From 5acb17200aa6ea911871a8114830dafb5345445b Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Sat, 10 Jan 2026 18:07:53 -0500
Subject: [PATCH] cmdStream: implement panbrello and pan slides

---
 src/engine/cmdStream.cpp | 90 +++++++++++++++++++++++++++++++++++++---
 src/engine/cmdStream.h   |  5 +++
 2 files changed, 90 insertions(+), 5 deletions(-)

diff --git a/src/engine/cmdStream.cpp b/src/engine/cmdStream.cpp
index 170aede4c..35c24bcd6 100644
--- a/src/engine/cmdStream.cpp
+++ b/src/engine/cmdStream.cpp
@@ -212,15 +212,26 @@ bool DivCSPlayer::tick() {
           unsigned char param=stream.readC();
           chan[i].panbrelloDepth=param&15;
           chan[i].panbrelloRate=param>>4;
+          if (chan[i].panbrelloDepth==0) {
+            chan[i].panbrelloPos=0;
+          } else {
+            chan[i].panSpeed=0;
+          }
           break;
         }
-        case 0xce: // pan slide (TODO)
-          stream.readC();
+        case 0xce: // pan slide
+          chan[i].panSpeed=stream.readC();
+          if (chan[i].panSpeed) {
+            // panbrello and slides are incompatible
+            chan[i].panbrelloDepth=0;
+            chan[i].panbrelloRate=0;
+            chan[i].panbrelloPos=0;
+          }
           break;
         case 0xcf: { // panning
-          int panL=(unsigned char)stream.readC();
-          int panR=(unsigned char)stream.readC();
-          e->dispatchCmd(DivCommand(DIV_CMD_PANNING,i,panL,panR));
+          chan[i].panL=(unsigned char)stream.readC();
+          chan[i].panR=(unsigned char)stream.readC();
+          e->dispatchCmd(DivCommand(DIV_CMD_PANNING,i,chan[i].panL,chan[i].panR));
           break;
         }
         case 0xe0: case 0xe1: case 0xe2: case 0xe3: case 0xe4: case 0xe5:
@@ -637,6 +648,74 @@ bool DivCSPlayer::tick() {
       }
       chan[i].arpTicks--;
     }
+
+    if (chan[i].panSpeed) {
+      int newPanL=chan[i].panL;
+      int newPanR=chan[i].panR;
+      // increase one side until it has reached max. then decrease the other.
+      if (chan[i].panSpeed>0) { // right
+        if (newPanR>=0xff) {
+          newPanL-=chan[i].panSpeed;
+        } else {
+          newPanR+=chan[i].panSpeed;
+        }
+      } else { // left
+        if (newPanL>=0xff) {
+          newPanR+=chan[i].panSpeed;
+        } else {
+          newPanL-=chan[i].panSpeed;
+        }
+      }
+
+      // clamp to boundaries
+      if (newPanL<0) newPanL=0;
+      if (newPanL>0xff) newPanL=0xff;
+      if (newPanR<0) newPanR=0;
+      if (newPanR>0xff) newPanR=0xff;
+
+      // set new pan
+      chan[i].panL=newPanL;
+      chan[i].panR=newPanR;
+
+      // send panning command
+      e->dispatchCmd(DivCommand(DIV_CMD_PANNING,i,chan[i].panL,chan[i].panR));
+    }
+
+    if (chan[i].panbrelloDepth>0) {
+      chan[i].panbrelloPos+=chan[i].panbrelloRate;
+      chan[i].panbrelloPos&=255;
+
+      // calculate inverted...
+      // split position into four sections and calculate panning value
+      switch (chan[i].panbrelloPos&0xc0) {
+        case 0: // center -> right
+          chan[i].panL=((chan[i].panbrelloPos&0x3f)<<2);
+          chan[i].panR=0;
+          break;
+        case 0x40: // right -> center
+          chan[i].panL=0xff-((chan[i].panbrelloPos&0x3f)<<2);
+          chan[i].panR=0;
+          break;
+        case 0x80: // center -> left
+          chan[i].panL=0;
+          chan[i].panR=((chan[i].panbrelloPos&0x3f)<<2);
+          break;
+        case 0xc0: // left -> center
+          chan[i].panL=0;
+          chan[i].panR=0xff-((chan[i].panbrelloPos&0x3f)<<2);
+          break;
+      }
+
+      // multiply by depth
+      chan[i].panL=(chan[i].panL*chan[i].panbrelloDepth)/15;
+      chan[i].panR=(chan[i].panR*chan[i].panbrelloDepth)/15;
+
+      // then invert it to get final panning
+      chan[i].panL^=0xff;
+      chan[i].panR^=0xff;
+
+      e->dispatchCmd(DivCommand(DIV_CMD_PANNING,i,chan[i].panL,chan[i].panR));
+    }
   }
 
   // cycle over access times in order to ensure deltas are always higher than 256
@@ -739,6 +818,7 @@ bool DivCSPlayer::init() {
   for (int i=0; i<128; i++) {
     tremTable[i]=255*0.5*(1.0-cos(((double)i/128.0)*(2*M_PI)));
   }
+  
 
   arpSpeed=1;
   bAccessTS=new unsigned short[bLen];
diff --git a/src/engine/cmdStream.h b/src/engine/cmdStream.h
index 24368fd6a..6c8a50654 100644
--- a/src/engine/cmdStream.h
+++ b/src/engine/cmdStream.h
@@ -41,6 +41,8 @@ struct DivCSChannelState {
   int panbrelloDepth, panbrelloRate, panbrelloPos;
   int portaTarget, portaSpeed;
   unsigned char arp, arpStage, arpTicks;
+  unsigned char panL, panR;
+  signed char panSpeed;
 
   unsigned int callStack[DIV_MAX_CSSTACK];
   unsigned char callStackPos, callStackSize;
@@ -76,6 +78,9 @@ struct DivCSChannelState {
     arp(0),
     arpStage(0),
     arpTicks(0),
+    panL(255),
+    panR(255),
+    panSpeed(0),
     callStackPos(0),
     callStackSize(0),
     tracePos(0) {