Fix touch scaling for high dpi windows.

ui/base/win/dpi.cc

 // Copyright (c) 2012 The Chromium 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 "ui/base/win/dpi.h"
 
 #include <windows.h>
 
 #include "base/win/scoped_hdc.h"
 #include "ui/base/layout.h"
+#include "base/win/registry.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
 
 namespace {
 
 int kDefaultDPIX = 96;
 int kDefaultDPIY = 96;
 
 float GetDeviceScaleFactorImpl() {
 #if defined(ENABLE_HIDPI)
   float scale = gfx::Display::HasForceDeviceScaleFactor() ?
       gfx::Display::GetForcedDeviceScaleFactor() : ui::GetDPIScale();
   // Quantize to nearest supported scale factor.
   scale = ui::GetScaleFactorScale(ui::GetScaleFactorFromScale(scale));
   return scale;
 #else
   return 1.0f;
 #endif
 }
 
+FARPROC GetProcAddressWrapper(LPCSTR module_name, LPCSTR proc_name) {
+  HMODULE module = ::GetModuleHandleA(module_name);
+  if (module) {
+    return ::GetProcAddress(module, proc_name);
+  }
+  return NULL;
+}
+
+BOOL IsProcessDPIAwareWrapper() {
+  typedef BOOL(WINAPI *IsProcessDPIAwarePtr)(VOID);
+  IsProcessDPIAwarePtr is_process_dpi_aware_func =
+      reinterpret_cast<IsProcessDPIAwarePtr>(
+          GetProcAddressWrapper("user32.dll", "IsProcessDPIAware"));
+  if (is_process_dpi_aware_func)
+    return is_process_dpi_aware_func();
+  return FALSE;
+}
+
 }  // namespace
 
 namespace ui {
 
 gfx::Size GetDPI() {
   static int dpi_x = 0;
   static int dpi_y = 0;
   static bool should_initialize = true;
 
   if (should_initialize) {
@@ skipping 15 matching lines @@
 
 bool IsInHighDPIMode() {
   gfx::Size dpi(GetDPI());
   return dpi.width() > kDefaultDPIX || dpi.height() > kDefaultDPIY;
 }
 
 void EnableHighDPISupport() {
   typedef BOOL(WINAPI *SetProcessDPIAwarePtr)(VOID);
   SetProcessDPIAwarePtr set_process_dpi_aware_func =
       reinterpret_cast<SetProcessDPIAwarePtr>(
-          GetProcAddress(GetModuleHandleA("user32.dll"), "SetProcessDPIAware"));
+          GetProcAddressWrapper("user32.dll", "SetProcessDPIAware"));
   if (set_process_dpi_aware_func)
     set_process_dpi_aware_func();
 }
 
 namespace win {
 
 float GetDeviceScaleFactor() {
   static const float device_scale_factor = GetDeviceScaleFactorImpl();
   return device_scale_factor;
 }
@@ skipping 17 matching lines @@
 
 gfx::Size ScreenToDIPSize(const gfx::Size& size_in_pixels) {
   return gfx::ToFlooredSize(
       gfx::ScaleSize(size_in_pixels, 1.0f / GetDeviceScaleFactor()));
 }
 
 gfx::Size DIPToScreenSize(const gfx::Size& dip_size) {
   return gfx::ToFlooredSize(gfx::ScaleSize(dip_size, GetDeviceScaleFactor()));
 }
 
+double GetDPIScaleFromRegistry() {
+  static double scale = -1.0;
+  if (scale == -1.0) {
+    double result = 1.0;
+    if (!IsProcessDPIAwareWrapper()) {
+      //HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics\AppliedDPI

[Ryan Sleevi, 2013/03/05 18:32:56]

nit: space between //

+      base::win::RegKey key(HKEY_CURRENT_USER,
+                            L"Control Panel\\Desktop\\WindowMetrics",
+                            KEY_QUERY_VALUE);
+
+      if (key.Valid()) {
+        DWORD value = 0;
+        if (key.ReadValueDW(L"AppliedDPI", &value) == ERROR_SUCCESS) {
+          result = ((double)value) / kDefaultDPIX;

[Ryan Sleevi, 2013/03/05 18:32:56]

style: Don't do C-casts

+        }
+      }
+    }
+    scale = result;
+  }
+
+  // Safety test to ignore invalid settings.
+  if (scale <= 0.0)
+    scale = 1.0;
+
+  return scale;
+}
+
 }  // namespace win
 
 }  // namespace ui