From b4f720e13af42ab8067464bb677410d364af7365 Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Tue, 1 Oct 2019 15:38:30 -0700
Subject: [PATCH 1/6] Support system dpi awareness for older versions of
 Windows

---
 shell/platform/windows/win32_dpi_helper.cc | 28 ++++++++++++++++++++--
 shell/platform/windows/win32_dpi_helper.h  | 15 ++++++++++++
 shell/platform/windows/win32_window.cc     | 25 ++++++++++++-------
 shell/platform/windows/win32_window.h      |  2 +-
 4 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.cc b/shell/platform/windows/win32_dpi_helper.cc
index c31044ce2c767..1b23430ca9ec2 100644
--- a/shell/platform/windows/win32_dpi_helper.cc
+++ b/shell/platform/windows/win32_dpi_helper.cc
@@ -1,5 +1,7 @@
 #include "flutter/shell/platform/windows/win32_dpi_helper.h"
 
+#include <iostream>
+
 namespace flutter {
 
 namespace {
@@ -18,7 +20,6 @@ Win32DpiHelper::Win32DpiHelper() {
   if (user32_module_ == nullptr) {
     return;
   }
-
   if (!AssignProcAddress(user32_module_, "EnableNonClientDpiScaling",
                          enable_non_client_dpi_scaling_)) {
     return;
@@ -33,7 +34,6 @@ Win32DpiHelper::Win32DpiHelper() {
                          set_process_dpi_awareness_context_)) {
     return;
   }
-
   permonitorv2_supported_ = true;
 }
 
@@ -43,6 +43,22 @@ Win32DpiHelper::~Win32DpiHelper() {
   }
 }
 
+// SetAwareness
+// Check the available api. Start with v2, then fall back.
+void Win32DpiHelper::SetDpiAwerenessAllVersions() {
+  if (permonitorv2_supported_) {
+    SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+  } else {
+    std::cerr << "Per Monitor V2 DPI awareness is not supported on this "
+                 "version of Windows. Setting System DPI awareness\n";
+    AssignProcAddress(user32_module_, "GetDpiForSystem", get_dpi_for_system_);
+    AssignProcAddress(user32_module_, "SetProcessDpiAware",
+                      set_process_dpi_aware_);
+
+    SetProcessDPIAware();
+  }
+}
+
 bool Win32DpiHelper::IsPerMonitorV2Available() {
   return permonitorv2_supported_;
 }
@@ -61,6 +77,10 @@ UINT Win32DpiHelper::GetDpiForWindow(HWND hwnd) {
   return get_dpi_for_window_(hwnd);
 }
 
+UINT Win32DpiHelper::GetDpiForSystem() {
+  return get_dpi_for_system_();
+}
+
 BOOL Win32DpiHelper::SetProcessDpiAwarenessContext(
     DPI_AWARENESS_CONTEXT context) {
   if (!permonitorv2_supported_) {
@@ -69,4 +89,8 @@ BOOL Win32DpiHelper::SetProcessDpiAwarenessContext(
   return set_process_dpi_awareness_context_(context);
 }
 
+BOOL Win32DpiHelper::SetProcessDpiAware() {
+  return set_process_dpi_aware_();
+}
+
 }  // namespace flutter
diff --git a/shell/platform/windows/win32_dpi_helper.h b/shell/platform/windows/win32_dpi_helper.h
index ddf51184bf956..8ba635cee0859 100644
--- a/shell/platform/windows/win32_dpi_helper.h
+++ b/shell/platform/windows/win32_dpi_helper.h
@@ -28,17 +28,32 @@ class Win32DpiHelper {
   // Wrapper for OS functionality to return the DPI for |HWND|
   UINT GetDpiForWindow(HWND);
 
+  // Wrapper for OS functionality to return the DPI for the System. Only used if
+  // Per Monitor V2 is not supported by the current Windows version.
+  UINT GetDpiForSystem();
+
   // Sets the current process to a specified DPI awareness context.
   BOOL SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT);
 
