From 417ebc04afe1fb98c6df4480be8725877697069a Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Sun, 16 May 2021 11:40:47 +0200
Subject: Restore effects using clocks

---
 examples/demo.scm         | 11 +++++------
 guile/starlet/clock.scm   | 19 ++++++++++---------
 guile/starlet/effects.scm | 16 ++++++++++------
 3 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/examples/demo.scm b/examples/demo.scm
index 11f0803..a49bf7b 100644
--- a/examples/demo.scm
+++ b/examples/demo.scm
@@ -93,15 +93,14 @@
 
 
 ;; Functions can be assigned to parameters
-;;   (temporarily disabled - time parameter is gone, should use
-;;      clock objects instead)
-;;(at foh1 'intensity (lambda (time)
-;;                      (* 50
-;;                         (+ 1 (sin (* 2 time))))))
+(let ((clock (make-clock)))
+  (at foh1 'intensity (lambda ()
+                        (* 50
+                           (+ 1 (sin (* 2 (elapsed-time clock))))))))
 
 
 ;; Effects library
-(at floor2 'intensity 100)
+(at floor2 'intensity (flash 1.3))
 (at floor2 'colour (make-colour-cmy 0 0 100))
 (at floor2 'pan 0)
 (at floor2 'tilt (sinewave 0.5 100 170))
diff --git a/guile/starlet/clock.scm b/guile/starlet/clock.scm
index 46dd316..29782a0 100644
--- a/guile/starlet/clock.scm
+++ b/guile/starlet/clock.scm
@@ -32,6 +32,7 @@
 
             clock-stopped?
             clock-reversed?
+            elapsed-time
             elapsed-fraction))
 
 
@@ -45,7 +46,7 @@
 ;; "Real" clocks are straightforward objects for measuring differences in time
 ;; between now and some point in the past, allowing for temporarily "pausing"
 ;; the clock.  The time difference cannot be negative: if the start time is in
-;; the future, then "time-elapsed" will return 0.
+;; the future, then "elapsed-time" will return 0.
 
 (define-class <starlet-clock> (<object>)
   (start-real-time
@@ -74,7 +75,7 @@
   (make <starlet-clock>))
 
 
-(define-method (time-elapsed (clock <starlet-clock>))
+(define-method (elapsed-time (clock <starlet-clock>))
   (if (clock-stopped? clock)
       (get-start-elapsed-time clock)
       (max 0
@@ -91,13 +92,13 @@
 
 ;; Stop the clock running
 (define-method (stop-clock! (clock <starlet-clock>))
-  (set-start-elapsed-time! clock (time-elapsed clock))
+  (set-start-elapsed-time! clock (elapsed-time clock))
   (set-clock-stopped! clock #t))
 
 
 ;; Start the clock running (forwards)
 (define-method (start-clock! (clock <starlet-clock>))
-  (set-start-elapsed-time! clock (time-elapsed clock))
+  (set-start-elapsed-time! clock (elapsed-time clock))
   (set-start-real-time! clock (time-now))
   (set-clock-reversed! clock #f)
   (set-clock-stopped! clock #f))
@@ -105,7 +106,7 @@
 
 ;; Start the clock running, backwards
 (define-method (reverse-clock! (clock <starlet-clock>))
-  (set-start-elapsed-time! clock (time-elapsed clock))
+  (set-start-elapsed-time! clock (elapsed-time clock))
   (set-start-real-time! clock (time-now))
   (set-clock-reversed! clock #t)
   (set-clock-stopped! clock #f))
@@ -139,18 +140,18 @@
   (clock-reversed? (get-parent-clock clock)))
 
 
-(define-method (time-elapsed (clock <starlet-delayed-clock>))
-  (max 0 (- (time-elapsed (get-parent-clock clock))
+(define-method (elapsed-time (clock <starlet-delayed-clock>))
+  (max 0 (- (elapsed-time (get-parent-clock clock))
             (get-delay-time clock))))
 
 
 (define-method (elapsed-fraction (clock <starlet-delayed-clock>))
   (if (= (get-duration clock) 0)
-      (if (> (time-elapsed clock) 0)
+      (if (> (elapsed-time clock) 0)
           1.0
           0.0)
       (min 1.0
-           (/ (time-elapsed clock)
+           (/ (elapsed-time clock)
               (get-duration clock)))))
 
 
diff --git a/guile/starlet/effects.scm b/guile/starlet/effects.scm
index fcffb3c..c14f5a0 100644
--- a/guile/starlet/effects.scm
+++ b/guile/starlet/effects.scm
@@ -19,6 +19,7 @@
 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ;;
 (define-module (starlet effects)
+  #:use-module (starlet clock)
   #:export (flash
              sinewave))
 
@@ -32,12 +33,15 @@
       0))
 
 (define (flash hz)
-  (lambda (time)
-    (square-wave time hz)))
+  (let ((clock (make-clock)))
+    (lambda ()
+      (square-wave (elapsed-time clock)
+                   hz))))
 
 
 (define (sinewave hz range-min range-max)
-  (lambda (time)
-    (+ range-min
-       (* (/ (- range-max range-min) 2)
-          (+ 1 (sin (* 2 pi hz time)))))))
+  (let ((clock (make-clock)))
+    (lambda ()
+      (+ range-min
+         (* (/ (- range-max range-min) 2)
+            (+ 1 (sin (* 2 pi hz (elapsed-time clock)))))))))
-- 
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