New transition effect syntax

Instead of this:
(cue 3
   (lighting-state ...)
   (crossfade 3 5))

We now have this:
(cue 3
   (crossfade 3 5
      (lighting-state ...)))

This makes a simple snap blackout very succinct:
(cue 6 (snap blackout))

5 files changed, 73 insertions, 125 deletions

diff --git a/guile/starlet/crossfade.scm b/guile/starlet/crossfade.scm
index 047fce9..65393b7 100644
--- a/guile/starlet/crossfade.scm
+++ b/guile/starlet/crossfade.scm
@@ -1,7 +1,7 @@
 ;;
 ;; starlet/crossfade.scm
 ;;
-;; Copyright © 2020-2021 Thomas White <taw@bitwiz.org.uk>
+;; Copyright © 2020-2023 Thomas White <taw@bitwiz.org.uk>
 ;;
 ;; This file is part of Starlet.
 ;;
@@ -24,13 +24,11 @@
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-26)
   #:use-module (ice-9 exceptions)
-  #:use-module (starlet playback)
   #:use-module (starlet clock)
-  #:use-module (starlet cue-list)
+  #:use-module (starlet cue-part)
   #:use-module (starlet colours)
   #:use-module (starlet fixture)
   #:use-module (starlet state)
-  #:use-module (starlet transition-effect)
   #:use-module (starlet attributes)
   #:export (crossfade))
 
@@ -204,21 +202,18 @@
                          (make-exception-with-irritants type))))))
 
 
-(define* (crossfade up-time
-                    #:optional
-                    down-time
-                    #:key
-                    (attr-time #f)
-                    (up-delay 0)
-                    (down-delay 0)
-                    (attr-delay 0))
-  (let* ((real-down-time (if down-time down-time up-time))
-         (real-attr-time (if attr-time attr-time (min up-time real-down-time))))
-    (make-transition
-      (incoming-state current-state clock)
+(define* (crossfade-real incoming-state up-time #:optional (down-time up-time)
+           #:key
+           (attr-time (min up-time down-time))
+           (up-delay 0)
+           (down-delay 0)
+           (attr-delay 0))
+  (cue-part
+    incoming-state
+    (lambda (incoming-state current-state clock)
       (let ((up-clock (make-delayed-clock clock up-delay up-time))
-            (down-clock (make-delayed-clock clock down-delay real-down-time))
-            (attribute-clock (make-delayed-clock clock attr-delay real-attr-time)))
+            (down-clock (make-delayed-clock clock down-delay down-time))
+            (attribute-clock (make-delayed-clock clock attr-delay attr-time)))
         (let ((overlay-state (make-empty-state)))
           (state-for-each
             (lambda (fixture attr target-val)
@@ -256,5 +251,11 @@
           (values overlay-state
                   (max
                     (+ up-time up-delay)
-                    (+ real-down-time down-delay)
-                    (+ real-attr-time attr-delay))))))))
+                    (+ down-time down-delay)
+                    (+ attr-time attr-delay))))))))
+
+
+;; Rearrange the arguments to put the lighting state (last argument)
+;; at the beginning.  This makes optional arguments in crossfade-real possible.
+(define (crossfade . args)
+  (apply crossfade-real (last args) (drop-right args 1)))
diff --git a/guile/starlet/cue-list.scm b/guile/starlet/cue-list.scm
index 681158f..b029713 100644
--- a/guile/starlet/cue-list.scm
+++ b/guile/starlet/cue-list.scm
@@ -33,19 +33,16 @@
   #:use-module (starlet clock)
   #:use-module (starlet utils)
   #:use-module (starlet attributes)
-  #:use-module (starlet transition-effect)
+  #:use-module (starlet cue-part)
   #:use-module (starlet snap-transition)
   #:use-module (starlet crossfade)
   #:export (cue
-            cue-part
             cue-list
             qnum
             get-cue-number
             get-cue-parts
             get-cue-clock
             get-preset-state
-            get-cue-part-state
-            get-cue-part-transition
             cue-number-to-index
             cue-index-to-number
             current-cue-clock
@@ -54,14 +51,6 @@
   #:re-export (snap crossfade))
 
