It will make this more usable (see xpra session to other account on localhost: mmap is hard to setup)
Links:
Done in r21245, which also adds the XPRA_KEEP_MMAP_FILE
env var so we can inspect the file before it gets deleted (normally removed as soon as the server has a handle on it):
$ XPRA_KEEP_MMAP_FILE=1 xpra attach --mmap=/tmp/shared-session --mmap-group=docker -d mmap (..) init_mmap('docker', '/run/user/1000/xpra/localhost.localdomain-13', 268435456, '/tmp/shared-session') setting mmap file /tmp/shared-session to group id=1001 using mmap file /tmp/shared-session, fd=11, size=268439552 write_mmap_token(<mmap.mmap object at 0x7f1242a28b20>, 0xe7308f4b674444ad03fba75da63e66, 0x200, 0x80) write_mmap_token(<mmap.mmap object at 0x7f1242a28b20>, 0xe7308f4b674444ad03fba75da63e66, 0x10000f80, 0x80) read_mmap_token(<mmap.mmap object at 0x7f1242a28b20>, 0x10000f80, 0x80)=0x39507ca907d24a008635ffe972217379
$ ls -la /tmp/shared-session -rw-rw----. 1 antoine docker 268439552 Dec 18 16:47 /tmp/shared-session
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2075