On Thu, Jun 16, 2022 at 09:54:46AM +0100, Mark Cave-Ayland wrote: > Hi all, > > Howard pointed me off-list to a corrupted screen display issue experienced > when changing the screen colour depth in MacOS under qemu-system-ppc. I was > able to reproduce it here, and noticed from the output that the issue was > likely due to the host display not updating its depth accordingly. > > After it was confirmed to me that this was working in QEMU 6.2, I was able > to eventually bisect the problem down to this commit: > > > cb8962c146b2633a4b04562281de9b2703bba849 is the first bad commit > commit cb8962c146b2633a4b04562281de9b2703bba849 > Author: Marc-André Lureau <marcandre.lur...@redhat.com> > Date: Tue Feb 15 00:13:37 2022 +0400 > > ui: do not create a surface when resizing a GL scanout > > qemu_console_resize() will create a blank surface and replace the > current scanout with it if called while the current scanout is > GL (texture or dmabuf). > > This is not only very costly, but also can produce glitches on the > display/listener side. > > Instead, compare the current console size with the fitting console > functions, which also works when the scanout is GL. > > Note: there might be still an unnecessary surface creation on calling > qemu_console_resize() when the size is actually changing, but display > backends currently rely on DisplaySurface details during > dpy_gfx_switch() to handle various resize aspects. We would need more > refactoring to handle resize without DisplaySurface, this is left for a > future improvement. > > Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com> > Message-Id: <20220214201337.1814787-4-marcandre.lur...@redhat.com> > Signed-off-by: Gerd Hoffmann <kra...@redhat.com> > > ui/console.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > > Some more background: the screen in qemu-system-ppc's MacOS is controlled > via a custom driver written by Ben which uses the Bochs VBE registers to > change the screen width/height/depth. The code used to do this can be found > at > https://gitlab.com/qemu-project/QemuMacDrivers/-/blob/master/QemuVGADriver/src/QemuVga.c#L354. > > Looking at the changes in cb8962c146 my guess would be that either the > updated check in qemu_console_resize() should also check to see if the > surface depth is unchanged before exiting early, or that there is an extra > update required in the VGA device when changing just the screen colour depth > by itself.
Can you try ditch the QEMU_ALLOCATED_FLAG check added by the commit? Which depth changes triggers this? Going from direct color to a paletted mode? take care, Gerd
