root/cc/input/page_scale_animation.cc

DEFINITIONS

1. NormalizeFromViewport
2. DenormalizeToViewport
3. InterpolateBetween
4. Create
5. timing_function_
6. ZoomTo
7. ZoomWithAnchor
8. InferTargetScrollOffsetFromStartAnchor
9. InferTargetAnchorFromScrollOffsets
10. ClampTargetScrollOffset
11. StartViewportSize
12. TargetViewportSize
13. ViewportSizeAt
14. IsAnimationStarted
15. StartAnimation
16. ScrollOffsetAtTime
17. PageScaleFactorAtTime
18. IsAnimationCompleteAtTime
19. InterpAtTime
20. ScrollOffsetAt
21. AnchorAt
22. ViewportRelativeAnchorAt
23. PageScaleFactorAt

// Copyright 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 "cc/input/page_scale_animation.h"

#include <math.h>

#include "base/logging.h"
#include "cc/animation/timing_function.h"
#include "ui/gfx/point_f.h"
#include "ui/gfx/rect_f.h"
#include "ui/gfx/vector2d_conversions.h"

namespace {

// This takes a viewport-relative vector and returns a vector whose values are
// between 0 and 1, representing the percentage position within the viewport.
gfx::Vector2dF NormalizeFromViewport(const gfx::Vector2dF& denormalized,
                                     const gfx::SizeF& viewport_size) {
  return gfx::ScaleVector2d(denormalized,
                            1.f / viewport_size.width(),
                            1.f / viewport_size.height());
}

gfx::Vector2dF DenormalizeToViewport(const gfx::Vector2dF& normalized,
                                     const gfx::SizeF& viewport_size) {
  return gfx::ScaleVector2d(normalized,
                            viewport_size.width(),
                            viewport_size.height());
}

gfx::Vector2dF InterpolateBetween(const gfx::Vector2dF& start,
                                  const gfx::Vector2dF& end,
                                  float interp) {
  return start + gfx::ScaleVector2d(end - start, interp);
}

}  // namespace

namespace cc {

scoped_ptr<PageScaleAnimation> PageScaleAnimation::Create(
    const gfx::Vector2dF& start_scroll_offset,
    float start_page_scale_factor,
    const gfx::SizeF& viewport_size,
    const gfx::SizeF& root_layer_size,
    scoped_ptr<TimingFunction> timing_function) {
  return make_scoped_ptr(new PageScaleAnimation(start_scroll_offset,
                                                start_page_scale_factor,
                                                viewport_size,
                                                root_layer_size,
                                                timing_function.Pass()));
}

PageScaleAnimation::PageScaleAnimation(
    const gfx::Vector2dF& start_scroll_offset,
    float start_page_scale_factor,
    const gfx::SizeF& viewport_size,
    const gfx::SizeF& root_layer_size,
    scoped_ptr<TimingFunction> timing_function)
    : start_page_scale_factor_(start_page_scale_factor),
      target_page_scale_factor_(0.f),
      start_scroll_offset_(start_scroll_offset),
      start_anchor_(),
      target_anchor_(),
      viewport_size_(viewport_size),
      root_layer_size_(root_layer_size),
      start_time_(-1.0),
      duration_(0.0),
      timing_function_(timing_function.Pass()) {}

PageScaleAnimation::~PageScaleAnimation() {}

void PageScaleAnimation::ZoomTo(const gfx::Vector2dF& target_scroll_offset,
                                float target_page_scale_factor,
                                double duration) {
  target_page_scale_factor_ = target_page_scale_factor;
  target_scroll_offset_ = target_scroll_offset;
  ClampTargetScrollOffset();
  duration_ = duration;

  if (start_page_scale_factor_ == target_page_scale_factor) {
    start_anchor_ = start_scroll_offset_;
    target_anchor_ = target_scroll_offset;
    return;
  }

  // For uniform-looking zooming, infer an anchor from the start and target
  // viewport rects.
  InferTargetAnchorFromScrollOffsets();
  start_anchor_ = target_anchor_;
}

void PageScaleAnimation::ZoomWithAnchor(const gfx::Vector2dF& anchor,
                                        float target_page_scale_factor,
                                        double duration) {
  start_anchor_ = anchor;
  target_page_scale_factor_ = target_page_scale_factor;
  duration_ = duration;

