// ScrollBars.js - Handle the combination of horizontal and vertical scroll bars

// This function ensures that the scroll bars are hidden so that they take up no space in the table.
// This allows the table to resize without being enlarged by the scroll bars (means the table can shrink).
function hideScrollBars()
	{
	//debug( "»hideScrollBars()" );

	// Hide both scroll bars.
	hScroll.hide();
	vScroll.hide();

	//debug( "«hideScrollBars()" );
	}

// Show the scroll bars.
function showScrollBars()
	{
	//debug( "»showScrollBars()" );

	// Show both scroll bars.
	hScroll.show();
	vScroll.show();

	//debug( "«showScrollBars()" );
	}

// Update and validate the scroll bar items counts and positions.
// Return true if any changes occurred.
function updateScrollBars()
	{
	//debug( "»updateScrollBars()" );

	var changed = hScroll.update();
	changed |= vScroll.update();

	//debug( "«updateScrollBars() " + changed );
	return changed;
	}

// Set a new number of items for the rows and columns and update the scroll bars.
function setScrollSizes( v, h )
	{
	//debug( "»setScrollSizes( " + v + ", " + h + " )" );

	hScroll.setItems( h );
	vScroll.setItems( v );

	updateScrollBars();

	//debug( "«setScrollSizes()" );
	}

// Handle mouse wheel events.
function onMouseWheelScrolling( e )
	{
	if( !e )
		e = window.event; // IE event model

	var handled = true;

	// wheelDelta is always multiples of 120. We divide by 40 to move by 3 lines per click.
	var rows = -e.wheelDelta / 40;

	// If the vertical scroll bar exists and is shown, scroll it. Otherwise, try horizontal.
	if( ( typeof( vScroll ) != "undefined" ) && ( vScroll.getVisible() != vScroll.getItems() ) )
		vScroll.scrollBy( rows );
	else if( ( typeof( hScroll ) != "undefined" ) && ( hScroll.getVisible() != hScroll.getItems() ) )
		hScroll.scrollBy( rows );
	else
		handled = false;

	// If we've handled this event, don't let anybody else see it.
	if( handled )
		{
		if( e.stopPropagation )
			e.stopPropagation();		// DOM Level 2
		else
			e.cancelBubble = true;		// IE

		// Now prevent any default action.
		if( e.preventDefault )
			e.preventDefault();			// DOM Level 2
		else
			e.returnValue = false;		// IE
		}
	}

// Define names of key events
var KeyCodePAGEUP     = 33;
var KeyCodePAGEDOWN   = 34;
var KeyCodeEND        = 35;
var KeyCodeHOME       = 36;
var KeyCodeARROWLEFT  = 37;
var KeyCodeARROWUP    = 38;
var KeyCodeARROWRIGHT = 39;
var KeyCodeARROWDOWN  = 40;

// Handle key down events
function onKeyDownScrolling( e )
	{
	if( !e )
		e = window.event; // IE event model

	var handled = false;
	
	if( ( typeof( vScroll ) != "undefined" ) && ( vScroll.getVisible() != vScroll.getItems() ) )
		{
		// Up Arrow (any Shift or Ctrl state)
		if( ( e.keyCode == KeyCodeARROWUP ) && !e.altKey )
			{
			var amount = 1;
			if( e.shiftKey )
				amount = vScroll.getVisible();
			else if( e.ctrlKey )
				amount = vScroll.getItems() + 1;
			vScroll.scrollBy( -amount );
			handled = true;
			}
		// Down Arrow (any Shift or Ctrl state)
		else if( ( e.keyCode == KeyCodeARROWDOWN ) && !e.altKey )
			{
			var amount = 1;
			if( e.shiftKey )
				amount = vScroll.getVisible();
			else if( e.ctrlKey )
				amount = vScroll.getItems() + 1;
			vScroll.scrollBy( amount );
			handled = true;
			}
		// Page Up (no modifiers)
		else if( ( e.keyCode == KeyCodePAGEUP ) && !e.altKey && !e.ctrlKey && !e.shiftKey )
			{
			vScroll.scrollBy( -vScroll.getVisible() );
			handled = true;
			}
		// Page Down (no modifiers)
		else if( ( e.keyCode == KeyCodePAGEDOWN ) && !e.altKey && !e.ctrlKey && !e.shiftKey )
			{
			vScroll.scrollBy( vScroll.getVisible() );
			handled = true;
			}
		// Home
		else if( ( e.keyCode == KeyCodeHOME ) && !e.altKey && !e.ctrlKey && !e.shiftKey )
			{
			vScroll.scrollBy( -( vScroll.getItems() + 1 ) );
			handled = true;
			}
		// End
		else if( ( e.keyCode == KeyCodeEND ) && !e.altKey && !e.ctrlKey && !e.shiftKey )
			{
			vScroll.scrollBy( vScroll.getItems() + 1 );
			handled = true;
			}
		}
	if( ( typeof( hScroll ) != "undefined" ) && ( hScroll.getVisible() != hScroll.getItems() ) )
		{
		// Arrow Left (any Shift or Ctrl state)
		if( ( e.keyCode == KeyCodeARROWLEFT ) && !e.altKey )
			{
			var amount = 1;
			if( e.shiftKey )
				amount = hScroll.getVisible();
			else if( e.ctrlKey )
				amount = hScroll.getItems() + 1;
			hScroll.scrollBy( -amount );
			handled = true;
			}
		// Arrow right (any Shift or Ctrl state)
		else if( ( e.keyCode == KeyCodeARROWRIGHT ) && !e.altKey )
			{
			var amount = 1;
			if( e.shiftKey )
				amount = hScroll.getVisible();
			else if( e.ctrlKey )
				amount = hScroll.getItems() + 1;
			hScroll.scrollBy( amount );
			handled = true;
			}
		}

	// If we've handled this event, don't let anybody else see it.
	if( handled )
		{
		if( e.stopPropagation )
			e.stopPropagation();		// DOM Level 2
		else
			e.cancelBubble = true;		// IE

		// Now prevent any default action.
		if( e.preventDefault )
			e.preventDefault();			// DOM Level 2
		else
			e.returnValue = false;		// IE
		}
	}