "flutter/shell/platform/common/cpp/incoming_message_dispatcher.h"
 #include "flutter/shell/platform/embedder/embedder.h"
+#include "flutter/shell/platform/windows/dpi_utils.h"
 #include "flutter/shell/platform/windows/key_event_handler.h"
 #include "flutter/shell/platform/windows/keyboard_hook_handler.h"
 #include "flutter/shell/platform/windows/platform_handler.h"
@@ -182,6 +183,14 @@ HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef view) {
   return view->window->GetWindowHandle();
 }
 
+UINT FlutterDesktopGetDpiForHWND(HWND hwnd) {
+  return flutter::GetDpiForHWND(hwnd);
+}
+
+UINT FlutterDesktopGetDpiForMonitor(HMONITOR monitor) {
+  return flutter::GetDpiForMonitor(monitor);
+}
+
 FlutterDesktopEngineRef FlutterDesktopRunEngine(const char* assets_path,
                                                 const char* icu_data_path,
                                                 const char** arguments,

shell/platform/windows/public/flutter_windows.h

@@ -77,6 +77,15 @@ FlutterDesktopProcessMessages(FlutterDesktopViewControllerRef controller);
 // Return backing HWND for manipulation in host application.
 FLUTTER_EXPORT HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef view);
 
+// Gets the DPI for a given |hwnd|, depending on the supported APIs per
+// windows version and DPI awareness mode. If nullptr is passed, returns the DPI
+// of the primary monitor.
+FLUTTER_EXPORT UINT FlutterDesktopGetDpiForHWND(HWND hwnd);
+
+// Gets the DPI for a given |monitor|. If the API is not available, a default
+// DPI of 96 is returned.
+FLUTTER_EXPORT UINT FlutterDesktopGetDpiForMonitor(HMONITOR monitor);
+
 // Runs an instance of a headless Flutter engine.
 //
 // The |assets_path| is the path to the flutter_assets folder for the Flutter

shell/platform/windows/testing/win32_flutter_window_test.h

@@ -4,18 +4,21 @@
 
 #include <windowsx.h>
 
-#include "flutter/fml/macros.h"
 #include "flutter/shell/platform/windows/win32_flutter_window.h"
 
 namespace flutter {
 namespace testing {
 
+/// Test class for Win32FlutterWindow.
 class Win32FlutterWindowTest : public Win32FlutterWindow {
  public:
   Win32FlutterWindowTest(int width, int height);
-
   virtual ~Win32FlutterWindowTest();
 
+  // Prevent copying.
+  Win32FlutterWindowTest(Win32FlutterWindowTest const&) = delete;
+  Win32FlutterWindowTest& operator=(Win32FlutterWindowTest const&) = delete;
+
   // |Win32Window|
   void OnFontChange() override;
 
@@ -23,8 +26,6 @@ class Win32FlutterWindowTest : public Win32FlutterWindow {
 
  private:
   bool on_font_change_called_ = false;
-
-  FML_DISALLOW_COPY_AND_ASSIGN(Win32FlutterWindowTest);
 };
 
 }  // namespace testing

shell/platform/windows/testing/win32_window_test.cc

+#include "flutter/shell/platform/windows/testing/win32_window_test.h"
+
+namespace flutter {
+namespace testing {
+
+Win32WindowTest::Win32WindowTest() : Win32Window(){};
+
+Win32WindowTest::~Win32WindowTest() = default;
+
+void Win32WindowTest::OnDpiScale(unsigned int dpi){};
+
+void Win32WindowTest::OnResize(unsigned int width, unsigned int height) {}
+
+void Win32WindowTest::OnPointerMove(double x, double y) {}
+
+void Win32WindowTest::OnPointerDown(double x, double y, UINT button) {}
+
+void Win32WindowTest::OnPointerUp(double x, double y, UINT button) {}
+
+void Win32WindowTest::OnPointerLeave() {}
+
+void Win32WindowTest::OnChar(char32_t code_point) {}
+
+void Win32WindowTest::OnKey(int key, int scancode, int action, int mods) {}
+
+void Win32WindowTest::OnScroll(double delta_x, double delta_y) {}
+
+void Win32WindowTest::OnFontChange() {}
+
+UINT Win32WindowTest::GetDpi() {
+  return GetCurrentDPI();
+}
+
+}  // namespace testing
+}  // namespace flutter

