glsl: Distinguish between no interpolation qualifier and 'smooth'

Previously, we treated the 'smooth' qualifier as equivalent to no
qualifier at all.  However, this is incorrect for the built-in color
variables (gl_FrontColor, gl_BackColor, gl_FrontSecondaryColor, and
gl_BackSecondaryColor).  For those variables, if there is no qualifier
at all, interpolation should be flat if the shade model is GL_FLAT,
and smooth if the shade model is GL_SMOOTH.

To make this possible, I added a new value to the
glsl_interp_qualifier enum, INTERP_QUALIFIER_NONE.

Reviewed-by: Kenneth Graunke <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 4ea8764b68f..0c0cccbd034 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -283,6 +283,10 @@ public:
     * \return The string that would be used in a shader to specify \c
     * mode will be returned.
     *
+    * This function is used to generate error messages of the form "shader
+    * uses %s interpolation qualifier", so in the case where there is no
+    * interpolation qualifier, it returns "no".
+    *
     * This function should only be used on a shader input or output variable.
     */
    const char *interpolation_string() const;