st/mesa: optionally apply texture swizzle to border color v2

This is the only sane solution for nv50 and nvc0 (really, trust me),
but since on other hardware the border colour is tightly coupled with
texture state they'd have to undo the swizzle, so I've added a cap.

The dependency of update_sampler on the texture updates was
introduced to avoid doing the apply_depthmode to the swizzle twice.

v2: Moved swizzling helper to u_format.c, extended the CAP to
provide more accurate information.

src/mesa/state_tracker/st_atom_sampler.c

@@ -48,6 +48,8 @@
 
 #include "cso_cache/cso_context.h"
 
+#include "util/u_format.h"
+
 
 /**
  * Convert GLenum texcoord wrap tokens to pipe tokens.
@@ -172,8 +174,10 @@ convert_sampler(struct st_context *st,
        msamp->BorderColor.ui[1] ||
        msamp->BorderColor.ui[2] ||
        msamp->BorderColor.ui[3]) {
+      struct st_texture_object *stobj = st_texture_object(texobj);
       struct gl_texture_image *teximg;
       GLboolean is_integer = GL_FALSE;
+      union pipe_color_union border_color;
 
       teximg = texobj->Image[0][texobj->BaseLevel];
 
@@ -181,9 +185,26 @@ convert_sampler(struct st_context *st,
          is_integer = _mesa_is_enum_format_integer(teximg->InternalFormat);
       }
 
-      st_translate_color(&msamp->BorderColor,
-                         &sampler->border_color,
-                         teximg ? teximg->_BaseFormat : GL_RGBA, is_integer);
+      if (st->apply_texture_swizzle_to_border_color && stobj->sampler_view) {
+         const unsigned char swz[4] =
+         {
+            stobj->sampler_view->swizzle_r,
+            stobj->sampler_view->swizzle_g,
+            stobj->sampler_view->swizzle_b,
+            stobj->sampler_view->swizzle_a,
+         };
+
+         st_translate_color(&msamp->BorderColor,
+                            &border_color,
+                            teximg ? teximg->_BaseFormat : GL_RGBA, is_integer);
+
+         util_format_apply_color_swizzle(&sampler->border_color,
+                                         &border_color, swz, is_integer);
+      } else {
+         st_translate_color(&msamp->BorderColor,
+                            &sampler->border_color,
+                            teximg ? teximg->_BaseFormat : GL_RGBA, is_integer);
+      }
    }
 
    sampler->max_anisotropy = (msamp->MaxAnisotropy == 1.0 ?