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, 18 insertions, 0 deletions

diff --git a/src/mesa/main/texcompress.c b/src/mesa/main/texcompress.c
index 82d02ed0ec..942d996695 100644
--- a/src/mesa/main/texcompress.c
+++ b/src/mesa/main/texcompress.c
@@ -173,6 +173,15 @@ _mesa_glenum_to_compressed_format(GLenum format)
    case GL_COMPRESSED_SIGNED_RG_RGTC2:
       return MESA_FORMAT_SIGNED_RG_RGTC2;
 
+   case GL_COMPRESSED_LUMINANCE_LATC1_EXT:
+      return MESA_FORMAT_L_LATC1;
+   case GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT:
+      return MESA_FORMAT_SIGNED_L_LATC1;
+   case GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT:
+      return MESA_FORMAT_LA_LATC2;
+   case GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT:
+      return MESA_FORMAT_SIGNED_LA_LATC2;
+
    default:
       return MESA_FORMAT_NONE;
    }
@@ -229,6 +238,15 @@ _mesa_compressed_format_to_glenum(struct gl_context *ctx, GLuint mesaFormat)
    case MESA_FORMAT_SIGNED_RG_RGTC2:
       return GL_COMPRESSED_SIGNED_RG_RGTC2;
 
+   case MESA_FORMAT_L_LATC1:
+      return GL_COMPRESSED_LUMINANCE_LATC1_EXT;
+   case MESA_FORMAT_SIGNED_L_LATC1:
+      return GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT;
+   case MESA_FORMAT_LA_LATC2:
+      return GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT;
+   case MESA_FORMAT_SIGNED_LA_LATC2:
+      return GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT;
+
    default:
       _mesa_problem(ctx, "Unexpected mesa texture format in"
                     " _mesa_compressed_format_to_glenum()");