KeyTable/js/KeyTable.js

/*
 * File:        KeyTable.js
 * Version:     1.1.7
 * CVS:         $Idj$
 * Description: Keyboard navigation for HTML tables
 * Author:      Allan Jardine (www.sprymedia.co.uk)
 * Created:     Fri Mar 13 21:24:02 GMT 2009
 * Modified:    $Date$ by $Author$
 * Language:    Javascript
 * License:     GPL v2 or BSD 3 point style
 * Project:     Just a little bit of fun :-)
 * Contact:     www.sprymedia.co.uk/contact
 * 
 * Copyright 2009-2011 Allan Jardine, all rights reserved.
 *
 * This source file is free software, under either the GPL v2 license or a
 * BSD style license, available at:
 *   http://datatables.net/license_gpl2
 *   http://datatables.net/license_bsd
 */


function KeyTable ( oInit )
{
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * API parameters
         * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
        
        /*
         * Variable: block
         * Purpose:  Flag whether or not KeyTable events should be processed
         * Scope:    KeyTable - public
         */
        this.block = false;
        
        /*
         * Variable: event
         * Purpose:  Container for all event application methods
         * Scope:    KeyTable - public
         * Notes:    This object contains all the public methods for adding and removing events - these
         *           are dynamically added later on
         */
        this.event = {
                "remove": {}
        };
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * API methods
         * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
        
        /*
         * Function: fnGetCurrentPosition
         * Purpose:  Get the currently focused cell's position
         * Returns:  array int: [ x, y ]
         * Inputs:   void
         */
        this.fnGetCurrentPosition = function ()
        {
                return [ _iOldX, _iOldY ];
        };
        
        
        /*
         * Function: fnGetCurrentData
         * Purpose:  Get the currently focused cell's data (innerHTML)
         * Returns:  string: - data requested
         * Inputs:   void
         */
        this.fnGetCurrentData = function ()
        {
                return _nOldFocus.innerHTML;
        };
        
        
        /*
         * Function: fnGetCurrentTD
         * Purpose:  Get the currently focused cell
         * Returns:  node: - focused element
         * Inputs:   void
         */
        this.fnGetCurrentTD = function ()
        {
                return _nOldFocus;
        };
        
        
        /*
         * Function: fnSetPosition
         * Purpose:  Set the position of the focused cell
         * Returns:  -
         * Inputs:   int:x - x coordinate
         *           int:y - y coordinate
         * Notes:    Thanks to Rohan Daxini for the basis of this function
         */
        this.fnSetPosition = function( x, y )
        {
                if ( typeof x == 'object' && x.nodeName )
                {
                        _fnSetFocus( x );
                }
                else
                {
                        _fnSetFocus( _fnCellFromCoords(x, y) );
                }
        };
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Private parameters
         * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
        
        /*
         * Variable: _nBody
         * Purpose:  Body node of the table - cached for renference
         * Scope:    KeyTable - private
         */
        var _nBody = null;
        
        /*
         * Variable: 
         * Purpose:  
         * Scope:    KeyTable - private
         */
        var _nOldFocus = null;
        
        /*
         * Variable: _iOldX and _iOldY
         * Purpose:  X and Y coords of the old elemet that was focused on
         * Scope:    KeyTable - private
         */
        var _iOldX = null;
        var _iOldY = null;
        
        /*
         * Variable: _that
         * Purpose:  Scope saving for 'this' after a jQuery event
         * Scope:    KeyTable - private
         */
        var _that = null;
        
        /*
         * Variable: sFocusClass
         * Purpose:  Class that should be used for focusing on a cell
         * Scope:    KeyTable - private
         */
        var _sFocusClass = "focus";
        
        /*
         * Variable: _bKeyCapture
         * Purpose:  Flag for should KeyTable capture key events or not
         * Scope:    KeyTable - private
         */
        var _bKeyCapture = false;
        
        /*
         * Variable: _oaoEvents
         * Purpose:  Event cache object, one array for each supported event for speed of searching
         * Scope:    KeyTable - private
         */
        var _oaoEvents = {
                "action": [],
                "esc": [],
                "focus": [],
                "blur": []
        };
        
