Introduce new type for attribute names

There's a serious problem with the design so far, where symbols are used
for attribute names (intensity, strobe, colour etc), and also for
attribute values (on, off, random etc).  There's no way for 'at' to
tell the difference between the two.  For example, this form is
ambiguous:  (at myfixture 'strobe 'on)

This commit introduces a new class, <starlet-attribute>, to replace the
use of symbols here.  The attributes are enumerated in (starlet attributes),
and new ones can be added later.  The attribute objects remember their
'canonical' names, to allow states to be printed.

Apart from solving the ambiguity problem, this has two further
advantages.  First, attribute names no longer need to be quoted
everywhere.  Second, multiple names can be used to refer to the same
attribute.  For example: (define color colour).

1 files changed, 10 insertions, 9 deletions

diff --git a/guile/starlet/fixture-library/stairville/z120m.scm b/guile/starlet/fixture-library/stairville/z120m.scm
index 46cd6cd..e1f40af 100644
--- a/guile/starlet/fixture-library/stairville/z120m.scm
+++ b/guile/starlet/fixture-library/stairville/z120m.scm
@@ -21,6 +21,7 @@
 (define-module (starlet fixture-library stairville z120m)
   #:use-module (starlet scanout)
   #:use-module (starlet fixture)
+  #:use-module (starlet attributes)
   #:use-module (starlet utils)
   #:use-module (starlet colours)
   #:export (<stairville-z120m-6ch>))
@@ -30,27 +31,27 @@
   <stairville-z120m-6ch>
 
   (fixture-attributes
-    (attr-continuous 'intensity '(0 100) 0)
-    (attr-colour 'colour white)
-    (attr-continuous 'strobe-frequency '(1 25) 1)
-    (attr-list 'strobe '(off on random) 'off))
+    (attr-continuous intensity '(0 100) 0)
+    (attr-colour colour white)
+    (attr-continuous strobe-frequency '(1 25) 1)
+    (attr-list strobe '(off on random) 'off))
 
-  (let ((intensity (get-attr 'intensity))
-        (rgbw (colour-as-rgbw (get-attr 'colour))))
+  (let ((intensity (get-attr intensity))
+        (rgbw (colour-as-rgbw (get-attr colour))))
     (set-chan8 1 (percent->dmxval8 intensity))
     (set-chan8 3 (percent->dmxval8 (car rgbw)))
     (set-chan8 4 (percent->dmxval8 (cadr rgbw)))
     (set-chan8 5 (percent->dmxval8 (caddr rgbw)))
     (set-chan8 6 (percent->dmxval8 (cadddr rgbw))))
   (cond
-    ((eq? (get-attr 'strobe) 'on)
+    ((eq? (get-attr strobe) 'on)
      (set-chan8 2 (scale-and-clamp-to-range
                     (get-attr 'strobe-frequency)
                     '(1 25)
                     '(106 165))))
-    ((eq? (get-attr 'strobe) 'random)
+    ((eq? (get-attr strobe) 'random)
      (set-chan8 2 (scale-and-clamp-to-range
-                    (get-attr 'strobe-frequency)
+                    (get-attr strobe-frequency)
                     '(1 25)
                     '(181 240))))
     (else (set-chan8 2 255))))