Track two sets of back-face stencil state

Track separate back-face stencil state for OpenGL 2.0 /
GL_ATI_separate_stencil and GL_EXT_stencil_two_side.  This allows all
three to be enabled in a driver.  One set of state is set via the 2.0
or ATI functions and is used when STENCIL_TEST_TWO_SIDE_EXT is
disabled.  The other is set by StencilFunc and StencilOp when the
active stencil face is set to BACK.  The GL_EXT_stencil_two_side spec has
more details.

http://opengl.org/registry/specs/EXT/stencil_two_side.txt

4 files changed, 93 insertions, 59 deletions

diff --git a/src/mesa/main/enable.c b/src/mesa/main/enable.c
index dae576ae5ac..1c026174b83 100644
--- a/src/mesa/main/enable.c
+++ b/src/mesa/main/enable.c
@@ -922,10 +922,13 @@ _mesa_set_enable(GLcontext *ctx, GLenum cap, GLboolean state)
             return;
          FLUSH_VERTICES(ctx, _NEW_STENCIL);
          ctx->Stencil.TestTwoSide = state;
-         if (state)
+         if (state) {
+            ctx->Stencil._BackFace = 2;
             ctx->_TriangleCaps |= DD_TRI_TWOSTENCIL;
-         else
+         } else {
+            ctx->Stencil._BackFace = 1;
             ctx->_TriangleCaps &= ~DD_TRI_TWOSTENCIL;
+         }
          break;
 
 #if FEATURE_ARB_fragment_program
diff --git a/src/mesa/main/getstring.c b/src/mesa/main/getstring.c
index 94bf5de1e8b..a9e22d340a3 100644
--- a/src/mesa/main/getstring.c
+++ b/src/mesa/main/getstring.c
@@ -82,7 +82,16 @@ compute_version(const GLcontext *ctx)
                               ctx->Extensions.ARB_vertex_shader &&
                               ctx->Extensions.ARB_fragment_shader &&
                               ctx->Extensions.ARB_texture_non_power_of_two &&
-                              ctx->Extensions.EXT_blend_equation_separate);
+                              ctx->Extensions.EXT_blend_equation_separate &&
+
+			      /* Technically, 2.0 requires the functionality
+			       * of the EXT version.  Enable 2.0 if either
+			       * extension is available, and assume that a
+			       * driver that only exposes the ATI extension
+			       * will fallback to software when necessary.
+			       */
+			      (ctx->Extensions.EXT_stencil_two_side
+			       || ctx->Extensions.ATI_separate_stencil));
    const GLboolean ver_2_1 = (ver_2_0 &&
                               /*ctx->Extensions.ARB_shading_language_120 &&*/
                               ctx->Extensions.EXT_pixel_buffer_object &&
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index f1da638ae66..088d45b1566 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1108,20 +1108,34 @@ struct gl_scissor_attrib
 
 /**
  * Stencil attribute group (GL_STENCIL_BUFFER_BIT).
+ *
+ * Three sets of stencil data are tracked so that OpenGL 2.0,
+ * GL_EXT_stencil_two_side, and GL_ATI_separate_stencil can all be supported
+ * simultaneously.  In each of the stencil state arrays, element 0 corresponds
+ * to GL_FRONT.  Element 1 corresponds to the OpenGL 2.0 /
+ * GL_ATI_separate_stencil GL_BACK state.  Element 2 corresponds to the
+ * GL_EXT_stencil_two_side GL_BACK state.
+ *
+ * The derived value \c _BackFace is either 1 or 2 depending on whether or
+ * not GL_STENCIL_TEST_TWO_SIDE_EXT is enabled.
+ *
+ * The derived value \c _TestTwoSide is set when the front-face and back-face
+ * stencil state are different.
  */
 struct gl_stencil_attrib
 {
    GLboolean Enabled;		/**< Enabled flag */
    GLboolean TestTwoSide;	/**< GL_EXT_stencil_two_side */
-   GLubyte ActiveFace;		/**< GL_EXT_stencil_two_side (0 or 1) */
+   GLubyte ActiveFace;		/**< GL_EXT_stencil_two_side (0 or 2) */
    GLboolean _TestTwoSide;
-   GLenum Function[2];		/**< Stencil function */
-   GLenum FailFunc[2];		/**< Fail function */
-   GLenum ZPassFunc[2];		/**< Depth buffer pass function */
-   GLenum ZFailFunc[2];		/**< Depth buffer fail function */
-   GLint Ref[2];		/**< Reference value */
-   GLuint ValueMask[2];		/**< Value mask */
-   GLuint WriteMask[2];		/**< Write mask */
+   GLubyte _BackFace;
+   GLenum Function[3];		/**< Stencil function */
+   GLenum FailFunc[3];		/**< Fail function */
+   GLenum ZPassFunc[3];		/**< Depth buffer pass function */
+   GLenum ZFailFunc[3];		/**< Depth buffer fail function */
+   GLint Ref[3];		/**< Reference value */
+   GLuint ValueMask[3];		/**< Value mask */
+   GLuint WriteMask[3];		/**< Write mask */
    GLuint Clear;		/**< Clear value */
 };
 
