Problem of screen getting cleard

Question

Hi,
I am simulating a paint application using graphics object. The problem happening is ,whenever i draw a new shape the previous one is getting cleared off. I don't want that to happen. I want the shape to be there howmuch ever time i redraw the shapes. Please tell me the solution for this....

Jan Montano · Answer

I understand now. Hmm... I am not an expert with gdi. I just did some workaround with your code. This is all I could think of right now. I'm not sure if we could preserve what's already painted in your form. I kept seeing in forums that it could be preserved if we use image. But I have no idea yet how to do it. Goodluck. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Drawing.Imaging; using System.Drawing.Drawing2D; using System.Text; using System.Windows.Forms; namespace CreateShapes { public partial class Form1 : Form { private System.Drawing.Bitmap myBitmap; public static int index; int FirstXCoordinate, FirstYCoordinate, SecondXCoordinate, SecondYCoordinate; bool mousePressed; Graphics[] g = new Graphics[100]; GraphicsState gs; List rectangles = new List (); public Form1() { InitializeComponent(); this.MouseDown += new MouseEventHandler(Form1_MouseDown); //this.Paint += new PaintEventHandler(Form1_Paint); this.MouseWheel += new MouseEventHandler(Form1_MouseWheel); this.MouseUp += new MouseEventHandler(Form1_MouseUp); } void Form1_MouseWheel(object sender, MouseEventArgs e) { SecondXCoordinate = e.X; SecondYCoordinate = e.Y; //MessageBox.Show(e.X.ToString()); if (mousePressed == true) { this.Paint += new PaintEventHandler(Form1_Paint); Refresh(); } else { this.Paint -= new PaintEventHandler(Form1_Paint); } } void Form1_Paint(object sender, PaintEventArgs e) { g[index] = e.Graphics; myBitmap = new Bitmap(50, 50); Rectangle rect = new Rectangle(50, 50, 20, 20); g[index].DrawImage(myBitmap, 0, 0, 20, 20); g[index].DrawRectangle(new Pen(Color.Black), FirstXCoordinate, FirstYCoordinate, (SecondXCoordinate - FirstXCoordinate), (SecondYCoordinate - FirstYCoordinate)); foreach (Rectangle rectangle in rectangles) { e.Graphics.DrawRectangle(Pens.Red, rectangle); } } void Form1_MouseDown(object sender, MouseEventArgs e) { //for (int i = 0; i //{ // MessageBox.Show(index.ToString()); // g[i].DrawRectangle(new Pen(Color.Black), FirstXCoordinate, FirstYCoordinate, (SecondXCoordinate - FirstXCoordinate), (SecondYCoordinate - FirstYCoordinate)); //} FirstXCoordinate = e.X; FirstYCoordinate = e.Y; mousePressed = true; MouseMove += new MouseEventHandler(Form1_MouseWheel); } void Form1_MouseUp(object sender, MouseEventArgs e) { //MessageBox.Show("up"); SecondXCoordinate = e.X; SecondYCoordinate = e.Y; ResetMouseEventArgs(); mousePressed = false; //ImageConverter img = new ImageConverter(); //g[index] = this.CreateGraphics(); //this.Paint += new PaintEventHandler(Form1_Paint); //index++; rectangles.Add(new Rectangle(FirstXCoordinate, FirstYCoordinate, SecondXCoordinate - FirstXCoordinate, SecondYCoordinate - FirstYCoordinate)); } private void Form1_Load(object sender, EventArgs e) { } } }

Vipin Mammen · Answer

This is my code..... using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Drawing.Imaging; using System.Drawing.Drawing2D; using System.Text; using System.Windows.Forms; namespace CreateShapes { public partial class Form1 : Form { private System.Drawing.Bitmap myBitmap; public static int index; int FirstXCoordinate, FirstYCoordinate, SecondXCoordinate, SecondYCoordinate; bool mousePressed; Graphics[] g =new Graphics[100]; GraphicsState gs; public Form1() { InitializeComponent(); this.MouseDown += new MouseEventHandler(Form1_MouseDown); this.Paint += new PaintEventHandler(Form1_Paint); this.MouseWheel+=new MouseEventHandler(Form1_MouseWheel); this.MouseUp+=new MouseEventHandler(Form1_MouseUp); } void Form1_MouseWheel(object sender, MouseEventArgs e) { SecondXCoordinate = e.X; SecondYCoordinate = e.Y; //MessageBox.Show(e.X.ToString()); if(mousePressed==true) { this.Paint += new PaintEventHandler(Form1_Paint); Refresh(); } } void Form1_Paint(object sender, PaintEventArgs e) { g[index] = e.Graphics; myBitmap = new Bitmap(50, 50); Rectangle rect = new Rectangle(50, 50, 20, 20); g[index].DrawImage(myBitmap, 0, 0, 20, 20); g[index].DrawRectangle(new Pen(Color.Black), FirstXCoordinate, FirstYCoordinate, (SecondXCoordinate - FirstXCoordinate), (SecondYCoordinate - FirstYCoordinate)); } void Form1_MouseDown(object sender, MouseEventArgs e) { for (int i = 0; i { MessageBox.Show(index.ToString()); g[i].DrawRectangle(new Pen(Color.Black), FirstXCoordinate, FirstYCoordinate, (SecondXCoordinate - FirstXCoordinate), (SecondYCoordinate - FirstYCoordinate)); } FirstXCoordinate = e.X; FirstYCoordinate = e.Y; mousePressed = true; MouseMove += new MouseEventHandler(Form1_MouseWheel); } void Form1_MouseUp(object sender, MouseEventArgs e) { //MessageBox.Show("up"); SecondXCoordinate = e.X; SecondYCoordinate = e.Y; ResetMouseEventArgs(); mousePressed = false; ImageConverter img = new ImageConverter(); g[index] = this.CreateGraphics(); this.Paint += new PaintEventHandler(Form1_Paint); index++; } private void Form1_Load(object sender, EventArgs e) { } } }

maveric · Answer

I think your form is refreshing for every user action, so only you are getting a new line and the old one deleted. If you could put your code for review, we could help you much better.

Jan Montano · Answer

Could you post some code related to the drawing of the shape.