> Subject: Re: [PATCH v2 12/14] ui/gtk-gl-area: Remove extra draw call in > refresh > > On 2025/05/10 21:12, Dmitry Osipenko wrote: > > On 5/10/25 07:52, Akihiko Odaki wrote: > >> On 2025/05/06 21:57, Alex Bennée wrote: > >>> From: Dongwon Kim <[email protected]> > >>> > >>> This partially reverts commit > >>> 77bf310084dad38b3a2badf01766c659056f1cf2 > >>> which causes some guest display corruption when gtk-gl-area is used > >>> for GTK rendering (e.g. Wayland Compositor) possibly due to > >>> simulataneous accesses on the guest frame buffer by host compositor > >>> and the guest. > >> > >> Simply reverting the part of the commit may re-introduce the problem > >> the commit tried to solve, which will be a regression as the commit > >> is already included in releases. > >> > >> I guess the problem is that the gl_block callback of GraphicHwOps is > >> not properly implemented and it is what should be fixed. > > > > The reverted commit made QEMU GTK GUI unusable under Wayland. It was > > fixing problem which requires very specific QEMU setup, while breaking > > generic setups. The offending change should be reverted as it > > introduced a bigger problem. A proper solution should be found, > > meanwhile QEMU GTK under Wayland should be restored, IMO. > > > > For the reference see [1]. First bug reports about a mirrored display > > problem were made to me on IRC a year ago and the root of the problem > > was identified only couple months ago. > > > > [1] > > https://lore.kernel.org/qemu-devel/5aedf1ad-d9b0-4edb-a050-f3d9bee9bcc > > [email protected]/ > > That describes the context well. It should also be described with an inline > comment so that we will not lose track of the known problem.
[Kim, Dongwon] Do you mean we should have this info in the commit message? > > > > > As of today, the GTK problem isn't understood. > > > > If your guess about simultaneous accesses on the guest frame buffer is > correct, > it's a bug of the emulated device, not GTK. [Kim, Dongwon] "Simultaneous accesses" was just a guess. This problem needs to be debugged further. BTW, the problem the original commit was trying to fix is some lockup due to suspended rendering on minimized or hidden GTK window. But according to Dmitry, this case wasn't hit in his setup with wayland compositor so I assume the risk of not having an extra draw in gtk-gl-area would be low. > > Regards, > Akihiko Odaki
