Interpolated transforms

ui/gfx/interpolated_transform.h

+// 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.
+
+#ifndef UI_GFX_INTERPOLATED_TRANSFORM_H_
+#define UI_GFX_INTERPOLATED_TRANSFORM_H_
+#pragma once
+
+#include "ui/gfx/transform.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/point.h"
+
+namespace ui {
+
+///////////////////////////////////////////////////////////////////////////////
+// class InterpolatedTransform
+//
+// Abstract base class for transforms that animate over time. These
+// interpolated transforms can be combined to allow for more sophisticated
+// animations. For example, you might combine a rotation of 90 degrees between
+// times 0 and 1, with a scale from 1 to 0.3 between times 0 and 0.25 and a
+// scale from 0.3 to 1 from between times 0.75 and 1.
+//
+///////////////////////////////////////////////////////////////////////////////
+class InterpolatedTransform {
+ public:
+  InterpolatedTransform();
+  // The interpolated transform varies only when t in (start_time, end_time).
+  // If t <= start_time, Interpolate(t) will return the initial transform, and
+  // if t >= end_time, Interpolate(t) will return the final transform.
+  InterpolatedTransform(float start_time, float end_time);
+  virtual ~InterpolatedTransform();
+
+  // Returns the interpolated transform at time t. Note: not virtual.
+  ui::Transform Interpolate(float t) const;
+
+  // The Intepolate ultimately returns the product of our transform at time t
+  // and our child's transform at time t (if we have one).
+  //
+  // This function takes ownership of the passed InterpolatedTransform.
+  void SetChild(InterpolatedTransform* child);
+
+ protected:
+  // Calculates the interpolated transform without considering our child.
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const = 0;
+
+  // If time in (start_time_, end_time_], this function linearly interpolates
+  // between start_value and end_value.  More precisely it returns
+  // (1 - t) * start_value + t * end_value where
+  // t = (start_time_ - time) / (end_time_ - start_time_).
+  // If time < start_time_ it returns start_value, and if time >= end_time_
+  // it returns end_value.
+  float ValueBetween(float time, float start_value, float end_value) const;
+
+ private:
+  const float start_time_;
+  const float end_time_;
+
+  // The child transform. If you consider an interpolated transform as a
+  // function of t. If, without a child, we are f(t), and our child is
+  // g(t), then with a child we become f'(t) = f(t) * g(t). Using a child
+  // transform, we can chain collections of transforms together.
+  scoped_ptr<InterpolatedTransform> child_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedTransform);
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// class InterpolatedRotation
+//
+// Represents an animated rotation.
+//
+///////////////////////////////////////////////////////////////////////////////
+class InterpolatedRotation : public InterpolatedTransform {
+ public:
+  InterpolatedRotation(float start_degrees, float end_degrees);
+  InterpolatedRotation(float start_degrees,
+                       float end_degrees,
+                       float start_time,
+                       float end_time);
+  virtual ~InterpolatedRotation();
+
+ protected:
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const OVERRIDE;
+
+ private:
+  const float start_degrees_;
+  const float end_degrees_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedRotation);
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// class InterpolatedScale
+//
+// Represents an animated scale.
+//
+///////////////////////////////////////////////////////////////////////////////
+class InterpolatedScale : public InterpolatedTransform {
+ public:
+  InterpolatedScale(float start_scale, float end_scale);
+  InterpolatedScale(float start_scale,
+                    float end_scale,
+                    float start_time,
+                    float end_time);
+  virtual ~InterpolatedScale();
+
+ protected:
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const OVERRIDE;
+
+ private:
+  const float start_scale_;
+  const float end_scale_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedScale);
+};
+
+class InterpolatedTranslation : public InterpolatedTransform {
+ public:
+  InterpolatedTranslation(const gfx::Point& start_pos,
+                          const gfx::Point& end_pos);
+  InterpolatedTranslation(const gfx::Point& start_pos,
+                          const gfx::Point& end_pos,
+                          float start_time,
+                          float end_time);
+  virtual ~InterpolatedTranslation();
+
+ protected:
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const OVERRIDE;
+
+ private:
+  const gfx::Point start_pos_;
+  const gfx::Point end_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedTranslation);
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// class InterpolatedConstantTransform
+//
+// Represents a transform that is constant over time. This is only useful when
+// composed with other interpolated transforms.
+//
+// See InterpolatedTransformAboutPivot for an example of its usage.
+//
+///////////////////////////////////////////////////////////////////////////////
+class InterpolatedConstantTransform : public InterpolatedTransform {
+ public:
+  InterpolatedConstantTransform(const ui::Transform& transform);
+  virtual ~InterpolatedConstantTransform();
+
+ protected:
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const OVERRIDE;
+
+ private:
+  const ui::Transform transform_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedConstantTransform);
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// class InterpolatedTransformAboutPivot
+//
+// Represents an animated transform with a transformed origin. Essentially,
+// at each time, t, the interpolated transform is created by composing
+// P * T * P^-1 where P is a constant transform to the new origin.
+//
+///////////////////////////////////////////////////////////////////////////////
+class InterpolatedTransformAboutPivot : public InterpolatedTransform {
+ public:
+  // Takes ownership of the passed transform.
+  InterpolatedTransformAboutPivot(const gfx::Point& pivot,
+                                  InterpolatedTransform* transform);
+
+  // Takes ownership of the passed transform.
+  InterpolatedTransformAboutPivot(const gfx::Point& pivot,
+                                  InterpolatedTransform* transform,
+                                  float start_time,
+                                  float end_time);
+  virtual ~InterpolatedTransformAboutPivot();
+
+ protected:
+  virtual ui::Transform InterpolateButDoNotCompose(float t) const OVERRIDE;
+
+ private:
+  void Init(const gfx::Point& pivot, InterpolatedTransform* transform);
+
+  scoped_ptr<InterpolatedTransform> transform_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterpolatedTransformAboutPivot);
+};
+
+} // namespace ui
+
+#endif // UI_GFX_INTERPOLATED_TRANSFORM_H_