/*
* 26/11/2006 - 17:02
*
* GraphMonkey - mono based graphing calculator
* Copyright (C) 2006 Lounis Bellabes
* nolius@users.sourceforge.net
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/

using System;
using Gtk;
using Pango;

class Ecran_Form : DrawingArea
{
	private Gtk.Window win;
	
	private HBox hbox;
	private VBox vbox;

	//Pango.Layout layout;
	public string equation;
	public string equation2;
	public string equation3;
        
	public double x_min;
	public double x_max;
	public double y_min;
	public double y_max;
	public double graduation;
		
	//for color
	private Gdk.GC gc_red;
	private Gdk.GC gc_green;
	private Gdk.GC gc_blue;
	private Gdk.GC gc_a;
	private Gdk.GC gc_black;
	private	Gdk.GC gc_white;
	private Gdk.GC gc_gray;
	private Gdk.GC gc_cyan;
	private Gdk.GC gc_orange;
	
	// for saving results
	public bool first_draw = true;
	
	private double[] tab_result1_x = new double[501];
	private double[] tab_result1_y = new double[501];
	private double[] tab_result2_x = new double[501];
	private double[] tab_result2_y = new double[501];
	private double[] tab_result3_x = new double[501];
	private double[] tab_result3_y = new double[501];
	private double[] tab_result_derivative_x = new double[501];
	private double[] tab_result_derivative_y = new double[501];
	private double[] tab_result_secondderivative_x = new double[501];
	private double[] tab_result_secondderivative_y = new double[501];
	
	public Label label_coord;
	
	//status of options
	private bool black_screen;
	private bool grid;
	
	// status of calculus
	private bool simpson;
	private bool derivative;
	private bool secondderivative;
	
	private bool extension_exist;
	private bool extension_show;
	private Statusbar statusbar;
	
	public Ecran_Form (string equation1, string equation21, string equation31, double x_min1, double x_max1, double y_min1, double y_max1, double graduation1)
	{
		/*
		Table tableLayout = new Table(10, 3, false);
		tableLayout.Attach(this,   0, 9, 0, 3);
		tableLayout.Attach(new Entry(), 9, 10, 0, 3);
		tableLayout.ShowAll();
		*/

		this.WidthRequest = 501;
		this.HeightRequest = 501;
		vbox = new VBox(false,3);
		
		MenuBar bar = new MenuBar ();
		
		Menu calculus_menu = new Menu ();
		MenuItem calculus_menu_item = new MenuItem ("_Calculus");
		calculus_menu_item.Submenu = calculus_menu;
		
		ImageMenuItem simpson_item = new ImageMenuItem("_Net Area Under Fn 1 [Xmin, Xmax]");
		simpson_item.Image = new Gtk.Image(Gtk.Stock.GoDown, Gtk.IconSize.Menu);
		simpson_item.Activated += new EventHandler(simpson_cb);
		calculus_menu.Append(simpson_item);

		ImageMenuItem averagevalue_item = new ImageMenuItem("A_verage Value of Fn 1 [Xmin, Xmax]");
		averagevalue_item.Image = new Gtk.Image(Gtk.Stock.Index, Gtk.IconSize.Menu);
		averagevalue_item.Activated += new EventHandler(averagevalue_cb);
		calculus_menu.Append(averagevalue_item);

		ImageMenuItem derivative_item = new ImageMenuItem("Graph _Derivative of Fn 1");
		derivative_item.Image = new Gtk.Image(Gtk.Stock.Execute,Gtk.IconSize.Menu);
		derivative_item.Activated += new EventHandler(derivative_cb);
		calculus_menu.Append(derivative_item);

		ImageMenuItem secondderivative_item = new ImageMenuItem("Graph _Second Derivative of Fn 1");
		secondderivative_item.Image = new Gtk.Image(Gtk.Stock.Execute,Gtk.IconSize.Menu);
		secondderivative_item.Activated += new EventHandler(secondderivative_cb);
		calculus_menu.Append(secondderivative_item);

		/*
		ImageMenuItem slopefield_item = new ImageMenuItem("Slope _Field of Fn 1 [f(x,y)]");
		slopefield_item.Image = new Gtk.Image(Gtk.Stock.Execute,Gtk.IconSize.Menu);
		//slopefield_item.Activated += new EventHandler(slopefield_cb);
		calculus_menu.Append(slopefield_item);
		*/
		
