cc: Rewrite PageScaleAnimation for new coordinate system.

cc/page_scale_animation.cc

Index: cc/page_scale_animation.cc
diff --git a/cc/page_scale_animation.cc b/cc/page_scale_animation.cc
index 49948abd333e9ce8aa72f83e6db51e143e58ebe2..877cacb96f501f3996ed4409a08a72c9abc522f1 100644
--- a/cc/page_scale_animation.cc
+++ b/cc/page_scale_animation.cc
@@ -5,29 +5,60 @@
 #include "config.h"
 
 #include "cc/page_scale_animation.h"
-
-#include "cc/geometry.h"
+#include "ui/gfx/point_f.h"
 #include "ui/gfx/rect_f.h"
-#include "ui/gfx/vector2d_conversions.h"
-#include "ui/gfx/vector2d_f.h"
 
+#include <algorithm>
 #include <math.h>
 
+namespace {
+
+gfx::PointF toPointF(const gfx::Vector2dF& vector)
+{
+    return gfx::PointF(vector.x(), vector.y());
+}
+
+// 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& viewportSize)
+{
+    gfx::Vector2dF normalized(denormalized);
+    normalized.Scale(1 / viewportSize.width(), 1 / viewportSize.height());
+    return normalized;
+}
+
+gfx::Vector2dF denormalizeToViewport(const gfx::Vector2dF& normalized, const gfx::SizeF& viewportSize)
+{
+    gfx::Vector2dF denormalized(normalized);
+    denormalized.Scale(viewportSize.width(), viewportSize.height());
+    return denormalized;
+}
+
+gfx::Vector2dF interpolateBetween(const gfx::Vector2dF& start, const gfx::Vector2dF end, float interp)
+{
+    gfx::Vector2dF result;
+    result.set_x(start.x() + interp * (end.x() - start.x()));
+    result.set_y(start.y() + interp * (end.y() - start.y()));
+    return result;
+}
+
+}
+
 namespace cc {
 
-scoped_ptr<PageScaleAnimation> PageScaleAnimation::create(gfx::Vector2d scrollStart, float pageScaleStart, const gfx::Size& windowSize, const gfx::Size& contentSize, double startTime)
+scoped_ptr<PageScaleAnimation> PageScaleAnimation::create(const gfx::Vector2dF& startScrollOffset, float startPageScaleFactor, const gfx::SizeF& viewportSize, const gfx::SizeF& rootLayerSize, double startTime)
 {
-    return make_scoped_ptr(new PageScaleAnimation(scrollStart, pageScaleStart, windowSize, contentSize, startTime));
+    return make_scoped_ptr(new PageScaleAnimation(startScrollOffset, startPageScaleFactor, viewportSize, rootLayerSize, startTime));
 }
 
-PageScaleAnimation::PageScaleAnimation(gfx::Vector2d scrollStart, float pageScaleStart, const gfx::Size& windowSize, const gfx::Size& contentSize, double startTime)
-    : m_scrollStart(scrollStart)
-    , m_pageScaleStart(pageScaleStart)
-    , m_windowSize(windowSize)
-    , m_contentSize(contentSize)
-    , m_anchorMode(false)
-    , m_scrollEnd(scrollStart)
-    , m_pageScaleEnd(pageScaleStart)
+PageScaleAnimation::PageScaleAnimation(const gfx::Vector2dF& startScrollOffset, float startPageScaleFactor, const gfx::SizeF& viewportSize, const gfx::SizeF& rootLayerSize, double startTime)
+    : m_startPageScaleFactor(startPageScaleFactor)
+    , m_targetPageScaleFactor(0)
+    , m_startScrollOffset(startScrollOffset)
+    , m_startAnchor()
+    , m_targetAnchor()
+    , m_viewportSize(viewportSize)
+    , m_rootLayerSize(rootLayerSize)
     , m_startTime(startTime)
     , m_duration(0)
 {
@@ -37,67 +68,93 @@ PageScaleAnimation::~PageScaleAnimation()
 {
 }
 
-void PageScaleAnimation::zoomTo(gfx::Vector2d 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.
-        gfx::RectF startRect(gfx::PointAtOffsetFromOrigin(m_scrollStart), m_windowSize);
-        gfx::RectF endRect(gfx::PointAtOffsetFromOrigin(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());
-
-        gfx::Vector2d 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 PageScaleAnimation::zoomTo(const gfx::Vector2dF& targetScrollOffset, float targetPageScaleFactor, double duration)
+{
+    m_targetPageScaleFactor = targetPageScaleFactor;
+    m_targetScrollOffset = targetScrollOffset;
+    clampTargetScrollOffset();
+    m_duration = duration;
+
+    if (m_startPageScaleFactor == targetPageScaleFactor) {
+        m_startAnchor = m_startScrollOffset;
+        m_targetAnchor = targetScrollOffset;
+        return;
     }
+
+    // For uniform-looking zooming, infer an anchor from the start and target
+    // viewport rects.
+    inferTargetAnchorFromScrollOffsets();
+    m_startAnchor = m_targetAnchor;
 }
 