 
-(define-record-type <cue-part>
-  (cue-part state transition)
-  cue-part?
-  (state        get-cue-part-state
-                set-cue-part-state!)
-  (transition   get-cue-part-transition))
-
-
 (define-record-type <cue>
   (make-cue number
             preset-state
@@ -72,7 +61,7 @@
   (number             get-cue-number)
   (preset-state       get-preset-state
                       set-preset-state!)
-  (track-intensities  track-intensities)
+  (track-intensities  track-intensities?)
   (cue-parts          get-cue-parts)
   (cue-clock          get-cue-clock))
 
@@ -113,53 +102,25 @@
               (fix-attrs-in-state state)))
 
 
-(define (cue-proc number . args)
-  (receive
-    (states transition-effects cue-parts rest)
-    (categorize args lighting-state? transition-effect? cue-part?)
-
-    (let-keywords
-      rest
-      #f  ;; allow-other-keys?
-      ((track-intensities #f))
-
-      (let ((n-tr-effs (length transition-effects))
-            (n-states (length states)))
-
-        (make-cue (qnum number)
-                  #f   ;; preset state, to be filled later
-                  track-intensities
-
-                  ;; Create the list of cue parts
-                  (cond
-
-                    ;; Only explicitly-stated cue parts
-                    [(= 0 n-tr-effs n-states)
-                     cue-parts]
-
-                    ;; Implicit first cue part
-                    [(= 1 n-tr-effs n-states)
-                     (cons
-                       (cue-part (car states)
-                                 (car transition-effects))
-                       cue-parts)]
-
-                    ;; Wrong number of states or transition effects
-                    [(not (= n-states 1))
-                     (error "Cue must contain exactly one state: " number)]
-                    [(not (= n-tr-effs 1))
-                     (error "Cue must contain exactly one transition effect: " number)])
-
-                  (current-cue-clock))))))
-
 
 (define current-cue-clock (make-parameter #f))
 
 (define-syntax cue
-  (syntax-rules ()
-    ((_ body ...)
+  (syntax-rules (track-intensities)
+    ((_ number track-intensities body ...)
+     (parameterize ((current-cue-clock (make-clock #:stopped #t)))
+       (make-cue (qnum number)
+                 #f   ;; preset state, to be filled later
+                 #t   ;; DO track intensities
+                 (list body ...)
+                 (current-cue-clock))))
+    ((_ number body ...)
      (parameterize ((current-cue-clock (make-clock #:stopped #t)))
-       (cue-proc body ...)))))
+       (make-cue (qnum number)
+                 #f   ;; preset state, to be filled later
+                 #f   ;; don't track intensities
+                 (list body ...)
+                 (current-cue-clock))))))
 
 
 (define (track-all-cues! the-cue-list)
@@ -167,7 +128,7 @@
     (lambda (idx prev-state the-cue)
       (let ((the-tracked-state (lighting-state
                                  (apply-state prev-state)
-                                 (unless (track-intensities the-cue)
+                                 (unless (track-intensities? the-cue)
                                    (blackout!))
                                  (apply-state
                                    (get-cue-part-state
@@ -242,9 +203,7 @@
              (list->vector
                (remove unspecified?
                        (list
-                         (cue 0
-                              (make-empty-state)
-                              (snap))
+                         (cue 0 (snap blackout))
                          body ...)))))
        (track-all-cues! the-cue-list)
        (preset-all-cues! the-cue-list)
diff --git a/guile/starlet/transition-effect.scm b/guile/starlet/cue-part.scm
index 43b7a6e..e98e422 100644
--- a/guile/starlet/transition-effect.scm
+++ b/guile/starlet/cue-part.scm
@@ -1,7 +1,7 @@
 ;;
-;; starlet/transition-effect.scm
+;; starlet/cue-part
 ;;
-;; Copyright © 2021-2022 Thomas White <taw@bitwiz.org.uk>
+;; Copyright © 2020-2023 Thomas White <taw@bitwiz.org.uk>
 ;;
 ;; This file is part of Starlet.
 ;;
@@ -18,28 +18,18 @@
 ;; You should have received a copy of the GNU General Public License
 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ;;
-(define-module (starlet transition-effect)
-  #:use-module (oop goops)
-  #:export (<transition-effect>
-             transition-effect?
-             transition-func
-             make-transition))
+(define-module (starlet cue-part)
+  #:use-module (srfi srfi-9)
+  #:export (cue-part
+            <cue-part>
+            get-cue-part-state
+            get-cue-part-transition
+            set-cue-part-state!))
 
