Add a new playback mode `ogg_shuffle` == `4`, truly random playback.

912b65ff74 changed mode `3` from random
playback to truly random playback, allowing the same track being played
several times in a row. Since some users might prefer the old behavior
move truly random playback to a new mode `4`. Add it to the menu and
finally document the `ogg_shuffle` cvar.

In addition to #1143

doc/040_cvarlist.md

@@ -291,6 +291,15 @@ it's `+set busywait 0` (setting the `busywait` cvar) and `-portable`
   0.  Setting this cvar to `1` disables this behavior, the music keeps
   playing.
 
+* **ogg_shuffle**: Ogg/Vorbis playback mode. Supported modes are:
+  `0`: Loop the current track (the default).
+  `1`: Play the current track once, then stop.
+  `2`: Play all available tracks in a linear sequence.
+  `3`: Shuffle through the available tracks, never play the same track
+       twice in a row.
+  `4`: Shuffle through the available tracks, may play the same track
+       multiple times in a row.
+
 * **s_doppler**: If set to `1` doppler effects are enabled. This is only
   supported by the OpenAL sound backend.
 

src/client/menu/menu.c

@@ -2371,6 +2371,7 @@ Options_MenuInit(void)
         "play once",
         "sequential",
         "random",
+        "truly random",
         0
     };
 

src/client/sound/ogg.c

@@ -530,6 +530,7 @@ OGG_PlayTrack(const char *track, qboolean cdtrack, qboolean immediate)
 		newtrack = (curtrack + 1) % (ogg_maxfileindex + 1) != 0 ? (curtrack + 1) : 2;
 	} break;
 	case 3:			// random
+	case 4:			// random with true randomness
 	{
 		int retries = 100;
 		newtrack = 0;
@@ -537,6 +538,14 @@ OGG_PlayTrack(const char *track, qboolean cdtrack, qboolean immediate)
 		while (retries-- > 0 && newtrack < 2)
 		{
 			newtrack = randk() % (ogg_maxfileindex + 1);
+
+			if (playback == 3)
+			{
+				if (newtrack == curtrack)
+				{
+					newtrack = 0;
+				}
+			}
 		}
 	} break;
 	}