  // We start zooming out from the anchor tapped by the user. But if
  // the target scale is impossible to attain without hitting the root layer
  // edges, then infer an anchor that doesn't collide with the edges.
  // We will interpolate between the two anchors during the animation.
  InferTargetScrollOffsetFromStartAnchor();
  ClampTargetScrollOffset();

  if (start_page_scale_factor_ == target_page_scale_factor_) {
    target_anchor_ = start_anchor_;
    return;
  }
  InferTargetAnchorFromScrollOffsets();
}

void PageScaleAnimation::InferTargetScrollOffsetFromStartAnchor() {
  gfx::Vector2dF normalized = NormalizeFromViewport(
      start_anchor_ - start_scroll_offset_, StartViewportSize());
  target_scroll_offset_ =
      start_anchor_ - DenormalizeToViewport(normalized, TargetViewportSize());
}

void PageScaleAnimation::InferTargetAnchorFromScrollOffsets() {
  // The anchor is the point which is at the same normalized relative position
  // within both start viewport rect and target viewport rect. For example, a
  // zoom-in double-tap to a perfectly centered rect will have normalized
  // anchor (0.5, 0.5), while one to a rect touching the bottom-right of the
  // screen will have normalized anchor (1.0, 1.0). In other words, it obeys
  // the equations:
  // anchor = start_size * normalized + start_offset
  // anchor = target_size * normalized + target_offset
  // where both anchor and normalized begin as unknowns. Solving
  // for the normalized, we get the following:
  float width_scale =
      1.f / (TargetViewportSize().width() - StartViewportSize().width());
  float height_scale =
      1.f / (TargetViewportSize().height() - StartViewportSize().height());
  gfx::Vector2dF normalized = gfx::ScaleVector2d(
      start_scroll_offset_ - target_scroll_offset_, width_scale, height_scale);
  target_anchor_ =
      target_scroll_offset_ + DenormalizeToViewport(normalized,
                                                    TargetViewportSize());
}

void PageScaleAnimation::ClampTargetScrollOffset() {
  gfx::Vector2dF max_scroll_offset =
      gfx::RectF(root_layer_size_).bottom_right() -
      gfx::RectF(TargetViewportSize()).bottom_right();
  target_scroll_offset_.SetToMax(gfx::Vector2dF());
  target_scroll_offset_.SetToMin(max_scroll_offset);
}

gfx::SizeF PageScaleAnimation::StartViewportSize() const {
  return gfx::ScaleSize(viewport_size_, 1.f / start_page_scale_factor_);
}

gfx::SizeF PageScaleAnimation::TargetViewportSize() const {
  return gfx::ScaleSize(viewport_size_, 1.f / target_page_scale_factor_);
}

gfx::SizeF PageScaleAnimation::ViewportSizeAt(float interp) const {
  return gfx::ScaleSize(viewport_size_, 1.f / PageScaleFactorAt(interp));
}

bool PageScaleAnimation::IsAnimationStarted() const {
  return start_time_ >= 0;
}

void PageScaleAnimation::StartAnimation(double time) {
  DCHECK_GT(0, start_time_);
  start_time_ = time;
}

gfx::Vector2dF PageScaleAnimation::ScrollOffsetAtTime(double time) const {
  DCHECK_GE(start_time_, 0);
  return ScrollOffsetAt(InterpAtTime(time));
}

float PageScaleAnimation::PageScaleFactorAtTime(double time) const {
  DCHECK_GE(start_time_, 0);
  return PageScaleFactorAt(InterpAtTime(time));
}

bool PageScaleAnimation::IsAnimationCompleteAtTime(double time) const {
  DCHECK_GE(start_time_, 0);
  return time >= end_time();
}

float PageScaleAnimation::InterpAtTime(double time) const {
  DCHECK_GE(start_time_, 0);
  DCHECK_GE(time, start_time_);
  if (IsAnimationCompleteAtTime(time))
    return 1.f;

  const double normalized_time = (time - start_time_) / duration_;
  return timing_function_->GetValue(normalized_time);
}

gfx::Vector2dF PageScaleAnimation::ScrollOffsetAt(float interp) const {
  if (interp <= 0.f)
    return start_scroll_offset_;
  if (interp >= 1.f)
    return target_scroll_offset_;

  return AnchorAt(interp) - ViewportRelativeAnchorAt(interp);
}

gfx::Vector2dF PageScaleAnimation::AnchorAt(float interp) const {
  // Interpolate from start to target anchor in absolute space.
  return InterpolateBetween(start_anchor_, target_anchor_, interp);
}

gfx::Vector2dF PageScaleAnimation::ViewportRelativeAnchorAt(
    float interp) const {
  // Interpolate from start to target anchor in normalized space.
  gfx::Vector2dF start_normalized =
      NormalizeFromViewport(start_anchor_ - start_scroll_offset_,
                            StartViewportSize());
  gfx::Vector2dF target_normalized =
      NormalizeFromViewport(target_anchor_ - target_scroll_offset_,
                            TargetViewportSize());
  gfx::Vector2dF interp_normalized =
      InterpolateBetween(start_normalized, target_normalized, interp);

  return DenormalizeToViewport(interp_normalized, ViewportSizeAt(interp));
}

float PageScaleAnimation::PageScaleFactorAt(float interp) const {
  if (interp <= 0.f)
    return start_page_scale_factor_;
  if (interp >= 1.f)
    return target_page_scale_factor_;

  // Linearly interpolate the magnitude in log scale.
  float diff = target_page_scale_factor_ / start_page_scale_factor_;
  float log_diff = log(diff);
  log_diff *= interp;
  diff = exp(log_diff);
  return start_page_scale_factor_ * diff;
}

}  // namespace cc