static const DeprecatedPaintLayer* findParentLayerOnClippingContainerChain(const DeprecatedPaintLayer* layer)
{
LayoutObject* current = layer->layoutObject();
while (current) {
if (current->style()->position() == FixedPosition) {
for (current = current->parent(); current && !current->canContainFixedPositionObjects(); current = current->parent()) {
// All types of clips apply to fixed-position descendants of other fixed-position elements.
// Note: it's unclear whether this is what the spec says. Firefox does not clip, but Chrome does.
if (current->style()->position() == FixedPosition && current->hasClipOrOverflowClip()) {
ASSERT(current->hasLayer());
return static_cast<const LayoutBoxModelObject*>(current)->layer();
}
// CSS clip applies to fixed position elements even for ancestors that are not what the
// fixed element is positioned with respect to.
if (current->hasClip()) {
ASSERT(current->hasLayer());
return static_cast<const LayoutBoxModelObject*>(current)->layer();
}
}
} else {
current = current->containingBlock();
}
if (current->hasLayer())
return static_cast<const LayoutBoxModelObject*>(current)->layer();
// Having clip or overflow clip forces the LayoutObject to become a layer.
ASSERT(!current->hasClipOrOverflowClip());
}
ASSERT_NOT_REACHED();
return nullptr;
}
