GUI Library/Core

import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.input.Mouse;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;


public class Core {

    final int WIDTH=800, HEIGHT=600;
    int lastFrame;

    GUI stack;

    public void Start(){

        try {
            Display.setDisplayMode(new DisplayMode(WIDTH,HEIGHT));
            Display.create();
        } catch (LWJGLException e) {
            e.printStackTrace();
            System.exit(0);
        }

        initGL();
        System.out.println("OpenGL version: " + GL11.glGetString(GL11.GL_VERSION));

        boolean Close = Display.isCloseRequested();

        Layer[] layers = new Layer[2];

        Element[] elementsA = new Element[2];

        Element[] elementsB = new Element[4];

        elementsA[0] = new Element("button one", 1, new Square(50,50,150,100));
        elementsA[1] = new Element("button two", 2, new Square(200,50,300,100));
        elementsB[0] = new Element("button three", 3, new Square(50,50,150,100));
        elementsB[1] = new Element("button four", 4, new Square(200,50,300,100));
        elementsB[2] = new Element("button five", 5, new Square(50,200,150,250));
        elementsB[3] = new Element("button six", 6, new Square(200,200,300,250));

        layers[0] = new Layer("layer one", elementsA, new Square(0,0,400,200), new Square(0,0,400,200));
        layers[1] = new Layer("layer two", elementsB, new Square(100,100,500,300), new Square(100,100,500,400));

        stack = new GUI(layers);

        while(!Close){
            GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);

            if(Keyboard.isKeyDown(Keyboard.KEY_ESCAPE) || Display.isCloseRequested())
                Close = true;

            int delta=getDelta();

            mouseHandler();
            draw();

            Display.update();
            //Display.sync(1);
        }

    }

    private void draw() {
        for(int i=stack.layers.length-1; i>=0; --i){
            double x1 = stack.layers[i].geomVisible.x1;
            double y1 = stack.layers[i].geomVisible.y1;
            double x2 = stack.layers[i].geomVisible.x2;
            double y2 = stack.layers[i].geomVisible.y2;
            double h1 = x1 + ((x2-x1)*(stack.layers[i].hMin));
            double h2 = x1 + ((x2-x1)*(stack.layers[i].hMax));
            double v1 = y1 + ((y2-y1)*(stack.layers[i].vMin));
            double v2 = y1 + ((y2-y1)*(stack.layers[i].vMax));

            //layer
            GL11.glColor3d(0.5,0.5,0.5);
            GL11.glBegin(GL11.GL_QUADS);
                GL11.glVertex2d(x1,y1);
                GL11.glVertex2d(x2,y1);
                GL11.glVertex2d(x2,y2);
                GL11.glVertex2d(x1,y2);
            GL11.glEnd();

            //scroll bars
            GL11.glColor3d(1, 1, 1);
            GL11.glBegin(GL11.GL_QUADS);
                GL11.glVertex2d(h1,y1);
                GL11.glVertex2d(h2,y1);
                GL11.glVertex2d(h2,y1+10);
                GL11.glVertex2d(h1,y1+10);
            GL11.glEnd();
            GL11.glColor3d(1, 1, 1);
            GL11.glBegin(GL11.GL_QUADS);
                GL11.glVertex2d(x2,v1);
                GL11.glVertex2d(x2-10,v1);
                GL11.glVertex2d(x2-10,v2);
                GL11.glVertex2d(x2,v2);
            GL11.glEnd();

            for(int j=0; j<stack.layers[i].elements.length; j++){
                double a1 = stack.layers[i].elements[j].geom.x1 +stack.layers[i].geomActual.x1;
                double b1 = stack.layers[i].elements[j].geom.y1 +stack.layers[i].geomActual.y1;
                double a2 = stack.layers[i].elements[j].geom.x2 +stack.layers[i].geomActual.x1;
                double b2 = stack.layers[i].elements[j].geom.y2 +stack.layers[i].geomActual.y1;

                //button
                GL11.glColor3d(1, 0, 0);
                GL11.glBegin(GL11.GL_QUADS);
                    GL11.glVertex2d(a1,b1);
                    GL11.glVertex2d(a2,b1);
                    GL11.glVertex2d(a2,b2);
                    GL11.glVertex2d(a1,b2);
                GL11.glEnd();
            }
        }
    }

    public void mouseHandler(){
        /*if(Mouse.isButtonDown(0)){
            stack.update(true, Mouse.getX(), HEIGHT-Mouse.getY(), Mouse.getDX(), -Mouse.getDY(), 0);
        }*/
        while(Mouse.next()){
            if(Mouse.getEventButton()==0){
                if(Mouse.getEventButtonState()){
                    stack.mouseX = Mouse.getEventX();
                    stack.mouseY = HEIGHT-Mouse.getEventY();
                    //stack.update();
                }else{
                    stack.deltaX = Mouse.getEventX()-stack.mouseX;
                    stack.deltaY = HEIGHT-Mouse.getEventY()-stack.mouseY;
                    stack.update();

                    stack.mouseX = 0;
                    stack.mouseY = 0;
                    stack.deltaX = 0;
                    stack.deltaY = 0;
                }
            }
        }
    }

    public int getDelta(){
        long time = getTime();
        int delta = (int) (time - lastFrame);
        lastFrame = (int) time;

        return delta;
    }

    public long getTime(){
        return (Sys.getTime()*1000)/Sys.getTimerResolution();
    }

    public void initGL(){
        GL11.glEnable(GL11.GL_TEXTURE_2D);

        //GL11.glClearColor(1.0f, 1.0f, 1.0f, 0.0f);

        GL11.glViewport(0,0,WIDTH,HEIGHT);

        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, WIDTH, HEIGHT, 0, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
    }

    public static void main(String args[]){
        Core m = new Core();
        m.Start();
    }


}