From d7a1dc1d7b80bb4614ffd9bdd36995746403984c Mon Sep 17 00:00:00 2001
From: viciious <vluchits@gmail.com>
Date: Fri, 21 Jun 2024 11:53:25 +0300
Subject: [PATCH] Support panning for Ricoh chips

---
 src-md/crt0.s |  8 ++++++++
 src-md/vgm.c  | 20 +++++++++++++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src-md/crt0.s b/src-md/crt0.s
index e21c2d90c..3412d0110 100644
--- a/src-md/crt0.s
+++ b/src-md/crt0.s
@@ -2646,6 +2646,7 @@ bump_fm:
         move.b  RF5C68_ENV.w,rf5c68_envelope
         move.b  RF5C68_CHN.w,rf5c68_chanmask
         move.b  RF5C68_CTL.w,rf5c68_chanctl
+        move.b  RF5C68_PAN.w,rf5c68_pan
         bra.b   7f
 
 6:
@@ -2705,8 +2706,12 @@ bump_fm:
         tst.w   pcm_env
         beq.b   20f                 /* PCM muted */
 
+        moveq   #0,d1
         move.b  rf5c68_envelope,d1
+        swap.w  d1
+        move.b  rf5c68_pan,d1
         move.l  d1,-(sp)
+        moveq   #0,d1
         move.w  rf5c68_freq_incr,d1
         move.l  d1,-(sp)
         move.w  rf5c68_loop_ofs,d1
@@ -3195,7 +3200,10 @@ rf5c68_envelope:
         dc.b    0
 rf5c68_chanmask:
         dc.b    255
+rf5c68_pan:
+        dc.b    128
 
+        .align  2
 offs68k:
         dc.w    0
 offsz80:
diff --git a/src-md/vgm.c b/src-md/vgm.c
index a685aed05..54acea5f8 100644
--- a/src-md/vgm.c
+++ b/src-md/vgm.c
@@ -237,12 +237,26 @@ void vgm_stop_rf5c68_samples(int chan)
     scd_queue_stop_src(VGM_MCD_SOURCE_ID+chan);
 }
 
-void vgm_play_rf5c68_samples(int chan, int offset, int loopstart, int incr, int vol)
+static uint8_t vgm_midipan2lcf(uint8_t pan)
+{
+    if (pan == 0b00001111) {
+        return 0; // full left
+    } else if (pan == 255) {
+        // no panning
+        return pan;
+    } else {
+        return (pan & 0xf0) | ((256 - pan) >> 4);
+    }
+}
+
+void vgm_play_rf5c68_samples(int chan, int offset, int loopstart, int incr, int volpan)
 {
     //int freq = ((uint16_t)incr * 32604) >> 11;
     int freq = incr << 4; // good enough
     int length = loopstart - offset;
     void *ptr = (char *)MCD_WORDRAM_VGM_PTR + rf5c68_dataofs + offset;
+    int vol = (volpan >> 16) & 0xff;
+    int pan = vgm_midipan2lcf(volpan & 0xff);
 
     if (!cd_ok)
         return;
@@ -252,7 +266,7 @@ void vgm_play_rf5c68_samples(int chan, int offset, int loopstart, int incr, int
     if (loopstart == 0)
     {
         // hacky hack
-        scd_queue_update_src(VGM_MCD_SOURCE_ID+chan, freq, 128, vol, 0);
+        scd_queue_update_src(VGM_MCD_SOURCE_ID+chan, freq, pan, vol, 0);
         return;
     }
 
@@ -260,7 +274,7 @@ void vgm_play_rf5c68_samples(int chan, int offset, int loopstart, int incr, int
         return;
 
     scd_queue_setptr_buf(VGM_MCD_BUFFER_ID+chan, ptr, length);
-    scd_queue_play_src(VGM_MCD_SOURCE_ID+chan, VGM_MCD_BUFFER_ID+chan, freq, 128, vol, 0);
+    scd_queue_play_src(VGM_MCD_SOURCE_ID+chan, VGM_MCD_BUFFER_ID+chan, freq, pan, vol, 0);
 }
 
 void vgm_stop_samples(void)