[Mesa-dev] [PATCH] mesa/swrast: fix inverted front buffer rendering with old-school swrast

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

I've no idea when this broke, but we have some people who wanted it fixed,
so here's my attempt.

reproducer, run readpix with swrast hit f, or run trival tri -sb things are
upside down, after this patch they aren't.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66213

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 src/mesa/drivers/dri/swrast/swrast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/swrast/swrast.c b/src/mesa/drivers/dri/swrast/swrast.c
index bfa2efd..06b4812 100644
--- a/src/mesa/drivers/dri/swrast/swrast.c
+++ b/src/mesa/drivers/dri/swrast/swrast.c
@@ -406,8 +406,8 @@ swrast_map_renderbuffer(struct gl_context *ctx,
 				     (char *) xrb->Base.Buffer,
 				     dPriv->loaderPrivate);
 
-      *out_map = xrb->Base.Buffer;
-      *out_stride = stride;
+      *out_map = xrb->Base.Buffer + (h - 1) * stride;
+      *out_stride = -stride;
       return;
    }
 
-- 
1.8.4.2