        /*
         * Variable: _oDatatable
         * Purpose:  DataTables object for if we are actually using a DataTables table
         * Scope:    KeyTable - private
         */
        var _oDatatable = null;
        
        var _bForm;
        var _nInput;
        var _bInputFocused = false;
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Private methods
         * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Key table events
         */
        
        /*
         * Function: _fnEventAddTemplate
         * Purpose:  Create a function (with closure for sKey) event addition API
         * Returns:  function: - template function
         * Inputs:   string:sKey - type of event to detect
         */
        function _fnEventAddTemplate( sKey )
        {
                /*
                 * Function: -
                 * Purpose:  API function for adding event to cache
                 * Returns:  -
                 * Inputs:   1. node:x - target node to add event for
                 *           2. function:y - callback function to apply
                 *         or
                 *           1. int:x - x coord. of target cell (can be null for live events)
                 *           2. int:y - y coord. of target cell (can be null for live events)
                 *           3. function:z - callback function to apply
                 * Notes:    This function is (interally) overloaded (in as much as javascript allows for
                 *           that) - the target cell can be given by either node or coords.
                 */
                return function ( x, y, z ) {
                        if ( (x===null || typeof x == "number") && 
                             (y===null || typeof y == "number") && 
                             typeof z == "function" )
                        {
                                _fnEventAdd( sKey, x, y, z );
                        }
                        else if ( typeof x == "object" && typeof y == "function" )
                        {
                                var aCoords = _fnCoordsFromCell( x );
                                _fnEventAdd( sKey, aCoords[0], aCoords[1], y );
                        }
                        else
                        {
                                alert( "Unhandable event type was added: x" +x+ "  y:" +y+ "  z:" +z );
                        }
                };
        }
        
        
        /*
         * Function: _fnEventRemoveTemplate
         * Purpose:  Create a function (with closure for sKey) event removal API
         * Returns:  function: - template function
         * Inputs:   string:sKey - type of event to detect
         */
        function _fnEventRemoveTemplate( sKey )
        {
                /*
                 * Function: -
                 * Purpose:  API function for removing event from cache
                 * Returns:  int: - number of events removed
                 * Inputs:   1. node:x - target node to remove event from
                 *           2. function:y - callback function to apply
                 *         or
                 *           1. int:x - x coord. of target cell (can be null for live events)
                 *           2. int:y - y coord. of target cell (can be null for live events)
                 *           3. function:z - callback function to remove - optional
                 * Notes:    This function is (interally) overloaded (in as much as javascript allows for
                 *           that) - the target cell can be given by either node or coords and the function
                 *           to remove is optional
                 */
                return function ( x, y, z ) {
                        if ( (x===null || typeof arguments[0] == "number") && 
                             (y===null || typeof arguments[1] == "number" ) )
                        {
                                if ( typeof arguments[2] == "function" )
                                {
                                        _fnEventRemove( sKey, x, y, z );
                                }
                                else
                                {
                                        _fnEventRemove( sKey, x, y );
                                }
                        }
                        else if ( typeof arguments[0] == "object" )
                        {
                                var aCoords = _fnCoordsFromCell( x );
                                if ( typeof arguments[1] == "function" )
                                {
                                        _fnEventRemove( sKey, aCoords[0], aCoords[1], y );
                                }
                                else
                                {
                                        _fnEventRemove( sKey, aCoords[0], aCoords[1] );
                                }
                        }
                        else
                        {
                                alert( "Unhandable event type was removed: x" +x+ "  y:" +y+ "  z:" +z );
                        }
                };
        }
        
        /* Use the template functions to add the event API functions */
        for ( var sKey in _oaoEvents )
        {
                if ( sKey )
                {
                        this.event[sKey] = _fnEventAddTemplate( sKey );
                        this.event.remove[sKey] = _fnEventRemoveTemplate( sKey );
                }
        }
        
        
        /*
         * Function: _fnEventAdd
         * Purpose:  Add an event to the internal cache
         * Returns:  -
         * Inputs:   string:sType - type of event to add, given by the available elements in _oaoEvents
         *           int:x - x-coords to add event to - can be null for "blanket" event
         *           int:y - y-coords to add event to - can be null for "blanket" event
         *           function:fn - callback function for when triggered
         */
        function _fnEventAdd( sType, x, y, fn )
        {
                _oaoEvents[sType].push( {
                        "x": x,
                        "y": y,
                        "fn": fn
                } );
        }
        
