text: // 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.
  
  #include "ash/rotator/screen_rotation.h"
  
  #include "base/time/time.h"
  #include "ui/compositor/layer.h"
  #include "ui/gfx/interpolated_transform.h"
  #include "ui/gfx/rect.h"
  #include "ui/gfx/transform.h"
  
  namespace ash {
  
  namespace {
  
  const int k90DegreeTransitionDurationMs = 350;
  const int k180DegreeTransitionDurationMs = 550;
  const int k360DegreeTransitionDurationMs = 750;
  
  base::TimeDelta GetTransitionDuration(int degrees) {
    if (degrees == 360)
      return base::TimeDelta::FromMilliseconds(k360DegreeTransitionDurationMs);
    if (degrees == 180)
      return base::TimeDelta::FromMilliseconds(k180DegreeTransitionDurationMs);
    if (degrees == 0)
      return base::TimeDelta::FromMilliseconds(0);
    return base::TimeDelta::FromMilliseconds(k90DegreeTransitionDurationMs);
  }
  
  }  // namespace
  
  ScreenRotation::ScreenRotation(int degrees, ui::Layer* layer)
      : ui::LayerAnimationElement(GetProperties(),
                                  GetTransitionDuration(degrees)),
        degrees_(degrees) {
    InitTransform(layer);
  }
  
  ScreenRotation::~ScreenRotation() {
  }
  
  void ScreenRotation::InitTransform(ui::Layer* layer) {
    // No rotation required, use the identity transform.
    if (degrees_ == 0) {
      interpolated_transform_.reset(
          new ui::InterpolatedConstantTransform(gfx::Transform()));
      return;
    }
  
    // Use the target transform/bounds in case the layer is already animating.
    const gfx::Transform& current_transform = layer->GetTargetTransform();
    const gfx::Rect& bounds = layer->GetTargetBounds();
  
    gfx::Point old_pivot;
    gfx::Point new_pivot;
  
    int width = bounds.width();
    int height = bounds.height();
  
    switch (degrees_) {
      case 90:
        new_origin_ = new_pivot = gfx::Point(width, 0);
        break;
      case -90:
        new_origin_ = new_pivot = gfx::Point(0, height);
        break;
      case 180:
      case 360:
        new_pivot = old_pivot = gfx::Point(width / 2, height / 2);
        new_origin_.SetPoint(width, height);
        break;
    }
  
    // Convert points to world space.
    current_transform.TransformPoint(&old_pivot);
    current_transform.TransformPoint(&new_pivot);
    current_transform.TransformPoint(&new_origin_);
  
    scoped_ptr<ui::InterpolatedTransform> rotation(
        new ui::InterpolatedTransformAboutPivot(
            old_pivot,
            new ui::InterpolatedRotation(0, degrees_)));
  
    scoped_ptr<ui::InterpolatedTransform> translation(
        new ui::InterpolatedTranslation(
            gfx::Point(0, 0),
            gfx::Point(new_pivot.x() - old_pivot.x(),
                       new_pivot.y() - old_pivot.y())));
  
    float scale_factor = 0.9f;
    scoped_ptr<ui::InterpolatedTransform> scale_down(
        new ui::InterpolatedScale(1.0f, scale_factor, 0.0f, 0.5f));
  
    scoped_ptr<ui::InterpolatedTransform> scale_up(
        new ui::InterpolatedScale(1.0f, 1.0f / scale_factor, 0.5f, 1.0f));
  
    interpolated_transform_.reset(
        new ui::InterpolatedConstantTransform(current_transform));
  
    scale_up->SetChild(scale_down.release());
    translation->SetChild(scale_up.release());
    rotation->SetChild(translation.release());
    interpolated_transform_->SetChild(rotation.release());
  }
  
  void ScreenRotation::OnStart(ui::LayerAnimationDelegate* delegate) {
  }
  
  bool ScreenRotation::OnProgress(double t,
                                  ui::LayerAnimationDelegate* delegate) {
    delegate->SetTransformFromAnimation(interpolated_transform_->Interpolate(t));
    return true;
  }
  
  void ScreenRotation::OnGetTarget(TargetValue* target) const {
    target->transform = interpolated_transform_->Interpolate(1.0);
  }
  
  void ScreenRotation::OnAbort(ui::LayerAnimationDelegate* delegate) {
  }
  
  // static
  const ui::LayerAnimationElement::AnimatableProperties&
  ScreenRotation::GetProperties() {
    static ui::LayerAnimationElement::AnimatableProperties properties;
    if (properties.empty())
      properties.insert(ui::LayerAnimationElement::TRANSFORM);
    return properties;
  }
  
  }  // namespace ash
  