Generates a unique filename in the GEGL swap directory, suitable for using as swap space.
When the file is no longer needed, it may be removed with swap_remove_file; otherwise, it will be removed when exit is called.
| suffix |
a string to suffix the filename with, for identification purposes, or null. |
|
a string containing the full file path, or null is the swap is disabled. The returned string should be freed with g_free when no longer needed. |