        
        /*
         * Function: _fnEventRemove
         * Purpose:  Remove an event from the event cache
         * Returns:  int: - number of matching events removed
         * Inputs:   string:sType - type of event to look for
         *           node:nTarget - target table cell
         *           function:fn - optional - remove this function. If not given all handlers of this
         *             type will be removed
         */
        function _fnEventRemove( sType, x, y, fn )
        {
                var iCorrector = 0;
                
                for ( var i=0, iLen=_oaoEvents[sType].length ; i<iLen-iCorrector ; i++ )
                {
                        if ( typeof fn != 'undefined' )
                        {
                                if ( _oaoEvents[sType][i-iCorrector].x == x &&
                                     _oaoEvents[sType][i-iCorrector].y == y &&
                                           _oaoEvents[sType][i-iCorrector].fn == fn )
                                {
                                        _oaoEvents[sType].splice( i-iCorrector, 1 );
                                        iCorrector++;
                                }
                        }
                        else
                        {
                                if ( _oaoEvents[sType][i-iCorrector].x == x &&
                                     _oaoEvents[sType][i-iCorrector].y == y )
                                {
                                        _oaoEvents[sType].splice( i, 1 );
                                        return 1;
                                }
                        }
                }
                return iCorrector;
        }
        
        
        /*
         * Function: _fnEventFire
         * Purpose:  Look thought the events cache and fire off the event of interest
         * Returns:  int:iFired - number of events fired
         * Inputs:   string:sType - type of event to look for
         *           int:x - x coord of cell
         *           int:y - y coord of  ell
         * Notes:    It might be more efficient to return after the first event has been tirggered,
         *           but that would mean that only one function of a particular type can be
         *           subscribed to a particular node.
         */
        function _fnEventFire ( sType, x, y )
        {
                var iFired = 0;
                var aEvents = _oaoEvents[sType];
                for ( var i=0 ; i<aEvents.length ; i++ )
                {
                        if ( (aEvents[i].x == x     && aEvents[i].y == y    ) ||
                             (aEvents[i].x === null && aEvents[i].y == y    ) ||
                             (aEvents[i].x == x     && aEvents[i].y === null ) ||
                             (aEvents[i].x === null && aEvents[i].y === null )
                        )
                        {
                                aEvents[i].fn( _fnCellFromCoords(x,y), x, y );
                                iFired++;
                        }
                }
                return iFired;
        }
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Focus functions
         */
        
        /*
         * Function: _fnSetFocus
         * Purpose:  Set focus on a node, and remove from an old node if needed
         * Returns:  -
         * Inputs:   node:nTarget - node we want to focus on
         *           bool:bAutoScroll - optional - should we scroll the view port to the display
         */
        function _fnSetFocus( nTarget, bAutoScroll )
        {
                /* If node already has focus, just ignore this call */
                if ( _nOldFocus == nTarget )
                {
                        return;
                }
                
                if ( typeof bAutoScroll == 'undefined' )
                {
                        bAutoScroll = true;
                }
                
                /* Remove old focus (with blur event if needed) */
                if ( _nOldFocus !== null )
                {
                        _fnRemoveFocus( _nOldFocus );
                }
                
                /* Add the new class to highlight the focused cell */
                jQuery(nTarget).addClass( _sFocusClass );
                jQuery(nTarget).parent().addClass( _sFocusClass );
                
                /* If it's a DataTable then we need to jump the paging to the relevant page */
                var oSettings;
                if ( _oDatatable )
                {
                        oSettings = _oDatatable.fnSettings();
                        var iRow = _fnFindDtCell( nTarget )[1];
                        var bKeyCaptureCache = _bKeyCapture;
                        
                        /* Page forwards */
                        while ( iRow >= oSettings.fnDisplayEnd() )
                        {
                                if ( oSettings._iDisplayLength >= 0 )
                                {
                                        /* Make sure we are not over running the display array */
                                        if ( oSettings._iDisplayStart + oSettings._iDisplayLength < oSettings.fnRecordsDisplay() )
                                        {
                                                oSettings._iDisplayStart += oSettings._iDisplayLength;
                                        }
                                }
                                else
                                {
                                        oSettings._iDisplayStart = 0;
                                }
                                _oDatatable.oApi._fnCalculateEnd( oSettings );
                        }
                        
