Is there any way to let compositor set the data in client space and then return back to client?

Pekka Paalanen ppaalanen at
Sat Feb 8 01:55:32 PST 2014

On Sat, 8 Feb 2014 08:19:06 +0000
"Wang, Quanxian" < at> wrote:

> Hi, All
> I want to allocate some space in client, and let compositor set
> some data in this space and then return back to client.
> It seems like user data mechanism.
> Any way to implement that?

Not really, it's nothing like user data.

You have to make the client bind to a new protocol interface you
designed, and then use events to pass the data to the client.

If you need to pass significant amounts of data, you can use a
mechanism similar to passing XKB keymaps, see wl_keyboard.keymap
event. There the compositor creates the shm file. If you want the
shm file created by the client, you pass the file descriptor in the
other direction, similar to wl_shm.create_pool, have the server
fill out the memory, and then send an event to say it's done or
rely on a wl_display.sync roundtrip.


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