		ImageMenuItem clear_item = new ImageMenuItem("_Clear");
		clear_item.Image = new Gtk.Image(Gtk.Stock.Clear,Gtk.IconSize.Menu);
		clear_item.Activated += new EventHandler(clear_cb);
		calculus_menu.Append(clear_item);

		bar.Append (calculus_menu_item);

		Menu option_menu = new Menu ();
		MenuItem option_menu_item = new MenuItem ("_Options");
		option_menu_item.Submenu = option_menu;
		
		
		ImageMenuItem wbscreen_item = new ImageMenuItem("White/Black _screen");
		wbscreen_item.Image = new Gtk.Image(Gtk.Stock.Preferences, Gtk.IconSize.Menu);
		wbscreen_item.Activated += new EventHandler (wbscreen_cb);
		option_menu.Append (wbscreen_item);
			
		ImageMenuItem grid_item = new ImageMenuItem("On/Off _grid");
		grid_item.Image = new Gtk.Image(Gtk.Stock.Preferences, Gtk.IconSize.Menu);
		grid_item.Activated += new EventHandler (grid_cb);
		option_menu.Append (grid_item);
		
		/*
		ImageMenuItem info_item = new ImageMenuItem("Curves _informations");
		info_item.Image = new Gtk.Image(Gtk.Stock.DialogInfo, Gtk.IconSize.Menu);
		info_item.Activated += new EventHandler (info_cb);
		option_menu.Append (info_item);
		*/
		
		bar.Append (option_menu_item);
		
		bar.ShowAll ();
		vbox.PackStart(bar,true,true,0);
		
		
		vbox.PackStart(this,true,true,0);
		//vbox.PackStart(new Entry(),true,true,0);
		
		hbox = new HBox(false,5);
		
		Image image_GoUp = new Gtk.Image(Gtk.Stock.GoUp , Gtk.IconSize.Button);
		Button button_zoom_up = new Button (image_GoUp);
		button_zoom_up.Clicked += new EventHandler (button_zoom_up_click);
		hbox.PackStart(button_zoom_up,false,false,0);
		
		Image image_GoDown = new Gtk.Image(Gtk.Stock.GoDown, Gtk.IconSize.Button);
		Button button_zoom_down = new Button (image_GoDown);
		button_zoom_down.Clicked += new EventHandler (button_zoom_down_click);
		hbox.PackStart(button_zoom_down,false,false,0);
		
		Image image_GoBack = new Gtk.Image(Gtk.Stock.GoBack , Gtk.IconSize.Button);
		Button button_zoom_left = new Button (image_GoBack );
		button_zoom_left.Clicked += new EventHandler (button_zoom_left_click);
		hbox.PackStart(button_zoom_left,false,false,0);
		
		Image image_GoForward = new Gtk.Image(Gtk.Stock.GoForward, Gtk.IconSize.Button);
		Button button_zoom_right = new Button (image_GoForward);
		button_zoom_right.Clicked += new EventHandler (button_zoom_right_click);
		hbox.PackStart(button_zoom_right,false,false,0);
		
		Image image_ZoomIn = new Gtk.Image(Gtk.Stock.ZoomIn, Gtk.IconSize.Button);
		Button button_zoom_in = new Button (image_ZoomIn);
		button_zoom_in.Clicked += new EventHandler (button_zoom_in_click);
		hbox.PackStart(button_zoom_in,false,false,0);
		
		Image image_ZoomOut = new Gtk.Image(Gtk.Stock.ZoomOut, Gtk.IconSize.Button);
		Button button_zoom_out = new Button (image_ZoomOut);
		button_zoom_out.Clicked += new EventHandler (button_zoom_out_click);
		hbox.PackStart(button_zoom_out,false,false,0);
		
		Image image_Zoom100 = new Gtk.Image(Gtk.Stock.Zoom100, Gtk.IconSize.Button);
		Button button_zoom_100 = new Button (image_Zoom100);
		button_zoom_100.Clicked += new EventHandler (button_zoom_100_click);
		hbox.PackStart(button_zoom_100,false,false,0);
		
