Gavr's gtk graph

//author gavr https://www.youtube.com/channel/UChHL_HIocsBbeLGhi50bSvw?view_as=subscriber
//compile with valac --pkg gtk+-3.0 TreeViewExample.vala
using Gtk;
public class StackClass : Gtk.Window {
   public Gtk.LevelBar[] barMass;
   public Gtk.Frame box3;
    private CustomWidget widget;
    public StackClass () {
        var header = new Gtk.HeaderBar();
        header.set_show_close_button(true);
        barMass = new Gtk.LevelBar[10];
 
        box3 = new Gtk.Frame("График");  
        widget = new CustomWidget ();
 
        var box1 = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 1);
//Стак
        var stack = new Gtk.Stack();
        Gtk.StackSwitcher switcher = new Gtk.StackSwitcher ();
        switcher.set_valign (Gtk.Align.CENTER);
        header.pack_start (switcher);
        stack.set_transition_duration (500);//скорость анимации
        stack.set_transition_type (SLIDE_LEFT_RIGHT);
        switcher.set_stack (stack);//устанавливаем переключателю стак
//создаем 10 прогрессБаров и заполняем ими бокс с флагами expand
        for (int i=0;i<10;i++){
            barMass[i] = new Gtk.LevelBar.for_interval (0.0, 10.0);
            box1.pack_start(barMass[i],true,true,2);
            barMass[i].set_orientation(Gtk.Orientation.VERTICAL);
            //barMass[i].set_mode (Gtk.LevelBarMode.DISCRETE);
            barMass[i].set_inverted(true);
            barMass[i].set_hexpand(true);
        }
 
        box3.add(widget);
        barMass[0].set_value(10.0);
   
        stack.add_titled(box1,"box1","box1");
        stack.add_titled(box3,"box3","box3");
 
        this.set_titlebar(header);
        this.destroy.connect(Gtk.main_quit);
        this.border_width = 10;
        this.set_size_request (600, 500);
        this.add(stack);
 
        this.key_press_event.connect ((key) => {
            print(key.str + " ");
            addNbar(double.parse(key.str));
            return false;
        });
 
    }
 
 
    public void addNbar(double newV){
        for(int i=0;i<10-1;i++){
            barMass[i].set_value(barMass[i+1].get_value());
        }
        barMass[9].set_value(newV);  
        widget.update((int) newV);
    }
 
 
    public static int main(string[] args){
        Gtk.init(ref args);
        var s = new StackClass();
        s.show_all();
        Gtk.main();
        return 0;
    }
}
 
public class CustomWidget : DrawingArea {
    public string text;
    public int newPoint;
    public int[] points;
 
    public CustomWidget () {
        set_size_request (get_allocated_width (), get_allocated_height ());
        points = new int [10];
        int height = get_allocated_height ();print (@"полученная высота в начале $height");
        for(int i=0;i<10;i++)points[i]=0;
        //this.newPoint = txt;
    }
   // public void setNewPoint(int y) {this.newPoint=y;}
    /* Widget is asked to draw itself */
 
    public override bool draw (Cairo.Context cr) {
        int width = get_allocated_width ();
        int height = get_allocated_height ();
        print ("ширина = %d, высота = %d \n",width,height);
        //цикл в котором отрисовываем массив points[j] с шагом в 1/10 экрана
        for(int i=0,j=0 ;i<width-width / 10 ;i+=width / 10, j++) {
            cr.line_to(i,height-((height/10) *points[j]));
            print("j = %d ",j);
            print(" x %d, y %d \n",i,height/10 *points[j]);
        }
       cr.line_to(10* width / 10,height-newPoint*height/10);
       print(" x %d, y %d \n",10* width/10,newPoint*height/10);
       cr.stroke ();
    return false;
    }
    public  bool update(int y){
        this.newPoint=y;
        for(int i=0;i<10-1;i++) {
            points[i]=points[i+1];
        }
        points[9]=y;
 
        redraw_canvas ();
            return true;
    }
    private void redraw_canvas () {
        var window = get_window ();
        if (null == window) {
            return;
        }
        var region = window.get_clip_region ();
        // redraw the cairo canvas completely by exposing it
        window.invalidate_region (region, true);
        window.process_updates (true);
    }
 
 
   
}