Re: [PATCH v3 12/12] ui/console: call gfx_switch() even if the current scanout is GL

[Marc-André Lureau]

Hi

On Mon, Mar 7, 2022 at 4:24 PM Akihiko Odaki <akihiko.odaki@gmail.com> wrote:
>
> On 2022/03/07 20:50, Marc-André Lureau wrote:
> > Hi
> >
> > On Mon, Mar 7, 2022 at 2:35 PM Akihiko Odaki <akihiko.odaki@gmail.com> 
> > wrote:
> >>
> >> On 2022/03/07 19:19, Marc-André Lureau wrote:
> >>> Hi Akihiko
> >>>
> >>> On Mon, Mar 7, 2022 at 12:09 PM Akihiko Odaki <akihiko.odaki@gmail.com> 
> >>> wrote:
> >>>>
> >>>> On 2022/03/07 16:46, marcandre.lureau@redhat.com wrote:
> >>>>> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >>>>>
> >>>>> egl-headless depends on the backing surface to be set before texture are
> >>>>> set and updated. Display it (update=true) iff the current scanout kind
> >>>>> is SURFACE.
> >>>>
> >>>> egl-headless does not dynamically call register_displaychangelistener
> >>>> and has console associated (console_select would not affect egl-headless
> >>>> itself) so this should not be necessary.
> >>>
> >>> Could you help me understand, what should not be necessary?
> >>
> >> I read the description as it sets the backing surface for egl-headless
> >> when register_displaychangelistener or console_select is called. The
> >> change is not necessary.
> >
> > Without it, gfx_switch is not called to set the new surface. Switching
> > console with VNC would fail (via ctrl+alt+num).
>
> Yes, but that is not because egl-headless requires its dpy_gfx_switch to
> be called. It is because vnc does not receive the surface. The patch
> adds a call of dpy_gfx_switch no matter if the receiver is an OpenGL
> display or not, but an OpenGL display would not need one.

That's why I added the "update" argument to
displaychangelistener_gfx_switch(). "gfx_switch" merely indicates that
the DisplaySurface has changed, not to show it.

> >
> >>
> >>>
> >>>> The remaining problem with egl-headless is that egl-headless renders the
> >>>> image to DisplaySurface, and a non-OpenGL display (namely vnc) has to
> >>>> consume it instead of texture even when con->scanout.kind is
> >>>> SCANOUT_TEXTURE or SCANOUT_DMABUF.
> >>>
> >>> This is already happening, because egl-headless calls dpy_gfx_update().
> >>
> >> It is not called when register_displaychangelistener or console_select
> >> is called by non-OpenGL display consuming the DisplaySurface.
> >
> > When displaychangelistener_display_console() is called with
> > con->scanount.kind == SCANOUT_SURFACE, it calls gfx_update(update ==
> > TRUE), and thus calls gfx_update on the whole surface.
> >
>
> con->scanout.kind is SCANOUT_TEXTURE or SCANOUT_DMABUF when egl-headless
> is rendering to surface. It would not call gfx_update in the case.

 GL updates go through egl_scanout_flush (dpy_gl_update callback),
which calls dpy_gfx_update() which is in turned handled by
vnc_dpy_update().

Could you provide a failing test case or a more concrete suggestion on
what to do instead? I am all ears :)

thanks