constrainedtextfield.java

FuncPlotter is a combined Java application and applet for displaying two-dimensional plots of explic

/*====================================================================*\

ConstrainedTextField.java

Constrained text field class.

------------------------------------------------------------------------

This file is part of FuncPlotter, a combined Java application and applet
for plotting explicit functions in one variable.
Copyright 2005-2007 Andy Morgan-Richards.

FuncPlotter 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 3 of the License, or (at your
option) 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, see <http://www.gnu.org/licenses/>.

\*====================================================================*/


// PACKAGE


package textfield;

//----------------------------------------------------------------------


// IMPORTS


import java.awt.Toolkit;

import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.PlainDocument;

//----------------------------------------------------------------------


// CONSTRAINED TEXT FIELD CLASS


public class ConstrainedTextField
    extends AbstractTextField
{

////////////////////////////////////////////////////////////////////////
//  Member classes : inner classes
////////////////////////////////////////////////////////////////////////


    // CONSTRAINED TEXT DOCUMENT CLASS


    private class ConstrainedTextDocument
        extends PlainDocument
    {

    ////////////////////////////////////////////////////////////////////
    //  Constants
    ////////////////////////////////////////////////////////////////////

        private static final    String  BEYOND_END_STR  = "Offset beyond end of text";

    ////////////////////////////////////////////////////////////////////
    //  Constructors
    ////////////////////////////////////////////////////////////////////

        private ConstrainedTextDocument( )
        {
        }

        //--------------------------------------------------------------

    ////////////////////////////////////////////////////////////////////
    //  Instance methods : overriding methods
    ////////////////////////////////////////////////////////////////////

        public void insertString( int          offset,
                                  String       str,
                                  AttributeSet attrSet )
            throws BadLocationException
        {

            // Test for offset beyond end of text

            int currentLength = getLength( );
            if ( offset > currentLength )
                throw new BadLocationException( BEYOND_END_STR, offset );

            // Translate string

            String srcStr = translateInsertString( str, offset );

            // Create an array of characters to be inserted from the valid characters in the string

            char[] insertBuf = new char[srcStr.length( )];
            int insertLength = 0;
            for ( int i = 0; i < srcStr.length( ); ++i )
            {
                char ch = validateCharacter( srcStr.charAt( i ), offset + insertLength );
                if ( ch != TextFieldConstants.INVALID_CHAR )
                    insertBuf[insertLength++] = ch;
            }
            boolean isError = (insertLength < srcStr.length( ));

            // If inserted characters would make the text too long, remove excess from end of text

            if ( currentLength + insertLength > maxLength )
            {
                isError = true;
                if ( insertLength > maxLength - offset )
                    insertLength = maxLength - offset;
                if ( (insertLength > 0) && (offset < currentLength) )
                {
                    int excessLength = currentLength + insertLength - maxLength;
                    if ( excessLength > 0 )
                        remove( currentLength - excessLength, excessLength );
                }
            }

            // Beep if not all input string will be inserted

            if ( isError )
                Toolkit.getDefaultToolkit( ).beep( );

            // Insert valid characters and set caret position to end of insertion

            if ( insertLength > 0 )
            {
                super.insertString( offset, new String( insertBuf, 0, insertLength ), attrSet );
                setCaretPosition( offset + insertLength );
            }

        }

        //--------------------------------------------------------------

    }

    //==================================================================

////////////////////////////////////////////////////////////////////////
//  Constructors
////////////////////////////////////////////////////////////////////////

    public ConstrainedTextField( int maxLength )
    {
        super( maxLength );
        this.maxLength = maxLength;
    }

    //------------------------------------------------------------------

    public ConstrainedTextField( int    maxLength,
                                 String text )
    {
        this( maxLength );
        setText( text );
    }

    //------------------------------------------------------------------

    public ConstrainedTextField( int maxLength,
                                 int columns )
    {
        super( columns );
        this.maxLength = (maxLength == 0) ? Integer.MAX_VALUE : maxLength;
    }

    //------------------------------------------------------------------

    public ConstrainedTextField( int    maxLength,
                                 int    columns,
                                 String text )
    {
        this( maxLength, columns );
        setText( text );
    }

    //------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////
//  Instance methods : overriding methods
////////////////////////////////////////////////////////////////////////

    protected Document createDefaultModel( )
    {
        return new ConstrainedTextDocument( );
    }

    //------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////
//  Instance methods
////////////////////////////////////////////////////////////////////////

    protected String translateInsertString( String str,
                                            int    offset )
    {
        return str;
    }

    //------------------------------------------------------------------

    protected char validateCharacter( char ch,
                                      int  index )
    {
        return ch;
    }

    //------------------------------------------------------------------

////////////////////////////////////////////////////////////////////////
//  Instance variables
////////////////////////////////////////////////////////////////////////

    private int maxLength;

}

//----------------------------------------------------------------------