shell/platform/windows/testing/win32_window_test.h

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <windowsx.h>
+
+#include "flutter/shell/platform/windows/win32_window.h"
+
+namespace flutter {
+namespace testing {
+
+/// Test class for the Win32Window base class. Used to access protected methods
+/// for testing.
+class Win32WindowTest : public Win32Window {
+ public:
+  Win32WindowTest();
+  virtual ~Win32WindowTest();
+
+  // Prevent copying.
+  Win32WindowTest(Win32WindowTest const&) = delete;
+  Win32WindowTest& operator=(Win32WindowTest const&) = delete;
+
+  // Wrapper for GetCurrentDPI() which is a protected method.
+  UINT GetDpi();
+
+  // |Win32Window|
+  void OnDpiScale(unsigned int dpi) override;
+
+  // |Win32Window|
+  void OnResize(unsigned int width, unsigned int height) override;
+
+  // |Win32Window|
+  void OnPointerMove(double x, double y) override;
+
+  // |Win32Window|
+  void OnPointerDown(double x, double y, UINT button) override;
+
+  // |Win32Window|
+  void OnPointerUp(double x, double y, UINT button) override;
+
+  // |Win32Window|
+  void OnPointerLeave() override;
+
+  // |Win32Window|
+  void OnChar(char32_t code_point) override;
+
+  // |Win32Window|
+  void OnKey(int key, int scancode, int action, int mods) override;
+
+  // |Win32Window|
+  void OnScroll(double delta_x, double delta_y) override;
+
+  // |Win32Window|
+  void OnFontChange() override;
+};
+
+}  // namespace testing
+}  // namespace flutter

shell/platform/windows/win32_dpi_helper.cc

-#include "flutter/shell/platform/windows/win32_dpi_helper.h"
-
-namespace flutter {
-
-namespace {
-
-constexpr UINT kDefaultDpi = 96;
-
-template <typename T>
-bool AssignProcAddress(HMODULE comBaseModule, const char* name, T*& outProc) {
-  outProc = reinterpret_cast<T*>(GetProcAddress(comBaseModule, name));
-  return *outProc != nullptr;
-}
-
-}  // namespace
-
-Win32DpiHelper::Win32DpiHelper() {
-  user32_module_ = LoadLibraryA("User32.dll");
-  if (user32_module_ == nullptr) {
-    return;
-  }
-
-  if (AssignProcAddress(user32_module_, "GetDpiForWindow",
-                        get_dpi_for_window_)) {
-    dpi_for_window_supported_ = true;
-    return;
-  }
-
-  shlib_module_ = LoadLibraryA("Shcore.dll");
-  if (shlib_module_ == nullptr) {
-    return;
-  }
-
-  if (AssignProcAddress(shlib_module_, "GetDpiForMonitor",
-                        get_dpi_for_monitor_) &&
-      AssignProcAddress(user32_module_, "MonitorFromWindow",
-                        monitor_from_window_)) {
-    dpi_for_monitor_supported_ = true;
-  }
-}
-
-Win32DpiHelper::~Win32DpiHelper() {
-  if (user32_module_ != nullptr) {
-    FreeLibrary(user32_module_);
-  }
-  if (shlib_module_ != nullptr) {
-    FreeLibrary(shlib_module_);
-  }
-}
-
-UINT Win32DpiHelper::GetDpi(HWND hwnd) {
-  // GetDpiForWindow returns the DPI for any awareness mode. If not available,
-  // fallback to a per monitor, system, or default DPI.
-  if (dpi_for_window_supported_) {
-    return get_dpi_for_window_(hwnd);
-  }
-
-  if (dpi_for_monitor_supported_) {
-    HMONITOR monitor = monitor_from_window_(hwnd, MONITOR_DEFAULTTONEAREST);
-    UINT dpi_x = 0, dpi_y = 0;
-    HRESULT result =
-        get_dpi_for_monitor_(monitor, MDT_EFFECTIVE_DPI, &dpi_x, &dpi_y);
-    return SUCCEEDED(result) ? dpi_x : kDefaultDpi;
-  }
-
-  HDC hdc = GetDC(hwnd);
-  UINT dpi = GetDeviceCaps(hdc, LOGPIXELSX);
-  ReleaseDC(hwnd, hdc);
-  return dpi;
-}
-}  // namespace flutter

