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Minimal support for "sticky" machines (ie, machines that can't be scrolled off the top of the page)

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Jeff Parsons 2017-01-02 22:17:12 -08:00 • committed by Jeff Parsons
commit 61be09d54a
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modules/shared/es6/sticky.js Normal file
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/**
* @fileoverview Support for "sticky" machines
* @author <a href="mailto:Jeff@pcjs.org">Jeff Parsons</a> (@jeffpar)
* @copyright © Jeff Parsons 2012-2017
*
* This file is part of PCjs, a computer emulation software project at <http://pcjs.org/>.
*
* PCjs is free software: you can redistribute it and/or modify it under the terms of the
* GNU General Public License as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* PCjs is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with PCjs. If not,
* see <http://www.gnu.org/licenses/gpl.html>.
*
* You are required to include the above copyright notice in every modified copy of this work
* and to display that copyright notice when the software starts running; see COPYRIGHT in
* <http://pcjs.org/modules/shared/lib/defines.js>.
*
* Some PCjs files also attempt to load external resource files, such as character-image files,
* ROM files, and disk image files. Those external resource files are not considered part of PCjs
* for purposes of the GNU General Public License, and the author does not claim any copyright
* as to their contents.
*/
"use strict";
/**
* addStickYMachine(idMachine)
*
* @param {string} idMachine
*/
function addStickyMachine(idMachine)
{
var machine = document.getElementById(idMachine);
if (machine) {
var machineFooter = document.getElementById(idMachine + '.footer');
if (machineFooter) {
var topMachine = findTop(machine);
var prevOnScroll = window.onscroll;
window.onscroll = function() {
if (window.pageYOffset <= topMachine) {
machine.style.position = 'relative';
machine.style.zIndex = 'auto';
machine.style.backgroundColor = '';
machine.style.paddingRight = 0;
if (machineFooter) machineFooter.style.paddingTop = 0;
} else {
machine.style.position = 'fixed';
machine.style.zIndex = 1;
machine.style.backgroundColor = 'white';
machine.style.paddingRight = '30px';
machine.style.top = 0;
if (machineFooter) machineFooter.style.paddingTop = machine.offsetHeight + 'px';
}
};
if (prevOnScroll) prevOnScroll();
}
}
}
/**
* findTop(obj)
*
* @param {Object} obj
*/
function findTop(obj)
{
var curTop = 0;
if (typeof obj.offsetParent != 'undefined' && obj.offsetParent) {
while (obj.offsetParent) {
curTop += obj.offsetTop;
obj = obj.offsetParent;
}
curTop += obj.offsetTop;
}
else if (obj.y) {
curTop += obj.y;
}
return curTop;
}