Scrolling is complicated. Nolan Lawson:
- User scrolls with two fingers on a touch pad
- User scrolls with one finger on a touch screen
- User scrolls with a mouse wheel on a physical mouse
- User clicks the sidebar and drags it up and down
- User presses up, down, PageUp, PageDown, or spacebar keys on a keyboard
As it turns out, all five of these input methods have vastly different characteristics, especially when it comes to performance and cross-browser behavior. Some of them (such as touch screen scrolling) are likely to be smooth even on a page with heavy JavaScript usage, whereas others (such as keyboard scrolling) will make the same page feel laggy and unresponsive. Furthermore, some kinds of scrolling can be slowed down by DOM event handlers, whereas others won’t.
