ash/system/power/power_button_screenshot_controller.cc

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ash/system/power/power_button_screenshot_controller.h"

#include "ash/accelerators/accelerator_controller_impl.h"
#include "ash/public/cpp/window_properties.h"
#include "ash/shell.h"
#include "ash/system/power/power_button_controller.h"
#include "ash/wm/window_util.h"
#include "base/functional/bind.h"
#include "base/metrics/user_metrics.h"
#include "base/time/tick_clock.h"
#include "ui/display/screen.h"
#include "ui/events/event.h"

namespace ash {

namespace {

bool VolumeKeyMaybeUsedByApp() {
  aura::Window* active = window_util::GetActiveWindow();
  return active && active->GetProperty(ash::kCanConsumeSystemKeysKey);
}

}  // namespace

constexpr base::TimeDelta
    PowerButtonScreenshotController::kScreenshotChordDelay;

PowerButtonScreenshotController::PowerButtonScreenshotController(
    const base::TickClock* tick_clock)
    : tick_clock_(tick_clock) {
  DCHECK(tick_clock_);
  // Using prepend to make sure this event handler is put in front of
  // AcceleratorFilter. See Shell::Init().
  Shell::Get()->AddPreTargetHandler(this, ui::EventTarget::Priority::kSystem);
}

PowerButtonScreenshotController::~PowerButtonScreenshotController() {
  Shell::Get()->RemovePreTargetHandler(this);
}

bool PowerButtonScreenshotController::OnPowerButtonEvent(
    bool down,
    const base::TimeTicks& timestamp) {
  if (!display::Screen::GetScreen()->InTabletMode()) {
    return false;
  }

  power_button_pressed_ = down;
  if (power_button_pressed_) {
    volume_down_timer_.Stop();
    volume_up_timer_.Stop();
    power_button_pressed_time_ = tick_clock_->NowTicks();
    if (InterceptScreenshotChord())
      return true;
  }

  if (!down)
    return false;

  // If volume key is pressed, mark power button as consumed. This invalidates
  // other power button's behavior when user tries to operate screenshot.
  return volume_down_key_pressed_ || volume_up_key_pressed_;
}

void PowerButtonScreenshotController::OnKeyEvent(ui::KeyEvent* event) {
  if (!display::Screen::GetScreen()->InTabletMode()) {
    return;
  }

  ui::KeyboardCode key_code = event->key_code();
  if (key_code != ui::VKEY_VOLUME_DOWN && key_code != ui::VKEY_VOLUME_UP)
    return;

  bool did_consume_volume_keys =
      volume_down_key_pressed_ || volume_up_key_pressed_;
  bool volume_key_maybe_used_by_app = VolumeKeyMaybeUsedByApp();
  // Even if the app is requesting to consume volume key, do not give it if
  // 1) power button is already pressed. This should trigger screenshot.
  // 2) if this is already handling volume key. We need to continue processing
  // volume eve after power button is released, until volume keys are released.
  if (volume_key_maybe_used_by_app && !power_button_pressed_ &&
      !did_consume_volume_keys) {
    return;
  }

  const bool is_volume_down = key_code == ui::VKEY_VOLUME_DOWN;
  if (event->type() == ui::ET_KEY_PRESSED) {
    if (!did_consume_volume_keys) {
      if (is_volume_down) {
        volume_down_key_pressed_ = true;
        volume_down_key_pressed_time_ = tick_clock_->NowTicks();
        consume_volume_down_ = false;
        InterceptScreenshotChord();
      } else {
        volume_up_key_pressed_ = true;
        volume_up_key_pressed_time_ = tick_clock_->NowTicks();
        consume_volume_up_ = false;
        InterceptScreenshotChord();
      }
    }

    // Do no pass the event to the app if the events are being
    // processed
    if (consume_volume_down_ || consume_volume_up_ ||
        volume_key_maybe_used_by_app) {
      event->StopPropagation();
    }
  } else {
    is_volume_down ? volume_down_key_pressed_ = false
                   : volume_up_key_pressed_ = false;
  }

  // When volume key is pressed, cancel the ongoing power button behavior.
  if (volume_down_key_pressed_ || volume_up_key_pressed_)
    Shell::Get()->power_button_controller()->CancelPowerButtonEvent();

  // On volume down/up key pressed while power button not pressed yet state, do
  // not propagate volume down/up key pressed event for chord delay time. Start
  // the timer to wait power button pressed for screenshot operation, and on
  // timeout perform the delayed volume down/up operation.
  if (power_button_pressed_)
    return;

  base::TimeTicks now = tick_clock_->NowTicks();
  if (volume_down_key_pressed_ && is_volume_down &&
      now <= volume_down_key_pressed_time_ + kScreenshotChordDelay) {
    event->StopPropagation();
    if (!volume_down_timer_.IsRunning()) {
      volume_down_timer_.Start(
          FROM_HERE, kScreenshotChordDelay,
          base::BindOnce(
              &PowerButtonScreenshotController::OnVolumeControlTimeout,
              base::Unretained(this), ui::Accelerator(*event), /*down=*/true));
    }
  } else if (volume_up_key_pressed_ && !is_volume_down &&
             now <= volume_up_key_pressed_time_ + kScreenshotChordDelay) {
    event->StopPropagation();
    if (!volume_up_timer_.IsRunning()) {
      volume_up_timer_.Start(
          FROM_HERE, kScreenshotChordDelay,
          base::BindOnce(
              &PowerButtonScreenshotController::OnVolumeControlTimeout,
              base::Unretained(this), ui::Accelerator(*event), /*down=*/false));
    }
  }
}

bool PowerButtonScreenshotController::InterceptScreenshotChord() {
  if (!power_button_pressed_ ||
      (!volume_down_key_pressed_ && !volume_up_key_pressed_)) {
    return false;
  }

  base::TimeTicks now = tick_clock_->NowTicks();
  if (now > power_button_pressed_time_ + kScreenshotChordDelay)
    return false;

  consume_volume_down_ =
      volume_down_key_pressed_ &&
      now <= volume_down_key_pressed_time_ + kScreenshotChordDelay;
  consume_volume_up_ =
      volume_up_key_pressed_ &&
      now <= volume_up_key_pressed_time_ + kScreenshotChordDelay;
  if (consume_volume_down_ || consume_volume_up_) {
    Shell::Get()->accelerator_controller()->PerformActionIfEnabled(
        AcceleratorAction::kTakeScreenshot, {});

    base::RecordAction(base::UserMetricsAction("Accel_PowerButton_Screenshot"));
  }
  return consume_volume_down_ || consume_volume_up_;
}

void PowerButtonScreenshotController::OnVolumeControlTimeout(
    const ui::Accelerator& accelerator,
    bool down) {
  Shell::Get()->accelerator_controller()->PerformActionIfEnabled(
      down ? AcceleratorAction::kVolumeDown : AcceleratorAction::kVolumeUp,
      accelerator);
}

}  // namespace ash