Limitations of Weston's screenshooter / Are there any plans to create an official screenshot protocol?

Pekka Paalanen ppaalanen at
Fri Dec 13 12:12:04 PST 2013

On Fri, 13 Dec 2013 15:26:36 +0100
Maarten Baert <maarten-baert at> wrote:

> - Why can the protocol only capture one screen at a time? I
> expect this will result in tearing because the screenshots won't
> correspond to the same point in time. Can this be avoided
> somehow? I realize that different outputs can have different
> pixel formats, but I thought compositors used a single big
> surface for all of them anyway, making it trivial to capture all
> of them at once.

You mean that each output, and the capture of it, can be from a
different time instant? Yes.

The one big framebuffer assumption is not true here. On Wayland,
every compositor can choose any way they want to organize and
render the framebuffers. Weston has a separate framebuffer for each
output, and each of them is rendered separately, and asynchronously
wrt. to each other. That is mostly because scanout refresh cycles
happen asynchronously in general, too.

In that respect, capturing one output at a time is on average as
good as the original thing the user sees on the monitors.

Like Giulio already said, the existing screencapturing protocol
(which is not even meant for video at all, only stills) is just a
demo. Nothing there is "official". You are warmly welcome to design
a generic screencapturing protocol and propose that to become a


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