Animated Rotation

views/animation/screen_rotation.cc

+// Copyright (c) 2011 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 "views/animation/screen_rotation.h"
+
+#include "base/debug/trace_event.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+#include "ui/base/animation/slide_animation.h"
+#include "ui/gfx/compositor/layer.h"
+#include "ui/gfx/interpolated_transform.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/transform.h"
+#include "views/view.h"
+
+namespace {
+const int kDefaultTransitionDurationMs = 500;

[sky, 2011/08/25 03:00:13]

500ms is pretty long for an animation, are you sure you want that?

+
+} // namespace
+
+namespace views {
+
+////////////////////////////////////////////////////////////////////////////////
+// ScreenRotation private:

[sky, 2011/08/25 03:00:13]

private -> public

+//
+
+ScreenRotation::ScreenRotation(View* view,
+                               float old_degrees,
+                               float new_degrees)
+    : view_(view),
+      listener_(NULL),
+      old_degrees_(old_degrees),
+      new_degrees_(new_degrees),
+      last_t_(0.0),
+      done_(false),
+      duration_(kDefaultTransitionDurationMs),
+      ALLOW_THIS_IN_INITIALIZER_LIST(method_factory_(this)) {
+  Start();
+}
+
+ScreenRotation::~ScreenRotation() {
+  animation_.reset();

[sky, 2011/08/25 03:00:13]

Why do you need to explicitly stop the animation here? If you do need this,
please document why. Also, what if the animation is running and you've marked
the view painting_enabled(false). Should it be reset?

+}
+
+void ScreenRotation::Finalize() {
+  done_ = true;

[sky, 2011/08/25 03:00:13]

DCHECK(!done_) ?

+  view_->SetBounds(0, 0, new_size_.width(), new_size_.height());
+  view_->SchedulePaint();
+  if (listener_)
+    listener_->OnScreenRotationCompleted(this);
+}
+
+void ScreenRotation::UpdateTarget(float degrees) {
+  if (new_degrees_ == degrees)
+    return;
+
+  new_degrees_ = degrees;
+  Init();
+}
+
+void ScreenRotation::AnimationProgressed(const ui::Animation* anim) {
+  if (!interpolated_transform_.get() || !view_->layer())
+    return;
+
+  last_t_ = static_cast<float>(anim->GetCurrentValue());
+  if (view_->painting_enabled())
+    view_->set_painting_enabled(false);

[sky, 2011/08/25 03:00:13]

Why do you need to disable painting here? Assuming you need this, do you really
need to check the current value?

+
+  view_->layer()->SetTransform(interpolated_transform_->Interpolate(last_t_));
+  view_->layer()->compositor()->SchedulePaint();
+}
+
+void ScreenRotation::AnimationEnded(const ui::Animation* anim) {
+  TRACE_EVENT_END0("ScreenRotation", "Start rotating");
+  // TODO(vollick) massage matrix so that entries sufficiently close
+  // to 0, 1, or -1 are clamped to these values. The idea is to fight
+  // accumulated numeric error due to successive rotations.
+  if (view_->layer()) {
+    ui::Transform xform = view_->layer()->transform();
+    gfx::Point origin;
+    xform.TransformPoint(origin);
+    ui::Transform translation;
+    translation.SetTranslate(new_origin_.x() - origin.x(),
+                             new_origin_.y() - origin.y());
+    xform.ConcatTransform(translation);
+    view_->layer()->SetTransform(xform);
+    view_->layer()->compositor()->SchedulePaint();
+  }
+  view_->set_painting_enabled(true);
+
+  // the last call to SchedulePaint may not have been processed yet, so if we
+  // set the bounds here, we may hang the ui in an 'almost-rotated' state for
+  // a moment while we layout. If we post a task to execute immediately, it
+  // will get processed after SchedulePaint, and we should be safe.
+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      method_factory_.NewRunnableMethod(&ScreenRotation::Finalize),

[sky, 2011/08/25 03:00:13]

ick. This seems easy to mess up, but I don't currently have a better idea. Maybe
we need a way to listen for painting to finish on the compositor so that post
processing like this has a cleaner way to complete. Can you add a TODO here to
improve this.

+      1);
+}
+
+void ScreenRotation::Init() {
+  if (!view_->layer()) {
+    view_->SetPaintToLayer(true);
+    view_->SchedulePaint();
+  }
+
+  // can't proceed without a layer.
+  if (!view_->layer())
+    return;

[sky, 2011/08/25 03:00:13]

If you early return here or at 121 should the animation stop?

+
+  // cache the inital transformation matrix.
+  if (!old_transform_.get())
+    old_transform_.reset(new ui::Transform(view_->layer()->transform()));

[sky, 2011/08/25 03:00:13]

How come you don't always reset old_transform_?

+
+  int degrees = new_degrees_ - old_degrees_;
+  degrees = NormalizeAngle(degrees);
+
+  // No rotation required.
+  if (degrees == 0)
+    return;
+
+  gfx::Point old_pivot;
+  gfx::Point new_pivot;
+  int width = view_->layer()->bounds().width();
+  int height = view_->layer()->bounds().height();
+
+  switch (degrees) {
+    case 90:
+      new_origin_ = new_pivot = gfx::Point(width, 0);
+      new_size_.SetSize(height, width);
+      break;
+    case -90:
+      new_origin_ = new_pivot = gfx::Point(0, height);
+      new_size_.SetSize(height, width);
+      break;
+    case 180:
+      duration_ = 750;
+      new_pivot = old_pivot = gfx::Point(width / 2, height / 2);
+      new_origin_.SetPoint(width, height);
+      new_size_.SetSize(width, height);
+      break;
+  }
+
+  // Convert points to world space.
+  old_transform_->TransformPoint(old_pivot);
+  old_transform_->TransformPoint(new_pivot);
+  old_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));
+
+  scoped_ptr<ui::InterpolatedTransform> transition(
+      new ui::InterpolatedConstantTransform(*old_transform_));
+
+  scale_up->SetChild(scale_down.release());
+  translation->SetChild(scale_up.release());
+  rotation->SetChild(translation.release());
+  transition->SetChild(rotation.release());
+
+  if (interpolated_transform_.get()) {
+    // We are in the middle of a transition. In this case, we need to create
+    // an interpolated transform that gets us from where we are to the target
+    // transform.
+    ui::Transform current = view_->layer()->transform();
+    ui::Transform target = transition->Interpolate(1.0);
+    interpolated_transform_.reset(new ui::InterpolatedTRSTransform(current,
+                                                                   target,
+                                                                   last_t_,
+                                                                   1.0));
+  } else {
+    interpolated_transform_.reset(transition.release());
+  }
+}
+
+void ScreenRotation::Start() {
+  TRACE_EVENT_BEGIN0("ScreenRotation", "Start rotating");
+  Init();
+  animation_.reset(new ui::SlideAnimation(this));
+  animation_->SetTweenType(ui::Tween::LINEAR);
+  animation_->SetSlideDuration(duration_);
+  animation_->Show();
+}
+
+int ScreenRotation::NormalizeAngle(int degrees) {
+  while (degrees <= -180) degrees += 360;
+  while (degrees > 180) degrees -= 360;
+  return degrees;
+}
+
+
+} // namespace views