		Image image_Save = new Gtk.Image(Gtk.Stock.Save, Gtk.IconSize.Button);
		Button button_save = new Button (image_Save);
		button_save.Clicked += new EventHandler (button_save_click);
		hbox.PackStart(button_save,false,false,0);
		
		label_coord = new Label ("( x ; y)");
		hbox.PackEnd(label_coord,false,false,0);
		
		
		this.MotionNotifyEvent += new MotionNotifyEventHandler(on_mouse_move_graph);
		this.LeaveNotifyEvent += new LeaveNotifyEventHandler(on_mouse_leave_graph);
		this.Events = Gdk.EventMask.ExposureMask | Gdk.EventMask.LeaveNotifyMask | Gdk.EventMask.ButtonPressMask | Gdk.EventMask.PointerMotionMask | Gdk.EventMask.PointerMotionHintMask;
		
		vbox.PackStart(hbox,true,true,0);

		win = new Gtk.Window ("Screen");
		
		Gdk.Pixbuf icon = new Gdk.Pixbuf(null, "gm.png");
		win.Icon = icon; 
		
		//Gdk.GC gc = new Gdk.GC (win);
		//Gdk.Color red_color = new Gdk.Color (0xff, 0, 0);
		//gc.Foreground = red_color;                                                                                     
                                                                                                                                                       
		win.SetDefaultSize (501, 501);
		win.Resizable = false;
		  
		this.ExposeEvent += OnExposed;
                    
		win.Add (vbox);
		win.ShowAll ();
                   
		this.equation = equation1;
		this.equation2 = equation21; 
		this.equation3 = equation31;  
		this.x_min = x_min1;
		this.x_max = x_max1;
		this.y_min = y_min1;
		this.y_max = y_max1;
		this.graduation = graduation1;
		
		this.black_screen = true;
		this.grid = false;
		
		this.simpson = false;
		this.derivative = false;
		this.secondderivative = false;
		
		this.extension_exist = false;
		this.extension_show = false;
		
		// color
		gc_red = new Gdk.GC (this.GdkWindow);
		gc_green = new Gdk.GC (this.GdkWindow);
		gc_blue = new Gdk.GC (this.GdkWindow);
		gc_a = new Gdk.GC (this.GdkWindow);
		gc_black = new Gdk.GC (this.GdkWindow);
		gc_white = new Gdk.GC (this.GdkWindow);
		gc_gray = new Gdk.GC (this.GdkWindow);
		gc_cyan = new Gdk.GC (this.GdkWindow);
		gc_orange = new Gdk.GC (this.GdkWindow);
		Gdk.Color red_color = new Gdk.Color (0xff, 0, 0);
		Gdk.Color green_color = new Gdk.Color (0 , 0xff, 0);
		Gdk.Color blue_color = new Gdk.Color (0 , 0, 0xff);
		Gdk.Color black_color = new Gdk.Color (0 , 0, 0);
		Gdk.Color a_color = new Gdk.Color (0xff, 0, 0xff);
		Gdk.Color white_color = new Gdk.Color (0xff, 0xff, 0xff);
		Gdk.Color gray_color = new Gdk.Color (195, 195, 195);
		Gdk.Color cyan_color = new Gdk.Color (0, 0xff, 0xff);
		Gdk.Color orange_color = new Gdk.Color (0xff, 140, 0);
		Gdk.Colormap colormap = Gdk.Colormap.System;     
		Gdk.Color[] tab_color = new Gdk.Color[100];
		tab_color[0] = red_color;
		tab_color[1] = green_color;
		tab_color[2] = blue_color;
		tab_color[3] = a_color;
		tab_color[4] = black_color;
		tab_color[5] = white_color;
		tab_color[6] = gray_color;
		tab_color[7] = cyan_color;
		tab_color[8] = orange_color;
		bool[] tab_bool = new bool[100];
		colormap.AllocColors(tab_color, 9, true, true, tab_bool);
		gc_red.Foreground = tab_color[0];
		gc_green.Foreground = tab_color[1];
		gc_blue.Foreground = tab_color[2];
		gc_a.Foreground = tab_color[3];
		gc_black.Foreground = tab_color[4];
		gc_white.Foreground = tab_color[5];
		gc_gray.Foreground = tab_color[6];
		gc_cyan.Foreground = tab_color[7];
		gc_orange.Foreground = tab_color[8];
	}
 
	void OnExposed (object o, ExposeEventArgs args)
	{
		trace_all();	
	}
	
	void trace_all()
	{		
		if(first_draw){
			clear_graph();
			if(simpson)
				trace_simpson();
				
