LazyLoadImageObserver.cpp [plain text]
#include "config.h"
#include "LazyLoadImageObserver.h"
#include "Frame.h"
#include "HTMLImageElement.h"
#include "IntersectionObserverCallback.h"
#include "RenderStyle.h"
#include <limits>
namespace WebCore {
class LazyImageLoadIntersectionObserverCallback final : public IntersectionObserverCallback {
public:
static Ref<LazyImageLoadIntersectionObserverCallback> create(Document& document)
{
return adoptRef(*new LazyImageLoadIntersectionObserverCallback(document));
}
private:
CallbackResult<void> handleEvent(IntersectionObserver&, const Vector<Ref<IntersectionObserverEntry>>& entries, IntersectionObserver&) final
{
ASSERT(!entries.isEmpty());
for (auto& entry : entries) {
if (!entry->isIntersecting())
continue;
auto* element = entry->target();
if (is<HTMLImageElement>(element)) {
downcast<HTMLImageElement>(*element).loadDeferredImage();
element->document().lazyLoadImageObserver().unobserve(*element, element->document());
}
}
return { };
}
LazyImageLoadIntersectionObserverCallback(Document& document)
: IntersectionObserverCallback(&document)
{
}
};
void LazyLoadImageObserver::observe(Element& element)
{
auto& observer = element.document().lazyLoadImageObserver();
auto* intersectionObserver = observer.intersectionObserver(element.document());
if (!intersectionObserver)
return;
intersectionObserver->observe(element);
}
void LazyLoadImageObserver::unobserve(Element& element, Document& document)
{
if (auto& observer = document.lazyLoadImageObserver().m_observer)
observer->unobserve(element);
}
IntersectionObserver* LazyLoadImageObserver::intersectionObserver(Document& document)
{
if (!m_observer) {
auto callback = LazyImageLoadIntersectionObserverCallback::create(document);
IntersectionObserver::Init options { WTF::nullopt, emptyString(), { } };
auto observer = IntersectionObserver::create(document, WTFMove(callback), WTFMove(options));
if (observer.hasException())
return nullptr;
m_observer = observer.returnValue().ptr();
}
return m_observer.get();
}
bool LazyLoadImageObserver::isObserved(Element& element) const
{
return m_observer && m_observer->observationTargets().contains(&element);
}
}