mesa: Add support for GL_ARB_ubo's glGetActiveUniformName().

This is like a stripped-down version of glGetActiveUniform that just
returns the name, since the other return values (type and size) of
that function are now meant to be handled with
glGetActiveUniformsiv().

Fixes piglit ARB_uniform_buffer_object/getactiveuniformname

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/main/uniforms.c

@@ -752,6 +752,44 @@ _mesa_GetActiveUniformBlockName(GLuint program,
    }
 }
 
+static void GLAPIENTRY
+_mesa_GetActiveUniformName(GLuint program, GLuint uniformIndex,
+			   GLsizei bufSize, GLsizei *length,
+			   GLchar *uniformName)
+{
+   GET_CURRENT_CONTEXT(ctx);
+   struct gl_shader_program *shProg;
+
+   if (!ctx->Extensions.ARB_uniform_buffer_object) {
+      _mesa_error(ctx, GL_INVALID_OPERATION, "glGetActiveUniformBlockiv");
+      return;
+   }
+
+   if (bufSize < 0) {
+      _mesa_error(ctx, GL_INVALID_VALUE,
+		  "glGetActiveUniformName(bufSize %d < 0)",
+		  bufSize);
+      return;
+   }
+
+   ASSERT_OUTSIDE_BEGIN_END(ctx);
+
+   shProg = _mesa_lookup_shader_program_err(ctx, program, "glGetActiveUniformName");
+
+   if (!shProg)
+      return;
+
+   if (uniformIndex >= shProg->NumUserUniformStorage) {
+      _mesa_error(ctx, GL_INVALID_VALUE, "glGetActiveUniform(index)");
+      return;
+   }
+
+   if (uniformName) {
+      _mesa_copy_string(uniformName, bufSize, length,
+			shProg->UniformStorage[uniformIndex].name);
+   }
+}
+
 /**
  * Plug in shader uniform-related functions into API dispatch table.
  */
@@ -815,6 +853,7 @@ _mesa_init_shader_uniform_dispatch(struct _glapi_table *exec)
    SET_GetActiveUniformsiv(exec, _mesa_GetActiveUniformsiv);
    SET_GetActiveUniformBlockiv(exec, _mesa_GetActiveUniformBlockiv);
    SET_GetActiveUniformBlockName(exec, _mesa_GetActiveUniformBlockName);
+   SET_GetActiveUniformName(exec, _mesa_GetActiveUniformName);
    SET_UniformBlockBinding(exec, _mesa_UniformBlockBinding);
 
 #endif /* FEATURE_GL */