Protocol for window previews/thumbnails

[adlo]

> On 12 May 2016, at 08:57, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> 
> On Wed, 11 May 2016 23:35:01 +0100
> ade low <adloconwy at gmail.com> wrote:
>> My use case is third-party window switcher applications, such as
>> xfdashboard or my program, xfce4-lightdash-plugin:
>> https://github.com/adlocode/xfce4-lightdash-plugin
> 
> The implementation of such things would have so much
> compositor-internal parts anyway, that making a protocol for it does
> not seem tractable to me. Why would anyone bother implementing such
> protocol in their compositor?

If there is no protocol, what could be an alternative way for third-party window switchers to be implemented on Wayland compositors?

> 
>> A little more tractable plan would be to communicate only surface
>>> meta-data to the client,
>>> which could then ask the compositor to draw
>>> the thumbnails relative to one of the client's surfaces. The client
>>> would never have access to window content itself.  
>> 
> The very point is, the client would not render the thumbnails at all.
> The compositor would. Painting a copy of a window at another location
> should be fairly easy in theory. From your client perspective it would
> be a little like a special sub-surface whose content magically just
> appears on screen.

If I wanted to try writing something like this as a Weston extension for testing purposes, how could I get the window's surface?

Regards

adlo