Add directionality to examples/growth

*There is a bug in here, but it may be in Interface.*
The sphere entities have a lifetime of 60s.
The first time the script is run, each click fires one clickReleaseOnEntity event.
If the entities expire (lifetime is reached), and the script is rerun a second time,
each click will fire two clickReleaseOnEntity events.
If this is repeated (waiting for expiration each time), then
the N-th repetition will fire N clickReleaseOnEntity events.
Note that each entity, across runs, has a unique uuid, as expected.

examples/growth.js

@@ -8,40 +8,87 @@
 //  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
 //
 var RADIUS = 5;
-var LIFETIME = 6000;
+var LIFETIME = 60; // only keep these entities around for a minute
+
+var SIZE = 1; // starting size
+var SIZE_MAX = 3;
+var SIZE_MIN = 0.5;
 
-var size = 1;
 var center = MyAvatar.position;
 var positions = [
     Vec3.sum(center, Vec3.multiply(RADIUS, Vec3.FRONT)),
     Vec3.sum(center, Vec3.multiply(-RADIUS, Vec3.FRONT)),
     Vec3.sum(center, Vec3.multiply(RADIUS, Vec3.RIGHT)),
     Vec3.sum(center, Vec3.multiply(-RADIUS, Vec3.RIGHT)),
-    Vec3.sum(center, Vec3.multiply(RADIUS, Vec3.UP)),
-    Vec3.sum(center, Vec3.multiply(-RADIUS, Vec3.UP)),
 ];
 
+// Create spheres around the avatar
 var spheres = map(positions, getSphere);
 
-Script.update.connect(function(delta) {
+// Toggle sphere growth
-    size += delta; // grow by 1 unit/s
+each(spheres, function(sphere) {
-    each(spheres, function(sphere) {
+    var state = {
-        Entities.editEntity(sphere, { dimensions: getDimensions(size) });
+        size: SIZE,
-    });
+        grow: true, // grow/shrink
+        state: false, // mutate/pause
+    };
+
+    // Grow or shrink on click
+    Script.addEventHandler(sphere, 'clickReleaseOnEntity', toggleGrowth);
+    // TODO: Toggle on collisions as well
+
+    function toggleGrowth() {
+        if (state.state) {
+            stop();
+        } else {
+            start();
+        }
+    }
+
+    function start() {
+        var verb = state.grow ? 'grow' : 'shrink';
+        print('starting to '+verb+' '+sphere);
+
+        Script.update.connect(grow);
+        state.state = true;
+    }
+
+    function stop() {
+        print('stopping '+sphere);
+
+        Script.update.disconnect(grow);
+        state.state = false;
+        state.grow = !state.grow;
+    }
+
+    function grow(delta) {
+        if ((state.grow && state.size > SIZE_MAX) || // cannot grow more
+            (!state.grow && state.size < SIZE_MIN)) { // cannot shrink more
+            stop();
+            return;
+        }
+
+        state.size += (state.grow ? 1 : -1) * delta; // grow/shrink
+        Entities.editEntity(sphere, { dimensions: getDimensions(state.size) });
+    }
 });
-Script.scriptEnding.connect(function() {
+
+Script.scriptEnding.connect(function() { // cleanup
     each(spheres, function(sphere) {
         Entities.deleteEntity(sphere);
     });
 });
 
+// NOTE: Everything below this line is a helper.
+//       The basic logic of this example is entirely above this note.
+
 // Entity helpers
 
 function getSphere(position) {
     return Entities.addEntity({
         type: 'Sphere',
         position: position,
-        dimensions: getDimensions(size),
+        dimensions: getDimensions(SIZE),
         color: getColor(),
         gravity: Vec3.ZERO,
         lifetime: LIFETIME,