Rotate screen in response to accelerator or device orientation sensors.

athena/system/orientation_controller.cc

+// Copyright 2014 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.
+
+#include "athena/screen/public/screen_manager.h"
+#include "athena/system/orientation_controller.h"
+#include "base/file_util.h"
+#include "base/files/file_path_watcher.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace athena {
+
+namespace {
+
+// Path of the socket which the sensor daemon creates.
+const char kSocketPath[] = "/dev/sensors/orientation";
+
+// Threshold after which to rotate in a given direction.
+const int kGravityThreshold = 6.0f;
+
+// Minimum delay before triggering another orientation change.
+const int kOrientationChangeDelayNS = 500000000;
+
+enum {
+  SENSOR_ACCELEROMETER,
+  SENSOR_LIGHT,
+  SENSOR_PROXIMITY
+};
+
+struct DeviceSensorEvent {

[oshima, 2014/08/01 17:15:11]

A short discription (meaning and range of values), plus a pointer to
documentation would be helpful.

[flackr, 2014/08/06 14:13:51]

Added a description of meaning and range of values as well as a pointer to
orientation information.

+  int32_t type;
+  int64_t timestamp;
+  union {
+    float data[3];
+    float temperature;
+    float distance;
+    float light;
+  };
+};
+
+}  // namespace
+
+OrientationController::OrientationController()
+    : DeviceSocketListener(kSocketPath, sizeof(DeviceSensorEvent)),
+      last_orientation_change_time_(0),
+      weak_factory_(this) {
+  base::FilePath socket_path(kSocketPath);
+  if (base::PathExists(socket_path)) {
+    StartListening();
+  } else {
+    // Watch for socket to be created if it doesn't already exist.
+    watcher_.reset(new base::FilePathWatcher);
+    watcher_->Watch(socket_path, false,
+                    base::Bind(&OrientationController::OnFilePathChanged,
+                               weak_factory_.GetWeakPtr()));
+  }
+}
+
+OrientationController::~OrientationController() {
+}
+
+void OrientationController::OnDataAvailableOnIO(const void* data) {
+  const DeviceSensorEvent* event =
+      static_cast<const DeviceSensorEvent*>(data);
+  if (event->type != SENSOR_ACCELEROMETER)
+    return;
+
+  float gravity_x = event->data[0];
+  float gravity_y = event->data[1];
+  gfx::Display::Rotation rotation;
+  if (gravity_x < -kGravityThreshold) {
+    rotation = gfx::Display::ROTATE_270;
+  } else if (gravity_x > kGravityThreshold) {
+    rotation = gfx::Display::ROTATE_90;
+  } else if (gravity_y < -kGravityThreshold) {
+    rotation = gfx::Display::ROTATE_180;
+  } else if (gravity_y > kGravityThreshold) {
+    rotation = gfx::Display::ROTATE_0;
+  } else {
+    // No rotation as gravity threshold was not hit.
+    return;
+  }
+
+  if (rotation == current_rotation_ ||
+      event->timestamp - last_orientation_change_time_ <
+          kOrientationChangeDelayNS) {
+    return;
+  }
+
+  last_orientation_change_time_ = event->timestamp;
+  current_rotation_ = rotation;
+
+  // TODO(flackr): Avoid callbacks using unretained pointers. This could
+  // technically call RotateOnUI after OrientationController has destructed. We
+  // should instead use callbacks with weak pointers similar to
+  // chromeos/accelerometer/accelerometer_reader.cc.
+  content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
+      base::Bind(&OrientationController::RotateOnUI,
+                 base::Unretained(this), rotation));
+}
+
+void OrientationController::RotateOnUI(gfx::Display::Rotation rotation) {
+  ScreenManager::Get()->SetRotation(rotation);
+}
+
+void OrientationController::OnFilePathChanged(const base::FilePath& path,
+                                              bool error) {
+  if (error)
+    return;
+
+  StartListening();
+  watcher_.reset();
+}
+
+}  // namespace athena