			trace_axe();
			
			if(derivative)
				trace_derivative();
			if(secondderivative)
				trace_secondderivative();
			trace_equation();
			first_draw = false;
		}
		else{
			clear_graph();
			if(simpson)
				trace_simpson();
				
			trace_axe();
			
			if(derivative)
				trace_derivative();
			if(secondderivative)
				trace_secondderivative();
			trace_equation_buffer();
		}
	}
 
 	void clear_graph()
 	{
 		if (this.black_screen)	
 			this.GdkWindow.DrawRectangle(gc_black, true, -10, -10, 520, 520);
 		else
 			this.GdkWindow.DrawRectangle(gc_white, true, -10, -10, 520, 520);
 	}
 
 	// draw axes
	void trace_axe()
	{
 		int x0 = (int) Math.Round(trans_x(0f));	
 		int y0 = (int) Math.Round(trans_y(0f));
 		int xmax = (int) Math.Round(trans_x(x_max));
 		int xmin = (int) Math.Round(trans_x(x_min));
 		int ymax = (int) Math.Round(trans_y(y_max));
 		int ymin = (int) Math.Round(trans_y(y_min));
            
		// graduation for x
		if (x_max>0){	
			//0 to max		
			for(double i2=trans_x(0f); i2<=trans_x(x_max); i2=i2+ graduation*500/(x_max - x_min) ){
				if (this.grid)
					this.GdkWindow.DrawLine(gc_gray, (int) Math.Round(i2), ymin, (int) Math.Round(i2), ymax );
				this.GdkWindow.DrawLine(gc_blue, (int) Math.Round(i2), y0, (int) Math.Round(i2), y0-5 );
			}
		}
		if (x_min<0){
			//0 to min
			for(double i2=trans_x(0f); i2>=trans_x(x_min); i2=i2-graduation*500/(x_max - x_min) ){
				if (this.grid)
					this.GdkWindow.DrawLine(gc_gray, (int) Math.Round(i2), ymin, (int) Math.Round(i2), ymax );
				this.GdkWindow.DrawLine(gc_blue, (int) Math.Round(i2), y0, (int) Math.Round(i2), y0-5 );
			}
		}					
				
		// graduation for y
		if (y_min<0){
			//0 to min
			for(double i2=trans_y(0f); i2<=trans_y(y_min); i2=i2+graduation*500/(y_max - y_min) ){
				if (this.grid)
					this.GdkWindow.DrawLine(gc_gray, xmin, (int) Math.Round(i2), xmax, (int) Math.Round(i2));
				this.GdkWindow.DrawLine(gc_blue, x0, (int) Math.Round(i2), x0+5, (int) Math.Round(i2));
			}
		}
		if (y_max>0){
			//0 to max	
			for(double i2=trans_y(0f); i2>=trans_y(y_max); i2=i2-graduation*500/(y_max - y_min) ){
				if (this.grid)
					this.GdkWindow.DrawLine(gc_gray, xmin, (int) Math.Round(i2), xmax,(int) Math.Round(i2));
				this.GdkWindow.DrawLine(gc_blue, x0, (int) Math.Round(i2), x0+5,(int) Math.Round(i2));
			}
		}
		
		 //axe
 		this.GdkWindow.DrawLine(gc_blue, xmin, y0, xmax, y0);
		this.GdkWindow.DrawLine(gc_blue, x0, ymin, x0, ymax);
 	}
 	
 	// draw 3 functions 	
	void trace_equation()
	{
		Gdk.GC gc_eq;	
		for(int i_eq=0; i_eq <3; i_eq++){
 			
			operation op = new operation(equation);
 			gc_eq = gc_red;
 				 	
			if(i_eq==1){
				op = new operation(equation2);				
				gc_eq = gc_a;
			}
			else if(i_eq==2){
				op = new operation(equation3);
				gc_eq = gc_green;
			}
 				
			op.corrige();

			try{
				double xc_1 = x_min;
				double yc_1 = op.calculer(x_min);			
				double xc_2;
				double yc_2;
												
				double pitch=(x_max-x_min)/500;
				double x_1;
				double y_1;
				double x_2;
				double y_2;
				
