[Mesa-dev] [PATCH] glx/dri3: request async pixmap present for swap interval 0

[Frank Binns]

On 24/04/14 13:19, Frank Binns wrote:
> Typically we want swaps to occur during vertical blank to avoid
> tearing. However, when the swap interval is 0 we want to go
> as quickly as possible even if this results in tearing.
>
> Indicate to the X server that it should attempt to do an
> asynchronise swap when the swap interval is 0.
>
> Signed-off-by: Frank Binns <frank.binns at imgtec.com>
> ---
>   src/glx/dri3_glx.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
> index b7dac8e..e385723 100644
> --- a/src/glx/dri3_glx.c
> +++ b/src/glx/dri3_glx.c
> @@ -1321,6 +1321,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
>      xcb_connection_t *c = XGetXCBConnection(dpy);
>      int buf_id = DRI3_BACK_ID(priv->cur_back);
>      int64_t ret = 0;
> +   uint32_t options = XCB_PRESENT_OPTION_NONE;
>   
>      unsigned flags = __DRI2_FLUSH_DRAWABLE;
>      if (flush)
> @@ -1339,6 +1340,9 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
>         if (target_msc == 0)
>            target_msc = priv->msc + priv->swap_interval * (priv->send_sbc - priv->recv_sbc);
>   
> +      if (priv->swap_interval == 0)
> +         options |= XCB_PRESENT_OPTION_ASYNC;
> +
>         priv->buffers[buf_id]->busy = 1;
>         priv->buffers[buf_id]->last_swap = priv->send_sbc;
>         xcb_present_pixmap(c,
> @@ -1352,7 +1356,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
>                            None,                                 /* target_crtc */
>                            None,
>                            priv->buffers[buf_id]->sync_fence,
> -                         XCB_PRESENT_OPTION_NONE,
> +                         options,
>                            target_msc,
>                            divisor,
>                            remainder, 0, NULL);

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