+  // Sets the current process to System-level DPI awareness.
+  BOOL SetProcessDpiAware();
+
+  // Sets the DPI awareness for the application. For versions >= Windows 1703,
+  // use Per Monitor V2. For any older versions, use System.
+  void SetDpiAwerenessAllVersions();
+
  private:
   using EnableNonClientDpiScaling_ = BOOL __stdcall(HWND);
   using GetDpiForWindow_ = UINT __stdcall(HWND);
   using SetProcessDpiAwarenessContext_ = BOOL __stdcall(DPI_AWARENESS_CONTEXT);
+  using SetProcessDpiAware_ = BOOL __stdcall();
+  using GetDpiForSystem_ = UINT __stdcall();
 
   EnableNonClientDpiScaling_* enable_non_client_dpi_scaling_ = nullptr;
   GetDpiForWindow_* get_dpi_for_window_ = nullptr;
   SetProcessDpiAwarenessContext_* set_process_dpi_awareness_context_ = nullptr;
+  SetProcessDpiAware_* set_process_dpi_aware_ = nullptr;
+  GetDpiForSystem_* get_dpi_for_system_ = nullptr;
 
   HMODULE user32_module_ = nullptr;
   bool permonitorv2_supported_ = false;
diff --git a/shell/platform/windows/win32_window.cc b/shell/platform/windows/win32_window.cc
index 43690efec2753..3462bd5067b09 100644
--- a/shell/platform/windows/win32_window.cc
+++ b/shell/platform/windows/win32_window.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "flutter/shell/platform/windows/win32_window.h"
+#include <iostream>
 
 namespace flutter {
 
@@ -26,7 +27,11 @@ void Win32Window::InitializeChild(const char* title,
   Destroy();
   std::wstring converted_title = NarrowToWide(title);
 
-  WNDCLASS window_class = ResgisterWindowClass(converted_title);
+  // Set DPI awareness for all Windows versions. This call has to be made before
+  // the HWND is created.
+  dpi_helper_->SetDpiAwerenessAllVersions();
+
+  WNDCLASS window_class = RegisterWindowClass(converted_title);
 
   auto* result = CreateWindowEx(
       0, window_class.lpszClassName, converted_title.c_str(),
@@ -54,7 +59,7 @@ std::wstring Win32Window::NarrowToWide(const char* source) {
   return wideTitle;
 }
 
-WNDCLASS Win32Window::ResgisterWindowClass(std::wstring& title) {
+WNDCLASS Win32Window::RegisterWindowClass(std::wstring& title) {
   window_class_name_ = title;
 
   WNDCLASS window_class{};
@@ -83,13 +88,17 @@ LRESULT CALLBACK Win32Window::WndProc(HWND const window,
 
     auto that = static_cast<Win32Window*>(cs->lpCreateParams);
 
-    // Since the application is running in Per-monitor V2 mode, turn on
-    // automatic titlebar scaling
-    BOOL result = that->dpi_helper_->EnableNonClientDpiScaling(window);
-    if (result != TRUE) {
-      OutputDebugString(L"Failed to enable non-client area autoscaling");
+    if (that->dpi_helper_->IsPerMonitorV2Available()) {
+      // Since the application is running in Per-monitor V2 mode, turn on
+      // automatic titlebar scaling
+      BOOL result = that->dpi_helper_->EnableNonClientDpiScaling(window);
+      if (result != TRUE) {
+        OutputDebugString(L"Failed to enable non-client area autoscaling");
+      }
+      that->current_dpi_ = that->dpi_helper_->GetDpiForWindow(window);
+    } else {
+      that->current_dpi_ = that->dpi_helper_->GetDpiForSystem();
     }
-    that->current_dpi_ = that->dpi_helper_->GetDpiForWindow(window);
     that->window_handle_ = window;
   } else if (Win32Window* that = GetThisFromHandle(window)) {
     return that->MessageHandler(window, message, wparam, lparam);
diff --git a/shell/platform/windows/win32_window.h b/shell/platform/windows/win32_window.h
index e670a52519308..63a00c355dea6 100644
--- a/shell/platform/windows/win32_window.h
+++ b/shell/platform/windows/win32_window.h
@@ -57,7 +57,7 @@ class Win32Window {
 