-void PageScaleAnimation::zoomWithAnchor(gfx::Vector2d anchor, float finalPageScale, double duration)
+void PageScaleAnimation::zoomWithAnchor(const gfx::Vector2dF& anchor, float targetPageScaleFactor, double duration)
 {
-    m_scrollEnd = m_scrollStart + anchor;
-    m_scrollEnd = gfx::ToFlooredVector2d(cc::ScaleVector2d(m_scrollEnd, finalPageScale / m_pageScaleStart));
-    m_scrollEnd -= anchor;
+    m_startAnchor = anchor;
+    m_targetPageScaleFactor = targetPageScaleFactor;
+    m_duration = duration;
 
-    m_scrollEnd = ClampFromBelow(m_scrollEnd, gfx::Vector2d());
-    gfx::SizeF scaledContentSize = m_contentSize.Scale(finalPageScale / m_pageScaleStart);
-    gfx::Vector2d maxScrollOffset = gfx::ToRoundedVector2d(BottomRight(gfx::RectF(scaledContentSize)) - BottomRight(gfx::Rect(m_windowSize)));
-    m_scrollEnd = m_scrollEnd;
-    m_scrollEnd = ClampFromAbove(m_scrollEnd, maxScrollOffset);
+    // 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();
+    inferTargetAnchorFromScrollOffsets();
+}
 
-    m_anchor = anchor;
-    m_pageScaleEnd = finalPageScale;
-    m_duration = duration;
-    m_anchorMode = true;
+gfx::SizeF PageScaleAnimation::viewportSizeAtScale(float pageScaleFactor) const
+{
+    return gfx::SizeF(m_viewportSize.width() / pageScaleFactor, m_viewportSize.height() / pageScaleFactor);
+}
+
+void PageScaleAnimation::inferTargetScrollOffsetFromStartAnchor()
+{
+    gfx::Vector2dF anchorRelativeToStartViewport = m_startAnchor - m_startScrollOffset;
+    gfx::Vector2dF normalized = normalizeFromViewport(anchorRelativeToStartViewport, viewportSizeAtScale(m_startPageScaleFactor));
+    m_targetScrollOffset = m_startAnchor - denormalizeToViewport(normalized, viewportSizeAtScale(m_targetPageScaleFactor));
+}
+
+void PageScaleAnimation::inferTargetAnchorFromScrollOffsets()
+{
+    gfx::RectF startRect(toPointF(m_startScrollOffset), viewportSizeAtScale(m_startPageScaleFactor));
+    gfx::RectF targetRect(toPointF(m_targetScrollOffset), viewportSizeAtScale(m_targetPageScaleFactor));
+
+    // The anchor is the point which is at the same normalized relative position
+    // within both startRect and endRect. 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:
+    // anchorX = start_width * normalizedX + start_x
+    // anchorX = target_width * normalizedX + target_x
+    // anchorY = start_height * normalizedY + start_y
+    // anchorY = target_height * normalizedY + target_y
+    // where both anchor{x,y} and normalized{x,y} begin as unknowns. Solving
+    // for the normalized, we get the following formulas:
+    gfx::Vector2dF normalized;
+    normalized.set_x((startRect.x() - targetRect.x()) / (targetRect.width() - startRect.width()));
+    normalized.set_y((startRect.y() - targetRect.y()) / (targetRect.height() - startRect.height()));
+    m_targetAnchor = m_targetScrollOffset + denormalizeToViewport(normalized, viewportSizeAtScale(m_targetPageScaleFactor));
+}
+
+void PageScaleAnimation::clampTargetScrollOffset()
+{
+    gfx::Vector2dF maxScrollPosition;
+    maxScrollPosition.set_x(m_rootLayerSize.width() - viewportSizeAtScale(m_targetPageScaleFactor).width());
+    maxScrollPosition.set_y(m_rootLayerSize.height() - viewportSizeAtScale(m_targetPageScaleFactor).height());
+    m_targetScrollOffset.set_x(std::max<float>(0, m_targetScrollOffset.x()));
+    m_targetScrollOffset.set_y(std::max<float>(0, m_targetScrollOffset.y()));
+    m_targetScrollOffset.set_x(std::min<float>(maxScrollPosition.x(), m_targetScrollOffset.x()));
+    m_targetScrollOffset.set_y(std::min<float>(maxScrollPosition.y(), m_targetScrollOffset.y()));
 }
 
-gfx::Vector2d PageScaleAnimation::scrollOffsetAtTime(double time) const
+gfx::Vector2dF PageScaleAnimation::scrollOffsetAtTime(double time) const
 {
-    return scrollOffsetAtRatio(progressRatioForTime(time));
+    return scrollOffsetAt(interpAtTime(time));
 }
 
