Re: Standardizing _METACITY_UPDATE_COUNTER
- From: gtg990h mail gatech edu
- To: Soeren Sandmann <sandmann daimi au dk>
- Cc: wm-spec-list gnome org, gtk-devel-list gnome org
- Subject: Re: Standardizing _METACITY_UPDATE_COUNTER
- Date: Tue, 24 Feb 2004 23:35:48 -0500
Quoting Soeren Sandmann <sandmann daimi au dk>:
> How so? There is no additional complexity, just a slightly different
> syntax. The basic protocol is exactly the same.
I was talking more about the complexity of the implementation. I was reviewing
the patches, and not using XSync would cut the size of the patches by a third
to a half. Anyway, I see that there is an advantage to using XSync, so I'm okay
with the extra implementation complexity.
<snip>
> Of course, this blocking algorithm _is_ much more complex than the
> simple non-blocking one, but since doing the replies through the SYNC
> extension isn't really any more complex than sending client messages,
> I don't see any reason to not make it _possible_.
Okay. I'm going to try to implement the blocking algorithm in kwin to see just
how much more complex it is :)
Anyway, I agree with the comments you made, so here is the revised protocol:
_NET_SYNC_REQUEST (client message)
window = top-level window being resized or moved
message_type = _NET_SYNC_REQUEST
format = 32
data.l[0] = low-bits of counter value
data.l[1] = high-bits of counter value
_NET_WM_SYNC_COUNTER (client window property)
type: XA_CARDINAL
format: 32
nelements: 1
XID of a SYNC extension counter associated with the client window.
The presence of this property, set to a value that is not None,
indicates the willingness of the client to participate in this protocol.
Client window behavior:
At startup, create a new SYNC counter object, initialized to 0.Set the
_NET_WM_SYNC_COUNTER window property to the XID of this counter.
On receiving a _NET_SYNC_REQUEST, note that the next ConfigureNotify
must be acknowledged.
On receiving a ConfigureNotify for which a _NET_SYNC_REQUEST is pending,
first complete all processing and drawing associated with the event.
Then, acknowledge the _NET_SYNC_REQUEST by setting the SYNC counter to
the value specified in the request.
It is permissable to compress acknowledgements to _NET_SYNC_REQUEST
messages by setting the SYNC counter to the value specified in the
latest handled message.
Window manager behavior:
When performing a window operation where synchronization is desired,
send a _NET_SYNC_REQUEST to the client before sending a synthetic
ConfigureNotify event, or causing a real one to be generated by calling
XMoveResizeWindow.
When sending a _NET_SYNC_REQUEST, set its counter value to a serial
number. This number should start at 1 and increase by 1 for each
_NET_SYNC_REQUEST sent to a given client window.
Implementation notes:
When resizing or moving a window, a window manager is advised to not
perform another XMoveResizeWindow, and not send the associated
_NET_SYNC_REQUEST until the client has acknowledged the previous request.
Window managers are advised to implement a timeout on how long they will
wait for a client to acknowledge a _NET_SYNC_REQUEST. After this timeout
expires, window managers are allowed to send another _NET_SYNC_REQUEST,
and perform another XMoveResizeWindow.
Sincerely,
Rayiner Hashem
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