   // Registers a window class with default style attributes, cursor and
   // icon.
-  WNDCLASS ResgisterWindowClass(std::wstring& title);
+  WNDCLASS RegisterWindowClass(std::wstring& title);
 
   // OS callback called by message pump.  Handles the WM_NCCREATE message which
   // is passed when the non-client area is being created and enables automatic

From e6db1e65567742c28f967bff1a9cea815a82cd2e Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Tue, 1 Oct 2019 18:42:24 -0700
Subject: [PATCH 2/6] Fix documentation

---
 shell/platform/windows/win32_dpi_helper.cc | 2 --
 shell/platform/windows/win32_window.cc     | 1 -
 2 files changed, 3 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.cc b/shell/platform/windows/win32_dpi_helper.cc
index 1b23430ca9ec2..eaa6be5765e01 100644
--- a/shell/platform/windows/win32_dpi_helper.cc
+++ b/shell/platform/windows/win32_dpi_helper.cc
@@ -43,8 +43,6 @@ Win32DpiHelper::~Win32DpiHelper() {
   }
 }
 
-// SetAwareness
-// Check the available api. Start with v2, then fall back.
 void Win32DpiHelper::SetDpiAwerenessAllVersions() {
   if (permonitorv2_supported_) {
     SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
diff --git a/shell/platform/windows/win32_window.cc b/shell/platform/windows/win32_window.cc
index 3462bd5067b09..1cda8cba0fb6b 100644
--- a/shell/platform/windows/win32_window.cc
+++ b/shell/platform/windows/win32_window.cc
@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 #include "flutter/shell/platform/windows/win32_window.h"
-#include <iostream>
 
 namespace flutter {
 

From c9b6c58a515e2ee8c0993b7fe265938656cb5cd0 Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Tue, 1 Oct 2019 18:46:26 -0700
Subject: [PATCH 3/6] Fix documentation

---
 shell/platform/windows/win32_dpi_helper.h |  3 +++
 shell/platform/windows/win32_window.cc    | 12 ++----------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.h b/shell/platform/windows/win32_dpi_helper.h
index 8ba635cee0859..196affab9f2e2 100644
--- a/shell/platform/windows/win32_dpi_helper.h
+++ b/shell/platform/windows/win32_dpi_helper.h
@@ -40,6 +40,9 @@ class Win32DpiHelper {
 
   // Sets the DPI awareness for the application. For versions >= Windows 1703,
   // use Per Monitor V2. For any older versions, use System.
+  //
+  // This call is overriden if DPI awareness is stated in the application
+  // manifest.
   void SetDpiAwerenessAllVersions();
 
  private:
diff --git a/shell/platform/windows/win32_window.cc b/shell/platform/windows/win32_window.cc
index 1cda8cba0fb6b..702827da2915b 100644
--- a/shell/platform/windows/win32_window.cc
+++ b/shell/platform/windows/win32_window.cc
@@ -6,16 +6,8 @@
 
 namespace flutter {
 
-Win32Window::Win32Window() {
-  // Assume Windows 10 1703 or greater for DPI handling.  When running on a
-  // older release of Windows where this context doesn't exist, DPI calls will
-  // fail and Flutter rendering will be impacted until this is fixed.
-  // To handle downlevel correctly, dpi_helper must use the most recent DPI
-  // context available should be used: Windows 1703: Per-Monitor V2, 8.1:
-  // Per-Monitor V1, Windows 7: System See
-  // https://docs.microsoft.com/en-us/windows/win32/hidpi/high-dpi-desktop-application-development-on-windows
-  // for more information.
-}
+Win32Window::Win32Window() {}
+
 Win32Window::~Win32Window() {
   Destroy();
 }

