v1.3.0: improved how the game handles seeds and PRNG internally

SPD-classes/src/main/java/com/watabou/utils/Random.java

@@ -49,7 +49,20 @@ public class Random {
 	}
 
 	public static synchronized void pushGenerator( long seed ){
-		generators.push( new java.util.Random( seed ) );
+		generators.push( new java.util.Random( scrambleSeed(seed) ) );
+	}
+
+	//scrambles a given seed, this helps eliminate patterns between the outputs of similar seeds
+	//Algorithm used is MX3 by Jon Maiga (jonkagstrom.com), CC0 license.
+	private static synchronized long scrambleSeed( long seed ){
+		seed ^= seed >>> 32;
+		seed *= 0xbea225f9eb34556dL;
+		seed ^= seed >>> 29;
+		seed *= 0xbea225f9eb34556dL;
+		seed ^= seed >>> 32;
+		seed *= 0xbea225f9eb34556dL;
+		seed ^= seed >>> 29;
+		return seed;
 	}
 
 	public static synchronized void popGenerator(){

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/Dungeon.java

@@ -190,8 +190,9 @@ public class Dungeon {
 
 		Actor.clear();
 		Actor.resetNextID();
-		
+
-		Random.pushGenerator( seed );
+		//offset seed slightly to avoid output patterns
+		Random.pushGenerator( seed+1 );
 
 			Scroll.initLabels();
 			Potion.initColors();

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogDzewa.java

@@ -109,7 +109,8 @@ public class YogDzewa extends Mob {
 	private ArrayList<Class> fistSummons = new ArrayList<>();
 	private ArrayList<Class> challengeSummons = new ArrayList<>();
 	{
-		Random.pushGenerator(Dungeon.seedCurDepth());
+		//offset seed slightly to avoid output patterns
+		Random.pushGenerator(Dungeon.seedCurDepth()+1);
 			fistSummons.add(Random.Int(2) == 0 ? YogFist.BurningFist.class : YogFist.SoiledFist.class);
 			fistSummons.add(Random.Int(2) == 0 ? YogFist.RottingFist.class : YogFist.RustedFist.class);
 			fistSummons.add(Random.Int(2) == 0 ? YogFist.BrightFist.class : YogFist.DarkFist.class);

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/levels/RegularLevel.java

@@ -387,7 +387,8 @@ public abstract class RegularLevel extends Level {
 		}
 
 		//use a separate generator for this to prevent held items, meta progress, and talents from affecting levelgen
-		Random.pushGenerator( Dungeon.seedCurDepth() );
+		//we can use a random long for the seed as it will be the same long every time
+		Random.pushGenerator( Random.Long() );
 
 		Item item = Bones.get();
 		if (item != null) {

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/levels/rooms/special/ShopRoom.java

@@ -270,10 +270,12 @@ public class ShopRoom extends SpecialRoom {
 		itemsToSpawn.add( rare );
 
 		//hard limit is 63 items + 1 shopkeeper, as shops can't be bigger than 8x8=64 internally
-		if (itemsToSpawn.size() > 63)
+		if (itemsToSpawn.size() > 63) {
 			throw new RuntimeException("Shop attempted to carry more than 63 items!");
+		}
 
 		//use a new generator here to prevent items in shop stock affecting levelgen RNG (e.g. sandbags)
+		//we can use a random long for the seed as it will be the same long every time
 		Random.pushGenerator(Random.Long());
 			Random.shuffle(itemsToSpawn);
 		Random.popGenerator();

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/scenes/GameScene.java

@@ -526,7 +526,8 @@ public class GameScene extends PixelScene {
 				}
 
 				//50%/75% chance, use level's seed so that we get the same result for the same level
-				Random.pushGenerator(Dungeon.seedCurDepth());
+				//offset seed slightly to avoid output patterns
+				Random.pushGenerator(Dungeon.seedCurDepth()+1);
 					if (reqSecrets <= 0 && Random.Int(4) <= Dungeon.hero.pointsInTalent(Talent.ROGUES_FORESIGHT)){
 						GLog.p(Messages.get(this, "secret_hint"));
 					}