Backdrop

Backdrop.hx

package;

import kha.Color;
import kha.Image;
import kha.System;
import kha.graphics2.Graphics;

class Backdrop
{
    public var image:Image;

    var width:Int;
    var height:Int;

    public var scrollX:Int;    
    public var scrollY:Int;

    var posX:Int;
    var posY:Int;

    var offsetX:Int;
    var offsetY:Int;

    var originalWidth:Int;
    var originalHeight:Int;
    
    public function new(image:Image, scrollX:Int = 0, scrollY:Int = 0):Void
    {

        this.scrollX = scrollX;
        this.scrollY = scrollY;

        originalWidth = image.width;
        originalHeight = image.height;
        
        width = System.windowWidth();
        height = System.windowHeight();   

        var composedImage = Image.createRenderTarget(
            originalWidth + width,
            originalHeight + height
        );
        this.image = composedImage;
        posX = -originalWidth;
        posY = -originalHeight;

        var horizontal:Int = Std.int(width / originalWidth + 1);
        var vertical:Int = Std.int(height / originalHeight + 1);

        if (width % image.width > 0) {
            horizontal += 1;
        }

        if (height % image.height > 0) {
            vertical += 1;
        }

        composedImage.g2.begin();
        
        var start:Int = 0;
        for (x in start...horizontal) {
            for (y in start...vertical) {
                composedImage.g2.drawImage(
                    image,
                    x * originalWidth,
                    y * originalHeight
                );
            }
        }

        composedImage.g2.end();
        
    }

    public function update():Void
    {
       offsetX = (offsetX + scrollX) % originalWidth;
       offsetY = (offsetY + scrollY) % originalHeight;
    }
    
    public function render(g:Graphics):Void 
	{
        g.color = Color.White;

        g.drawScaledSubImage(
            image,
            0,
            0, 
            image.width, 
            image.height,
            posX + offsetX,
            posY + offsetY,
            image.width,
            image.height 
        );
       
	}        
}