prepare to add channel pair and mode hints

src/engine/platform/abstract.cpp

@@ -37,6 +37,14 @@ unsigned short DivDispatch::getPan(int chan) {
   return 0;
 }
 
+DivChannelPair DivDispatch::getPaired(int chan) {
+  return DivChannelPair();
+}
+
+DivChannelModeHints DivDispatch::getModeHints(int chan) {
+  return DivChannelModeHints();
+}
+
 DivMacroInt* DivDispatch::getChanMacroInt(int chan) {
   return NULL;
 }

src/engine/platform/opl.cpp

@@ -1582,6 +1582,15 @@ unsigned short DivPlatformOPL::getPan(int ch) {
   return ((chan[ch].pan&1)<<8)|((chan[ch].pan&2)>>1);
 }
 
+DivChannelPair DivPlatformOPL::getPaired(int ch) {
+  if (oplType==3 && ch<12 && !(ch&1)) {
+    if (chan[ch].fourOp) {
+      return DivChannelPair("4OP",ch+1);
+    }
+  }
+  return DivChannelPair();
+}
+
 DivDispatchOscBuffer* DivPlatformOPL::getOscBuffer(int ch) {
   if (oplType==759 || chipType==8950) {
     if (ch>=totalChans+1) return NULL;

src/engine/platform/opl.h

@@ -115,6 +115,7 @@ class DivPlatformOPL: public DivDispatch {
     void* getChanState(int chan);
     DivMacroInt* getChanMacroInt(int ch);
     unsigned short getPan(int chan);
+    DivChannelPair getPaired(int chan);
     DivDispatchOscBuffer* getOscBuffer(int chan);
     unsigned char* getRegisterPool();
     int getRegisterPoolSize();