Source/WebCore/page/scrolling/cocoa/ScrollingTreeFixedNode.mm

/*
 * Copyright (C) 2012 Apple 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:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS 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.
 */

#import "config.h"
#import "ScrollingTreeFixedNode.h"

#if ENABLE(ASYNC_SCROLLING)

#import "Logging.h"
#import "ScrollingStateFixedNode.h"
#import "ScrollingTree.h"
#import "ScrollingTreeFrameScrollingNode.h"
#import "ScrollingTreeOverflowScrollProxyNode.h"
#import "ScrollingTreeOverflowScrollingNode.h"
#import "ScrollingTreePositionedNode.h"
#import "ScrollingTreeStickyNode.h"
#import "WebCoreCALayerExtras.h"
#import <wtf/text/TextStream.h>

namespace WebCore {

Ref<ScrollingTreeFixedNode> ScrollingTreeFixedNode::create(ScrollingTree& scrollingTree, ScrollingNodeID nodeID)
{
    return adoptRef(*new ScrollingTreeFixedNode(scrollingTree, nodeID));
}

ScrollingTreeFixedNode::ScrollingTreeFixedNode(ScrollingTree& scrollingTree, ScrollingNodeID nodeID)
    : ScrollingTreeNode(scrollingTree, ScrollingNodeType::Fixed, nodeID)
{
    scrollingTree.fixedOrStickyNodeAdded();
}

ScrollingTreeFixedNode::~ScrollingTreeFixedNode()
{
    scrollingTree().fixedOrStickyNodeRemoved();
}

void ScrollingTreeFixedNode::commitStateBeforeChildren(const ScrollingStateNode& stateNode)
{
    const ScrollingStateFixedNode& fixedStateNode = downcast<ScrollingStateFixedNode>(stateNode);

    if (fixedStateNode.hasChangedProperty(ScrollingStateNode::Layer))
        m_layer = fixedStateNode.layer();

    if (stateNode.hasChangedProperty(ScrollingStateFixedNode::ViewportConstraints))
        m_constraints = fixedStateNode.viewportConstraints();
}

void ScrollingTreeFixedNode::applyLayerPositions()
{
    auto computeLayerPosition = [&] {
        FloatSize overflowScrollDelta;
        ScrollingTreeStickyNode* lastStickyNode = nullptr;
        for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
            if (is<ScrollingTreeFrameScrollingNode>(*ancestor)) {
                // Fixed nodes are positioned relative to the containing frame scrolling node.
                // We bail out after finding one.
                auto layoutViewport = downcast<ScrollingTreeFrameScrollingNode>(*ancestor).layoutViewport();
                return m_constraints.layerPositionForViewportRect(layoutViewport) - overflowScrollDelta;
            }

            if (is<ScrollingTreeOverflowScrollingNode>(*ancestor)) {
                // To keep the layer still during async scrolling we adjust by how much the position has changed since layout.
                auto& overflowNode = downcast<ScrollingTreeOverflowScrollingNode>(*ancestor);
                overflowScrollDelta -= overflowNode.scrollDeltaSinceLastCommit();
                continue;
            }

            if (is<ScrollingTreeOverflowScrollProxyNode>(*ancestor)) {
                // To keep the layer still during async scrolling we adjust by how much the position has changed since layout.
                auto& overflowNode = downcast<ScrollingTreeOverflowScrollProxyNode>(*ancestor);
                overflowScrollDelta -= overflowNode.scrollDeltaSinceLastCommit();
                continue;
            }

            if (is<ScrollingTreePositionedNode>(*ancestor)) {
                auto& positioningAncestor = downcast<ScrollingTreePositionedNode>(*ancestor);
                // See if sticky node already handled this positioning node.
                // FIXME: Include positioning node information to sticky/fixed node to avoid these tests.
                if (lastStickyNode && lastStickyNode->layer() == positioningAncestor.layer())
                    continue;
                if (positioningAncestor.layer() != m_layer)
                    overflowScrollDelta -= positioningAncestor.scrollDeltaSinceLastCommit();
                continue;
            }

            if (is<ScrollingTreeStickyNode>(*ancestor)) {
                auto& stickyNode = downcast<ScrollingTreeStickyNode>(*ancestor);
                overflowScrollDelta += stickyNode.scrollDeltaSinceLastCommit();
                lastStickyNode = &stickyNode;
                continue;
            }

            if (is<ScrollingTreeFixedNode>(*ancestor)) {
                // The ancestor fixed node has already applied the needed corrections to say put.
                return m_constraints.layerPositionAtLastLayout() - overflowScrollDelta;
            }
        }
        ASSERT_NOT_REACHED();
        return FloatPoint();
    };

    auto layerPosition = computeLayerPosition();

    LOG_WITH_STREAM(Scrolling, stream << "ScrollingTreeFixedNode " << scrollingNodeID() << " relatedNodeScrollPositionDidChange: viewportRectAtLastLayout " << m_constraints.viewportRectAtLastLayout() << " last layer pos " << m_constraints.layerPositionAtLastLayout() << " layerPosition " << layerPosition);

    [m_layer _web_setLayerTopLeftPosition:layerPosition - m_constraints.alignmentOffset()];
}

void ScrollingTreeFixedNode::dumpProperties(TextStream& ts, ScrollingStateTreeAsTextBehavior behavior) const
{
    ts << "fixed node";
    ScrollingTreeNode::dumpProperties(ts, behavior);
    ts.dumpProperty("fixed constraints", m_constraints);
    
    if (behavior & ScrollingStateTreeAsTextBehaviorIncludeLayerPositions) {
        FloatRect layerBounds = [m_layer bounds];
        FloatPoint anchorPoint = [m_layer anchorPoint];
        FloatPoint position = [m_layer position];
        FloatPoint layerTopLeft = position - toFloatSize(anchorPoint) * layerBounds.size() + m_constraints.alignmentOffset();
        ts.dumpProperty("layer top left", layerTopLeft);
    }
}

} // namespace WebCore

#endif // ENABLE(ASYNC_SCROLLING)