				// save results
				int i_save = 0;
				if(i_eq ==0){
					tab_result1_x[i_save] = trans_x(xc_1);
					tab_result1_y[i_save] = trans_y(yc_1);
				}
				else if(i_eq ==1){
					tab_result2_x[i_save] = trans_x(xc_1);
					tab_result2_y[i_save] = trans_y(yc_1);
				}
				else if(i_eq ==2){
					tab_result3_x[i_save] = trans_x(xc_1);
					tab_result3_y[i_save] = trans_y(yc_1);
				}							
												
				for(double i_graph=x_min; i_graph<=x_max; i_graph=i_graph+pitch){
					xc_2 = xc_1+pitch;
					yc_2 = op.calculer(xc_2);
															
					x_1 = trans_x(xc_1);
					y_1 = trans_y(yc_1);
					x_2 = trans_x(xc_2);
					y_2 = trans_y(yc_2);
					
					// save results
					i_save++;
					if(i_eq ==0){
						tab_result1_x[i_save] = x_2;
						tab_result1_y[i_save] = y_2;
					}
					else if(i_eq ==1){
						tab_result2_x[i_save] = x_2;
						tab_result2_y[i_save] = y_2;
					}
					else if(i_eq ==2){
						tab_result3_x[i_save] = x_2;
						tab_result3_y[i_save] = y_2;
					}

					if(!Double.IsNaN(yc_1) && !Double.IsNaN(yc_2)){
						if((yc_1>y_min && yc_1<y_max) || (yc_2>y_min && yc_2<y_max)){
							this.GdkWindow.DrawLine(gc_eq, (int) Math.Round(x_1), (int) Math.Round(y_1), (int) Math.Round(x_2), (int) Math.Round(y_2));
						}
					}
															
					// next point
					xc_1=xc_2;
					yc_1=yc_2;
					
				}
			}	
			catch(Exception ex)
			{	
			} 
				
		}		
 		
	}
	
	// draw 3 functions using buffers
	void trace_equation_buffer()
	{
		for(int i =0; i<500; i++){
			if(!Double.IsNaN(tab_result1_y[i]) && !Double.IsNaN(tab_result1_y[i+1])){
				if((tab_result1_y[i]>0 && tab_result1_y[i]<500) || (tab_result1_y[i+1]>0 && tab_result1_y[i+1]<500)){	
					this.GdkWindow.DrawLine(gc_red, (int) Math.Round(tab_result1_x[i]), (int) Math.Round(tab_result1_y[i]), (int) Math.Round(tab_result1_x[i+1]), (int) Math.Round(tab_result1_y[i+1]));
				}
			}
		}
		
		for(int i =0; i<500; i++){
			if(!Double.IsNaN(tab_result2_y[i]) && !Double.IsNaN(tab_result2_y[i+1])){
				if((tab_result2_y[i]>0 && tab_result2_y[i]<500) || (tab_result2_y[i+1]>0 && tab_result2_y[i+1]<500)){	
					this.GdkWindow.DrawLine(gc_a, (int) Math.Round(tab_result2_x[i]), (int) Math.Round(tab_result2_y[i]), (int) Math.Round(tab_result2_x[i+1]), (int) Math.Round(tab_result2_y[i+1]));
				}
			}
		}
		
		for(int i =0; i<500; i++){
			if(!Double.IsNaN(tab_result3_y[i]) && !Double.IsNaN(tab_result3_y[i+1])){
				if((tab_result3_y[i]>0 && tab_result3_y[i]<500) || (tab_result3_y[i+1]>0 && tab_result3_y[i+1]<500)){	
					this.GdkWindow.DrawLine(gc_green, (int) Math.Round(tab_result3_x[i]), (int) Math.Round(tab_result3_y[i]), (int) Math.Round(tab_result3_x[i+1]), (int) Math.Round(tab_result3_y[i+1]));
				}
			}
		}
	}
	
	// drawing net aera
	void trace_simpson()
	{
		try{
			if (first_draw){
				operation op = new operation(equation);
			
				double xc_1 = x_min;
				double yc_1 = op.calculer(x_min);
				double xc_2;
				double yc_2;
											
				double pitch=(x_max-x_min)/500;
				double x_1;
				double y_1;
				double x_2;
				double y_2;
																
				for(double i_graph=x_min; i_graph<=x_max; i_graph=i_graph+pitch){
					xc_2 = xc_1+pitch;
					yc_2 = op.calculer(xc_2);
														
					x_1 = trans_x(xc_1);
					y_1 = trans_y(yc_1);
					x_2 = trans_x(xc_2);
					y_2 = trans_y(yc_2);
	
