Implement HiDPI support in Pepper dev interface

ppapi/cpp/private/view_private.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 PPAPI_CPP_PRIVATE_VIEW_PRIVATE_H_
+#define PPAPI_CPP_PRIVATE_VIEW_PRIVATE_H_
+
+#include "ppapi/cpp/view.h"
+
+namespace pp {
+
+// ViewPrivate is a version of View that exposes private APIs related to HiDPI
+class ViewPrivate : public View {
+ public:
+  ViewPrivate() : View() {}
+  ViewPrivate(const View& other) : View(other) {}
+
+  virtual ~ViewPrivate() {}
+
+  /// GetDeviceScale returns the scale factor between device pixels and DIPs
+  /// (also known as logical pixels or UI pixels on some platforms). This allows
+  /// the developer to render their contents at device resolution, even as
+  /// coordinates / sizes are given in DIPs through the API.
+  ///
+  /// Note that the coordinate system for Pepper APIs is DIPs. Also note that
+  /// one DIP might not equal one CSS pixel - when page scale/zoom is in effect.
+  ///
+  /// @param[in] resource A <code>PP_Resource</code> corresponding to a
+  /// <code>PPB_View</code> resource.
+  ///
+  /// @return A <code>float</code> value representing the number of device
+  /// pixels per DIP.
+  float GetDeviceScale() const;
+
+  /// GetCSSScale returns the scale factor between DIPs and CSS pixels. This
+  /// allows proper scaling between DIPs - as sent via the Pepper API - and CSS
+  /// pixel coordinates used for Web content.
+  ///
+  /// @param[in] resource A <code>PP_Resource</code> corresponding to a
+  /// <code>PPB_View</code> resource.
+  ///
+  /// @return A <code>float</code> value representing the number of DIPs per CSS
+  /// pixel.
+  float GetCSSScale() const;
+};
+
+}  // namespace pp
+
+#endif  // PPAPI_CPP_PRIVATE_VIEW_PRIVATE_H_