                        /* Page backwards */
                        while ( iRow < oSettings._iDisplayStart )
                        {
                                oSettings._iDisplayStart = oSettings._iDisplayLength>=0 ?
                                        oSettings._iDisplayStart - oSettings._iDisplayLength :
                                        0;
                                        
                                if ( oSettings._iDisplayStart < 0 )
                                {
                                  oSettings._iDisplayStart = 0;
                                }
                                _oDatatable.oApi._fnCalculateEnd( oSettings );
                        }
                        
                        /* Re-draw the table */
                        _oDatatable.oApi._fnDraw( oSettings );
                        
                        /* Restore the key capture */
                        _bKeyCapture = bKeyCaptureCache;
                }
                
                /* Cache the information that we are interested in */
                var aNewPos = _fnCoordsFromCell( nTarget );
                _nOldFocus = nTarget;
                _iOldX = aNewPos[0];
                _iOldY = aNewPos[1];
                
                var iViewportHeight, iViewportWidth, iScrollTop, iScrollLeft, iHeight, iWidth, aiPos;
                if ( bAutoScroll )
                {
                        /* Scroll the viewport such that the new cell is fully visible in the rendered window */
                        iViewportHeight = document.documentElement.clientHeight;
                        iViewportWidth = document.documentElement.clientWidth;
                        iScrollTop = document.body.scrollTop || document.documentElement.scrollTop;
                        iScrollLeft = document.body.scrollLeft || document.documentElement.scrollLeft;
                        iHeight = nTarget.offsetHeight;
                        iWidth = nTarget.offsetWidth;
                        aiPos = _fnGetPos( nTarget );
                        
                        /* Take account of scrolling in DataTables 1.7 - remove scrolling since that would add to
                         * the positioning calculation
                         */
                        if ( _oDatatable && typeof oSettings.oScroll != 'undefined' &&
                          (oSettings.oScroll.sX !== "" || oSettings.oScroll.sY !== "") )
                        {
                                aiPos[1] -= $(oSettings.nTable.parentNode).scrollTop();
                                aiPos[0] -= $(oSettings.nTable.parentNode).scrollLeft();
                        }
                        
                        /* Correct viewport positioning for vertical scrolling */
                        if ( aiPos[1]+iHeight > iScrollTop+iViewportHeight )
                        {
                                /* Displayed element if off the bottom of the viewport */
                                _fnSetScrollTop( aiPos[1]+iHeight - iViewportHeight );
                        }
                        else if ( aiPos[1] < iScrollTop )
                        {
                                /* Displayed element if off the top of the viewport */
                                _fnSetScrollTop( aiPos[1] );
                        }
                        
                        /* Correct viewport positioning for horizontal scrolling */
                        if ( aiPos[0]+iWidth > iScrollLeft+iViewportWidth )
                        {
                                /* Displayed element is off the bottom of the viewport */
                                _fnSetScrollLeft( aiPos[0]+iWidth - iViewportWidth );
                        }
                        else if ( aiPos[0] < iScrollLeft )
                        {
                                /* Displayed element if off the Left of the viewport */
                                _fnSetScrollLeft( aiPos[0] );
                        }
                }
                
                /* Take account of scrolling in DataTables 1.7 */
                if ( _oDatatable && typeof oSettings.oScroll != 'undefined' &&
                  (oSettings.oScroll.sX !== "" || oSettings.oScroll.sY !== "") )
                {
                        var dtScrollBody = oSettings.nTable.parentNode;
                        iViewportHeight = dtScrollBody.clientHeight;
                        iViewportWidth = dtScrollBody.clientWidth;
                        iScrollTop = dtScrollBody.scrollTop;
                        iScrollLeft = dtScrollBody.scrollLeft;
                        iHeight = nTarget.offsetHeight;
                        iWidth = nTarget.offsetWidth;
                        
                        /* Correct for vertical scrolling */
                        if ( nTarget.offsetTop + iHeight > iViewportHeight+iScrollTop )
                        {
                                dtScrollBody.scrollTop = (nTarget.offsetTop + iHeight) - iViewportHeight;
                        }
                        else if ( nTarget.offsetTop < iScrollTop )
                        {
                                dtScrollBody.scrollTop = nTarget.offsetTop;
                        }
                        
