// Listbox logic

// This script and the listbox on this page illustrates one
// way to create an "auto-complete" listbox, where the

var toFind = ""; // Variable that acts as keyboard buffer
var timeoutID = ""; // Process id for timer (used when stopping
// the timeout)
timeoutInterval = 250; // Milliseconds. Shorten to cause keyboard
// buffer to be cleared faster
var timeoutCtr = 0; // Initialization of timer count down
var timeoutCtrLimit = 3 ; // Number of times to allow timer to count

function listbox_onkeypress()
{
	// This function is called when the user presses a key while focus is in
	// the listbox. It maintains the keyboard buffer.
	// Each time the user presses a key, the timer is restarted.
	// First, stop the previous timer; this function will restart it.
	window.clearInterval(timeoutID)

	// If no window event, give up (occurs if the user hit a tab to leave the element.)
	if (!window.event) 
	{ 
		return; 
	} 

	// Which control raised the event? We'll need to know which control to
	// set the selection in.
	oControl = (window.event.target)?window.event.target:window.event.srcElement;

	var keycode = window.event.keyCode;

	if(keycode >= 32 )
	{
		// What character did the user type?
		var c = String.fromCharCode(keycode);
		c = c.toUpperCase();
		// 	Convert it to uppercase so that comparisons don't fail
		toFind += c ; // Add to the keyboard buffer
		find(oControl); // Search the listbox
		timeoutID = window.setInterval("idle()", timeoutInterval);
		// Restart the timer
	}
} // end function listbox_onkeypress()


function listbox_onblur()
{
	// This function is called when the user leaves the listbox.
	window.clearInterval(timeoutID);
	resetToFind();
} // end listbox_onblur()

function idle()
{
	// This function is called if the timeout expires. If this is the
	// third (by default) time that the idle function has been called,
	// it stops the timer and clears the keyboard buffer
	
	timeoutCtr += 1
	if(timeoutCtr > timeoutCtrLimit)
	{
		resetToFind();
		timeoutCtr = 0;
		window.clearInterval(timeoutID);
	}
} // end idle()

function resetToFind()
{
	toFind = ""
}

function find(oControl)
{
	// Walk through the select list looking for a match

	var allOptions = document.all.item(oControl.name);

	for (i=0; i < allOptions.length; i++)
	{
		// Gets the next item from the listbox
		nextOptionText = allOptions(i).text.toUpperCase();
		
		// By default, the values in the listbox and as entered by the
		// user are strings. This causes a string comparison to be made,
		// which is not correct for numbers (1 < 11 < 2).
		// The following lines coerce numbers into an (internal) number
		// format so that the subsequent comparison is done as a
		// number (1 < 2 < 11).
		
		if(!isNaN(nextOptionText) && !isNaN(toFind) )
		{
			nextOptionText *= 1; // coerce into number
			toFind *= 1;
		}
		
		// Does the next item match exactly what the user typed?
		if(toFind == nextOptionText)
		{
			// OK, we can stop at this option. Set focus here
			oControl.selectedIndex = i;
			window.event.returnValue = false;
			break;
		}
		
		// If the string does not match exactly, find which two entries
		// it should be between.
		if(i < allOptions.length-1)
		{
			// If we are not yet at the last listbox item, see if the
			// search string comes between the current entry and the next
			// one. If so, place the selection there.
			
			lookAheadOptionText = allOptions(i+1).text.toUpperCase() ;
			if( (toFind > nextOptionText) &&
			(toFind < lookAheadOptionText) )
			{
				oControl.selectedIndex = i+1;
				window.event.cancelBubble = true;
				window.event.returnValue = false;
				break;
			} // if
		} // if
		else
		{
			// If we are at the end of the entries and the search string
			// is still higher than the entries, select the last entry
			
			if(toFind > nextOptionText)
			{
				oControl.selectedIndex = allOptions.length-1 // stick it
				// at the end
				window.event.cancelBubble = true;
				window.event.returnValue = false;
				break;
			} // if
		} // else
	} // end for
} // end find()