Add new cvar operation 'reset' and 'resetall'.

cvar operations are special commands that allow the programmatic
manipulation of cvar values. 'reset' resets a given cvar to it's
default value, e.g. `reset r_mode' would reset `r_mode` to `4`.
'resetall' resets all known cvar with the exception of `game`.

The code is based upon q2pro.

This is part of issue #414.

doc/04_cvarlist.md

@@ -253,3 +253,13 @@ it's `+set busywait 0` (setting the `busywait` cvar) and `-portable`
 
 * **gl3_particle_square**: If set to `1`, particles are rendered as
   squares, like in the old software renderer or Quake 1. Default is `0`.
+
+
+## cvar operations
+
+cvar operations are special commands that allow the manipulation of cvar
+values. They can be used for simple scripts and the like.
+
+* **reset <cvar>**: Reset the cvar to it's default value.
+
+* **resetall**: Reset all known cvar to their default values.

src/common/cvar.c

@@ -189,6 +189,7 @@ Cvar_Get(char *var_name, char *var_value, int flags)
 	if (var)
 	{
 		var->flags |= flags;
+		var->default_string = CopyString(var_value);
 		return var;
 	}
 
@@ -216,6 +217,7 @@ Cvar_Get(char *var_name, char *var_value, int flags)
 	var = Z_Malloc(sizeof(*var));
 	var->name = CopyString(var_name);
 	var->string = CopyString(var_value);
+	var->default_string = CopyString(var_value);
 	var->modified = true;
 	var->value = strtod(var->string, (char **)NULL);
 
@@ -648,14 +650,60 @@ Cvar_Serverinfo(void)
 	return Cvar_BitInfo(CVAR_SERVERINFO);
 }
 
+/*
+ * Resets a cvar to its default value.
+ */
+void Cvar_Reset_f(void)
+{
+    cvar_t *var;
+
+    if (Cmd_Argc() < 2)
+	{
+        Com_Printf("Usage: %s <cvar>\n", Cmd_Argv(0));
+        return;
+    }
+
+    var = Cvar_FindVar(Cmd_Argv(1));
+
+    if (!var)
+	{
+        Com_Printf("%s is not a cvar\n", Cmd_Argv(1));
+        return;
+    }
+
+	Com_Printf("%s: %s\n", var->name, var->default_string);
+    Cvar_Set(var->name, var->default_string);
+}
+
+void Cvar_ResetAll_f(void)
+{
+    cvar_t *var;
+
+    for (var = cvar_vars; var; var = var->next)
+	{
+        if ((var->flags & CVAR_NOSET))
+		{
+            continue;
+		}
+		else if (strcmp(var->name, "game") == 0)
+		{
+            continue;
+		}
+
+        Cvar_Set(var->name, var->default_string);
+    }
+}
+
 /*
  * Reads in all archived cvars
  */
 void
 Cvar_Init(void)
 {
-	Cmd_AddCommand("set", Cvar_Set_f);
 	Cmd_AddCommand("cvarlist", Cvar_List_f);
+	Cmd_AddCommand("reset", Cvar_Reset_f);
+	Cmd_AddCommand("resetall", Cvar_ResetAll_f);
+	Cmd_AddCommand("set", Cvar_Set_f);
 }
 
 /*
@@ -676,6 +724,8 @@ Cvar_Fini(void)
 	}
 
 	Cmd_RemoveCommand("cvarlist");
+	Cmd_RemoveCommand("reset");
+	Cmd_RemoveCommand("resetall");
 	Cmd_RemoveCommand("set");
 }
 

src/common/header/shared.h

@@ -354,6 +354,9 @@ typedef struct cvar_s
 	qboolean modified; /* set each time the cvar is changed */
 	float value;
 	struct cvar_s *next;
+
+	/* Added by YQ2. Must be at the end to preserve ABI. */
+	char *default_string;
 } cvar_t;
 
 #endif /* CVAR */