[PATCH] glx: Skip multisampled configs when matching pre-existing X visuals.

[Ian Romanick]

On 07/31/2012 03:15 PM, Paul Berry wrote:
> In __glXScreenInit() we generate the set of GLX visuals in two steps:
> first we match each pre-existing X visual with a corresponding
> FBConfig, then we generate a new X visual to correspond to all the
> remaining FBConfigs.
>
> The first step is used for the two default 24-bit visuals (true color
> and direct color) and for the 32-bit visual.  If windowsystem
> multisampling is enabled in Mesa, we need to ensure that none of these
> three visuals gets matched to a multisampled config.
>
> Fixes a bug with windowsystem multisampling in gnome-shell.  If the X
> server happens to match up a multisampled FBConfig to the 32-bit
> visual, gnome-shell will try to use it to read pixels from
> alpha-blended windows (such as gnome-terminal), resulting in no window
> appearing on screen.

I believe we're the only ones (soon to be) advertising multisample 
configs, so I don't think anyone else could have encountered this issue.

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

> ---
>   glx/glxscreens.c |    3 +++
>   1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/glx/glxscreens.c b/glx/glxscreens.c
> index 74b4c42..ff3dcdd 100644
> --- a/glx/glxscreens.c
> +++ b/glx/glxscreens.c
> @@ -288,6 +288,9 @@ pickFBConfig(__GLXscreen * pGlxScreen, VisualPtr visual)
>               continue;
>           if (config->visualRating != GLX_NONE)
>               continue;
> +        /* Ignore multisampled configs */
> +        if (config->sampleBuffers)
> +            continue;
>           if (glxConvertToXVisualType(config->visualType) != visual->class)
>               continue;
>           /* If it's the 32-bit RGBA visual, demand a 32-bit fbconfig. */
>