// ==UserScript==
// @name         Extended SPACE Key Page Scroller
// @namespace    ExtendedSpaceKeyPageScroller
// @version      1.0.3
// @description  By default the SPACE key scrolls the page down by full height of browser view. With this script, pressing SHIFT+SPACE will scroll half of the view height. Page scroll by a quarter view height can be done using either LEFTSHIFT+RIGHTSHIFT+SPACE or SHIFT+CAPSLOCK+SPACE (configurable via variable).
// @author       jcunews
// @match        *://*/*
// @grant        none
// @run-at       document-start
// ==/UserScript==
// *** Configuration Start ***
// QuarterScrollKey: Determine what key combination to use for scrolling page by a quarter height of view.
// 0      = Use both SHIFT keys. i.e. LeftShift+RightShift+Space
// 1/else = Use CAPSLOCK key. i.e. Shift+CapsLock+Space
var QuarterScrollKey = 1;
// *** Configuration End ***
var shiftKeys = 0, capsLock = false;
addEventListener("keydown", function(ev) {
switch (ev.which) {
case 16: //SHIFT
shiftKeys |= ev.location;
break;
case 20: //CAPSLOCK
capsLock = true;
}
}, true);
addEventListener("keyup", function(ev) {
switch (ev.which) {
case 16: //SHIFT
shiftKeys &= ~ev.location;
break;
case 20: //CAPSLOCK
capsLock = false;
}
}, true);
addEventListener("keypress", function(ev, delta) {
if (!ev.shiftKey) {
shiftKeys = 0;
} else if (!shiftKeys) {
shiftKeys = 1;
}
if ((ev.which === 32) && !ev.altKey && (["INPUT", "TEXTAREA"].indexOf(document.activeElement.tagName) < 0)) {
if (((shiftKeys === 3) && !capsLock && !QuarterScrollKey) || //with both SHIFT key
(shiftKeys && (shiftKeys < 3) && capsLock && QuarterScrollKey)) { //with SHIFT+CAPSLOCK key
delta = 4;
} else if (shiftKeys) { //with one SHIFT key
delta = 2;
} else delta = 0;
if (delta) {
scrollBy(0, innerHeight / delta);
ev.preventDefault();
ev.stopPropagation();
ev.stopImmediatePropagation();
}
}
}, true);