                        /* Correct for horizontal scrolling */
                        if ( nTarget.offsetLeft + iWidth > iViewportWidth+iScrollLeft )
                        {
                                dtScrollBody.scrollLeft = (nTarget.offsetLeft + iWidth) - iViewportWidth;
                        }
                        else if ( nTarget.offsetLeft < iScrollLeft )
                        {
                                dtScrollBody.scrollLeft = nTarget.offsetLeft;
                        }
                }

                /* Focused - so we want to capture the keys */
                _fnCaptureKeys();
                
                /* Fire of the focus event if there is one */
                _fnEventFire( "focus", _iOldX, _iOldY );
        }
        
        
        /*
         * Function: _fnBlur
         * Purpose:  Blur focus from the whole table
         * Returns:  -
         * Inputs:   -
         */
        function _fnBlur()
        {
                _fnRemoveFocus( _nOldFocus );
                _iOldX = null;
                _iOldY = null;
                _nOldFocus = null;
                _fnReleaseKeys();
        }
        
        
        /*
         * Function: _fnRemoveFocus
         * Purpose:  Remove focus from a cell and fire any blur events which are attached
         * Returns:  -
         * Inputs:   node:nTarget - cell of interest
         */
        function _fnRemoveFocus( nTarget )
        {
                jQuery(nTarget).removeClass( _sFocusClass );
                jQuery(nTarget).parent().removeClass( _sFocusClass );
                _fnEventFire( "blur", _iOldX, _iOldY );
        }
        
        
        /*
         * Function: _fnClick
         * Purpose:  Focus on the element that has been clicked on by the user
         * Returns:  -
         * Inputs:   event:e - click event
         */
        function _fnClick ( e )
        {
                var nTarget = this;
                while ( nTarget.nodeName != "TD" )
                {
                        nTarget = nTarget.parentNode;
                }
                
                _fnSetFocus( nTarget );
                _fnCaptureKeys();
        }
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Key events
         */
        
        /*
         * Function: _fnKey
         * Purpose:  Deal with a key events, be it moving the focus or return etc.
         * Returns:  bool: - allow browser default action
         * Inputs:   event:e - key event
         */
        function _fnKey ( e )
        {
                /* If user or system has blocked KeyTable from doing anything, just ignore this event */
                if ( _that.block || !_bKeyCapture )
                {
                        return true;
                }
                
                /* If a modifier key is pressed (exapct shift), ignore the event */
                if ( e.metaKey || e.altKey || e.ctrlKey )
                {
                    return true;
                }
                var
                        x, y,
                        iTableWidth = _nBody.getElementsByTagName('tr')[0].getElementsByTagName('td').length, 
                        iTableHeight;
                
                /* Get table height and width - done here so as to be dynamic (if table is updated) */
                if ( _oDatatable )
                {
                        /* 
                         * Locate the current node in the DataTable overriding the old positions - the reason for
                         * is is that there might have been some DataTables interaction between the last focus and
                         * now
                         */
                        var oSettings = _oDatatable.fnSettings();
                        iTableHeight = oSettings.aiDisplay.length;
                        
                        var aDtPos = _fnFindDtCell( _nOldFocus );
                        if ( aDtPos === null )
                        {
                                /* If the table has been updated such that the focused cell can't be seen - do nothing */
                                return;
                        }
                        _iOldX = aDtPos[ 0 ];
                        _iOldY = aDtPos[ 1 ];
                }
                else
                {
                        iTableHeight = _nBody.getElementsByTagName('tr').length;
                }
                
                /* Capture shift+tab to match the left arrow key */
                var iKey = (e.keyCode == 9 && e.shiftKey) ? -1 : e.keyCode;
                
                switch( iKey )
                {
                        case 13: /* return */
                                e.preventDefault();
                                e.stopPropagation();
                                _fnEventFire( "action", _iOldX, _iOldY );
                                return true;
                                
                        case 27: /* esc */
                                if ( !_fnEventFire( "esc", _iOldX, _iOldY ) )
                                {
                                        /* Only lose focus if there isn't an escape handler on the cell */
                                        _fnBlur();
                                        return;
                                }
                                x = _iOldX;
                                y = _iOldY;
                                break;
                        
