Click here to Skip to main content
11,411,312 members (69,013 online)
Click here to Skip to main content

A marquee control in C#

, 19 Feb 2003 CPOL
Rate this:
Please Sign up or sign in to vote.
A marquee control written in C#

Overview

This application demonstrates how to create a "string loop" in C#. A common use of "string loops" is in web advertisements, where the slogan or product name appears to be revolving in a circle. The code creates a rectangle in the middle of the client area that is just large enough to fit the entire message, minus any trailing white space. Clicking on the form or resizing it will cause the "string loop" to restart.

Points to Notice

Rather than use a string to represent the message ("Catch Me If You Can…" ) it is far more efficient and intuitive to use the StringBuilder class, found in the System.Text namespace. StringBuilder allows you to directly manipulate a string, rather than having to make copies of a regular string. The manipulation of the StringBuilder’s internal string is quite straightforward:

private void DrawMovingText()
{
    Graphics grfx = CreateGraphics();
    Font font = new Font( "Courier New", 20, FontStyle.Bold );
    string spaces = " ";
    // 
    // StringBuilder is used to allow for efficient manipulation of 
    // one string, rather than generating many separate strings
    //
    StringBuilder str = 
        new StringBuilder( "Catch Me If You Can..." + spaces );

    Rectangle rect = CreateRect( grfx, str, font );

    int numCycles = str.Length * 3 + 1;
    for( int i = 0; i < numCycles; ++i )
    {
        grfx.FillRectangle( Brushes.White, rect );
        grfx.DrawString( str.ToString(), font, Brushes.Red, rect );
        // relocate the first char to the end of the string
        str.Append( str[0] );
        str.Remove( 0, 1 );
        // pause for visual effect
        Thread.Sleep( 150 );
    }
    grfx.Dispose();
}

To avoid having DrawMovingText() eat up all of the CPU's attention it is placed on a worker thread. Every time the user clicks on the form or resizes it, the thread is killed and reborn. Obviously, if you wanted to alter the speed at which the letters "move" you would simply adjust the number of milliseconds that the thread sleeps for.

//
// All of these events will restart the thread that draws 
// the text
//
private void Form_Load( object sender, System.EventArgs e )
{
    StartThread();
}
private void Form_MouseUp(object sender, 
                          System.Windows.Forms.MouseEventArgs e)
{
    StartThread();
}
private void Form_Resize( object sender, System.EventArgs e )
{
    StartThread();
}
private void label_Click(object sender, System.EventArgs e)
{
    StartThread();
}
private void StartThread()
{
    thread.Abort();
    // give the thread time to die
    Thread.Sleep( 100 ); 
    Invalidate();
    thread = new Thread(new ThreadStart(DrawMovingText));
    thread.Start();
}

The final point of interest is how the size and location of the rectangle that contains the message are determined. The Graphics class has a MeasureString method that will give you the width or height of the string that you are passing in. Those are used for the width and height of the rectangle. You then use those values in tandem with the dimensions of the form to determine the coordinates of where the rectangle will originate from.

private Rectangle CreateRect
( Graphics grfx, StringBuilder str, Font font )
{
    // + 5 to allow last char to fit
    int w = (int)grfx.MeasureString(str.ToString(), font).Width + 5; 
    int h = (int)grfx.MeasureString( str.ToString(), font ).Height;
    int x = (int)this.Width / 2 - w / 2;
    int y = (int)this.Height / 2 - h;
    return new Rectangle( x, y, w, h );
}

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Josh Smith
Software Developer (Senior) Cynergy Systems
United States United States
Josh creates software, for iOS and Windows.

He works at Cynergy Systems as a Senior Experience Developer.

Read his iOS Programming for .NET Developers[^] book to learn how to write iPhone and iPad apps by leveraging your existing .NET skills.

Use his Master WPF[^] app on your iPhone to sharpen your WPF skills on the go.

Check out his Advanced MVVM[^] book.

Visit his WPF blog[^] or stop by his iOS blog[^].
Follow on   Twitter

Comments and Discussions

 
QuestionNice piece of app! PinmemberDaniel Quiming2-Nov-14 20:54 
GeneralMy vote of 5 Pinmembermanoj kumar choubey5-Mar-12 3:27 
GeneralMy vote of 1 Pinmemberali32b21-Nov-10 5:30 
QuestionTransparent background of rectangle PinmemberMember 273427022-Jun-09 19:45 
AnswerRe: Transparent background of rectangle Pinmemberrootjumper17-Sep-09 23:22 
GeneralWidth of scrolling text. PinmemberDivermarv27-Aug-04 13:44 
GeneralRe: Width of scrolling text. PinmemberIcemanlaw30-Jan-05 5:34 
GeneralThread.Join PinmemberThong Nguyen20-Feb-03 18:23 
GeneralRe: Thread.Join PinmemberThong Nguyen20-Feb-03 18:26 
GeneralRe: Thread.Join PinmemberMichael Potter21-Feb-03 3:53 
GeneralRe: Thread.Join Pinmemberleppie21-Feb-03 7:12 
GeneralRe: Thread.Join PinmemberMichael Potter21-Feb-03 7:51 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web01 | 2.8.150414.5 | Last Updated 20 Feb 2003
Article Copyright 2003 by Josh Smith
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid