FlxState: replace transition functions by switchTo(), closes #1676

flixel/FlxG.hx

@@ -297,26 +297,18 @@ class FlxG
 	}
 
 	/**
-	 * Switch from the current game state to the one specified here.
+	 * Attempts to switch from the current game state to `nextState`.
+	 * The state switch is successful if `switchTo()` of the current `state` returns `true`.
 	 */
-	public static inline function switchState(State:FlxState):Void
+	public static inline function switchState(nextState:FlxState):Void
 	{
-		//If a transition is required
-		if (game._state.isTransitionNeeded())
-		{
-			//Do the transition and exit early
-			game._state.transitionToState(State);
-			return;
-		}
-		//Otherwise do the switch normally
-		else
-		{
-			game._requestedState = State; 
-		}
+		if (state.switchTo(nextState))
+			game._requestedState = nextState;
 	}
 
 	/**
 	 * Request a reset of the current game state.
+	 * Calls `switchState()` with a new instance of the current `state`.
 	 */
 	public static inline function resetState():Void
 	{

flixel/FlxState.hx

@@ -130,22 +130,14 @@ class FlxState extends FlxGroup
 	}
 
 	/**
-	 * Checked by FlxG.switchState to see if a transition is required before switching states
-	 * @return
-	 */
-	public function isTransitionNeeded():Bool
-	{
-		//override in your subclass to enable this functionality
-		return false;
-	}
-
-	/**
-	 * Perform a visual transition, and when it's complete, call FlxG.switchState
-	 * @param	State
+	 * Called from `FlxG.switchState()`. If `false` is returned, the state
+	 * switch is cancelled - the default implementation returns `true`.
+	 * 
+	 * Useful for customizing state switches, e.g. for transition effects.
 	 */
-	public function transitionToState(State:FlxState):Void
+	public function switchTo(nextState:FlxState):Bool
 	{
-		//override in your subclass to enable this functionality
+		return true;
 	}
 
 	/**