From a1ff82e77a7e6c5e84083dade38b37eee1435d31 Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Wed, 2 Oct 2019 09:46:16 -0700
Subject: [PATCH 4/6] Address comments

---
 shell/platform/windows/win32_dpi_helper.cc | 34 +++++-----------------
 shell/platform/windows/win32_dpi_helper.h  | 11 +++----
 shell/platform/windows/win32_window.cc     | 11 +++----
 3 files changed, 18 insertions(+), 38 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.cc b/shell/platform/windows/win32_dpi_helper.cc
index eaa6be5765e01..5843def87e43f 100644
--- a/shell/platform/windows/win32_dpi_helper.cc
+++ b/shell/platform/windows/win32_dpi_helper.cc
@@ -1,7 +1,5 @@
 #include "flutter/shell/platform/windows/win32_dpi_helper.h"
 
-#include <iostream>
-
 namespace flutter {
 
 namespace {
@@ -43,17 +41,17 @@ Win32DpiHelper::~Win32DpiHelper() {
   }
 }
 
-void Win32DpiHelper::SetDpiAwerenessAllVersions() {
+BOOL Win32DpiHelper::SetDpiAwareness() {
   if (permonitorv2_supported_) {
-    SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+    return set_process_dpi_awareness_context_(
+        DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+
   } else {
-    std::cerr << "Per Monitor V2 DPI awareness is not supported on this "
-                 "version of Windows. Setting System DPI awareness\n";
     AssignProcAddress(user32_module_, "GetDpiForSystem", get_dpi_for_system_);
     AssignProcAddress(user32_module_, "SetProcessDpiAware",
                       set_process_dpi_aware_);
 
-    SetProcessDPIAware();
+    return set_process_dpi_aware_();
   }
 }
 
@@ -68,27 +66,11 @@ BOOL Win32DpiHelper::EnableNonClientDpiScaling(HWND hwnd) {
   return enable_non_client_dpi_scaling_(hwnd);
 }
 
-UINT Win32DpiHelper::GetDpiForWindow(HWND hwnd) {
-  if (!permonitorv2_supported_) {
-    return false;
+UINT Win32DpiHelper::GetDpi(HWND hwnd) {
+  if (permonitorv2_supported_) {
+    return get_dpi_for_window_(hwnd);
   }
-  return get_dpi_for_window_(hwnd);
-}
-
-UINT Win32DpiHelper::GetDpiForSystem() {
   return get_dpi_for_system_();
 }
 
-BOOL Win32DpiHelper::SetProcessDpiAwarenessContext(
-    DPI_AWARENESS_CONTEXT context) {
-  if (!permonitorv2_supported_) {
-    return false;
-  }
-  return set_process_dpi_awareness_context_(context);
-}
-
-BOOL Win32DpiHelper::SetProcessDpiAware() {
-  return set_process_dpi_aware_();
-}
-
 }  // namespace flutter
diff --git a/shell/platform/windows/win32_dpi_helper.h b/shell/platform/windows/win32_dpi_helper.h
index 196affab9f2e2..3d55f72f6c9f2 100644
--- a/shell/platform/windows/win32_dpi_helper.h
+++ b/shell/platform/windows/win32_dpi_helper.h
@@ -25,12 +25,9 @@ class Win32DpiHelper {
   // Wrapper for OS functionality to turn on automatic window non-client scaling
   BOOL EnableNonClientDpiScaling(HWND);
 
-  // Wrapper for OS functionality to return the DPI for |HWND|
-  UINT GetDpiForWindow(HWND);
-
-  // Wrapper for OS functionality to return the DPI for the System. Only used if
-  // Per Monitor V2 is not supported by the current Windows version.
-  UINT GetDpiForSystem();
+  // Wrapper for OS functionality to return the DPI for |HWND| if Per Monitor V2
+  // awareness has been set. Otherwise, returns the DPI for the System.
+  UINT GetDpi(HWND);
 
