function getStyleObject(objectId) {
    // cross-browser function to get an object's style object given its id
    if(document.getElementById && document.getElementById(objectId)) {
	// W3C DOM
	return document.getElementById(objectId).style;
    } else if (document.all && document.all(objectId)) {
	// MSIE 4 DOM
	return document.all(objectId).style;
    } else if (document.layers && document.layers[objectId]) {
	// NN 4 DOM.. note: this won't find nested layers
	return document.layers[objectId];
    } else {
	return false;
    }
} // getStyleObject

function changeObjectVisibility(objectId, newVisibility) {
    // get a reference to the cross-browser style object and make sure the object exists
    var styleObject = getStyleObject(objectId);
    if(styleObject) {
	styleObject.visibility = newVisibility;
	return true;
    } else {
	// we couldn't find the object, so we can't change its visibility
	return false;
    }
} // changeObjectVisibility

function moveObject(objectId, newXCoordinate, newYCoordinate) {
    // get a reference to the cross-browser style object and make sure the object exists
    var styleObject = getStyleObject(objectId);
    if(styleObject) {
	styleObject.left = newXCoordinate;
	styleObject.top = newYCoordinate;
	return true;
    } else {
	// we couldn't find the object, so we can't very well move it
	return false;
    }
} // moveObject


// ********************************
// application-specific functions *
// ********************************

// store variables to control where the popup will appear relative to the cursor position
// positive numbers are below and to the right of the cursor, negative numbers are above and to the left
var xOffset = 30;
var yOffset = -5;

function showPopup (targetObjectId, eventObj) {
    if(eventObj) {
		hideCurrentPopup();
		eventObj.cancelBubble = true;
		if( changeObjectVisibility(targetObjectId, 'visible') ) {
		    window.currentlyVisiblePopup = targetObjectId;
		    return true;
		} else {
		    return false;
		}
    } else {
		if( changeObjectVisibility(targetObjectId, 'visible') ) {
		    window.currentlyVisiblePopup = targetObjectId;
		    return true;
			}
		return false;
    }
} // showPopup

function hideCurrentPopup() {
    // note: we've stored the currently-visible popup on the global object window.currentlyVisiblePopup
    if(window.currentlyVisiblePopup) {
	changeObjectVisibility(window.currentlyVisiblePopup, 'hidden');
	window.currentlyVisiblePopup = false;
    }
} // hideCurrentPopup



// ***********************
// hacks and workarounds *
// ***********************

// initialize hacks whenever the page loads
window.onload = initializeHacks;

// setup an event handler to hide popups for generic clicks on the document
document.onclick = hideCurrentPopup;

function initializeHacks() {
    // this ugly little hack resizes a blank div to make sure you can click
    // anywhere in the window for Mac MSIE 5
    if ((navigator.appVersion.indexOf('MSIE 5') != -1) 
	&& (navigator.platform.indexOf('Mac') != -1)
	&& getStyleObject('blankDiv')) {
	window.onresize = explorerMacResizeFix;
    }
    resizeBlankDiv();
    // this next function creates a placeholder object for older browsers
    createFakeEventObj();
}

function createFakeEventObj() {
    // create a fake event object for older browsers to avoid errors in function call
    // when we need to pass the event object to functions
    if (!window.event) {
	window.event = false;
    }
} // createFakeEventObj

function resizeBlankDiv() {
    // resize blank placeholder div so IE 5 on mac will get all clicks in window
    if ((navigator.appVersion.indexOf('MSIE 5') != -1) 
	&& (navigator.platform.indexOf('Mac') != -1)
	&& getStyleObject('blankDiv')) {
	getStyleObject('blankDiv').width = document.body.clientWidth - 20;
	getStyleObject('blankDiv').height = document.body.clientHeight - 20;
    }
}

function explorerMacResizeFix () {
    location.reload(false);
}