lca2020-pay-it-forward/js/slideshow.js
2011-06-07 21:10:59 +02:00

283 lines
7.1 KiB
JavaScript

/**
* Copyright (C) 2011 Hakim El Hattab, http://hakim.se
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* Handles the very minimal navigation logic involved in the
* slideshow. Including keyboard navigation, touch interaction
* and URL history behavior.
*
* Slides are given unique hash based URL's so that they can be
* opened directly. I didn't use the HTML5 History API for this
* as it would have required the addition of server side rewrite
* rules and hence require more effort for anyone to set up.
*
* This component can be called from other scripts via a tiny API:
* - Slideshow.navigateTo( indexh, indexv );
* - Slideshow.navigateLeft();
* - Slideshow.navigateRight();
* - Slideshow.navigateUp();
* - Slideshow.navigateDown();
*
*
* version 0.1:
* - First release
*
* version 0.2:
* - Refactored code and added inline documentation
* - Slides now have unique URL's
* - A basic API to invoke navigation was added
*
* version 0.3:
* - Added licensing terms
*
*
* @author Hakim El Hattab
* @version 0.3
*/
var Slideshow = (function(){
var indexh = 0,
indexv = 0;
/**
* Activates the main program logic.
*/
function initialize() {
document.addEventListener('keydown', onDocumentKeyDown, false);
document.addEventListener('touchstart', onDocumentTouchStart, false);
window.addEventListener('hashchange', onWindowHashChange, false);
// Read the initial state of the URL (hash)
readURL();
}
/**
* Handler for the document level 'keydown' event.
*
* @param {Object} event
*/
function onDocumentKeyDown( event ) {
if( event.keyCode >= 37 && event.keyCode <= 40 ) {
switch( event.keyCode ) {
case 37: navigateLeft(); break; // left
case 39: navigateRight(); break; // right
case 38: navigateUp(); break; // up
case 40: navigateDown(); break; // down
}
slide();
event.preventDefault();
}
}
/**
* Handler for the document level 'touchstart' event.
*
* This enables very basic tap interaction for touch
* devices. Added mainly for performance testing of 3D
* transforms on iOS but was so happily surprised with
* how smoothly it runs so I left it in here. Apple +1
*
* @param {Object} event
*/
function onDocumentTouchStart( event ) {
// We're only interested in one point taps
if (event.touches.length == 1) {
event.preventDefault();
var point = {
x: event.touches[0].clientX,
y: event.touches[0].clientY
};
// Define the extent of the areas that may be tapped
// to navigate
var wt = window.innerWidth * 0.3;
var ht = window.innerHeight * 0.3;
if( point.x < wt ) {
navigateLeft();
}
else if( point.x > window.innerWidth - wt ) {
navigateRight();
}
else if( point.y < ht ) {
navigateUp();
}
else if( point.y > window.innerHeight - ht ) {
navigateDown();
}
slide();
}
}
/**
* Handler for the window level 'hashchange' event.
*
* @param {Object} event
*/
function onWindowHashChange( event ) {
readURL();
}
/**
* Updates one dimension of slides by showing the slide
* with the specified index.
*
* @param {String} selector A CSS selector that will fetch
* the group of slides we are working with
* @param {Number} index The index of the slide that should be
* shown
*
* @return {Number} The index of the slide that is now shown,
* might differ from the passed in index if it was out of
* bounds.
*/
function updateSlides( selector, index ) {
// Select all slides and convert the NodeList result to
// an array
var slides = Array.prototype.slice.call( document.querySelectorAll( selector ) );
if( slides.length ) {
// Enforce max and minimum index bounds
index = Math.max(Math.min(index, slides.length - 1), 0);
slides[index].setAttribute('class', 'present');
// Any element previous to index is given the 'past' class
slides.slice(0, index).map(function(element){
element.setAttribute('class', 'past');
});
// Any element subsequent to index is given the 'future' class
slides.slice(index + 1).map(function(element){
element.setAttribute('class', 'future');
});
}
else {
// Since there are no slides we can't be anywhere beyond the
// zeroth index
index = 0;
}
return index;
}
/**
* Updates the visual slides to represent the currently
* set indices.
*/
function slide() {
indexh = updateSlides( '#main>section', indexh );
indexv = updateSlides( 'section.present>section', indexv );
writeURL();
}
/**
* Reads the current URL (hash) and navigates accordingly.
*/
function readURL() {
// Break the hash down to separate components
var bits = window.location.hash.slice(2).split('/');
// Read the index components of the hash
indexh = bits[0] ? parseInt( bits[0] ) : 0;
indexv = bits[1] ? parseInt( bits[1] ) : 0;
navigateTo( indexh, indexv );
}
/**
* Updates the page URL (hash) to reflect the current
* navigational state.
*/
function writeURL() {
var url = '/';
// Only include the minimum possible number of components in
// the URL
if( indexh > 0 || indexv > 0 ) url += indexh
if( indexv > 0 ) url += '/' + indexv
window.location.hash = url;
}
/**
* Triggers a navigation to the specified indices.
*
* @param {Number} h The horizontal index of the slide to show
* @param {Number} v The vertical index of the slide to show
*/
function navigateTo( h, v ) {
indexh = h === undefined ? indexh : h;
indexv = v === undefined ? indexv : v;
slide();
}
function navigateLeft() {
indexh --;
indexv = 0;
slide();
}
function navigateRight() {
indexh ++;
indexv = 0;
slide();
}
function navigateUp() {
indexv --;
slide();
}
function navigateDown() {
indexv ++;
slide();
}
// Initialize the program. Done right before returning to ensure
// that any inline variable definitions are available to all
// functions
initialize();
// Expose some methods publicly
return {
navigateTo: navigateTo,
navigateLeft: navigateLeft,
navigateRight: navigateRight,
navigateUp: navigateUp,
navigateDown: navigateDown
};
})();