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

[Alexandre Janniaux]

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.

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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