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, 17 insertions, 0 deletions

diff --git a/src/mesa/main/texcompress_rgtc.h b/src/mesa/main/texcompress_rgtc.h
index 424edc4581c..18766770d74 100644
--- a/src/mesa/main/texcompress_rgtc.h
+++ b/src/mesa/main/texcompress_rgtc.h
@@ -57,4 +57,21 @@ _mesa_fetch_texel_2d_f_rg_rgtc2(const struct gl_texture_image *texImage,
 extern void
 _mesa_fetch_texel_2d_f_signed_rg_rgtc2(const struct gl_texture_image *texImage,
 				       GLint i, GLint j, GLint k, GLfloat *texel);
+
+extern void
+_mesa_fetch_texel_2d_f_l_latc1(const struct gl_texture_image *texImage,
+                                 GLint i, GLint j, GLint k, GLfloat *texel);
+
+extern void
+_mesa_fetch_texel_2d_f_signed_l_latc1(const struct gl_texture_image *texImage,
+                                        GLint i, GLint j, GLint k, GLfloat *texel);
+
+extern void
+_mesa_fetch_texel_2d_f_la_latc2(const struct gl_texture_image *texImage,
+                                 GLint i, GLint j, GLint k, GLfloat *texel);
+
+extern void
+_mesa_fetch_texel_2d_f_signed_la_latc2(const struct gl_texture_image *texImage,
+                                       GLint i, GLint j, GLint k, GLfloat *texel);
+
 #endif