					if(!Double.IsNaN(yc_1) && !Double.IsNaN(yc_2)){
						this.GdkWindow.DrawLine(gc_red, (int) Math.Round(x_1), (int) Math.Round(trans_y(0f)), (int) Math.Round(x_1), (int) Math.Round(y_1));
						this.GdkWindow.DrawLine(gc_red, (int) Math.Round(x_2), (int) Math.Round(trans_y(0f)), (int) Math.Round(x_2), (int) Math.Round(y_2));
					}										
					// next point
					xc_1=xc_2;
					yc_1=yc_2;	
				}
			}
			else {	// using buffer of Fn 1
				for(int i =0; i<500; i++){
					if(!Double.IsNaN(tab_result1_y[i]) && !Double.IsNaN(tab_result1_y[i+1])){
							this.GdkWindow.DrawLine(gc_red, (int) Math.Round(tab_result1_x[i]), (int) Math.Round(trans_y(0f)), (int) Math.Round(tab_result1_x[i]), (int) Math.Round(tab_result1_y[i]));
							this.GdkWindow.DrawLine(gc_red, (int) Math.Round(tab_result1_x[i+1]), (int) Math.Round(trans_y(0f)), (int) Math.Round(tab_result1_x[i+1]), (int) Math.Round(tab_result1_y[i+1]));
					}
				}
			}
		}	
		catch(Exception ex)
		{	
		}
	}
	
	void trace_derivative()
	{
		try{
			if (first_draw){
				Calculus c = new Calculus(equation);
			
				double xc_1 = x_min;
				double yc_1 = c.ndfdx(this.x_min);			
				double xc_2;
				double yc_2;
											
				double pitch=(x_max-x_min)/500;
				double x_1;
				double y_1;
				double x_2;
				double y_2;
				
				// save results
				int i_save = 0;
				
				tab_result_derivative_x[i_save] = trans_x(xc_1);
				tab_result_derivative_y[i_save] = trans_y(yc_1);
																
				for(double i_graph=x_min; i_graph<=x_max; i_graph=i_graph+pitch){
					xc_2 = xc_1+pitch;
					yc_2 = c.ndfdx(xc_2);
														
					x_1 = trans_x(xc_1);
					y_1 = trans_y(yc_1);
					x_2 = trans_x(xc_2);
					y_2 = trans_y(yc_2);
					
					// save results
					i_save++;
					tab_result_derivative_x[i_save] = x_2;
					tab_result_derivative_y[i_save] = y_2;
	
					if(!Double.IsNaN(yc_1) && !Double.IsNaN(yc_2)){
						if((yc_1>y_min && yc_1<y_max) || (yc_2>y_min && yc_2<y_max)){
							this.GdkWindow.DrawLine(gc_cyan, (int) Math.Round(x_1), (int) Math.Round(y_1), (int) Math.Round(x_2), (int) Math.Round(y_2));
						}
					}										
					// next point
					xc_1=xc_2;
					yc_1=yc_2;	
				}
			}
			else {	// using buffer tab_result_derivative
				for(int i =0; i<500; i++){
					if(!Double.IsNaN(tab_result_derivative_y[i]) && !Double.IsNaN(tab_result_derivative_y[i+1])){
						if((tab_result_derivative_y[i]>0 && tab_result_derivative_y[i]<500) || (tab_result_derivative_y[i+1]>0 && tab_result_derivative_y[i+1]<500)){	
							this.GdkWindow.DrawLine(gc_cyan, (int) Math.Round(tab_result_derivative_x[i]), (int) Math.Round(tab_result_derivative_y[i]), (int) Math.Round(tab_result_derivative_x[i+1]), (int) Math.Round(tab_result_derivative_y[i+1]));
						}
					}
				}
			}
		}	
		catch(Exception ex)
		{	
		}
	}
	
	void trace_secondderivative()
	{
		try{
			if (first_draw){
				Calculus c = new Calculus(equation);
			
				double xc_1 = x_min;
				double yc_1 = c.n2dfdx(this.x_min);			
				double xc_2;
				double yc_2;
											
				double pitch=(x_max-x_min)/500;
				double x_1;
				double y_1;
				double x_2;
				double y_2;
				
