| <!DOCTYPE html> |
| <svg width="400" height="100"> |
| <filter id="notFirst"> |
| <feFlood flood-color="green"/> |
| <feComposite in2="SourceGraphic" in="unknown" operator="atop"/> |
| </filter> |
| <filter id="notFirstEmpty"> |
| <feFlood flood-color="green"/> |
| <feComposite in2="SourceGraphic" in="" operator="atop"/> |
| </filter> |
| <filter id="first"> |
| <feComposite in2="SourceGraphic" in="unknown" operator="atop"/> |
| </filter> |
| <filter id="firstEmpty"> |
| <feComposite in2="SourceGraphic" in="" operator="atop"/> |
| </filter> |
| <rect width="100" height="100" fill="red" filter="url(#notFirst)"/> |
| <rect x="100" width="100" height="100" fill="red" filter="url(#notFirstEmpty)"/> |
| <rect x="200" width="100" height="100" fill="green" filter="url(#first)"/> |
| <rect x="300" width="100" height="100" fill="green" filter="url(#firstEmpty)"/> |
| </svg> |
