Enable maximize mode when keyboard is open past 180 degrees.

ash/wm/maximize_mode/maximize_mode_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 "ash/wm/maximize_mode/maximize_mode_controller.h"
+
+#include "ash/accelerometer/accelerometer_controller.h"
+#include "ash/shell.h"
+#include "ui/gfx/vector3d_f.h"
+
+namespace ash {
+
+namespace {
+
+// The hinge angle at which to enter maximize mode.
+const float kEnterMaximizeModeAngle = 200.0f;
+
+// The angle at which to exit maximize mode, this is specifically less than the
+// angle to enter maximize mode to prevent rapid toggling when near the angle.
+const float kExitMaximizeModeAngle = 160.0f;
+
+// When the lid is fully open 360 degrees, the accelerometer readings can
+// occasionally appear as though the lid is almost closed. If the lid appears
+// near closed but the device is on we assume it is an erroneous reading from
+// it being open 360 degrees.
+const float kFullyOpenAngleErrorTolerance = 10.0f;
+
+// When the device approaches vertical orientation (i.e. portrait orientation)
+// the accelerometers for the base and lid approach the same values (i.e.
+// gravity pointing in the direction of the hinge). When this happens we cannot
+// compute the hinge angle reliably and must turn ignore accelerometer readings.
+// This is the angle from vertical under which we will not compute a hinge
+// angle.
+const float kHingeAxisAlignedThreshold = 15.0f;
+
+const float kRadiansToDegrees = 180.0f / 3.14159265f;
+
+// Returns the angle between |base| and |other| in degrees.
+float AngleBetweenVectorsInDegrees(const gfx::Vector3dF& base,
+                                 const gfx::Vector3dF& other) {
+  return acos(gfx::DotProduct(base, other) /
+              base.Length() / other.Length()) * kRadiansToDegrees;
+}
+
+// Returns the clockwise angle between |base| and |other| where |normal| is the
+// normal of the virtual surface to measure clockwise according to.
+float ClockwiseAngleBetweenVectorsInDegrees(const gfx::Vector3dF& base,
+                                            const gfx::Vector3dF& other,
+                                            const gfx::Vector3dF& normal) {
+  float angle = AngleBetweenVectorsInDegrees(base, other);
+  gfx::Vector3dF cross(base);
+  cross.Cross(other);
+  // If the dot product of this cross product is normal, it means that the
+  // shortest angle between |base| and |other| was counterclockwise with respect
+  // to the surface represented by |normal| and this angle must be reversed.
+  if (gfx::DotProduct(cross, normal) > 0.0f)
+    angle = 360.0f - angle;
+  return angle;
+}
+
+}  // namespace
+
+MaximizeModeController::MaximizeModeController() {
+  Shell::GetInstance()->accelerometer_controller()->AddObserver(this);
+}
+
+MaximizeModeController::~MaximizeModeController() {
+  Shell::GetInstance()->accelerometer_controller()->RemoveObserver(this);
+}
+
+void MaximizeModeController::OnAccelerometerUpdated(
+    const gfx::Vector3dF& base,
+    const gfx::Vector3dF& lid) {
+  static const gfx::Vector3dF hinge_vector(0.0f, 1.0f, 0.0f);
+
+  // As the hinge approaches a vertical angle, the base and lid accelerometers
+  // approach the same values making any angle calculations highly inaccurate.
+  // Bail out early when it is too close.
+  float hinge_angle = AngleBetweenVectorsInDegrees(base, hinge_vector);
+  if (hinge_angle < kHingeAxisAlignedThreshold ||
+      hinge_angle > 180.0f - kHingeAxisAlignedThreshold)
+    return;
+
+  // Compute the angle between the base and the lid.
+  float angle = ClockwiseAngleBetweenVectorsInDegrees(base, lid, hinge_vector);
+
+  // Toggle maximize mode on or off when corresponding thresholds are passed.
+  // TODO(flackr): Make MaximizeModeController own the MaximizeModeWindowManager
+  // such that observations of state changes occur after the change and shell
+  // has fewer states to track.
+  bool maximize_mode_engaged =
+      Shell::GetInstance()->IsMaximizeModeWindowManagerEnabled();
+  if (maximize_mode_engaged &&
+      angle > kFullyOpenAngleErrorTolerance &&
+      angle < kExitMaximizeModeAngle) {
+    Shell::GetInstance()->EnableMaximizeModeWindowManager(false);
+  } else if (!maximize_mode_engaged &&
+      angle > kEnterMaximizeModeAngle) {
+    Shell::GetInstance()->EnableMaximizeModeWindowManager(true);
+  }
+}
+
+}  // namespace ash