                        case -1:
                        case 37: /* left arrow */
                                if ( _iOldX > 0 ) {
                                        x = _iOldX - 1;
                                        y = _iOldY;
                                } else if ( _iOldY > 0 ) {
                                        x = iTableWidth-1;
                                        y = _iOldY - 1;
                                } else {
                                        /* at start of table */
                                        if ( iKey == -1 && _bForm )
                                        {
                                                /* If we are in a form, return focus to the 'input' element such that tabbing will
                                                 * follow correctly in the browser
                                                 */
                                                _bInputFocused = true;
                                                _nInput.focus();
                                                
                                                /* This timeout is a little nasty - but IE appears to have some asyhnc behaviour for 
                                                 * focus
                                                 */
                                                setTimeout( function(){ _bInputFocused = false; }, 0 );
                                                _bKeyCapture = false;
                                                _fnBlur();
                                                return true; 
                                        }
                                        else
                                        {
                                                return false;
                                        }
                                }
                                break;
                        
                        case 38: /* up arrow */
                                if ( _iOldY > 0 ) {
                                        x = _iOldX;
                                        y = _iOldY - 1;
                                } else {
                                        return false;
                                }
                                break;
                        
                        case 9: /* tab */
                        case 39: /* right arrow */
                                if ( _iOldX < iTableWidth-1 ) {
                                        x = _iOldX + 1;
                                        y = _iOldY;
                                } else if ( _iOldY < iTableHeight-1 ) {
                                        x = 0;
                                        y = _iOldY + 1;
                                } else {
                                        /* at end of table */
                                        if ( iKey == 9 && _bForm )
                                        {
                                                /* If we are in a form, return focus to the 'input' element such that tabbing will
                                                 * follow correctly in the browser
                                                 */
                                                _bInputFocused = true;
                                                _nInput.focus();
                                                
                                                /* This timeout is a little nasty - but IE appears to have some asyhnc behaviour for 
                                                 * focus
                                                 */
                                                setTimeout( function(){ _bInputFocused = false; }, 0 );
                                                _bKeyCapture = false;
                                                _fnBlur();
                                                return true; 
                                        }
                                        else
                                        {
                                                return false;
                                        }
                                }
                                break;
                        
                        case 40: /* down arrow */
                                if ( _iOldY < iTableHeight-1 ) {
                                        x = _iOldX;
                                        y = _iOldY + 1;
                                } else {
                                        return false;
                                }
                                break;
                        
                        default: /* Nothing we are interested in */
                                return true;
                }
                
                _fnSetFocus( _fnCellFromCoords(x, y) );
                return false;
        }
        
        
        /*
         * Function: _fnCaptureKeys
         * Purpose:  Start capturing key events for this table
         * Returns:  -
         * Inputs:   -
         */
        function _fnCaptureKeys( )
        {
                if ( !_bKeyCapture )
                {
                        _bKeyCapture = true;
                }
        }
        
        
        /*
         * Function: _fnReleaseKeys
         * Purpose:  Stop capturing key events for this table
         * Returns:  -
         * Inputs:   -
         */
        function _fnReleaseKeys( )
        {
                _bKeyCapture = false;
        }
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Support functions
         */
        
        /*
         * Function: _fnCellFromCoords
         * Purpose:  Calulate the target TD cell from x and y coordinates
         * Returns:  node: - TD target
         * Inputs:   int:x - x coordinate
         *           int:y - y coordinate
         */
        function _fnCellFromCoords( x, y )
        {
                if ( _oDatatable )
                {
                        var oSettings = _oDatatable.fnSettings();
                        if ( typeof oSettings.aoData[ oSettings.aiDisplay[ y ] ] != 'undefined' )
                        {
                                return oSettings.aoData[ oSettings.aiDisplay[ y ] ].nTr.getElementsByTagName('td')[x];
                        }
                        else
                        {
                                return null;
                        }
                }
                else
                {
                        return jQuery('tr:eq('+y+')>td:eq('+x+')', _nBody )[0];
                }
        }
        
