how to normalize scroll on different mouse
// Reasonable defaults
var PIXEL_STEP = 10;
var LINE_HEIGHT = 40;
var PAGE_HEIGHT = 800;
function normalizeWheel(/*object*/ event) /*object*/ {
var sX = 0, sY = 0, // spinX, spinY
pX = 0, pY = 0; // pixelX, pixelY
// Legacy
if ('detail' in event) { sY = event.detail; }
if ('wheelDelta' in event) { sY = -event.wheelDelta / 120; }
if ('wheelDeltaY' in event) { sY = -event.wheelDeltaY / 120; }
if ('wheelDeltaX' in event) { sX = -event.wheelDeltaX / 120; }
// side scrolling on FF with DOMMouseScroll
if ( 'axis' in event && event.axis === event.HORIZONTAL_AXIS ) {
sX = sY;
sY = 0;
}
pX = sX * PIXEL_STEP;
pY = sY * PIXEL_STEP;
if ('deltaY' in event) { pY = event.deltaY; }
if ('deltaX' in event) { pX = event.deltaX; }
if ((pX || pY) && event.deltaMode) {
if (event.deltaMode == 1) { // delta in LINE units
pX *= LINE_HEIGHT;
pY *= LINE_HEIGHT;
} else { // delta in PAGE units
pX *= PAGE_HEIGHT;
pY *= PAGE_HEIGHT;
}
}
// Fall-back if spin cannot be determined
if (pX && !sX) { sX = (pX < 1) ? -1 : 1; }
if (pY && !sY) { sY = (pY < 1) ? -1 : 1; }
return { spinX : sX,
spinY : sY,
pixelX : pX,
pixelY : pY };
}