Fix high-DPI on Windows to make use of DIP scaling in WebKit.

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/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)

[sky, 2013/01/28 20:56:35]

Why the ifdef?

[kevers, 2013/01/28 22:53:40]

Removing the ifdef would expose the forced device scale factor flag on Windows
regardless of whether high-DPI is enabled.  If we are OK with this, I can
certainly remove the flag, as GetDPIScale() returns 1 unless the process is
DPI-aware, which in turn, is behind the ENABLE_HIDPI flag.

[sky, 2013/01/29 15:34:56]

Why wouldn't we do this? I assume we're going to nuke the ifdef eventually,
right?

[kevers, 2013/01/29 17:08:29]

Yes, ENABLE_HIDPI ifdefs are going away once the feature is stable.  Tested with
this particular ifdef removed and high-DPI disabled. Seeing strange rendering if
a forced scale factor is explicitly set, but behaves as expected if setting an
OS-level scale factor with fonts set to 180% (large blurry text).

+  return gfx::Display::HasForceDeviceScaleFactor() ?
+      gfx::Display::GetForcedDeviceScaleFactor() : ui::GetDPIScale();
+#else
+  return 1.0f;
+#endif
+}
+
 }  // 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 20 matching lines @@
 
 void EnableHighDPISupport() {
   typedef BOOL(WINAPI *SetProcessDPIAwarePtr)(VOID);
   SetProcessDPIAwarePtr set_process_dpi_aware_func =
       reinterpret_cast<SetProcessDPIAwarePtr>(
           GetProcAddress(GetModuleHandleA("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();

[sky, 2013/01/28 20:56:35]

Why do we need to cache this?

[kevers, 2013/01/28 22:53:40]

See this caching pattern used in several places where we need to do a
non-trivial amount of work to retrieve a value that doesn't change.  In this
case, without the cache, we need to check the command line on each call, which
seems somewhat wasteful.

+  return device_scale_factor;
+}
+

[sky, 2013/01/28 20:56:35]

nit: remove one newline.

[kevers, 2013/01/29 17:08:29]

Done.

+
+gfx::Point ScreenToDIPPoint(const gfx::Point& pixel_point) {
+  return gfx::ToFlooredPoint(
+      gfx::ScalePoint(pixel_point, 1.0f / GetDeviceScaleFactor()));
+}
+
+gfx::Rect ScreenToDIPRect(const gfx::Rect& pixel_bounds) {
+  // TODO(kevers): Switch to non-deprecated method for float to int conversions.
+  return gfx::ToFlooredRectDeprecated(
+      gfx::ScaleRect(pixel_bounds, 1.0f / GetDeviceScaleFactor()));
+}
+
+gfx::Rect DIPToScreenRect(const gfx::Rect& dip_bounds) {
+  // TODO(kevers): Switch to non-deprecated method for float to int conversions.
+  return gfx::ToFlooredRectDeprecated(
+      gfx::ScaleRect(dip_bounds, GetDeviceScaleFactor()));
+}
+
+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()));
+}
+
+}  // namespace win
+
 }  // namespace ui