prepare for end of song effect

papers/doc/3-pattern/effects.md

@@ -46,5 +46,6 @@ however, effects are continuous, which means you only need to type it once and t
 - `EFxx`: add or subtract global pitch.
   - this effect is rather weird. use with caution.
   - `80` is center.
+- `FFxx`: end of song/stop playback.
 
 additionally each system has its own effects. more details in another section of the manual.

src/engine/engine.cpp

@@ -1446,6 +1446,8 @@ const char* DivEngine::getEffectDesc(unsigned char effect, int chan) {
       return "EExx: Send external command";
     case 0xef:
       return "EFxx: Set global tuning";
+    case 0xff:
+      return "FFxx: Stop song";
     default:
       if (chan>=0 && chan<chans) {
         const char* ret=disCont[dispatchOfChan[chan]].dispatch->getEffectName(effect);

src/engine/playback.cpp

@@ -683,6 +683,8 @@ void DivEngine::processRow(int i, bool afterDelay) {
       case 0xef: // global pitch
         globalPitch+=(signed char)(effectVal-0x80);
         break;
+      case 0xff: // stop song TODO
+        break;
     }
   }