From bfb801538606999234acc51f49b580a12d3525e2 Mon Sep 17 00:00:00 2001
From: Chris Forbes <chrisf@ijw.co.nz>
Date: Mon, 13 May 2013 21:17:29 +1200
Subject: [PATCH] mesa: add accessor for effective stencil ref

Clamps the stencil reference value to the range representable in the
currently-bound draw framebuffer's stencil attachment.

V2: Add spec quote.

NOTE: This is a candidate for stable branches.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
(cherry picked from commit 38f65162af772af6d05627e3af6e8b7caf03ec8f)
---
 src/mesa/main/stencil.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/mesa/main/stencil.h b/src/mesa/main/stencil.h
index b772bfd6e6f..38d48488cd6 100644
--- a/src/mesa/main/stencil.h
+++ b/src/mesa/main/stencil.h
@@ -78,4 +78,18 @@ _mesa_update_stencil(struct gl_context *ctx);
 extern void 
 _mesa_init_stencil( struct gl_context * ctx );
 
+/* From the GL 4.3 spec, 17.3.5:
+ *    "Stencil comparison operations and queries of <ref> clamp its value
+ *    to the range [0, 2^s-1], where <s> is the number of bits in the
+ *    stencil buffer attached to the draw framebuffer."
+ */
+
+static inline GLint
+_mesa_get_stencil_ref(struct gl_context const *ctx, int face)
+{
+   GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
+   GLint ref = ctx->Stencil.Ref[face];
+   return CLAMP(ref, 0, stencilMax);
+}
+
 #endif