Disable win/ash on high dpi screens

BUG=321694

Review URL: https://codereview.chromium.org/79033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236762 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 26 insertions, 3 deletions

diff --git a/ui/gfx/win/dpi.cc b/ui/gfx/win/dpi.cc
index acd7ee3..33abdf6 100644
--- a/ui/gfx/win/dpi.cc
+++ b/ui/gfx/win/dpi.cc
@@ -36,10 +36,30 @@ float GetUnforcedDeviceScaleFactor() {
   return static_cast<float>(gfx::GetDPI().width()) /
       static_cast<float>(kDefaultDPIX);
 }
+
+float GetModernUIScaleWrapper() {
+  float result = 1.0f;
+  typedef float(WINAPI *GetModernUIScalePtr)(VOID);
+  HMODULE lib = LoadLibraryA("metro_driver.dll");
+  if (lib) {
+    GetModernUIScalePtr func =
+        reinterpret_cast<GetModernUIScalePtr>(
+        GetProcAddress(lib, "GetModernUIScale"));
+    if (func)
+      result = func();
+    FreeLibrary(lib);
+  }
+  return result;
+}
+
 }  // namespace
 
 namespace gfx {
 
+float GetModernUIScale() {
+  return GetModernUIScaleWrapper();
+}
+
 void InitDeviceScaleFactor(float scale) {
   DCHECK_NE(0.0f, scale);
   g_device_scale_factor = scale;
@@ -163,7 +183,6 @@ double GetUndocumentedDPIScale() {
   return scale;
 }
 
-
 double GetUndocumentedDPITouchScale() {
   static double scale =
       (base::win::GetVersion() < base::win::VERSION_WIN8_1) ?
@@ -171,6 +190,5 @@ double GetUndocumentedDPITouchScale() {
   return scale;
 }
 
-
 }  // namespace win
 }  // namespace gfx
diff --git a/ui/gfx/win/dpi.h b/ui/gfx/win/dpi.h
index 0193ac0..772944f 100644
--- a/ui/gfx/win/dpi.h
+++ b/ui/gfx/win/dpi.h
@@ -22,9 +22,14 @@ GFX_EXPORT void InitDeviceScaleFactor(float scale);
 GFX_EXPORT Size GetDPI();
 
 // Gets the scale factor of the display. For example, if the display DPI is
-// 96 then the scale factor is 1.0.
+// 96 then the scale factor is 1.0. Note that this is the "desktop" scale, which
+// may be differnt than GetModernUIScale().
 GFX_EXPORT float GetDPIScale();
 
+// Gets the scale factor of the modern (metro) UI display. Returns 1.0 for
+// unscaled or "not running on win8+"
+GFX_EXPORT float GetModernUIScale();
+
 // Tests to see if the command line flag "--high-dpi-support" is set.
 GFX_EXPORT bool IsHighDPIEnabled();