[PATCH Mesa] Enable throttling in SwapBuffers

[Kristian Høgsberg]

On Tue, Dec 03, 2013 at 05:04:10PM +0100, Axel Davy wrote:
> flush_with_flags, when available, allows the driver to throttle.
> Using this suppress input lag issues that can be observed in heavy
> rendering situations on non-intel cards.
> 
> Signed-off-by: Axel Davy <axel.davy at ens.fr>

That makes sense, we need to use that.  Patch applied and I added a CC
for the stable branch.  Please follow the coding style used in the
file though, I made a few edits as described below.

Kristian

> ---
> We must fight input lag, since we can have situations where
> the sent buffer hasn't been touched yet at all by the driver.
> In this corner case, there is no lock on the buffer, and Weston
> would display the buffer which has not been rendered yet.
> 
>  src/egl/drivers/dri2/platform_wayland.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/src/egl/drivers/dri2/platform_wayland.c b/src/egl/drivers/dri2/platform_wayland.c
> index f9065bb..7e3733b 100644
> --- a/src/egl/drivers/dri2/platform_wayland.c
> +++ b/src/egl/drivers/dri2/platform_wayland.c
> @@ -557,6 +557,8 @@ dri2_swap_buffers_with_damage(_EGLDriver *drv,
>  {
>     struct dri2_egl_display *dri2_dpy = dri2_egl_display(disp);
>     struct dri2_egl_surface *dri2_surf = dri2_egl_surface(draw);
> +   _EGLContext *ctx;
> +   struct dri2_egl_context *dri2_ctx;
>     int i, ret = 0;
>  
>     while (dri2_surf->frame_callback && ret != -1)
> @@ -612,7 +614,17 @@ dri2_swap_buffers_with_damage(_EGLDriver *drv,
>  
>     wl_surface_commit(dri2_surf->wl_win->surface);
>  
> -   (*dri2_dpy->flush->flush)(dri2_surf->dri_drawable);
> +   if (dri2_dpy->flush->base.version >= 4)
> +   {

I put this { back on the same line as the if statement

> +      ctx = _eglGetCurrentContext();
> +      dri2_ctx = dri2_egl_context(ctx);
> +      (*dri2_dpy->flush->flush_with_flags)(dri2_ctx->dri_context,
> +                                           dri2_surf->dri_drawable,
> +                                           __DRI2_FLUSH_DRAWABLE,
> +                                           __DRI2_THROTTLE_SWAPBUFFER);
> +   }
> +   else

and this else on the same line as the } and added { } around the flush
call.  If one branch of the if statement has braces, the other one
should too.

> +      (*dri2_dpy->flush->flush)(dri2_surf->dri_drawable);
>     (*dri2_dpy->flush->invalidate)(dri2_surf->dri_drawable);
>  
>     return EGL_TRUE;
> -- 
> 1.8.1.2
> 
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