-float PageScaleAnimation::pageScaleAtTime(double time) const
+float PageScaleAnimation::pageScaleFactorAtTime(double time) const
 {
-    return pageScaleAtRatio(progressRatioForTime(time));
+    return pageScaleFactorAt(interpAtTime(time));
 }
 
 bool PageScaleAnimation::isAnimationCompleteAtTime(double time) const
@@ -105,7 +162,7 @@ bool PageScaleAnimation::isAnimationCompleteAtTime(double time) const
     return time >= endTime();
 }
 
-float PageScaleAnimation::progressRatioForTime(double time) const
+float PageScaleAnimation::interpAtTime(double time) const
 {
     if (isAnimationCompleteAtTime(time))
         return 1;
@@ -113,52 +170,52 @@ float PageScaleAnimation::progressRatioForTime(double time) const
     return (time - m_startTime) / m_duration;
 }
 
-gfx::Vector2d PageScaleAnimation::scrollOffsetAtRatio(float ratio) const
-{
-    if (ratio <= 0)
-        return m_scrollStart;
-    if (ratio >= 1)
-        return m_scrollEnd;
-
-    float currentPageScale = pageScaleAtRatio(ratio);
-    gfx::Vector2d currentScrollOffset;
-    if (m_anchorMode) {
-        // Keep the anchor stable on the screen at the current scale.
-        gfx::Vector2dF documentAnchor = m_scrollStart + m_anchor;
-        documentAnchor.Scale(currentPageScale / m_pageScaleStart);
-        currentScrollOffset = gfx::ToRoundedVector2d(documentAnchor - m_anchor);
-    } else {
-        // First move both scroll offsets to the current coordinate space.
-        gfx::Vector2dF scaledStartScroll(m_scrollStart);
-        scaledStartScroll.Scale(currentPageScale / m_pageScaleStart);
-        gfx::Vector2dF scaledEndScroll(m_scrollEnd);
-        scaledEndScroll.Scale(currentPageScale / m_pageScaleEnd);
-
-        // Linearly interpolate between them.
-        gfx::Vector2dF delta = scaledEndScroll - scaledStartScroll;
-        delta.Scale(ratio);
-        currentScrollOffset = gfx::ToRoundedVector2d(scaledStartScroll + delta);
-    }
+gfx::Vector2dF PageScaleAnimation::scrollOffsetAt(float interp) const
+{
+    if (interp <= 0)
+        return m_startScrollOffset;
+    if (interp >= 1)
+        return m_targetScrollOffset;
+
+    return anchorAt(interp) - viewportRelativeAnchorAt(interp);
+}
+
+gfx::Vector2dF PageScaleAnimation::anchorAt(float interp) const
+{
+    // Interpolate from start to target anchor in absolute space.
+    gfx::Vector2dF delta = m_targetAnchor - m_startAnchor;
+    delta.Scale(interp);
+    return m_startAnchor + delta;
+}
+
+gfx::Vector2dF PageScaleAnimation::viewportRelativeAnchorAt(float interp) const
+{
+    // Interpolate from start to target anchor in the space relative to the
+    // viewport at its current scale level.
+    gfx::Vector2dF anchorRelativeToStartViewport = m_startAnchor - m_startScrollOffset;
+    gfx::Vector2dF anchorRelativeToTargetViewport = m_targetAnchor - m_targetScrollOffset;
+
+    gfx::Vector2dF startNormalized = normalizeFromViewport(anchorRelativeToStartViewport, viewportSizeAtScale(m_startPageScaleFactor));
+    gfx::Vector2dF targetNormalized = normalizeFromViewport(anchorRelativeToTargetViewport, viewportSizeAtScale(m_targetPageScaleFactor));
+    gfx::Vector2dF interpNormalized = interpolateBetween(startNormalized, targetNormalized, interp);
 
-    return currentScrollOffset;
+    gfx::SizeF currentViewportSize = viewportSizeAtScale(pageScaleFactorAt(interp));
+    return denormalizeToViewport(interpNormalized, currentViewportSize);
 }
 
-float PageScaleAnimation::pageScaleAtRatio(float ratio) const
+float PageScaleAnimation::pageScaleFactorAt(float interp) const
 {
-    if (ratio <= 0)
-        return m_pageScaleStart;
-    if (ratio >= 1)
-        return m_pageScaleEnd;
+    if (interp <= 0)
+        return m_startPageScaleFactor;
+    if (interp >= 1)
+        return m_targetPageScaleFactor;
 
     // 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 diff = m_targetPageScaleFactor / m_startPageScaleFactor;
     float logDiff = log(diff);
-    logDiff *= ratio;
+    logDiff *= interp;
     diff = exp(logDiff);
-    return m_pageScaleStart * diff;
+    return m_startPageScaleFactor * diff;
 }
 
 }  // namespace cc