HaxeFlixel/flixel

package flixel.system.scaleModes;

import flixel.FlxG;

/**
 * `RatioScaleMode` is a scaling mode which maintains the game's aspect ratio.
 * When you shrink or grow the window, the width and height of the game will adjust,
 * either scaling the game or adding black bars as needed.
 *
 * This is the default scaling mode used by HaxeFlixel.
 */
class RatioScaleMode extends BaseScaleMode
{
    var fillScreen:Bool;

    /**
     * @param fillScreen Whether to cut the excess side to fill the
     * screen or always display everything.
     */
    public function new(fillScreen:Bool = false)
    {
        super();
        this.fillScreen = fillScreen;
    }

    override function updateGameSize(Width:Int, Height:Int):Void
    {
        var ratio:Float = FlxG.width / FlxG.height;
        var realRatio:Float = Width / Height;

        var scaleY:Bool = realRatio < ratio;
        if (fillScreen)
        {
            scaleY = !scaleY;
        }

        if (scaleY)
        {
            gameSize.x = Width;
            gameSize.y = Math.floor(gameSize.x / ratio);
        }
        else
        {
            gameSize.y = Height;
            gameSize.x = Math.floor(gameSize.y * ratio);
        }
    }
}