Re: Corrupted display changing screen colour depth in qemu-system-ppc/MacOS

[Marc-André Lureau]

Hi

On Fri, Jul 22, 2022 at 4:28 PM Howard Spoelstra <hsp.cat7@gmail.com> wrote:
>
>
>
> On Fri, Jun 17, 2022 at 2:38 PM Marc-André Lureau 
> <marcandre.lureau@redhat.com> wrote:
>>
>> Hi
>>
>> On Fri, Jun 17, 2022 at 1:56 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
>> >
>> >   Hi,
>> >
>> > > > Can you try ditch the QEMU_ALLOCATED_FLAG check added by the commit?
>> > >
>> > > Commit cb8962c146 drops the QEMU_ALLOCATED_FLAG check: if I add it back 
>> > > in
>> > > with the following diff on top then everything works again:
>> >
>> > Ah, the other way around.
>> >
>> > > diff --git a/ui/console.c b/ui/console.c
>> > > index 365a2c14b8..decae4287f 100644
>> > > --- a/ui/console.c
>> > > +++ b/ui/console.c
>> > > @@ -2400,11 +2400,12 @@ static void vc_chr_open(Chardev *chr,
>> > >
>> > >  void qemu_console_resize(QemuConsole *s, int width, int height)
>> > >  {
>> > > -    DisplaySurface *surface;
>> > > +    DisplaySurface *surface = qemu_console_surface(s);
>> > >
>> > >      assert(s->console_type == GRAPHIC_CONSOLE);
>> > >
>> > > -    if (qemu_console_get_width(s, -1) == width &&
>> > > +    if (surface && (surface->flags & QEMU_ALLOCATED_FLAG) &&
>> > > +        qemu_console_get_width(s, -1) == width &&
>> > >          qemu_console_get_height(s, -1) == height) {
>> > >          return;
>> > >      }
>> > >
>> > > > Which depth changes triggers this?  Going from direct color to a
>> > > > paletted mode?
>> > >
>> > > A quick test suggests anything that isn't 32-bit colour is affected.
>> >
>> > Hmm, I think the commit should simply be reverted.
>> >
>> > Short-cutting the qemu_console_resize() call is only valid in case the
>> > current surface was created by qemu_console_resize() too.  When it is
>> > something else -- typically a surface backed by vga vram -- it's not.
>> > Looking at the QEMU_ALLOCATED_FLAG checks exactly that ...
>>
>> Oh ok, it might be worth adding a comment to clarify that. By
>> reverting, we are going back to the situation where
>> qemu_console_resize() will create a needless surface when rendering
>> with GL. As I tried to explain in the commit message, it will need
>> more changes to prevent that. I can take a look later.
>>
>
> Hi Marc-André,
>
> I wondered whether you've had a chance to look at this?
>

No, it's not clear to me how to reproduce it. Someone that can
actually test it should send a patch with some comments to explain it.

thanks