diff --git a/src/mesa/main/stencil.c b/src/mesa/main/stencil.c
index 2a4c38b1f25..b4ea9978d87 100644
--- a/src/mesa/main/stencil.c
+++ b/src/mesa/main/stencil.c
@@ -27,21 +27,6 @@
  * \file stencil.c
  * Stencil operations.
  *
- * Note: There's an incompatibility between GL_EXT_stencil_two_side and
- * OpenGL 2.0's two-sided stencil feature.
- *
- * With GL_EXT_stencil_two_side, calling glStencilOp/Func/Mask() only the
- * front OR back face state (as set by glActiveStencilFaceEXT) is set.
- *
- * But with OpenGL 2.0, calling glStencilOp/Func/Mask() sets BOTH the
- * front AND back state.
- *
- * So either we advertise the GL_EXT_stencil_two_side extension, or OpenGL
- * 2.0, but not both.
- *
- * Also, note that GL_ATI_separate_stencil is different as well:
- * glStencilFuncSeparateATI(GLenum frontfunc, GLenum backfunc, ...)  vs.
- * glStencilFuncSeparate(GLenum face, GLenum func, ...).
  */
 
 
@@ -198,6 +183,7 @@ _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
 {
    GET_CURRENT_CONTEXT(ctx);
    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
+   const GLint face = ctx->Stencil.ActiveFace;
    ASSERT_OUTSIDE_BEGIN_END(ctx);
 
    if (!validate_stencil_func(ctx, func)) {
@@ -207,9 +193,7 @@ _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
 
    ref = CLAMP( ref, 0, stencilMax );
 
-   if (ctx->Extensions.EXT_stencil_two_side) {
-      /* only set active face state */
-      const GLint face = ctx->Stencil.ActiveFace;
+   if (face != 0) {
       if (ctx->Stencil.Function[face] == func &&
           ctx->Stencil.ValueMask[face] == mask &&
           ctx->Stencil.Ref[face] == ref)
@@ -218,9 +202,12 @@ _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
       ctx->Stencil.Function[face] = func;
       ctx->Stencil.Ref[face] = ref;
       ctx->Stencil.ValueMask[face] = mask;
-      if (ctx->Driver.StencilFuncSeparate) {
-         ctx->Driver.StencilFuncSeparate(ctx, face ? GL_BACK : GL_FRONT,
-                                         func, ref, mask);
+
+      /* Only propagate the change to the driver if EXT_stencil_two_side
+       * is enabled.
+       */
+      if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
+         ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
       }
    }
    else {
@@ -237,7 +224,9 @@ _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
       if (ctx->Driver.StencilFuncSeparate) {
-         ctx->Driver.StencilFuncSeparate(ctx, GL_FRONT_AND_BACK,
+         ctx->Driver.StencilFuncSeparate(ctx,
+					 ((ctx->Stencil.TestTwoSide)
+					  ? GL_FRONT : GL_FRONT_AND_BACK),
                                          func, ref, mask);
       }
    }
@@ -259,17 +248,23 @@ void GLAPIENTRY
 _mesa_StencilMask( GLuint mask )
 {
    GET_CURRENT_CONTEXT(ctx);
+   const GLint face = ctx->Stencil.ActiveFace;
+
    ASSERT_OUTSIDE_BEGIN_END(ctx);
 
-   if (ctx->Extensions.EXT_stencil_two_side) {
-      /* only set active face state */
-      const GLint face = ctx->Stencil.ActiveFace;
+   if (face != 0) {
+      /* Only modify the EXT_stencil_two_side back-face state.
+       */
       if (ctx->Stencil.WriteMask[face] == mask)
          return;
       FLUSH_VERTICES(ctx, _NEW_STENCIL);
       ctx->Stencil.WriteMask[face] = mask;
-      if (ctx->Driver.StencilMaskSeparate) {
-         ctx->Driver.StencilMaskSeparate(ctx, face ? GL_BACK : GL_FRONT, mask);
+
+      /* Only propagate the change to the driver if EXT_stencil_two_side
+       * is enabled.
+       */
+      if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
+         ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
       }
    }
    else {
@@ -280,7 +275,10 @@ _mesa_StencilMask( GLuint mask )
       FLUSH_VERTICES(ctx, _NEW_STENCIL);
       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
       if (ctx->Driver.StencilMaskSeparate) {
-         ctx->Driver.StencilMaskSeparate(ctx, GL_FRONT_AND_BACK, mask);
+         ctx->Driver.StencilMaskSeparate(ctx,
+					 ((ctx->Stencil.TestTwoSide)
+					  ? GL_FRONT : GL_FRONT_AND_BACK),
+					  mask);
       }
    }
 }
@@ -304,6 +302,8 @@ void GLAPIENTRY
 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 {
    GET_CURRENT_CONTEXT(ctx);
+   const GLint face = ctx->Stencil.ActiveFace;
+
    ASSERT_OUTSIDE_BEGIN_END(ctx);
 
