mesa: add EXT_texture_compression_latc

The encoding/decoding algorithms are shared with RGTC.
Thanks to some magic with the base format, the RGTC texstore functions work
for LATC too.

swrast passes the related piglit tests besides two things:
- The alpha channel is wrong (it's always 1), however the incorrect alpha
  channel makes some other tests fail too, so I guess it's unrelated to LATC.
- Signed LATC fetches aren't correct yet (signed values are clamped to [0,1]),
  however RGTC has the same problem.

Further testing (with other of my patches) shows that hardware drivers
and softpipe work.

BTW, ETQW uses this extension.

1 files changed, 40 insertions, 0 deletions

diff --git a/src/mesa/main/formats.c b/src/mesa/main/formats.c
index 947db84a69..db10c9b4c2 100644
--- a/src/mesa/main/formats.c
+++ b/src/mesa/main/formats.c
@@ -927,6 +927,42 @@ static struct gl_format_info format_info[MESA_FORMAT_COUNT] =
      0, 0, 0, 0, 0,
      4, 4, 16                     /* 16 bytes per 4x4 block */
    },
+   {
+     MESA_FORMAT_L_LATC1,
+     "MESA_FORMAT_L_LATC1",
+     GL_LUMINANCE,
+     GL_UNSIGNED_NORMALIZED,
+     0, 0, 0, 0,
+     4, 0, 0, 0, 0,
+     4, 4, 8                     /* 8 bytes per 4x4 block */
+   },
+   {
+     MESA_FORMAT_SIGNED_L_LATC1,
+     "MESA_FORMAT_SIGNED_L_LATC1",
+     GL_LUMINANCE,
+     GL_SIGNED_NORMALIZED,
+     0, 0, 0, 0,
+     4, 0, 0, 0, 0,
+     4, 4, 8                     /* 8 bytes per 4x4 block */
+   },
+   {
+     MESA_FORMAT_LA_LATC2,
+     "MESA_FORMAT_LA_LATC2",
+     GL_LUMINANCE_ALPHA,
+     GL_UNSIGNED_NORMALIZED,
+     0, 0, 0, 4,
+     4, 0, 0, 0, 0,
+     4, 4, 16                     /* 16 bytes per 4x4 block */
+   },
+   {
+     MESA_FORMAT_SIGNED_LA_LATC2,
+     "MESA_FORMAT_SIGNED_LA_LATC2",
+     GL_LUMINANCE_ALPHA,
+     GL_SIGNED_NORMALIZED,
+     0, 0, 0, 4,
+     4, 0, 0, 0, 0,
+     4, 4, 16                     /* 16 bytes per 4x4 block */
+   },
 };
 
 
@@ -1570,6 +1606,10 @@ _mesa_format_to_type_and_comps(gl_format format,
    case MESA_FORMAT_SIGNED_RED_RGTC1:
    case MESA_FORMAT_RG_RGTC2:
    case MESA_FORMAT_SIGNED_RG_RGTC2:
+   case MESA_FORMAT_L_LATC1:
+   case MESA_FORMAT_SIGNED_L_LATC1:
+   case MESA_FORMAT_LA_LATC2:
+   case MESA_FORMAT_SIGNED_LA_LATC2:
       /* XXX generate error instead? */
       *datatype = GL_UNSIGNED_BYTE;
       *comps = 0;