From b04e6c00b0824d3dc409b48e8c3cdba5854ce3b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Hillerstr=C3=B6m?= <progr@mmer.nu>
Date: Fri, 13 Nov 2015 22:06:43 +0100
Subject: [PATCH 1/4] Introduce a global volume variable

---
 xm.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/xm.js b/xm.js
index ff31034..462b42e 100644
--- a/xm.js
+++ b/xm.js
@@ -22,6 +22,7 @@ player.cur_row = 64;
 player.cur_ticksamp = 0;
 player.cur_tick = 6;
 player.xm = {};  // contains all song data
+player.xm.global_volume = player.max_global_volume = 128;
 
 // exposed for testing
 player.nextTick = nextTick;
@@ -369,8 +370,8 @@ function MixChannelIntoBuf(ch, start, end, dataL, dataR) {
   var volE = ch.volE / 64.0;    // current volume envelope
   var panE = 4*(ch.panE - 32);  // current panning envelope
   var p = panE + ch.pan - 128;  // final pan
-  var volL = volE * (128 - p) * ch.vol / 8192.0;
-  var volR = volE * (128 + p) * ch.vol / 8192.0;
+  var volL = player.xm.global_volume * volE * (128 - p) * ch.vol / (64 * 128 * 128);
+  var volR = player.xm.global_volume * volE * (128 + p) * ch.vol / (64 * 128 * 128);
   if (volL < 0) volL = 0;
   if (volR < 0) volR = 0;
   if (volR === 0 && volL === 0)
@@ -645,6 +646,7 @@ function load(arrayBuf) {
   player.xm.tempo = dv.getUint16(0x4c, true);
   player.xm.bpm = dv.getUint16(0x4e, true);
   player.xm.channelinfo = [];
+  player.xm.global_volume = player.max_global_volume;
 
   var i, j, k;
 
@@ -915,6 +917,7 @@ function stop() {
   player.cur_row = 64;
   player.cur_songpos = -1;
   player.cur_ticksamp = 0;
+  player.xm.global_volume = player.max_global_volume;
   if (XMView.stop) XMView.stop();
   init();
 }

From eff3fd1ed6dfcb72a1817ae6ebdea8748bd95d2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Hillerstr=C3=B6m?= <progr@mmer.nu>
Date: Sat, 14 Nov 2015 13:04:29 +0100
Subject: [PATCH 2/4] Implement the Gxx effect

---
 xmeffects.js | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/xmeffects.js b/xmeffects.js
index 5832d3d..7dffb75 100644
--- a/xmeffects.js
+++ b/xmeffects.js
@@ -182,6 +182,16 @@ function eff_t0_f(ch, data) {  // set tempo
   }
 }
 
+function eff_t0_g(ch, data) {  // set global volume
+  if (data <= 0x40) {
+    // volume gets multiplied by 2 to match
+    // the initial max global volume of 128
+    player.xm.global_volume = Math.max(0, data * 2);
+  } else {
+    player.xm.global_volume = player.max_global_volume;
+  }
+}
+
 function eff_t0_r(ch, data) {  // retrigger
   if (data & 0x0f) ch.retrig = (ch.retrig & 0xf0) + (data & 0x0f);
   if (data & 0xf0) ch.retrig = (ch.retrig & 0x0f) + (data & 0xf0);
@@ -234,7 +244,7 @@ player.effects_t0 = [  // effect functions on tick 0
   eff_t0_d,  // d
   eff_t0_e,  // e
   eff_t0_f,  // f
-  eff_unimplemented_t0,  // g
+  eff_t0_g,  // g
   eff_unimplemented_t0,  // h
   eff_unimplemented_t0,  // i
   eff_unimplemented_t0,  // j
@@ -273,7 +283,7 @@ player.effects_t1 = [  // effect functions on tick 1+
   null,   // d
   eff_t1_e,  // e
   null,   // f
-  eff_unimplemented,  // g
+  null,  // g
   eff_unimplemented,  // h
   eff_unimplemented,  // i
   eff_unimplemented,  // j

From 88584b9cd09d1c48cabdf959f771ea484308c607 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Hillerstr=C3=B6m?= <progr@mmer.nu>
Date: Sat, 14 Nov 2015 13:04:43 +0100
Subject: [PATCH 3/4] Add test case for Gxx

---
 test/effects.js | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/test/effects.js b/test/effects.js
index 247fec6..056c2ef 100644
--- a/test/effects.js
+++ b/test/effects.js
@@ -152,3 +152,25 @@ exports['test 4xy vibrato'] = function(assert) {
   assert.equal(p.toFixed(3), "-1.546", 'row 5 tick 1 period -1.546');
 };
 
+exports['test Gxx global volume'] = function(assert) {
+  var xm = testdata.resetXMData();
+  // [pat][row][channel]
+  // 1 channel, 3 row blank pattern
+  xm.patterns = [
+    [
+      [[48, 1, -1, 16, 0x40]], // C-4  1 -- G40
+      [[48, 1, -1, 16, 0x2B]], // C-4  1 -- G2B
+      // test out of bounds volume
+      [[48, 1, -1, 16, 0x80]]  // C-4  1 -- G80
+    ]
+  ];
+  XMPlayer.xm.tempo = 1;
+  XMPlayer.nextTick();
+  // volume gets multiplied by 2 to match
+  // the initial max global volume of 128
+  assert.equal(XMPlayer.xm.global_volume, 0x40*2, 'global volume set to 0x40');
+  XMPlayer.nextTick();
+  assert.equal(XMPlayer.xm.global_volume, 0x2B*2, 'global volume set to 0x2B');
+  XMPlayer.nextTick();
+  assert.equal(XMPlayer.xm.global_volume, 0x40*2, 'global volume set to 0x40');
+};

From 8fe05fb89d1e4ec395df63579f41ae24204bcaff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Hillerstr=C3=B6m?= <progr@mmer.nu>
Date: Sat, 14 Nov 2015 13:07:51 +0100
Subject: [PATCH 4/4] Remove Gxx from missing effects

---
 index.html | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/index.html b/index.html
index 0dfe25d..7dca2ce 100644
--- a/index.html
+++ b/index.html
@@ -74,7 +74,7 @@ todo:
  - missing XM effects:
    - E3x, E4x, E5x, E6x, E7x, E9x, EDx, EEx
    - 7xy - tremolo
-   - Gxx, Hxy, Kxx, Lxx, Pxy, Txy
+   - Hxy, Kxx, Lxx, Pxy, Txy
  - render pattern with the wider fonts for fewer channels
  - fix occasional rendering/audio hiccups when switching songs
 </pre>