    if (!validate_stencil_op(ctx, fail)) {
@@ -319,9 +319,8 @@ _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
       return;
    }
 
-   if (ctx->Extensions.EXT_stencil_two_side) {
+   if (face != 0) {
       /* only set active face state */
-      const GLint face = ctx->Stencil.ActiveFace;
       if (ctx->Stencil.ZFailFunc[face] == zfail &&
           ctx->Stencil.ZPassFunc[face] == zpass &&
           ctx->Stencil.FailFunc[face] == fail)
@@ -330,9 +329,12 @@ _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
       ctx->Stencil.ZFailFunc[face] = zfail;
       ctx->Stencil.ZPassFunc[face] = zpass;
       ctx->Stencil.FailFunc[face] = fail;
-      if (ctx->Driver.StencilOpSeparate) {
-         ctx->Driver.StencilOpSeparate(ctx, face ? GL_BACK : GL_FRONT,
-                                       fail, zfail, zpass);
+
+      /* Only propagate the change to the driver if EXT_stencil_two_side
+       * is enabled.
+       */
+      if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
+         ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
       }
    }
    else {
@@ -349,7 +351,9 @@ _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
       if (ctx->Driver.StencilOpSeparate) {
-         ctx->Driver.StencilOpSeparate(ctx, GL_FRONT_AND_BACK,
+         ctx->Driver.StencilOpSeparate(ctx,
+				       ((ctx->Stencil.TestTwoSide)
+					? GL_FRONT : GL_FRONT_AND_BACK),
                                        fail, zfail, zpass);
       }
    }
@@ -372,7 +376,7 @@ _mesa_ActiveStencilFaceEXT(GLenum face)
 
    if (face == GL_FRONT || face == GL_BACK) {
       FLUSH_VERTICES(ctx, _NEW_STENCIL);
-      ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 1;
+      ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
    }
    else {
       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
@@ -513,19 +517,16 @@ _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 void
 _mesa_update_stencil(GLcontext *ctx)
 {
-   if (ctx->Extensions.EXT_stencil_two_side) {
-      ctx->Stencil._TestTwoSide = ctx->Stencil.TestTwoSide;
-   }
-   else {
-      ctx->Stencil._TestTwoSide = 
-         (ctx->Stencil.Function[0] != ctx->Stencil.Function[1] ||
-          ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[1] ||
-          ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[1] ||
-          ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[1] ||
-          ctx->Stencil.Ref[0] != ctx->Stencil.Ref[1] ||
-          ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[1] ||
-          ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[1]);
-   }
+   const GLint face = ctx->Stencil._BackFace;
+
+   ctx->Stencil._TestTwoSide =
+       (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
+	ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
+	ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
+	ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
+	ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
+	ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
+	ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 }
 
 
@@ -544,17 +545,24 @@ _mesa_init_stencil(GLcontext *ctx)
    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 1 = GL_BACK */
    ctx->Stencil.Function[0] = GL_ALWAYS;
    ctx->Stencil.Function[1] = GL_ALWAYS;
+   ctx->Stencil.Function[2] = GL_ALWAYS;
    ctx->Stencil.FailFunc[0] = GL_KEEP;
    ctx->Stencil.FailFunc[1] = GL_KEEP;
+   ctx->Stencil.FailFunc[2] = GL_KEEP;
    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
+   ctx->Stencil.ZPassFunc[2] = GL_KEEP;
    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
+   ctx->Stencil.ZFailFunc[2] = GL_KEEP;
    ctx->Stencil.Ref[0] = 0;
    ctx->Stencil.Ref[1] = 0;
+   ctx->Stencil.Ref[2] = 0;
    ctx->Stencil.ValueMask[0] = ~0U;
    ctx->Stencil.ValueMask[1] = ~0U;
+   ctx->Stencil.ValueMask[2] = ~0U;
    ctx->Stencil.WriteMask[0] = ~0U;
    ctx->Stencil.WriteMask[1] = ~0U;
+   ctx->Stencil.WriteMask[2] = ~0U;
    ctx->Stencil.Clear = 0;
 }