				// save results
				int i_save = 0;
				
				tab_result_secondderivative_x[i_save] = trans_x(xc_1);
				tab_result_secondderivative_y[i_save] = trans_y(yc_1);
																
				for(double i_graph=x_min; i_graph<=x_max; i_graph=i_graph+pitch){
					xc_2 = xc_1+pitch;
					yc_2 = c.n2dfdx(xc_2);
														
					x_1 = trans_x(xc_1);
					y_1 = trans_y(yc_1);
					x_2 = trans_x(xc_2);
					y_2 = trans_y(yc_2);
					
					// save results
					i_save++;
					tab_result_secondderivative_x[i_save] = x_2;
					tab_result_secondderivative_y[i_save] = y_2;
	
					if(!Double.IsNaN(yc_1) && !Double.IsNaN(yc_2)){
						if((yc_1>y_min && yc_1<y_max) || (yc_2>y_min && yc_2<y_max)){
							this.GdkWindow.DrawLine(gc_orange, (int) Math.Round(x_1), (int) Math.Round(y_1), (int) Math.Round(x_2), (int) Math.Round(y_2));
						}
					}										
					// next point
					xc_1=xc_2;
					yc_1=yc_2;	
				}
			}
			else {	// using buffer tab_result_derivative
				for(int i =0; i<500; i++){
					if(!Double.IsNaN(tab_result_secondderivative_y[i]) && !Double.IsNaN(tab_result_secondderivative_y[i+1])){
						if((tab_result_secondderivative_y[i]>0 && tab_result_secondderivative_y[i]<500) || (tab_result_secondderivative_y[i+1]>0 && tab_result_secondderivative_y[i+1]<500)){	
							this.GdkWindow.DrawLine(gc_orange, (int) Math.Round(tab_result_secondderivative_x[i]), (int) Math.Round(tab_result_secondderivative_y[i]), (int) Math.Round(tab_result_secondderivative_x[i+1]), (int) Math.Round(tab_result_secondderivative_y[i+1]));
						}
					}
				}
			}
		}	
		catch(Exception ex)
		{	
		}
	}
 		
	// transformation on x
	double trans_x(double x){
		return (500/(x_max - x_min) * (x - x_min) );	
	}
		
	// transformation on y
	double trans_y(double y){
		return ( -500/(y_max - y_min) * (y - y_max) );
	}
	
	void button_zoom_up_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (y_max-y_min)/10;
		y_min = y_min+diff;
		y_max = y_max+diff;
		this.simpson = false;
		trace_all();		
	}
	
	void button_zoom_down_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (y_max-y_min)/10;
		y_min = y_min-diff;
		y_max = y_max-diff;
		this.simpson = false;
		trace_all();		
	}
	
	void button_zoom_right_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (x_max-x_min)/10;
		x_min = x_min+diff;
		x_max = x_max+diff;
		this.simpson = false;
		trace_all();		
	}
	
	void button_zoom_left_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (x_max-x_min)/10;
		x_min = x_min-diff;
		x_max = x_max-diff;
		this.simpson = false;
		trace_all();		
	}
	
	void button_zoom_in_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (y_max-y_min)/10;
		y_min = y_min+diff;
		y_max = y_max-diff;
		x_min = x_min+diff;
		x_max = x_max-diff;
		this.simpson = false;
		trace_all();
				
	}
	
	void button_zoom_out_click (object o, EventArgs args)
	{
		first_draw = true;
		double diff = (y_max-y_min)/10;
		y_min = y_min-diff;
		y_max = y_max+diff;
		x_min = x_min-diff;
		x_max = x_max+diff;
		this.simpson = false;
		trace_all();				
	}
	
	void button_zoom_100_click (object o, EventArgs args)
	{
		first_draw = true;
		y_min = -10;
		y_max = 10;
		x_min = -10;
		x_max = 10;
		this.simpson = false;
		trace_all();				
	}
	
	// save graph on PNG file
	void button_save_click (object o, EventArgs args)
	{
	
		Gdk.Pixbuf dbuf = new Gdk.Pixbuf(Gdk.Colorspace.Rgb,false,8,500,500);
		dbuf.GetFromImage(this.GdkWindow.GetImage(0,0,500,500), this.Colormap,0,0,0,0,500,500);
		
		FileChooserDialog fc = new FileChooserDialog("Save Graph As...", null, FileChooserAction.Save);
		
		fc.LocalOnly = false;
		fc.AddButton (Stock.Cancel, ResponseType.Cancel);
		fc.AddButton (Stock.Save, ResponseType.Ok);
		
