ported over charter multikey and other stuff

Co-Authored-By: Ne_Eo <NeeEoo@users.noreply.github.com>

source/funkin/backend/chart/Chart.hx

@@ -168,6 +168,14 @@ class Chart {
 			base.events = base.events.concat(extraEvents);
 		#end
 
+		/**
+		 * Set defaults on strum lines
+		*/
+		for(strumLine in base.strumLines) {
+			if(strumLine.keyCount == null)
+				strumLine.keyCount = 4;
+		}
+
 		return base;
 	}
 

source/funkin/backend/chart/ChartData.hx

@@ -42,6 +42,7 @@ typedef ChartStrumLine = {
 	var ?strumScale:Float;
 	var ?scrollSpeed:Float;
 	var ?vocalsSuffix:String;
+	var ?keyCount:Int; // default=4
 
 	var ?strumLinePos:Float; // Backwards compatability
 }

source/funkin/backend/scripting/events/AmountEvent.hx

@@ -4,7 +4,7 @@ final class AmountEvent extends CancellableEvent {
 	/**
 	 * Amount
 	 */
-	public var amount:Int;
+	public var amount:Null<Int>;
 
 	/**
 	 * Shows whether or not psych users complained about this class

source/funkin/backend/utils/CoolUtil.hx

@@ -839,6 +839,13 @@ class CoolUtil
 		return file.file;
 	}
 
+	@:noUsing public static function getClosestAngle(angle:Float, targetAngle:Float):Float {
+		var diff:Float = angle - targetAngle;
+		if (diff < -180) diff += 360;
+		else if (diff > 180) diff -= 360;
+		return angle - diff;
+	}
+
 	public static function sortAlphabetically(array:Array<String>, ?lowercase:Bool=false) {
 		array.sort(function(a1, a2):Int {
 			if(lowercase) {