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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_DISPLAY_WIN_UWP_TEXT_SCALE_FACTOR_H_
#define UI_DISPLAY_WIN_UWP_TEXT_SCALE_FACTOR_H_
#include "base/observer_list.h"
#include "ui/display/display_export.h"
namespace display {
namespace win {
// Provides access to UWP TextScaleFactor, an accessibility feature.
//
// TODO(dfried): In the future we may need to expand this class to capture
// other UWP-only metrics and functionality. At that point, we probably want to
// rename the class and/or put it in base/win.
class DISPLAY_EXPORT UwpTextScaleFactor {
public:
// Observer for UWP screen metrics and accessibility events.
class DISPLAY_EXPORT Observer : public base::CheckedObserver {
public:
// Notifies the observer that the text scale has changed. Will be called on
// the main thread.
virtual void OnUwpTextScaleFactorChanged() = 0;
// Notifies the observer that this object is about to go out of scope and
// that it should release any references to this object. The base
// implementation removes this object as a listener, so remember to call
// it when you're done with derived class cleanup.
virtual void OnUwpTextScaleFactorCleanup(UwpTextScaleFactor* source);
};
// Retrieves the one global instance. Lazily-created unless you want to mock
// it out with SetImplementationForTesting().
static UwpTextScaleFactor* Instance();
UwpTextScaleFactor(const UwpTextScaleFactor&) = delete;
UwpTextScaleFactor& operator=(const UwpTextScaleFactor&) = delete;
virtual ~UwpTextScaleFactor();
// Retrieves the Windows Text Zoom scale factor. Guaranteed to be >= 1.
virtual float GetTextScaleFactor() const;
// Registers and observer that will be notified of any changes to UWP screen
// or accessibility metrics.
void AddObserver(Observer* observer);
// Removes an observer that has been added. Observers should remove
// themselves either during OnUwpScreenMetricsCleanup() or at destruction
// (whichever is first).
void RemoveObserver(Observer* observer);
// Override creation of the default UwpTextScaleFactor implementation, using
// a mock or other stub implementation of your choice. The caller is
// responsible for cleaning up this object.
static void SetImplementationForTesting(UwpTextScaleFactor* mock_impl);
protected:
UwpTextScaleFactor();
void NotifyUwpTextScaleFactorChanged();
// The observers that need to be notified when a display is modified, added
// or removed.
base::ObserverList<Observer> observer_list_;
};
} // namespace win
} // namespace display
#endif // UI_DISPLAY_WIN_UWP_TEXT_SCALE_FACTOR_H_
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