cc/input/page_scale_animation.cc

// 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 "base/memory/ptr_util.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/rect_f.h"
#include "ui/gfx/geometry/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 {

using base::TimeTicks;
using base::TimeDelta;

std::unique_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) {
  return base::WrapUnique(
      new PageScaleAnimation(start_scroll_offset, start_page_scale_factor,
                             viewport_size, root_layer_size));
}

PageScaleAnimation::PageScaleAnimation(
    const gfx::Vector2dF& start_scroll_offset,
    float start_page_scale_factor,
    const gfx::SizeF& viewport_size,
    const gfx::SizeF& root_layer_size)
    : 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),
      // Easing constants experimentally determined.
      timing_function_(.8, 0, .3, .9) {}

PageScaleAnimation::~PageScaleAnimation() = default;

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_ = TimeDelta::FromSecondsD(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_ = TimeDelta::FromSecondsD(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(gfx::SizeF(TargetViewportSize())).bottom_right();
  target_scroll_offset_.SetToMin(max_scroll_offset);
  target_scroll_offset_.SetToMax(gfx::Vector2dF());
}

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_ > base::TimeTicks();
}

void PageScaleAnimation::StartAnimation(base::TimeTicks time) {
  DCHECK(start_time_.is_null());
  start_time_ = time;
}

gfx::Vector2dF PageScaleAnimation::ScrollOffsetAtTime(
    base::TimeTicks time) const {
  DCHECK(!start_time_.is_null());
  return ScrollOffsetAt(InterpAtTime(time));
}

float PageScaleAnimation::PageScaleFactorAtTime(base::TimeTicks time) const {
  DCHECK(!start_time_.is_null());
  return PageScaleFactorAt(InterpAtTime(time));
}

bool PageScaleAnimation::IsAnimationCompleteAtTime(base::TimeTicks time) const {
  DCHECK(!start_time_.is_null());
  return time >= end_time();
}

float PageScaleAnimation::InterpAtTime(base::TimeTicks monotonic_time) const {
  DCHECK(!start_time_.is_null());
  DCHECK(monotonic_time >= start_time_);
  if (IsAnimationCompleteAtTime(monotonic_time))
    return 1.f;
  const double normalized_time =
      (monotonic_time - start_time_).InSecondsF() / duration_.InSecondsF();

  return static_cast<float>(timing_function_.Solve(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