Call EnableNonClientDpiScaling

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index c9eb44424c31ada6f659d4a4bcf1d6207b343f1d..73ae35021d3b1fd6f097b6539b6fba0587c684c2 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -329,6 +329,7 @@ HWNDMessageHandler::HWNDMessageHandler(HWNDMessageHandlerDelegate* delegate)
       current_cursor_(NULL),
       previous_cursor_(NULL),
       dpi_(0),
+      called_enable_non_client_dpi_scaling_(false),
       active_mouse_tracking_flags_(0),
       is_right_mouse_pressed_on_caption_(false),
       lock_updates_count_(0),
@@ -362,7 +363,9 @@ void HWNDMessageHandler::Init(HWND parent, const gfx::Rect& bounds) {
   // Create the window.
   WindowImpl::Init(parent, bounds);
 
-  if (delegate_->HasFrame() && base::win::IsProcessPerMonitorDpiAware()) {
+  if (!called_enable_non_client_dpi_scaling_ &&
+      delegate_->HasFrame() &&
+      base::win::IsProcessPerMonitorDpiAware()) {
     static auto enable_child_window_dpi_message_func = []() {
       // Derived signature; not available in headers.
       // This call gets Windows to scale the non-client area when WM_DPICHANGED
@@ -1795,6 +1798,24 @@ LRESULT HWNDMessageHandler::OnNCCalcSize(BOOL mode, LPARAM l_param) {
   return mode ? WVR_REDRAW : 0;
 }
 
+LRESULT HWNDMessageHandler::OnNCCreate(LPCREATESTRUCT lpCreateStruct) {
+  SetMsgHandled(FALSE);
+  if (delegate_->HasFrame() && base::win::IsProcessPerMonitorDpiAware()) {
+    static auto enable_non_client_dpi_scaling_func = []() {
+      // Signature only available in the 10.0.14393.0 API. As of this writing,
+      // Chrome built against 10.0.10586.0.
+      using EnableNonClientDpiScalingPtr = LRESULT (WINAPI*)(HWND);
+      return reinterpret_cast<EnableNonClientDpiScalingPtr>(
+                 GetProcAddress(GetModuleHandle(L"user32.dll"),
+                                "EnableNonClientDpiScaling"));
+    }();
+    called_enable_non_client_dpi_scaling_ =
+        !!(enable_non_client_dpi_scaling_func &&
+           enable_non_client_dpi_scaling_func(hwnd()));
+  }
+  return 0;

[sky, 2016/12/14 02:42:41]

Should this return TRUE (old code did).

[robliao, 2016/12/14 18:50:19]

It should return FALSE, to doubly reenforce that we're not handling the message
here. (Normally, if you return FALSE during WM_NCCREATE, this should fail the
CreateWindow[Ex] call. This is useful to signal to the CreateWindow[Ex] caller
that something fatal happened and we cannot proceed in creating the HWND).

While we do special initialization with WM_NCCREATE, we're not "handling" it
(e.g. intending to override default behavior). As a result, we should let
DefWindowProc take its course.

The SetMsgHandled(FALSE) at the top signals to WindowImpl that DefWindowProc
should receive this message. This causes the caller to ignore this functions
return value.

+}
+
 LRESULT HWNDMessageHandler::OnNCHitTest(const gfx::Point& point) {
   if (!delegate_->HasNonClientView()) {
     SetMsgHandled(FALSE);