From 0e47b13d833b3a7e5f826b2af59f6cea2debf28a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Hillerstr=C3=B6m?= <progr@mmer.nu>
Date: Sat, 21 Nov 2015 02:26:04 +0100
Subject: [PATCH] Implement all vibrato waveforms

---
 xmeffects.js | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/xmeffects.js b/xmeffects.js
index 27d2eda..dad153d 100644
--- a/xmeffects.js
+++ b/xmeffects.js
@@ -65,7 +65,7 @@ function eff_t0_4(ch, data) {  // vibrato
 }
 
 function eff_t1_4(ch) {  // vibrato
-  ch.periodoffset = Math.sin(ch.vibratopos * Math.PI / 32) * ch.vibratodepth;
+  ch.periodoffset = getVibratoDelta(ch.vibratotype, ch.vibratopos) * ch.vibratodepth;
   if (isNaN(ch.periodoffset)) {
     console.log("vibrato periodoffset NaN?",
         ch.vibratopos, ch.vibratospeed, ch.vibratodepth);
@@ -75,6 +75,24 @@ function eff_t1_4(ch) {  // vibrato
   ch.vibratopos &= 63;
 }
 
+function getVibratoDelta(type, x) {
+  var delta = 0;
+  switch (type & 0x03) {
+    case 1: // sawtooth (ramp-down)
+      delta = ((1 + x * 2 / 64) % 2) - 1;
+      break;
+    case 2: // square
+    case 3: // random (in FT2 these two are the same)
+      delta = x < 32 ? 1 : -1;
+      break;
+    case 0:
+    default: // sine
+      delta = Math.sin(x * Math.PI / 32);
+      break;
+  }
+  return delta;
+}
+
 function eff_t1_5(ch) {  // portamento + volume slide
   eff_t1_a(ch);
   eff_t1_3(ch);