shell/platform/windows/win32_dpi_helper.h

-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_HELPER_H_
-#define FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_HELPER_H_
-
-#include <ShellScalingApi.h>
-#include <VersionHelpers.h>
-
-namespace flutter {
-
-/// A helper class for abstracting various Windows DPI related functions across
-/// Windows OS versions.
-class Win32DpiHelper {
- public:
-  Win32DpiHelper();
-
-  ~Win32DpiHelper();
-
-  /// Returns the current DPI. Supports all DPI awareness modes, and is backward
-  /// compatible down to Windows Vista.
-  UINT GetDpi(HWND);
-
- private:
-  using GetDpiForWindow_ = UINT __stdcall(HWND);
-  using GetDpiForMonitor_ = HRESULT __stdcall(HMONITOR hmonitor,
-                                              MONITOR_DPI_TYPE dpiType,
-                                              UINT* dpiX,
-                                              UINT* dpiY);
-  using MonitorFromWindow_ = HMONITOR __stdcall(HWND hwnd, DWORD dwFlags);
-
-  GetDpiForWindow_* get_dpi_for_window_ = nullptr;
-  GetDpiForMonitor_* get_dpi_for_monitor_ = nullptr;
-  MonitorFromWindow_* monitor_from_window_ = nullptr;
-
-  HMODULE user32_module_ = nullptr;
-  HMODULE shlib_module_ = nullptr;
-  bool dpi_for_window_supported_ = false;
-  bool dpi_for_monitor_supported_ = false;
-};
-
-}  // namespace flutter
-
-#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_DPI_HELPER_H_

shell/platform/windows/win32_flutter_window_unittests.cc

+#include "flutter/shell/platform/windows/testing/win32_flutter_window_test.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+
+TEST(Win32FlutterWindowTest, CreateDestroy) {
+  Win32FlutterWindowTest window(800, 600);
+  ASSERT_TRUE(TRUE);
+}
+
+TEST(Win32FlutterWindowTest, CanFontChange) {
+  Win32FlutterWindowTest window(800, 600);
+  HWND hwnd = window.GetWindowHandle();
+  LRESULT result = SendMessage(hwnd, WM_FONTCHANGE, NULL, NULL);
+  ASSERT_EQ(result, 0);
+  ASSERT_TRUE(window.OnFontChangeWasCalled());
+}
+
+}  // namespace testing
+}  // namespace flutter

shell/platform/windows/win32_window.cc

@@ -4,9 +4,16 @@
 
 #include "flutter/shell/platform/windows/win32_window.h"
 
+#include "dpi_utils.h"
+
 namespace flutter {
 
-Win32Window::Win32Window() {}
+Win32Window::Win32Window() {
+  // Get the DPI of the primary monitor as the initial DPI. If Per-Monitor V2 is
+  // supported, |current_dpi_| should be updated in the
+  // kWmDpiChangedBeforeParent message.
+  current_dpi_ = GetDpiForHWND(nullptr);
+}
 
 Win32Window::~Win32Window() {
   Destroy();
@@ -74,7 +81,6 @@ LRESULT CALLBACK Win32Window::WndProc(HWND const window,
                      reinterpret_cast<LONG_PTR>(cs->lpCreateParams));
 
