Constant source nodes

src/cljs_bach/synthesis.cljs

@@ -195,6 +195,45 @@
 (def ^:export square (partial oscillator "square"))
 (def ^:export triangle (partial oscillator "triangle"))
 
+; Inputs (constant source nodes)
+
+(defn set-input! [input val]
+  "Set the value of an input (with immediate effect)."
+  (set! (-> input .-offset .-value) val))
+
+(defn make-input! [context init-val]
+  "Create a mutable 'input' (constant source node)."
+  (let [input (.createConstantSource context)]
+    (doto input
+      (.start)
+      (set-input! init-val))))
+
+(defn ramp-end-time [input target vel]
+  "Calculates the end time (according to the clock of the given
+  input's audio context) for ramping input to the target value at a
+  rate of vel (which is the value-change per second)."
+  (let [now (-> input .-context .-currentTime)
+        current-val (-> input .-offset .-value)
+        val-diff (.abs js/Math (- current-val target))
+        ramp-duration (/ val-diff vel)]
+    (+ now ramp-duration)))
+
+(defn lin-ramp-input! [input target vel]
+  "Linearly ramp the given input's value toward the target value at
+  the given change/sec velociy."
+  (let [end-time (ramp-end-time input target vel)]
+    (-> input .-offset (.linearRampToValueAtTime target end-time))))
+
+(defn exp-ramp-input! [input target vel]
+  "Exponentially ramp the given input's value toward the target value
+  at the given change/sec velociy."
+  (let [end-time (ramp-end-time input target vel)]
+    (-> input .-offset (.exponentialRampToValueAtTime target end-time))))
+
+(defn jack [input]
+  "Wrap an input so that it can be used as a source node."
+  (fn [context at duration]
+    (subgraph input)))
 
 ; Filters