   // Sets the current process to a specified DPI awareness context.
   BOOL SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT);
@@ -43,7 +40,7 @@ class Win32DpiHelper {
   //
   // This call is overriden if DPI awareness is stated in the application
   // manifest.
-  void SetDpiAwerenessAllVersions();
+  BOOL SetDpiAwareness();
 
  private:
   using EnableNonClientDpiScaling_ = BOOL __stdcall(HWND);
diff --git a/shell/platform/windows/win32_window.cc b/shell/platform/windows/win32_window.cc
index 702827da2915b..2b1c2bdc12141 100644
--- a/shell/platform/windows/win32_window.cc
+++ b/shell/platform/windows/win32_window.cc
@@ -20,7 +20,9 @@ void Win32Window::InitializeChild(const char* title,
 
   // Set DPI awareness for all Windows versions. This call has to be made before
   // the HWND is created.
-  dpi_helper_->SetDpiAwerenessAllVersions();
+  if (!dpi_helper_->SetDpiAwareness()) {
+    OutputDebugString(L"Failed to set DPI awareness");
+  }
 
   WNDCLASS window_class = RegisterWindowClass(converted_title);
 
@@ -86,10 +88,9 @@ LRESULT CALLBACK Win32Window::WndProc(HWND const window,
       if (result != TRUE) {
         OutputDebugString(L"Failed to enable non-client area autoscaling");
       }
-      that->current_dpi_ = that->dpi_helper_->GetDpiForWindow(window);
-    } else {
-      that->current_dpi_ = that->dpi_helper_->GetDpiForSystem();
     }
+    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);
@@ -282,7 +283,7 @@ Win32Window::HandleDpiChange(HWND hwnd,
     // 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_->GetDpiForWindow(hwnd);
+      uDpi = dpi_helper_->GetDpi(hwnd);
     }
     current_dpi_ = uDpi;
     window->OnDpiScale(uDpi);

From 924e8cea08b08312e3b00fff6bd5b6060590e2e0 Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Wed, 2 Oct 2019 09:46:57 -0700
Subject: [PATCH 5/6] Remove unused call

---
 shell/platform/windows/win32_dpi_helper.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.h b/shell/platform/windows/win32_dpi_helper.h
index 3d55f72f6c9f2..6f06d8024d79e 100644
--- a/shell/platform/windows/win32_dpi_helper.h
+++ b/shell/platform/windows/win32_dpi_helper.h
@@ -29,9 +29,6 @@ class Win32DpiHelper {
   // awareness has been set. Otherwise, returns the DPI for the System.
   UINT GetDpi(HWND);
 
-  // Sets the current process to a specified DPI awareness context.
-  BOOL SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT);
-
   // Sets the current process to System-level DPI awareness.
   BOOL SetProcessDpiAware();
 

From 2b900a07a22703b00a2c5241af2ff7972b0d0e47 Mon Sep 17 00:00:00 2001
From: Francisco Madgaleno <franciscojma86@gmail.com>
Date: Wed, 2 Oct 2019 09:51:04 -0700
Subject: [PATCH 6/6] Another one

---
 shell/platform/windows/win32_dpi_helper.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/shell/platform/windows/win32_dpi_helper.h b/shell/platform/windows/win32_dpi_helper.h
index 6f06d8024d79e..013f215e540ae 100644
--- a/shell/platform/windows/win32_dpi_helper.h
+++ b/shell/platform/windows/win32_dpi_helper.h
@@ -29,9 +29,6 @@ class Win32DpiHelper {
   // awareness has been set. Otherwise, returns the DPI for the System.
   UINT GetDpi(HWND);
 
-  // Sets the current process to System-level DPI awareness.
-  BOOL SetProcessDpiAware();
-
   // Sets the DPI awareness for the application. For versions >= Windows 1703,
   // use Per Monitor V2. For any older versions, use System.
   //