Zoom in at mouse (SLICK2D)

[zacpier]

I’ve been working on a RTS game and I wanted to be able to zoom in with the mouse wheel toward the mouse.
In a lot of RTS games, you can hover over a unit, scroll upwards, and end up with the unit in the middle of your screen very zoomed.
That’s what I’m trying to accomplish.

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Here's my World.java: [spoiler]

package net.space.render;

import java.util.ArrayList;

import net.space.entity.Entity;
import net.space.main.ReducedSpace;

import org.lwjgl.input.Mouse;
import org.newdawn.slick.Graphics;

public class World {

	public float zX=0, zY=0;

	private float zoomLevel;
	private static final float zoomStep=0.0625f;
	
	private ArrayList<Entity> entities = new ArrayList<Entity>();
	
	
	
	public void draw(Graphics g) {
		g.scale(getZoomLevel(), getZoomLevel());
		g.translate(zX, zY);
		
		for(Entity e:entities) {
			if(e!=null) {
				e.draw(g);
			}
		}
	}
	
	
	
	public float getZoomLevel() {
		return zoomLevel;
	}
	
	public void setZoomLevel(float z) {
		zoomLevel = z;
	}
	
	
	
	public void mouseWheelZoom() {
		
		  int mouseWheel = Mouse.getDWheel();
		  
		  if(mouseWheel==0) {
			  
			  return;
		  }
		  
		  boolean positive = mouseWheel>0;
		  
		  
		  if (positive) {
			  
			  addZoomLevel(zoomStep);
		  }
		  
		  else {

			  addZoomLevel(-zoomStep);
		  }
		  
		  if(mouseWheel != 0) {
			  
			  zX+=(Mouse.getX()*(mouseWheel/240f))/zoomLevel;
			  zY-=((ReducedSpace.h-Mouse.getY())*(mouseWheel/240f))/zoomLevel;
		  }
		  
		  System.out.println("RAWX: "+Mouse.getX()+"\nRAWY: "+Mouse.getY()+"\nEXP: "+mouseWheel+"|"+(mouseWheel/240f)+"\nWHEEL: "+mouseWheel);
		  System.out.println("X: "+zX+"\nY: "+zY);
	}
	
	public void addZoomLevel(float a) {
		
		zoomLevel+=a;
		
		if(zoomLevel>1.2375f) {
			zoomLevel=1.2375f;
		}
		
		if(zoomLevel<.1f) {
			
			zoomLevel=.1f;
		}
	}
	
	public int addEntity(Entity e) {
		entities.add(e);
		return entities.size();
	}
	public void removeEntity(int index) {
		entities.set(index, null);
	}
	public void removeEntity(String name) {
		for(int i=0;i<entities.size();i++) {
			if(entities.get(i).name.matches(name)) {
				removeEntity(i);
				return;
			}
		}
	}
	public Entity getEntity(int index) {
		return entities.get(index);
	}
	public Entity getEntity(String name) {
		for(int i=0;i<entities.size();i++) {
			if(entities.get(i).name.matches(name)) {
				return getEntity(i);
			}
		}
		return null;
	}
}

[/spoiler]

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Thanks for any help!