		FileFilter fil = new FileFilter();
		fil.Name = "PNG Files";
		fil.AddPattern("*.png");
		fc.AddFilter(fil);
		fc.DefaultResponse = ResponseType.Ok;
		int resp = fc.Run();
		fc.Hide();
		
		if (resp == (int)ResponseType.Ok)
			dbuf.Save(fc.Filename,"png");
				
	}
	
	void on_mouse_leave_graph(object o, LeaveNotifyEventArgs args) {
		label_coord.Text = "( x ; y )";
	}
	
	// display (X,Y) of the mouse point
	void on_mouse_move_graph(object o, MotionNotifyEventArgs args)
	{
		int x=0;
		int y=0;
		Gdk.Window window = args.Event.Window;

		if (args.Event.IsHint) {
			Gdk.ModifierType s;
			window.GetPointer (out x, out y, out s);
		} 
		else {
			x = (int) args.Event.X;
			y = (int) args.Event.Y;
		}
		
		label_coord.Text= "( "+Math.Round(x_min+x*((x_max-x_min)/500), 2).ToString() + " ; "+Math.Round((y_max+y*((y_max-y_min)/(-500))), 2).ToString()+" )";
		args.RetVal = true;
	}
	
	// change color of screen
	void wbscreen_cb (object o, EventArgs args)
	{
		this.black_screen = !this.black_screen;
		trace_all();
	}
	
	// display or not the grid
	void grid_cb (object o, EventArgs args)
	{
		this.grid = !this.grid;
		trace_all();
	}
	
	/*
	void info_cb (object o, EventArgs args)
	{
		InfoCurve_Form ic = new InfoCurve_Form();
		ic.Show();
	}
	*/
	
	// Net Area
	void simpson_cb (object o, EventArgs args)
	{
		if(!extension_exist){
			statusbar = new Statusbar();
			statusbar.HeightRequest = 25;
			vbox.PackStart(statusbar,true,true,0);
			//statusbar.Push(0,"test");
			win.ShowAll ();
			extension_exist = true;
			extension_show = true;
			
		}
		else if(!extension_show){
			statusbar.Show();
			extension_show = true;
		}
			
		first_draw = true;
		this.simpson = true;
		trace_all();
		
		if(extension_exist){
			if (this.equation != ""){
				try {
					Calculus c = new Calculus(this.equation);
					double s = c.simpsonsrule(x_min, x_max);
					statusbar.Push(0,"Net Area Under Fn 1 = " + s.ToString());
				}
				catch (Exception ex) {
					statusbar.Push(0,"Could not calculate area under curve!");

				}
			}
			else
				statusbar.Push(0,"Fn 1 does not exist!");
		}
	}
	
	// average value
	void averagevalue_cb (object o, EventArgs args)
	{
		if(!extension_exist){
			statusbar = new Statusbar();
			statusbar.HeightRequest = 25;
			vbox.PackStart(statusbar,true,true,0);
			//statusbar.Push(0,"test");
			win.ShowAll ();
			extension_exist = true;
			extension_show = true;
		}
		else if(!extension_show){
			statusbar.Show();
			extension_show = true;
		}
		
		if(extension_exist)
		{
			if (this.equation != ""){
				try {
					Calculus c = new Calculus(this.equation);
					double s = c.averagevalue(x_min, x_max);
					statusbar.Push(0,"Average Value of Eq 1 = " + s.ToString());
				}
				catch (Exception ex) {
					statusbar.Push(0,"Could not calculate the average value!");

				}
			}
			else
				statusbar.Push(0,"Fn 1 does not exist!");
		}
	}
	
	// draw derivative
	void derivative_cb (object o, EventArgs args)
	{
		first_draw = true;
		this.derivative = true;
		trace_all();
	}
	
	// draw second derivative
	void secondderivative_cb (object o, EventArgs args)
	{
		first_draw = true;
		this.secondderivative = true;
		trace_all();
	}
	
	// clear all calculus
	void clear_cb (object o, EventArgs args)
	{
		if (extension_show)
		{
			statusbar.Hide();
			extension_show = false;
		}
		
		first_draw = true;
		this.simpson = false;
		this.derivative = false;
		this.secondderivative = false;
		trace_all();
	}
 
}