1 files changed, 159 insertions, 0 deletions
diff --git a/cc/page_scale_animation.cc b/cc/page_scale_animation.cc
new file mode 100644
index 0000000..12dda09
--- /dev/null
+++ b/cc/page_scale_animation.cc
@@ -0,0 +1,159 @@
+// 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 "config.h"
+
+#include "CCPageScaleAnimation.h"
+
+#include "FloatRect.h"
+#include "FloatSize.h"
+
+#include <math.h>
+
+namespace cc {
+
+PassOwnPtr<CCPageScaleAnimation> CCPageScaleAnimation::create(const IntSize& scrollStart, float pageScaleStart, const IntSize& windowSize, const IntSize& contentSize, double startTime)
+{
+    return adoptPtr(new CCPageScaleAnimation(scrollStart, pageScaleStart, windowSize, contentSize, startTime));
+}
+
+
+CCPageScaleAnimation::CCPageScaleAnimation(const IntSize& scrollStart, float pageScaleStart, const IntSize& windowSize, const IntSize& contentSize, double startTime)
+    : m_scrollStart(scrollStart)
+    , m_pageScaleStart(pageScaleStart)
+    , m_windowSize(windowSize)
+    , m_contentSize(contentSize)
+    , m_anchorMode(false)
+    , m_scrollEnd(scrollStart)
+    , m_pageScaleEnd(pageScaleStart)
+    , m_startTime(startTime)
+    , m_duration(0)
+{
+}
+
+void CCPageScaleAnimation::zoomTo(const IntSize& finalScroll, float finalPageScale, double duration)
+{
+    if (m_pageScaleStart != finalPageScale) {
+        // For uniform-looking zooming, infer the anchor (point that remains in
+        // place throughout the zoom) from the start and end rects.
+        FloatRect startRect(IntPoint(m_scrollStart), m_windowSize);
+        FloatRect endRect(IntPoint(finalScroll), m_windowSize);
+        endRect.scale(m_pageScaleStart / finalPageScale);
+
+        // The anchor is the point which is at the same ratio of the sides of
+        // both startRect and endRect. For example, a zoom-in double-tap to a
+        // perfectly centered rect will have anchor ratios (0.5, 0.5), while one
+        // to a rect touching the bottom-right of the screen will have anchor
+        // ratios (1.0, 1.0). In other words, it obeys the equations:
+        // anchorX = start_width * ratioX + start_x
+        // anchorX = end_width * ratioX + end_x
+        // anchorY = start_height * ratioY + start_y
+        // anchorY = end_height * ratioY + end_y
+        // where both anchor{x,y} and ratio{x,y} begin as unknowns. Solving
+        // for the ratios, we get the following formulas:
+        float ratioX = (startRect.x() - endRect.x()) / (endRect.width() - startRect.width());
+        float ratioY = (startRect.y() - endRect.y()) / (endRect.height() - startRect.height());
+
+        IntSize anchor(m_windowSize.width() * ratioX, m_windowSize.height() * ratioY);
+        zoomWithAnchor(anchor, finalPageScale, duration);
+    } else {
+        // If this is a pure translation, then there exists no anchor. Linearly
+        // interpolate the scroll offset instead.
+        m_scrollEnd = finalScroll;
+        m_pageScaleEnd = finalPageScale;
+        m_duration = duration;
+        m_anchorMode = false;
+    }
+}
+
+void CCPageScaleAnimation::zoomWithAnchor(const IntSize& anchor, float finalPageScale, double duration)
+{
+    m_scrollEnd = m_scrollStart + anchor;
+    m_scrollEnd.scale(finalPageScale / m_pageScaleStart);
+    m_scrollEnd -= anchor;
+
+    m_scrollEnd.clampNegativeToZero();
+    FloatSize scaledContentSize(m_contentSize);
+    scaledContentSize.scale(finalPageScale / m_pageScaleStart);
+    IntSize maxScrollPosition = roundedIntSize(scaledContentSize - m_windowSize);
+    m_scrollEnd = m_scrollEnd.shrunkTo(maxScrollPosition);
+
+    m_anchor = anchor;
+    m_pageScaleEnd = finalPageScale;
+    m_duration = duration;
+    m_anchorMode = true;
+}
+
+IntSize CCPageScaleAnimation::scrollOffsetAtTime(double time) const
+{
+    return scrollOffsetAtRatio(progressRatioForTime(time));
+}
+
+float CCPageScaleAnimation::pageScaleAtTime(double time) const
+{
+    return pageScaleAtRatio(progressRatioForTime(time));
+}
+
+bool CCPageScaleAnimation::isAnimationCompleteAtTime(double time) const
+{
+    return time >= endTime();
+}
+
+float CCPageScaleAnimation::progressRatioForTime(double time) const
+{
+    if (isAnimationCompleteAtTime(time))
+        return 1;
+
+    return (time - m_startTime) / m_duration;
+}
+
+IntSize CCPageScaleAnimation::scrollOffsetAtRatio(float ratio) const
+{
+    if (ratio <= 0)
+        return m_scrollStart;
+    if (ratio >= 1)
+        return m_scrollEnd;
+
+    float currentPageScale = pageScaleAtRatio(ratio);
+    IntSize currentScrollOffset;
+    if (m_anchorMode) {
+        // Keep the anchor stable on the screen at the current scale.
+        IntSize documentAnchor = m_scrollStart + m_anchor;
+        documentAnchor.scale(currentPageScale / m_pageScaleStart);
+        currentScrollOffset = documentAnchor - m_anchor;
+    } else {
+        // First move both scroll offsets to the current coordinate space.
+        FloatSize scaledStartScroll(m_scrollStart);
+        scaledStartScroll.scale(currentPageScale / m_pageScaleStart);
+        FloatSize scaledEndScroll(m_scrollEnd);
+        scaledEndScroll.scale(currentPageScale / m_pageScaleEnd);
+
+        // Linearly interpolate between them.
+        FloatSize delta = scaledEndScroll - scaledStartScroll;
+        delta.scale(ratio);
+        currentScrollOffset = roundedIntSize(scaledStartScroll + delta);
+    }
+
+    return currentScrollOffset;
+}
+
+float CCPageScaleAnimation::pageScaleAtRatio(float ratio) const
+{
+    if (ratio <= 0)
+        return m_pageScaleStart;
+    if (ratio >= 1)
+        return m_pageScaleEnd;
+
+    // Linearly interpolate the magnitude in log scale.
+    // Log scale is needed to maintain the appearance of uniform zoom. For
+    // example, if we zoom from 0.5 to 4.0 in 3 seconds, then we should
+    // be zooming by 2x every second.
+    float diff = m_pageScaleEnd / m_pageScaleStart;
+    float logDiff = log(diff);
+    logDiff *= ratio;
+    diff = exp(logDiff);
+    return m_pageScaleStart * diff;
+}
+
+} // namespace cc