mesa: document a/s keys
diff --git a/progs/xdemos/glthreads.c b/progs/xdemos/glthreads.c
index 767aef9..b90e6b4 100644
--- a/progs/xdemos/glthreads.c
+++ b/progs/xdemos/glthreads.c
@@ -565,6 +565,8 @@
    printf("Keyboard:\n");
    printf("   Esc  Exit\n");
    printf("   t    Change texture image (requires -t option)\n");
+   printf("   a    Toggle animation\n");
+   printf("   s    Step rotation (when not animating)\n");
 }