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| function RecordingsList(id) {
if (arguments.length > 0)
this.init(id);
}
RecordingsList.prototype.init = function(id) {
this.id = id;
this.idElt = document.getElementById(id);
if (this.idElt == undefined) return;
this.idStyle = document.defaultView.getComputedStyle(this.idElt, null);
this.listElt = this.idElt.getElementsByTagName("ul")[0];
this.listItemElt = this.listElt.getElementsByTagName("li");
this.listLength = this.listItemElt.length;
this.listItemStyle = document.defaultView.getComputedStyle(this.listItemElt[0], null);
this.listItemHeight = parseInt(this.listItemStyle.height)
+ parseInt(this.listItemStyle.paddingTop)
+ parseInt(this.listItemStyle.paddingBottom)
+ parseInt(this.listItemStyle.borderTopWidth)
+ parseInt(this.listItemStyle.borderBottomWidth)
+ parseInt(this.listItemStyle.marginTop)
+ parseInt(this.listItemStyle.marginBottom);
this.addHighlight();
this.addFaders();
this.addVideoPreviews();
this.addFocusHandlers();
// Nav left and nav right should do nothing for any list item.
for (var li = 0; li < this.listLength; li++) {
this.listItemElt[li].style.navLeft = "#" + this.listItemElt[li].id;
this.listItemElt[li].style.navRight = "#" + this.listItemElt[li].id;
}
// Down from bottom goes to top, and vice versa
this.listItemElt[0].style.navUp = "#" + this.listItemElt[this.listLength - 1].id;
this.listItemElt[this.listLength - 1].style.navDown = "#" + this.listItemElt[0].id;
this.scroller = new VerticalScroller(this.listElt);
// Make sure the first list item is under the highlight and has focus.
this.listItemElt[0].focus();
}
// The highlight is styled and positioned by CSS.
// We just add the appropriate element to the document.
// NB it's added to the document, NOT into the div.
// This is to ensure it isn't affected by any styles set for
// the div itself.
RecordingsList.prototype.addHighlight = function() {
var highlight = document.createElement("div");
highlight.className = "highlight";
document.body.appendChild(highlight);
// We'll need to know where it's actually positioned, relative
// to the top of the list, so that we can move list items into
// the appropriate position.
this.highlightDelta =
parseInt(document.defaultView.getComputedStyle(highlight, null).top)
- parseInt(this.idStyle.top);
}
// Same applies to the two faders.
RecordingsList.prototype.addFaders = function() {
var topFader = document.createElement("div");
var botFader = document.createElement("div");
topFader.className = "fade top";
botFader.className = "fade bottom";
document.body.appendChild(topFader);
document.body.appendChild(botFader);
}
// Create an array of Image objects, holding video previews.
// Add an img element to the document with the appropriate id.
// These are then tied together in the showVideo method.
// A more exotic example might create an img element for each image
// and animate between the images.
RecordingsList.prototype.addVideoPreviews = function() {
this.vidPreview = new Array();
for (var li = 0; li < this.listLength; li++) {
var id = this.listItemElt[li].id;
var imgPath = "images/show-" + id + ".jpg";
this.vidPreview[id] = document.createElement("img");
this.vidPreview[id].id = "vidPreview-"+id;
this.vidPreview[id].src = imgPath;
this.vidPreview[id].className = "vidPreview";
document.body.appendChild(this.vidPreview[id]);
}
}
// When a list item receives focus, it is moved into the highlight area.
RecordingsList.prototype.addFocusHandlers = function() {
var me = this;
for (var li = 0; li < this.listLength; li++) {
this.listItemElt[li].itemDelta = li * this.listItemHeight; // handy
this.listItemElt[li].addEventListener("focus",
function(e) { me.highlightElt(e.target) }, false);
// Show and hide the video preview appropriately.
this.listItemElt[li].addEventListener("focus",
function(e) { me.showVideo(e.target) }, false);
this.listItemElt[li].addEventListener("blur",
function(e) { me.hideVideo(e.target) }, false);
}
}
// Move the list so that elt sits inside the highlight area.
RecordingsList.prototype.highlightElt = function(elt) {
this.scroller.scrollTo(this.highlightDelta - elt.itemDelta);
}
// Show the video preview for this recording.
RecordingsList.prototype.showVideo = function(elt) {
this.vidPreview[elt.id].style.play = "focus"
;
}
// Hide the video preview for this recording.
RecordingsList.prototype.hideVideo = function(elt) {
this.vidPreview[elt.id].style.display = "none";
}
// A VerticalScroller object scrolls an element up or down smoothly.
// Instantiate it with an element, and call the scrollTo method
// to scroll that element to a new position.
function VerticalScroller(elt) {
if (arguments.length > 0)
this.init(elt);
}
VerticalScroller.prototype.init = function(elt) {
this.elt = elt;
// How far the list is moved up or down from its top=0 position.
// Initially, the style sheet determines this. We store locally
// to avoid calling getComputedStyle repeatedly.
this.currentDelta = parseInt(document.defaultView.getComputedStyle(this.elt, null).top);
// Holds a timeout handle so we can cancel scrolling when we need to.
this.scrollHandle = null;
}
VerticalScroller.prototype.scrollTo = function(targetDelta) {
if (this.scrollHandle) clearTimeout(this.scrollHandle);
var diff = targetDelta - this.currentDelta;
this.scrollAnim(diff, 8); // magic move factor
}
// To get a move-past-target-and-spring-back effect we note that
// 8+7+6+5+4+3+2+1+0-1-2-3 = 30
// So decrementing a moveFactor from 8 to -3, and moving
// moveFactor/30 of the total distance each time, eventually gets
// us there. We could just scroll a fixed amount each time, of course,
// but this looks prettier.
VerticalScroller.prototype.scrollAnim = function(diff, moveFactor) {
var me = this;
this.currentDelta += (moveFactor * diff) / 30;
this.elt.style.top = this.currentDelta + "px";
if (moveFactor != -3)
this.scrollHandle = setTimeout(function() { me.scrollAnim(diff, moveFactor - 1) }, 35);
}
// Initialise the page
function initPage() {
var stateList = new RecordingsList("rec-list");
if (top.loadListener) top.loadListener.hasLoaded();
}
window.onload = initPage; |