        
        /*
         * Function: _fnCoordsFromCell
         * Purpose:  Calculate the x and y position in a table from a TD cell
         * Returns:  array[2] int: [x, y]
         * Inputs:   node:n - TD cell of interest
         * Notes:    Not actually interested in this for DataTables since it might go out of date
         */
        function _fnCoordsFromCell( n )
        {
                if ( _oDatatable )
                {
                        var oSettings = _oDatatable.fnSettings();
                        return [
                                jQuery('td', n.parentNode).index(n),
                                jQuery('tr', n.parentNode.parentNode).index(n.parentNode) + oSettings._iDisplayStart
                        ];
                }
                else
                {
                        return [
                                jQuery('td', n.parentNode).index(n),
                                jQuery('tr', n.parentNode.parentNode).index(n.parentNode)
                        ];
                }
        }
        
        
        /*
         * Function: _fnSetScrollTop
         * Purpose:  Set the vertical scrolling position
         * Returns:  -
         * Inputs:   int:iPos - scrolltop
         * Notes:    This is so nasty, but without browser detection you can't tell which you should set
         *           So on browsers that support both, the scroll top will be set twice. I can live with
         *           that :-)
         */
        function _fnSetScrollTop( iPos )
        {
                document.documentElement.scrollTop = iPos;
                document.body.scrollTop = iPos;
        }
        
        
        /*
         * Function: _fnSetScrollLeft
         * Purpose:  Set the horizontal scrolling position
         * Returns:  -
         * Inputs:   int:iPos - scrollleft
         */
        function _fnSetScrollLeft( iPos )
        {
                document.documentElement.scrollLeft = iPos;
                document.body.scrollLeft = iPos;
        }
        
        
        /*
         * Function: _fnGetPos
         * Purpose:  Get the position of an object on the rendered page
         * Returns:  array[2] int: [left, right]
         * Inputs:   node:obj - element of interest
         */
        function _fnGetPos ( obj )
        {
                var iLeft = 0;
                var iTop = 0;
                
                if (obj.offsetParent) 
                {
                        iLeft = obj.offsetLeft;
                        iTop = obj.offsetTop;
                        obj = obj.offsetParent;
                        while (obj) 
                        {
                                iLeft += obj.offsetLeft;
                                iTop += obj.offsetTop;
                                obj = obj.offsetParent;
                        }
                }
                return [iLeft,iTop];
        }
        
        
        /*
         * Function: _fnFindDtCell
         * Purpose:  Get the coords. of a cell from the DataTables internal information
         * Returns:  array[2] int: [x, y] coords. or null if not found
         * Inputs:   node:nTarget - the node of interest
         */
        function _fnFindDtCell( nTarget )
        {
                var oSettings = _oDatatable.fnSettings();
                for ( var i=0, iLen=oSettings.aiDisplay.length ; i<iLen ; i++ )
                {
                        var nTr = oSettings.aoData[ oSettings.aiDisplay[i] ].nTr;
                        var nTds = nTr.getElementsByTagName('td');
                        for ( var j=0, jLen=nTds.length ; j<jLen ; j++ )
                        {
                                if ( nTds[j] == nTarget )
                                {
                                        return [ j, i ];
                                }
                        }
                }
                return null;
        }
        
        
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Initialisation
         */
        
        /*
         * Function: _fnInit
         * Purpose:  Initialise the KeyTable
         * Returns:  -
         * Inputs:   object:oInit - optional - Initalisation object with the following parameters:
         *   array[2] int:focus - x and y coordinates of the initial target
         *     or
         *     node:focus - the node to set initial focus on
         *   node:table - the table to use, if not given, first table with class 'KeyTable' will be used
         *   string:focusClass - focusing class to give to table elements
         *           object:that - focus
         *   bool:initScroll - scroll the view port on load, default true
         *   int:tabIndex - the tab index to give the hidden input element
         */
        function _fnInit( oInit, that )
        {
                /* Save scope */
                _that = that;
                
                /* Capture undefined initialisation and apply the defaults */
                if ( typeof oInit == 'undefined' ) {
                        oInit = {};
                }
                
                if ( typeof oInit.focus == 'undefined' ) {
                        oInit.focus = [0,0];
                }
                
                if ( typeof oInit.table == 'undefined' ) {
                        oInit.table = jQuery('table.KeyTable')[0];
                } else {
                        $(oInit.table).addClass('KeyTable');
                }
                
                if ( typeof oInit.focusClass != 'undefined' ) {
                        _sFocusClass = oInit.focusClass;
                }
                
                if ( typeof oInit.datatable != 'undefined' ) {
                        _oDatatable = oInit.datatable;
                }
                
                if ( typeof oInit.initScroll == 'undefined' ) {
                        oInit.initScroll = true;
                }
                
                if ( typeof oInit.form == 'undefined' ) {
                        oInit.form = false;
                }
                _bForm = oInit.form;
                
