RE: [PATCH 1/3] ui/gtk: skip drawing guest scanout when associated VC is invisible

[Kim, Dongwon]

Hi Daniel,

> -----Original Message-----
> From: Daniel P. Berrangé <berrange@redhat.com>
> Sent: Thursday, March 7, 2024 1:46 AM
> To: Kim, Dongwon <dongwon.kim@intel.com>
> Cc: Marc-André Lureau <marcandre.lureau@gmail.com>; qemu-
> devel@nongnu.org
> Subject: Re: [PATCH 1/3] ui/gtk: skip drawing guest scanout when associated
> VC is invisible
> 
> On Thu, Feb 01, 2024 at 06:48:58PM +0000, Kim, Dongwon wrote:
> > Hi Marc-André,
> >
> > Thanks for your feedback. Yes, you are right, rendering doesn't stop
> > on Ubuntu system as it has preview even after the window is minimized. But
> this is not always the case.
> > Some simple windows managers don't have this preview (thumbnail)
> > feature and this visible flag is not toggled. And the rendering stops
> > right away there when the window is minimized.
> 
> This makes me pretty uncomfortable. This is proposing changing QEMU
> behaviour to workaround a problem whose behaviour varies based on what 3rd
> party software QEMU is running on
> 
> What you say "window managers" are you referring to a traditional
> X11 based host display only, or does the problem also exist on modern
> Wayland host display ?

[Kim, Dongwon]  I didn't mean anything about the compositor/display server 
itself. And I am not sure about the general behavior of Wayland compositors but 
the point here is the rendering while the app is being iconized (minimized) is 
not always the case. For example, ICE-WM on Yocto Linux doesn't have any 
preview for the iconized or minimized applications, which means all drawing 
activities on the minimized app are paused. This is the problem in case blob 
scanout is used with virtio-gpu on the guest because the guest won't receive 
the response for the frame submission until the frame is fully rendered on the 
host. This is causing timeout and further issue on the display pipeline in 
virtio-gpu driver in the guest.

> 
> If the problem is confined to X11, that would steer towards saying we 
> shouldn't
> try to workaround it given that X11 is very much obsolete at this point.

[Kim, Dongwon]  I think I should try Wayland too but I guess it depends on the 
compositor and the shell design. Of course I need to test but what if it works 
ok on the Ubuntu running with wayland backend but not with Weston?

> 
> With regards,
> Daniel
> --
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