third_party/WebKit/Source/core/layout/HitTestCache.cpp

// Copyright (c) 2015 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 "core/layout/HitTestCache.h"

#include "public/platform/Platform.h"

namespace blink {

bool HitTestCache::lookupCachedResult(HitTestResult& hitResult, uint64_t domTreeVersion)
{
    bool result = false;
    HitHistogramMetric metric = HitHistogramMetric::MISS;
    if (hitResult.hitTestRequest().avoidCache()) {
        metric = HitHistogramMetric::MISS_EXPLICIT_AVOID;
    // For now we don't support rect based hit results.
    } else if (domTreeVersion == m_domTreeVersion && !hitResult.hitTestLocation().isRectBasedTest()) {
        for (const auto& cachedItem : m_items) {
            if (cachedItem.hitTestLocation().point() == hitResult.hitTestLocation().point()) {
                if (hitResult.hitTestRequest().equalForCacheability(cachedItem.hitTestRequest())) {
                    metric = HitHistogramMetric::HIT_EXACT_MATCH;
                    result = true;
                    hitResult = cachedItem;
                    break;
                }
                metric = HitHistogramMetric::MISS_VALIDITY_RECT_MATCHES;
            }
        }
    }
    Platform::current()->histogramEnumeration("Event.HitTest", static_cast<int>(metric), static_cast<int>(HitHistogramMetric::MAX_HIT_METRIC));
    return result;
}

void HitTestCache::addCachedResult(const HitTestResult& result, uint64_t domTreeVersion)
{
    if (!result.isCacheable())
        return;

    // If the result was a hit test on an LayoutPart and the request allowed
    // querying of the layout part; then the part hasn't been loaded yet.
    if (result.isOverWidget() && result.hitTestRequest().allowsChildFrameContent())
        return;

    // For now don't support rect based or list based requests.
    if (result.hitTestLocation().isRectBasedTest() || result.hitTestRequest().listBased())
        return;
    if (domTreeVersion != m_domTreeVersion)
        clear();
    if (m_items.size() < HIT_TEST_CACHE_SIZE)
        m_items.resize(m_updateIndex + 1);

    m_items.at(m_updateIndex).cacheValues(result);
    m_domTreeVersion = domTreeVersion;

    m_updateIndex++;
    if (m_updateIndex >= HIT_TEST_CACHE_SIZE)
        m_updateIndex = 0;
}

void HitTestCache::clear()
{
    m_updateIndex = 0;
    m_items.clear();
}

DEFINE_TRACE(HitTestCache)
{
    visitor->trace(m_items);
}

} // namespace blink