ui/base/layout.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_BASE_LAYOUT_H_
#define UI_BASE_LAYOUT_H_

#include <vector>

#include "build/build_config.h"
#include "ui/base/ui_export.h"
#include "ui/gfx/native_widget_types.h"

namespace ui {

enum DisplayLayout {
  // The typical layout for e.g. Windows, Mac and Linux.
  LAYOUT_DESKTOP,

  // Layout optimized for touch.  Used e.g. for Windows 8 Metro mode.
  LAYOUT_TOUCH,
};

// Returns the display layout that should be used.  This could be used
// e.g. to tweak hard-coded padding that's layout specific, or choose
// the .pak file of theme resources to load.
// WARNING: this is deprecated and will be nuked as soon as aura is the default
// on windows.
UI_EXPORT DisplayLayout GetDisplayLayout();

// Supported UI scale factors for the platform. This is used as an index
// into the array |kScaleFactorScales| which maps the enum value to a float.
// SCALE_FACTOR_NONE is used for density independent resources such as
// string, html/js files or an image that can be used for any scale factors
// (such as wallpapers).
enum ScaleFactor {
  SCALE_FACTOR_NONE = 0,
  SCALE_FACTOR_100P,
  SCALE_FACTOR_125P,
  SCALE_FACTOR_133P,
  SCALE_FACTOR_140P,
  SCALE_FACTOR_150P,
  SCALE_FACTOR_180P,
  SCALE_FACTOR_200P,

  NUM_SCALE_FACTORS  // This always appears last.
};

// Changes the value of GetSupportedScaleFactors() to |scale_factors|.
// Use ScopedSetSupportedScaleFactors for unit tests as not to affect the
// state of other tests.
UI_EXPORT void SetSupportedScaleFactors(
    const std::vector<ScaleFactor>& scale_factors);

// Returns a vector with the scale factors which are supported by this
// platform, in ascending order.
UI_EXPORT const std::vector<ScaleFactor>& GetSupportedScaleFactors();

// Returns the float scale value for |scale_factor|.
UI_EXPORT float GetImageScale(ScaleFactor scale_factor);

// Returns the supported ScaleFactor which most closely matches |scale|.
// Converting from float to ScaleFactor is inefficient and should be done as
// little as possible.
// TODO(oshima): Make ScaleFactor a class and remove this.
UI_EXPORT ScaleFactor GetSupportedScaleFactor(float image_scale);

// Returns the ScaleFactor used by |view|.
UI_EXPORT ScaleFactor GetScaleFactorForNativeView(gfx::NativeView view);

// Returns true if |scale_factor| is supported by this platform.
UI_EXPORT bool IsScaleFactorSupported(ScaleFactor scale_factor);

// Returns the scale factor closest to |scale| from the full list of factors.
// Note that it does NOT rely on the list of supported scale factors.
// Finding the closest match is inefficient and shouldn't be done frequently.
UI_EXPORT ScaleFactor FindClosestScaleFactorUnsafe(float scale);

namespace test {
// Class which changes the value of GetSupportedScaleFactors() to
// |new_scale_factors| for the duration of its lifetime.
class UI_EXPORT ScopedSetSupportedScaleFactors {
 public:
  explicit ScopedSetSupportedScaleFactors(
      const std::vector<ui::ScaleFactor>& new_scale_factors);
  ~ScopedSetSupportedScaleFactors();

 private:
  std::vector<ui::ScaleFactor>* original_scale_factors_;

  DISALLOW_COPY_AND_ASSIGN(ScopedSetSupportedScaleFactors);
};

}  // namespace test

}  // namespace ui

#endif  // UI_BASE_LAYOUT_H_