Implement CSSOM Smooth Scroll API

Source/platform/scroll/ProgrammaticScrollAnimator.cpp

+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "platform/scroll/ProgrammaticScrollAnimator.h"
+
+#include "platform/geometry/FloatPoint.h"
+#include "platform/geometry/IntPoint.h"
+#include "platform/graphics/GraphicsLayer.h"
+#include "platform/scroll/ScrollableArea.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebAnimation.h"
+#include "public/platform/WebAnimationCurve.h"
+#include "public/platform/WebCompositorSupport.h"
+#include "public/platform/WebScrollOffsetAnimationCurve.h"
+
+namespace WebCore {
+
+PassOwnPtr<ProgrammaticScrollAnimator> ProgrammaticScrollAnimator::create(ScrollableArea* scrollableArea)
+{
+    return adoptPtr(new ProgrammaticScrollAnimator(scrollableArea));
+}
+
+ProgrammaticScrollAnimator::ProgrammaticScrollAnimator(ScrollableArea* scrollableArea)
+    : m_scrollableArea(scrollableArea)
+    , m_animationId(0)
+    , m_startTime(0.0)
+{
+}
+
+ProgrammaticScrollAnimator::~ProgrammaticScrollAnimator()
+{
+}
+
+void ProgrammaticScrollAnimator::resetAnimationState()
+{
+    m_animationCurve.clear();
+    m_animationId = 0;
+    m_startTime = 0.0;
+    m_scrollableArea->deregisterForAnimation();
+}
+
+void ProgrammaticScrollAnimator::animateToOffset(FloatPoint offset)
+{
+    m_startTime = 0.0;
+    m_targetOffset = offset;
+    OwnPtr<blink::WebScrollOffsetAnimationCurve> curve = adoptPtr(blink::Platform::current()->compositorSupport()->createScrollOffsetAnimationCurve(m_targetOffset, blink::WebAnimationCurve::TimingFunctionTypeEaseInOut));
+    if (m_scrollableArea->canUseCompositedScrollAnimations()) {
+        OwnPtr<blink::WebAnimation> animation = adoptPtr(blink::Platform::current()->compositorSupport()->createAnimation(*curve, blink::WebAnimation::TargetPropertyScrollOffset));
+        m_animationId = animation->id();
+        m_scrollableArea->layerForScrolling()->addAnimation(animation.release());
+        return;
+    }
+
+    m_animationCurve = curve.release();
+    m_animationCurve->setInitialValue(FloatPoint(m_scrollableArea->scrollPosition()));

[Ian Vollick, 2014/02/06 16:02:31]

Will ::tickAnimation continue to be called throughout a composited scroll
animation? It looks like it will, since we don't return any info here to let
anyone know whether we've started an accelerated animation?

I realize that m_animationCurve would be NULL in that case, so the function wout
do nothing, but it does feel like it would be wasted ticking.

+    if (!m_scrollableArea->registerForAnimation() || !m_scrollableArea->scheduleAnimation()) {
+        resetAnimationState();
+        m_scrollableArea->setScrollOffsetFromProgrammaticAnimation(IntPoint(offset.x(), offset.y()));
+    }
+}
+
+void ProgrammaticScrollAnimator::cancelAnimation()
+{
+    if (m_animationId && m_scrollableArea->layerForScrolling())
+        m_scrollableArea->layerForScrolling()->removeAnimation(m_animationId);
+
+    resetAnimationState();
+}
+
+void ProgrammaticScrollAnimator::tickAnimation(double monotonicTime)
+{
+    if (m_animationCurve) {
+        if (!m_startTime)
+            m_startTime = monotonicTime;
+        double elapsedTime = monotonicTime - m_startTime;
+        bool isFinished = (elapsedTime > m_animationCurve->duration());
+        FloatPoint offset = m_animationCurve->getValue(elapsedTime);
+        m_scrollableArea->setScrollOffsetFromProgrammaticAnimation(IntPoint(offset.x(), offset.y()));
+
+        if (isFinished) {
+            resetAnimationState();
+        } else if (!m_scrollableArea->scheduleAnimation()) {
+            m_scrollableArea->setScrollOffsetFromProgrammaticAnimation(IntPoint(m_targetOffset.x(), m_targetOffset.y()));
+            resetAnimationState();
+        }
+    }
+}
+
+void ProgrammaticScrollAnimator::notifyAnimationStarted(double monotonicTime)
+{
+    m_startTime = monotonicTime;
+}
+
+void ProgrammaticScrollAnimator::notifyAnimationFinished(double monotonicTime)
+{
+    resetAnimationState();
+}
+
+void ProgrammaticScrollAnimator::canUseCompositedScrollAnimationsDidChange()
+{
+    // If we're running an animation on the compositor thread but composited
+    // scrolling is no longer available, we need to take over the animation on
+    // the main thread.
+    if (m_animationId && !m_scrollableArea->canUseCompositedScrollAnimations()) {
+        cancelAnimation();
+        animateToOffset(m_targetOffset);
+    }
+}
+
+} // namespace WebCore