ui/display/display_observer.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_DISPLAY_DISPLAY_OBSERVER_H_
#define UI_DISPLAY_DISPLAY_OBSERVER_H_

#include <stdint.h>

#include "base/observer_list_types.h"
#include "ui/display/display_export.h"

namespace display {
class Display;
enum class TabletState;

// Observers for display configuration changes.
class DISPLAY_EXPORT DisplayObserver : public base::CheckedObserver {
 public:
  enum DisplayMetric {
    DISPLAY_METRIC_NONE = 0,
    DISPLAY_METRIC_BOUNDS = 1 << 0,
    DISPLAY_METRIC_WORK_AREA = 1 << 1,
    DISPLAY_METRIC_DEVICE_SCALE_FACTOR = 1 << 2,
    DISPLAY_METRIC_ROTATION = 1 << 3,
    DISPLAY_METRIC_PRIMARY = 1 << 4,
    DISPLAY_METRIC_MIRROR_STATE = 1 << 5,
    DISPLAY_METRIC_COLOR_SPACE = 1 << 6,
    DISPLAY_METRIC_REFRESH_RATE = 1 << 7,
    DISPLAY_METRIC_INTERLACED = 1 << 8,
    DISPLAY_METRIC_LABEL = 1 << 9,
  };

  // This may be called before other methods to signal changes are about to
  // happen. Not all classes that support DisplayObserver call this.
  virtual void OnWillProcessDisplayChanges();

  // Called after OnWillProcessDisplayChanges() to indicate display changes have
  // completed. Not all classes that support DisplayObserver call this.
  virtual void OnDidProcessDisplayChanges();

  // Called when |new_display| has been added.
  virtual void OnDisplayAdded(const Display& new_display);

  // Called when |old_display| has been removed.
  // In Ash, this is called *before* the display has been removed.
  // Everywhere else, this is called *after* the display has been removed.
  virtual void OnDisplayRemoved(const Display& old_display);

  // Called *after* any displays have been removed.  Not called per display.
  // TODO(enne): resolve the Ash inconsistency for OnDisplayRemoved and
  // remove this function.
  virtual void OnDidRemoveDisplays();

  // Called when the metrics of a display change.
  // |changed_metrics| is a bitmask of DisplayMatric types indicating which
  // metrics have changed. Eg; if mirroring changes (either from true to false,
  // or false to true), than the DISPLAY_METRIC_MIRROR_STATE bit is set in
  // changed_metrics.
  virtual void OnDisplayMetricsChanged(const Display& display,
                                       uint32_t changed_metrics);

  // Called when the (platform-specific) workspace ID changes to
  // |new_workspace|.
  virtual void OnCurrentWorkspaceChanged(const std::string& new_workspace);

  // Called when display changes between conventional and tablet mode.
  virtual void OnDisplayTabletStateChanged(TabletState state);

 protected:
  ~DisplayObserver() override;
};

// Caller must ensure the lifetime of `observer` outlives ScopedDisplayObserver
// and ScopedOptionalDisplayObserver.  The "Optional" version does not care
// whether there is a display::Screen::GetScreen() to observe or not and will
// silently noop when there is not.  The non-optional ScopedDisplayObserver
// will CHECK that display::Screen::GetScreen() exists on construction to
// receive events from.
class DISPLAY_EXPORT ScopedOptionalDisplayObserver {
 public:
  explicit ScopedOptionalDisplayObserver(DisplayObserver* observer);
  ~ScopedOptionalDisplayObserver();

 private:
  DisplayObserver* observer_ = nullptr;
};

class DISPLAY_EXPORT ScopedDisplayObserver
    : public ScopedOptionalDisplayObserver {
 public:
  explicit ScopedDisplayObserver(DisplayObserver* observer);
};

}  // namespace display

#endif  // UI_DISPLAY_DISPLAY_OBSERVER_H_