How to implement OSD overlay in Wayland/Weston

[Ilia Bozhinov]

Hi,

I am not entirely familiar with your setup, but you can try to use a
combination of:

1. Setting your on-top window's input region to empty as you already have
tried.
2. Use xdg-foreign protocol to set the main window as parent of your on-top
window.


This will work on all compositors that support xdg-foreign, however I am
not sure whether weston supports it.

Regards,
Ilia Bozhinov

On Tue, 19 Nov 2019, 09:53 Guillermo Rodriguez, <
guillerodriguez.dev at gmail.com> wrote:

> Hi all,
>
> This is a follow up to my earlier email "Let pointer events pass through".
>
> I have an use case where there is one full screen application (I'll
> call this the "main" application) and I need to show a OSD overlay on
> top of it. The OSD overlay is actually based on GStreamer (think PiP)
> and is managed by a different process.
> The OSD overlay should not handle pointer events; these should pass
> through to the main application, which knows how to handle them.
>
> I am not sure how to approach this in Wayland/Weston. I have
> considered the following:
>
> 1.
> Use wl_surface::set_input_region so that pointer events are not
> delivered to the OSD overlay, but instead pass through and are handled
> by the main application.
> This "almost" works, however when the main application receives the
> event, Weston brings it on top, thus hiding the OSD overlay.
> I searched for a way to specify that a given surface should always
> stay "on top". This does not seem to be supported in Wayland.
>
> 2.
> Setup things so that the OSD overlay is not an additional top level
> surface, but a child surface owned by the main application.
> This would mean having the main application create a child surface for
> the OSD, and pass this surface to the OSD process.
> In X this could be achieved by passing a Windows ID. In Wayland
> apparently it is not possible to share surfaces between processes.
>
> 3.
> Let the OSD overlay actually handle pointer events, but "send" them to
> the main application.
> In X this could be achieved with XSendEvent. In Wayland apparently it
> is not possible to have one process send events to another process.
>
> Not sure what else to try.
>
> Any ideas? Either ways to make one of the above work, or new approaches...
>
> TIA,
>
> Guillermo Rodriguez
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