                /* Cache the tbody node of interest */
                _nBody = oInit.table.getElementsByTagName('tbody')[0];
                
                /* If the table is inside a form, then we need a hidden input box which can be used by the
                 * browser to catch the browser tabbing for our table
                 */
                if ( _bForm )
                {
                        var nDiv = document.createElement('div');
                        _nInput = document.createElement('input');
                        nDiv.style.height = "1px"; /* Opera requires a little something */
                        nDiv.style.width = "0px";
                        nDiv.style.overflow = "hidden";
                        if ( typeof oInit.tabIndex != 'undefined' )
                        {
                                _nInput.tabIndex = oInit.tabIndex;
                        }
                        nDiv.appendChild(_nInput);
                        oInit.table.parentNode.insertBefore( nDiv, oInit.table.nextSibling );
                        
                        jQuery(_nInput).focus( function () {
                                /* See if we want to 'tab into' the table or out */
                                if ( !_bInputFocused )
                                {
                                        _bKeyCapture = true;
                                        _bInputFocused = false;
                                        if ( typeof oInit.focus.nodeName != "undefined" )
                                        {
                                                _fnSetFocus( oInit.focus, oInit.initScroll );
                                        }
                                        else
                                        {
                                                _fnSetFocus( _fnCellFromCoords( oInit.focus[0], oInit.focus[1]), oInit.initScroll );
                                        }
                                        
                                        /* Need to interup the thread for this to work */
                                        setTimeout( function() { _nInput.blur(); }, 0 );
                                }
                        } );
                        _bKeyCapture = false;
                }
                else
                {
                        /* Set the initial focus on the table */
                        if ( typeof oInit.focus.nodeName != "undefined" )
                        {
                                _fnSetFocus( oInit.focus, oInit.initScroll );
                        }
                        else
                        {
                                _fnSetFocus( _fnCellFromCoords( oInit.focus[0], oInit.focus[1]), oInit.initScroll );
                        }
                        _fnCaptureKeys();
                }
                
                /*
                 * Add event listeners
                 * Well - I hate myself for doing this, but it would appear that key events in browsers are
                 * a complete mess, particulay when you consider arrow keys, which of course are one of the
                 * main areas of interest here. So basically for arrow keys, there is no keypress event in
                 * Safari and IE, while there is in Firefox and Opera. But Firefox and Opera don't repeat the
                 * keydown event for an arrow key. OUCH. See the following two articles for more:
                 *   http://www.quirksmode.org/dom/events/keys.html
                 *   https://lists.webkit.org/pipermail/webkit-dev/2007-December/002992.html
                 *   http://unixpapa.com/js/key.html
                 * PPK considers the IE / Safari method correct (good enough for me!) so we (urgh) detect
                 * Mozilla and Opera and apply keypress for them, while everything else gets keydown. If
                 * Mozilla or Opera change their implemention in future, this will need to be updated... 
                 * although at the time of writing (14th March 2009) Minefield still uses the 3.0 behaviour.
                 */
                if ( jQuery.browser.mozilla || jQuery.browser.opera )
                {
                        jQuery(document).bind( "keypress", _fnKey );
                }
                else
                {
                        jQuery(document).bind( "keydown", _fnKey );
                }
                
                if ( _oDatatable )
                {
                        jQuery('tbody td', _oDatatable.fnSettings().nTable).live( 'click', _fnClick );
                }
                else
                {
                        jQuery('td', _nBody).live( 'click', _fnClick );
                }
                
                /* Loose table focus when click outside the table */
                jQuery(document).click( function(e) {
                        var nTarget = e.target;
                        var bTableClick = false;
                        while ( nTarget )
                        {
                                if ( nTarget == oInit.table )
                                {
                                        bTableClick = true;
                                        break;
                                }
                                nTarget = nTarget.parentNode;
                        }
                        if ( !bTableClick )
                        {
                                _fnBlur();
                        }
                } );
        }
        
        /* Initialise our new object */
        _fnInit( oInit, this );
}