// Code taken from "Special Edition Using Javascript" - Listings 34.1 and 34.2

function set_visibility(new_visibility) {
    // Is this a W3C or DHTML DOM browser?
    if (!document.layers) {
        // If so, just set the visibility to the value of the argument
        this.css.visibility=new_visibility
    }
    else {
        // Otherwise, set the proprietary visibility values
        if (new_visibility=="visible") {
            this.css.visibility="show"
        }
        else if (new_visibility=="hidden") {
            this.css.visibility="hide"
        }
        else {
            this.css.visibility="inherit"
        }
    }
}

function get_visibility() {

    // Is this a W3C or DHTML DOM browser?
    if (!document.layers) {
        // If so, is the visibility defined?
        if (this.css.visibility) {
            // If so, return the visibility property
            return this.css.visibility
        }
    }
    else {
        // Otherwise, it's an LDOM browser, so handle the proprietary visibility values
        if (this.css.visibility=="show") {
            return "visible"
        }
        if (this.css.visibility=="hide") {
            return "hidden"
        }
    }
    // If we get this far, just return "inherit"
    return "inherit"
}

function set_zIndex(new_zindex) {
    // Is the new z-index greater than 0?
    if (new_zindex>0) {
        // If so, set it
        this.css.zIndex=new_zindex
    }
    else {
        // If not, set it to 0
        this.css.zIndex=0
    }
}

function set_left(new_left) {
    this.css.left=new_left
}

//The Constructor Function for the Custom Object

function dhtml_object (obj, css, id) {
    this.obj = obj
    this.css = css
    this.id = id
//    this.left = get_left
//    this.right = get_right
//    this.top = get_top
//    this.bottom = get_bottom
//    this.width = get_width
//    this.height = get_height
    this.visibility = get_visibility
//    this.zIndex = get_zIndex
//    this.move_to = move_to
//    this.move_by = move_by
    this.set_left = set_left
//    this.set_top = set_top
//    this.set_width = set_width
//    this.set_height = set_height
    this.set_visibility = set_visibility
    this.set_zIndex = set_zIndex
//    this.move_above = move_above
//    this.move_below = move_below
//    this.set_backgroundColor = set_backgroundColor
//    this.set_backgroundImage = set_backgroundImage
//    this.set_html = set_html
//    this.get_clip_top = get_clip_top
//    this.get_clip_right = get_clip_right
//    this.get_clip_bottom = get_clip_bottom
//    this.get_clip_left = get_clip_left
//    this.get_clip_width = get_clip_width
//    this.get_clip_height = get_clip_height
//    this.resize_clip_to = resize_clip_to
//    this.resize_clip_by = resize_clip_by
}

var my_dhtml_objects

// This function creates the custom object that serve as cross-browser front-ends

function create_object_array() {
    // All the <div> and <span> tags are stored in these variables
    var div_tags
    var span_tags
    var css_tags

    // This array holds all of the document's DHTML-able objects
    var dhtml_objects = new Array()

    // Is the browser W3C DOM compliant?
    if (document.getElementById) {
        // If so, use getElementsByTagName() to get the <div> tags
        div_tags = document.getElementsByTagName("div")
        // Loop through the <div> tags
        for (var counter = 0; counter < div_tags.length; counter++) {
            // Store the current object
            current_object = div_tags[counter]
            // Store how the browser accesses styles
            object_css = current_object.style 
            // Store the object's id
            object_id = current_object.id
            // Only store those tags that have an id
            if (object_id) {
                // Create a new dhtml_object and store it in dhtml_objects
                dhtml_objects[object_id] = new dhtml_object(current_object,object_css,object_id)
            }
        }

        // Use getElementsByTagName() to get the <span> tags
        span_tags = document.getElementsByTagName("span")
        // Loop through the <span> tags
        for (var counter = 0; counter < span_tags.length; counter++) {
            // Store the current object
            current_object = span_tags[counter]
            // Store how the browser accesses styles
            object_css = current_object.style
            // Store the object's id
            object_id = current_object.id
            // Only store those tags that have an id
            if (object_id) {
                // Create a new dhtml_object and store it in dhtml_objects
                dhtml_objects[object_id] = new dhtml_object(current_object,object_css,object_id)
            }
        }
    }

    // Is the browser DHTML DOM compliant?
    else if (document.all) {
        // If so, use document.all to get the <div> tags
        div_tags = document.all.tags("div")
        // Loop through the <div> tags
        for (var counter = 0; counter < div_tags.length; counter++) {
            // Store the current object
            current_object = div_tags[counter] 
            // Store how the browser accesses styles
            object_css = current_object.style
            // Store the object's id
            object_id = current_object.id
            // Only store those tags that have an id
            if (object_id) {
                // Create a new dhtml_object and store it in dhtml_objects
                dhtml_objects[object_id] = new dhtml_object(current_object,object_css,object_id)
            }
        }

        // Use document.all to get the <span> tags
        span_tags = document.all.tags("span")

        // Loop through the <span> tags
        for (var counter = 0; counter < span_tags.length; counter++) {
            // Store the current object
            current_object = span_tags[counter] 
            // Store how the browser accesses styles
            object_css = current_object.style
            // Store the object's id
            object_id = current_object.id
            // Only store those tags that have an id
            if (object_id) {
                // Create a new dhtml_object and store it in dhtml_objects
                dhtml_objects[object_id] = new dhtml_object(current_object,object_css,object_id)
            }
        }
    }

    // Is the browser LDOM compliant?
    else if (document.layers) {
        // Use document.layers to get the positioned <div> and <span> tags
        css_tags = document.layers
        // Loop through the layers
        for (var counter = 0; counter < css_tags.length; counter++) {
            // Store the current object
            current_object = css_tags[counter] 
            // Store how the browser accesses styles
            object_css = current_object
            // Store the object's id
            object_id = current_object.id
            // Only store those tags that have an id
            if (object_id) {
                // Create a new dhtml_object and store it in dhtml_objects
                dhtml_objects[object_id] = new dhtml_object(current_object,object_css,object_id)
            }
        }
    }
    my_dhtml_objects=dhtml_objects
}

// My functions

function showLayer(layer_name)
{
	my_dhtml_objects[layer_name].set_visibility("visible")
}

function hideLayer(layer_name)
{
	my_dhtml_objects[layer_name].set_visibility("hidden")
}

function isVisible(layer_name)
{
	if (my_dhtml_objects[layer_name].visibility()=="hidden")
		return false
	return true
}

function setLayerZ(layer_name,z_index)
{
	my_dhtml_objects[layer_name].set_zIndex(z_index)
}

function setLayerLeft(layer_name,left_pos)
{
	my_dhtml_objects[layer_name].set_left(left_pos)
}