Enable hidpi on Linux, refactor a bit on Windows to share

ui/gfx/dpi.h

 // 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.
 
-#ifndef UI_GFX_DPI_WIN_H_
-#define UI_GFX_DPI_WIN_H_
+#ifndef UI_GFX_DPI_H_
+#define UI_GFX_DPI_H_
 
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
 namespace gfx {

[sky, 2014/10/22 21:11:18]

I have always found this file confusing. It's a mix of functions used for
different purposes: testing, initialization and general purposes.

Can we clean it up, perhaps separating into files, so that the purpose is clear?
I'm hoping this file can remain general purpose and have dpi_init and
dpi_testing.

I also think it needs to be made clear when you want to use scale factor in this
file vs scale factor from Display.

[scottmg, 2014/10/22 23:56:18]

Yes, I find it very confusing too, since it seems like it should just be one
float that determines the scale between points<->pixels.

I started trying to clean it up:
- delete IsInHighDPIMode()
- move ForceHighDPISupportForTesting to dpi_testing.h
- delete IsDeviceScaleFactorSet
- move EnableHighDPISupport to chrome/app
- delete IsHighDPIEnabled
- and mostly, we delete GetDeviceScaleFactor(), and have all callers switch to
GetDPI or GetDPIScale. 

I think it's too big to include in this CL though.

I don't really understand the difference between display and this file, but I
think Display is mostly a debug/testing thing. I think the dpi related things in
display should be merge into here.

Umm, yeah. So we need to clean this up.

It'd be easier to do all that after this CL to avoid having to rebase this CL on
the cleanup one, but if you prefer I can do the cleanup first.

 
 // Initialization of the scale factor that should be applied for rendering
 // in this process. Must be called before attempts to call any of the getter
 // methods below in this file, e.g. in the early toolkit/resource bundle setup.
 // This can be called multiple times during various tests, but subsequent calls
 // have no effect.
 GFX_EXPORT void InitDeviceScaleFactor(float scale);
 
+GFX_EXPORT float GetDeviceScaleFactor();
+
+// Returns true if the global device scale factor has been explicitly set for
+// the process.
+GFX_EXPORT bool IsDeviceScaleFactorSet();
+
+GFX_EXPORT void ForceHighDPISupportForTesting(float scale);
+
+GFX_EXPORT bool IsInHighDPIMode();

[sky, 2014/10/22 21:11:18]

Can this function be nuked and callers use  GetDPIScale() > 1.0?

+
 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.
 GFX_EXPORT float GetDPIScale();
 
-// Tests to see if the command line flag "--high-dpi-support" is set.
-GFX_EXPORT bool IsHighDPIEnabled();
-
-GFX_EXPORT bool IsInHighDPIMode();
-
-GFX_EXPORT void EnableHighDPISupport();
-
-GFX_EXPORT void ForceHighDPISupportForTesting(float scale);
-
-// TODO(kevers|girard):  Move above methods into win namespace.
-
-namespace win {
-
-GFX_EXPORT float GetDeviceScaleFactor();
-
 GFX_EXPORT Point ScreenToDIPPoint(const Point& pixel_point);
 
 GFX_EXPORT Point DIPToScreenPoint(const Point& dip_point);
 
 // WARNING: there is no right way to scale sizes and rects. The implementation
 // of these strives to maintain a constant size by scaling the size independent
 // of the origin. An alternative is to get the enclosing rect, which is the
 // right way for some situations. Understand which you need before blindly
 // assuming this is the right way.
 GFX_EXPORT Rect ScreenToDIPRect(const Rect& pixel_bounds);
 GFX_EXPORT Rect DIPToScreenRect(const Rect& dip_bounds);
 GFX_EXPORT Size ScreenToDIPSize(const Size& size_in_pixels);
 GFX_EXPORT Size DIPToScreenSize(const Size& dip_size);
 
+// Tests to see if the command line flag "--high-dpi-support" is set on Windows,
+// always true on Linux.
+GFX_EXPORT bool IsHighDPIEnabled();

[sky, 2014/10/22 21:11:18]

Can this be nuked too?

+
+#if defined(OS_WIN)
+namespace win {
+
+GFX_EXPORT void EnableHighDPISupport();
+
 // Win32's GetSystemMetrics uses pixel measures. This function calls
 // GetSystemMetrics for the given |metric|, then converts the result to DIP.
 GFX_EXPORT int GetSystemMetricsInDIP(int metric);
 
-// Returns true if the global device scale factor has been explicitly set for
-// the process.
-GFX_EXPORT bool IsDeviceScaleFactorSet();
+}  // namespace win
+#endif  // OS_WIN
 
-GFX_EXPORT extern const wchar_t kRegistryProfilePath[];
-GFX_EXPORT extern const wchar_t kHighDPISupportW[];
-
-}  // namespace win
 }  // namespace gfx
 
-#endif  // UI_GFX_DPI_WIN_H_
+#endif  // UI_GFX_DPI_H_