paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

jeffkreeftmeijer

.mouse, #preview{
  position: absolute;
  background-repeat: no-repeat;
  height: 22px;
  min-width: 15px;
  z-index: 100;
}

.mouse{
  background-image: url('../images/cursor.png');