 
-(define-class <transition-effect> (<object>)
-  (func
-    #:init-value #f
-    #:init-keyword #:func
-    #:getter transition-func))
-
-
-(define (transition-effect? a)
-  (is-a? a <transition-effect>))
-
-
-(define-syntax make-transition
-  (syntax-rules ()
-    ((_ (a b c) expr ...)
-     (make <transition-effect>
-           #:func (lambda (a b c)
-                    expr ...)))))
+(define-record-type <cue-part>
+  (cue-part state transition)
+  cue-part?
+  (state        get-cue-part-state
+                set-cue-part-state!)
+  (transition   get-cue-part-transition))
diff --git a/guile/starlet/playback.scm b/guile/starlet/playback.scm
index 2d20137..423abd2 100644
--- a/guile/starlet/playback.scm
+++ b/guile/starlet/playback.scm
@@ -34,8 +34,8 @@
   #:use-module (starlet utils)
   #:use-module (starlet clock)
   #:use-module (starlet cue-list)
+  #:use-module (starlet cue-part)
   #:use-module (starlet colours)
-  #:use-module (starlet transition-effect)
   #:use-module (starlet attributes)
   #:export (make-playback
             cut-to-cue-number!
@@ -303,8 +303,8 @@
     ;; "main" transition effect
     (receive
       (overlay-part transition-time)
-      ((transition-func (get-cue-part-transition
-                          (car (get-cue-parts the-cue))))
+      ((get-cue-part-transition
+         (car (get-cue-parts the-cue)))
        (blank-everything pb)
        pb
        cue-clock)
@@ -318,7 +318,7 @@
       (lambda (part)
         (receive
           (overlay-part transition-time)
-          ((transition-func (get-cue-part-transition part))
+          ((get-cue-part-transition part)
            (get-cue-part-state part)
            pb
            cue-clock)
diff --git a/guile/starlet/snap-transition.scm b/guile/starlet/snap-transition.scm
index e658b73..46993cd 100644
--- a/guile/starlet/snap-transition.scm
+++ b/guile/starlet/snap-transition.scm
@@ -1,7 +1,7 @@
 ;;
 ;; starlet/snap-transition.scm
 ;;
-;; Copyright © 2021 Thomas White <taw@bitwiz.org.uk>
+;; Copyright © 2021-2023 Thomas White <taw@bitwiz.org.uk>
 ;;
 ;; This file is part of Starlet.
 ;;
@@ -19,11 +19,8 @@
 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ;;
 (define-module (starlet snap-transition)
-  #:use-module (oop goops)
-  #:use-module (starlet playback)
+  #:use-module (starlet cue-part)
   #:use-module (starlet state)
-  #:use-module (starlet fixture)
-  #:use-module (starlet transition-effect)
   #:use-module (starlet attributes)
   #:export (snap))
 
@@ -39,15 +36,16 @@
     out-state))
 
 
-(define (snap)
-  (make-transition
-    (incoming-state current-state clock)
-    (let ((overlay-state (blank-everything current-state)))
-      (state-for-each
-        (lambda (fix attr val)
-          (set-in-state! overlay-state
-                         fix
-                         attr
-                         (lambda () val)))
-        incoming-state)
-      (values overlay-state 0))))
+(define (snap to-state)
+  (cue-part
+    to-state
+    (lambda (incoming-state current-state clock)
+      (let ((overlay-state (blank-everything current-state)))
+        (state-for-each
+          (lambda (fix attr val)
+            (set-in-state! overlay-state
+                           fix
+                           attr
+                           (lambda () val)))
+          incoming-state)
+        (values overlay-state 0)))))