[vlc-devel] [PATCH] opengl: fix vertical alignment on control events

[Romain Vimont]

On Thu, Jun 18, 2020 at 10:18:45AM +0200, Alexandre Janniaux wrote:
> Hi,
> 
> LGTM, but the commit message is not 100% correct.
> The issue here is not that the textures are potentially
> vertically flipped, but that default opengl convention
> orients the Y axis upwards while VLC convention orients
> it downwards.

Yes, but as a result, the texture content is vertically flipped (because
it is initialized from a picture stored in the VLC convention).

But ok, if you think it's more clear, I changed the text to:

> In OpenGL, the vertical alignment is reversed, because the default
> OpenGL convention orients the Y axis upwards while VLC convention
> orients it downwards.

> 
> Regards,
> --
> Alexandre Janniaux
> Videolabs
> 
> On Wed, Jun 17, 2020 at 09:31:04PM +0200, Romain Vimont wrote:
> > The video can be top-aligned (--align=4) or bottom-aligned (--align=8)
> > in the window.
> >
> > In OpenGL, the vertical alignment is reversed, because the textures are
> > vertically flipped.
> >
> > It was correctly handled for some control events (e.g.
> > CHANGE_DISPLAY_SIZE), but not for others (e.g. CHANGE_SOURCE_CROP).
> > ---
> >  modules/video_output/opengl/display.c | 28 +++++++++++++++++----------
> >  1 file changed, 18 insertions(+), 10 deletions(-)
> >
> > diff --git a/modules/video_output/opengl/display.c b/modules/video_output/opengl/display.c
> > index ebb313926a80..f4e46f6f33d2 100644
> > --- a/modules/video_output/opengl/display.c
> > +++ b/modules/video_output/opengl/display.c
> > @@ -206,6 +206,16 @@ static void PictureDisplay (vout_display_t *vd, picture_t *pic)
> >      }
> >  }
> >
> > +static void
> > +FlipVerticalAlign(vout_display_cfg_t *cfg)
> > +{
> > +    /* Reverse vertical alignment as the GL tex are Y inverted */
> > +    if (cfg->align.vertical == VLC_VIDEO_ALIGN_TOP)
> > +        cfg->align.vertical = VLC_VIDEO_ALIGN_BOTTOM;
> > +    else if (cfg->align.vertical == VLC_VIDEO_ALIGN_BOTTOM)
> > +        cfg->align.vertical = VLC_VIDEO_ALIGN_TOP;
> > +}
> > +
> >  static int Control (vout_display_t *vd, int query, va_list ap)
> >  {
> >      vout_display_sys_t *sys = vd->sys;
> > @@ -221,27 +231,25 @@ static int Control (vout_display_t *vd, int query, va_list ap)
> >        case VOUT_DISPLAY_CHANGE_DISPLAY_FILLED:
> >        case VOUT_DISPLAY_CHANGE_ZOOM:
> >        {
> > -        vout_display_cfg_t c = *va_arg (ap, const vout_display_cfg_t *);
> > +        vout_display_cfg_t cfg = *va_arg(ap, const vout_display_cfg_t *);
> >          const video_format_t *src = &vd->source;
> >
> > -        /* Reverse vertical alignment as the GL tex are Y inverted */
> > -        if (c.align.vertical == VLC_VIDEO_ALIGN_TOP)
> > -            c.align.vertical = VLC_VIDEO_ALIGN_BOTTOM;
> > -        else if (c.align.vertical == VLC_VIDEO_ALIGN_BOTTOM)
> > -            c.align.vertical = VLC_VIDEO_ALIGN_TOP;
> > +        FlipVerticalAlign(&cfg);
> >
> > -        vout_display_PlacePicture(&sys->place, src, &c);
> > +        vout_display_PlacePicture(&sys->place, src, &cfg);
> >          sys->place_changed = true;
> > -        vlc_gl_Resize (sys->gl, c.display.width, c.display.height);
> > +        vlc_gl_Resize (sys->gl, cfg.display.width, cfg.display.height);
> >          return VLC_SUCCESS;
> >        }
> >
> >        case VOUT_DISPLAY_CHANGE_SOURCE_ASPECT:
> >        case VOUT_DISPLAY_CHANGE_SOURCE_CROP:
> >        {
> > -        const vout_display_cfg_t *cfg = va_arg (ap, const vout_display_cfg_t *);
> > +        vout_display_cfg_t cfg = *va_arg(ap, const vout_display_cfg_t *);
> > +
> > +        FlipVerticalAlign(&cfg);
> >
> > -        vout_display_PlacePicture(&sys->place, &vd->source, cfg);
> > +        vout_display_PlacePicture(&sys->place, &vd->source, &cfg);
> >          sys->place_changed = true;
> >          return VLC_SUCCESS;
> >        }
> > --
> > 2.27.0
> >
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