Add a -allowdesync parameter that will allow individual demos to desync. Warning is still shown, but player position will not be modified.

src/d_main.c

@@ -1664,10 +1664,10 @@ void D_SRB2Main(void)
 		if (M_CheckParm("-playdemo"))
 		{
 			singledemo = true; // quit after one demo
-			G_DeferedPlayDemo(tmp);
+			G_DeferedPlayDemo(tmp, M_CheckParm("-allowdemodesync") != 0);
 		}
 		else
-			G_TimeDemo(tmp);
+			G_TimeDemo(tmp, M_CheckParm("-allowdemodesync") != 0);
 
 		G_SetGamestate(GS_NULL);
 		wipegamestate = GS_NULL;

src/f_finale.c

@@ -3513,6 +3513,7 @@ void F_TitleScreenTicker(boolean run)
 
 		titledemo = true;
 		demofileoverride = DFILE_OVERRIDE_NONE;
+		demoallowdesync = false;
 		G_DoPlayDemo(dname);
 	}
 }

src/g_demo.c

@@ -51,6 +51,7 @@ boolean demorecording;
 boolean demoplayback;
 boolean titledemo; // Title Screen demo can be cancelled by any key
 demo_file_override_e demofileoverride;
+boolean demoallowdesync = false; // Allow demo files to de-sync
 static UINT8 *demobuffer = NULL;
 static UINT8 *demo_p, *demotime_p;
 static UINT8 *demoend;
@@ -660,12 +661,15 @@ void G_ConsGhostTic(void)
 			CONS_Alert(CONS_WARNING, M_GetText("Demo playback has desynced!\n"));
 		demosynced = false;
 
+		if (!demoallowdesync)
+		{
 			P_UnsetThingPosition(testmo);
 			testmo->x = oldghost.x;
 			testmo->y = oldghost.y;
 			P_SetThingPosition(testmo);
 			testmo->z = oldghost.z;
 		}
+	}
 
 	if (*demo_p == DEMOMARKER)
 	{
@@ -1975,7 +1979,7 @@ UINT8 G_CmpDemoTime(char *oldname, char *newname)
 //
 // G_PlayDemo
 //
-void G_DeferedPlayDemo(const char *name)
+void G_DeferedPlayDemo(const char *name, boolean allowdesync)
 {
 	COM_BufAddText("playdemo \"");
 	COM_BufAddText(name);
@@ -2633,7 +2637,7 @@ void G_FreeGhosts(void)
 //
 static INT32 restorecv_vidwait;
 
-void G_TimeDemo(const char *name)
+void G_TimeDemo(const char *name, boolean allowdesync)
 {
 	nodrawers = M_CheckParm("-nodraw");
 	noblit = M_CheckParm("-noblit");
@@ -2644,7 +2648,7 @@ void G_TimeDemo(const char *name)
 	singletics = true;
 	framecount = 0;
 	demostarttime = I_GetTime();
-	G_DeferedPlayDemo(name);
+	G_DeferedPlayDemo(name, allowdesync);
 }
 
 void G_DoPlayMetal(void)

src/g_demo.h

@@ -35,6 +35,7 @@ typedef enum
 } demo_file_override_e;
 
 extern demo_file_override_e demofileoverride;
+extern boolean demoallowdesync;
 
 // Quit after playing a demo from cmdline.
 extern boolean singledemo;
@@ -94,9 +95,9 @@ void G_WriteMetalTic(mobj_t *metal);
 void G_SaveMetal(UINT8 **buffer);
 void G_LoadMetal(UINT8 **buffer);
 
-void G_DeferedPlayDemo(const char *demo);
+void G_DeferedPlayDemo(const char *demo, boolean allowdesync);
 void G_DoPlayDemo(char *defdemoname);
-void G_TimeDemo(const char *name);
+void G_TimeDemo(const char *name, boolean allowdesync);
 void G_AddGhost(char *defdemoname);
 void G_FreeGhosts(void);
 void G_DoPlayMetal(void);

src/m_menu.c

@@ -10529,6 +10529,7 @@ static void M_StartTimeAttackReplay(INT32 choice)
 	{
 		M_ClearMenus(true);
 		modeattacking = ATTACKING_RECORD; // set modeattacking before G_DoPlayDemo so the map loader knows
+		demoallowdesync = false;
 		G_DoPlayDemo(ra_demoname);
 	}
 }

src/netcode/d_netcmd.c

@@ -1596,6 +1596,8 @@ static void Command_Playdemo_f(void)
 		demofileoverride = DFILE_OVERRIDE_SKIP;
 	}
 
+	demoallowdesync = COM_CheckParm("-allowdesync");
+
 	// Internal if no extension, external if one exists
 	// If external, convert the file name to a path in SRB2's home directory
 	if (FIL_CheckExtension(name))
@@ -1643,7 +1645,7 @@ static void Command_Timedemo_f(void)
 
 	CONS_Printf(M_GetText("Timing demo '%s'.\n"), timedemo_name);
 
-	G_TimeDemo(timedemo_name);
+	G_TimeDemo(timedemo_name, COM_CheckParm("-allowdesync"));
 }
 
 // stop current demo