     auto that = static_cast<Win32Window*>(cs->lpCreateParams);
-    that->current_dpi_ = that->dpi_helper_->GetDpi(window);
     that->window_handle_ = window;
   } else if (Win32Window* that = GetThisFromHandle(window)) {
     return that->MessageHandler(window, message, wparam, lparam);
@@ -106,12 +112,10 @@ Win32Window::MessageHandler(HWND hwnd,
   UINT button_pressed = 0;
   if (window != nullptr) {
     switch (message) {
-      case WM_DPICHANGED:
-        return HandleDpiChange(window_handle_, wparam, lparam, true);
-        break;
       case kWmDpiChangedBeforeParent:
-        return HandleDpiChange(window_handle_, wparam, lparam, false);
-        break;
+        current_dpi_ = GetDpiForHWND(window_handle_);
+        window->OnDpiScale(current_dpi_);
+        return 0;
       case WM_SIZE:
         width = LOWORD(lparam);
         height = HIWORD(lparam);
@@ -248,40 +252,6 @@ void Win32Window::Destroy() {
   UnregisterClass(window_class_name_.c_str(), nullptr);
 }
 
-// DPI Change handler. on WM_DPICHANGE resize the window
-LRESULT
-Win32Window::HandleDpiChange(HWND hwnd,
-                             WPARAM wparam,
-                             LPARAM lparam,
-                             bool toplevel) {
-  if (hwnd != nullptr) {
-    auto window =
-        reinterpret_cast<Win32Window*>(GetWindowLongPtr(hwnd, GWLP_USERDATA));
-
-    UINT uDpi = HIWORD(wparam);
-
-    // The DPI is only passed for DPI change messages on top level windows,
-    // hence call function to get DPI if needed.
-    if (uDpi == 0) {
-      uDpi = dpi_helper_->GetDpi(hwnd);
-    }
-    current_dpi_ = uDpi;
-    window->OnDpiScale(uDpi);
-
-    if (toplevel) {
-      // Resize the window only for toplevel windows which have a suggested
-      // size.
-      auto lprcNewScale = reinterpret_cast<RECT*>(lparam);
-      LONG newWidth = lprcNewScale->right - lprcNewScale->left;
-      LONG newHeight = lprcNewScale->bottom - lprcNewScale->top;
-
-      SetWindowPos(hwnd, nullptr, lprcNewScale->left, lprcNewScale->top,
-                   newWidth, newHeight, SWP_NOZORDER | SWP_NOACTIVATE);
-    }
-  }
-  return 0;
-}
-
 void Win32Window::HandleResize(UINT width, UINT height) {
   current_width_ = width;
   current_height_ = height;

shell/platform/windows/win32_window.h

@@ -11,8 +11,6 @@
 #include <memory>
 #include <string>
 
-#include "flutter/shell/platform/windows/win32_dpi_helper.h"
-
 namespace flutter {
 
 // Struct holding the mouse state. The engine doesn't keep track of which mouse
@@ -169,11 +167,6 @@ class Win32Window {
   // Member variable to hold the window title.
   std::wstring window_class_name_;
 
-  // Member variable referencing an instance of dpi_helper used to abstract some
-  // aspects of win32 High DPI handling across different OS versions.
-  std::unique_ptr<Win32DpiHelper> dpi_helper_ =
-      std::make_unique<Win32DpiHelper>();
-
   // Set to true to be notified when the mouse leaves the window.
   bool tracking_mouse_leave_ = false;
 

shell/platform/windows/win32_window_unittests.cc

-#include "flutter/shell/platform/windows/testing/win32_flutter_window_test.h"
+#include "flutter/shell/platform/windows/testing/win32_window_test.h"
 #include "gtest/gtest.h"
 
 namespace flutter {
 namespace testing {
 
-TEST(Win32FlutterWindowTest, CreateDestroy) {
-  Win32FlutterWindowTest window(800, 600);
+TEST(Win32WindowTest, CreateDestroy) {
+  Win32WindowTest window;
   ASSERT_TRUE(TRUE);
 }
 
-TEST(Win32FlutterWindowTest, CanFontChange) {
-  Win32FlutterWindowTest window(800, 600);
-  HWND hwnd = window.GetWindowHandle();
-  LRESULT result = SendMessage(hwnd, WM_FONTCHANGE, NULL, NULL);
-  ASSERT_EQ(result, 0);
-  ASSERT_TRUE(window.OnFontChangeWasCalled());
+TEST(Win32WindowTest, GetDpiAfterCreate) {
+  Win32WindowTest window;
+  ASSERT_TRUE(window.GetDpi() > 0);
 }
 
 }  // namespace testing