Weston window move to second monitor

Terry Barnaby terry1 at beam.ltd.uk
Mon Oct 3 19:13:47 UTC 2022

On 03/10/2022 08:25, Alexandros Frantzis wrote:
> On Sun, Oct 02, 2022 at 09:13:27AM +0100, Terry Barnaby wrote:
>> Hi,
>> I am developing software for an instrument embedded system using NXP 
>> CPU's
>> and the Wayland/Weston GUI system.
>> The hardware platform has a main LCD panel and an optional plug-in HDMI
>> monitor. The GUI is currently running with the Weston kiosk-shell and a
>> single application is shown full screen on the LCD. Weston is 
>> configured so
>> that the HDMI monitor appears to the right of the LCD screen and if the
>> desktop-shell is used applications can be dragged across.
>> Now what I would like is for the application to be moved to the HDMI
>> monitor/screen when the monitor is plugged in (resizing as needed).
>> With X11 I would have simply, from the application, moved its top level
>> window coordinates and without a window manager or with a simple window
>> manager the window would move to the area of the second screen.
>> Now I understand that Weston and the standard Wayland protocol's do 
>> not even
>> allow a window move request to be made.
>> So I assume I might have to implement a whole new Weston shell, perhaps
>> based on the kiosk-shell, and either invent some form of protocol to 
>> allow
>> the application to request the shell to move it or get the shell to 
>> see HDMI
>> plug in events and move the application and tell it to resize.
>> I don't have much knowledge of Wayland/Weston internals (lots of X11), so
>> can anyone give me any pointers on how I might achieve this in the
>> simplest/quickest way ?
>> Terry
> Hi Terry,
> Assuming you only care about the fullscreen case, an application can
> request (but not force) a fullscreen placement for a toplevel surface
> with:
> xdg_toplevel_set_fullscreen(xdg_toplevel, wl_output)
> In your application you could listen for advertised wl_output globals
> and issue a set_fullscreen request for the preferred wl_output (e.g.,
> based on the wl_output/xdg_output name). Since you are only dealing with
> a specific compositor under your control, you can be fairly confident
> that you will get consistent behavior here, i.e., the compositor will
> honor your request.
> Note that kiosk-shell provides a mechanism in the .ini file to declare
> the placement of applications on specific outputs. However, the output
> placement decision is static, made only when the surface is first
> created/committed to, not for any subsequent output reconfigurations.
> Making this output placement in kiosk-shell work more dynamically
> (optionally), with the shell moving the surface to the preferred output,
> could possibly be a useful enhancement for some use cases.
> HTH,
> Alexandros

Many thanks for the reply and info.

I will have a go with xdg_toplevel_set_fullscreen() and maybe have a 
look at creating a special shell to do this as well. Actually I have got 
this working to a degree in a copy of the kiosk-shell adding code to the 
kiosk_shell_handle_output_created() and 
kiosk_shell_surface_notify_output_destroy() to move the views. But I 
can't get the shell to clear its background when I move the application 
window, indeed it doesn't seem like the kiosk-shell code is actually 
setting the background at all as looking at the code it should set it to 
grey but it is black on my system using Weston 9.0.0. I will investigate 


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