JarCastingPointer Events Polyfill - making pointer events usable today
PEP polyfills pointer events in all browsers that haven't yet implemented them, providing a unified, responsive input model for all devices and input types. You can read more about pointer events below.
Project status
PEP development ceased in 2018. A few minor maintenance patches have been pushed since then, and the latest version (0.5.3) has been published to npm. However, native support for Pointer Events is relatively good in most browsers at this point - see caniuse: Pointer Events. This project is now archived.
Getting Started
- Place the PEP script in the document head
<script src="https://code.jquery.com/pep/0.4.3/pep.js"></script>
-
By default, no pointer events are sent from an element. This maximizes the possibility that a browser can deliver smooth scrolling and jank-free gestures. If you want to receive events, you must set the
touch-actionproperty of that element. Set up some elements to create events with thetouch-actionattribute. -
Listen for the desired events
pointermove: a pointer moves, similar to touchmove or mousemove.pointerdown: a pointer is activated, or a device button held.pointerup: a pointer is deactivated, or a device button released.pointerover: a pointer has moved onto an element.pointerout: a pointer is no longer on an element it once was.pointerenter: a pointer enters the bounding box of an element.pointerleave: a pointer leaves the bounding box of an element.pointercancel: a pointer will no longer generate events.
- As elements come and go, or have their
touch-actionattribute changed, they will send the proper set of pointer events.
<html lang="en">
<head>
<meta charset="utf-8">
<title>PEP (Pointer Events Polyfill)</title>
<meta name="viewport" content="width=device-width">
<!-- include PEP -->
<script src="https://code.jquery.com/pep/0.4.3/pep.js"></script>
</head>
<body>
<button id="b" touch-action="none">Test button!</button>
<p><output id="o"></output></p>
<script>
document.getElementById( "b" ).addEventListener( "pointerdown", function( e ) {
document.getElementById( "o" ).innerHTML = "that was a " +
e.pointerType + " " + e.type + " on a "+ e.target.nodeName;
} );
</script>
</body>
</html>
See also the examples in the W3C Pointer Events Specification and our own samples for using PEP.
Using PEP as a module
npm install pepjs
import 'pepjs'
Using PEP with jQuery
You can use pointer events with jQuery and PEP:
<div id="canvas" touch-action="none"></div>
<script src="pep.dist.js"></script>
<script src="jquery.js"></script>
<script>
$("#canvas").on("pointermove", function(event) {
draw(event);
});
</script>
Check out this jsbin demo for a full demo.
jQuery doesn't copy all properties from the original event object to the event object provided in the event handler. You can find a list of copied and normalized properties on the jQuery API docs. To access any other original properties, use event.originalEvent.
Using PEP with React
As of version 16.4, React comes with first class support for pointer events. To use pointer events on unsupported browsers, you can include PEP before mounting your React application. You can also use the touch-action property on any JSX node:
export function Pointable() {
return <div touch-action="none" onPointerDown={(e) => console.log(e)} />
}
Why Pointer Events?
Mouse events and touch events are fundamentally different beasts in browsers today, and that makes it hard to write cross-platform apps.
For example, a simple finger paint app needs plenty of work to behave correctly with mouse and touch:
Current platforms that implement touch events also provide mouse events for backward compatibility; however, only a subset of mouse events are fired and the semantics are changed.
- Mouse events are only fired after the touch sequence ends.
- Mouse events are not fired on elements without a
clickevent handler. One must be attached by default, or directly on the element withonclick. clickevents are not fired if the content of the page changes in amousemoveormouseoverevent.clickevents are fired 300ms after the touch sequence ends.- More information: Apple Developer Documentation.
Additionally, touch events are sent only to the element that received the touchstart. This is fundamentally different than mouse events, which fire on the element that is under the mouse. To make them behave similarly, touch events need to be retargeted with document.elementFromPoint.
These incompatibilities lead to applications having to listen to 2 sets of events, mouse on desktop and touch for mobile.
This forked interaction experience is cumbersome and hard to maintain.
Instead, there should exist a set of events that are normalized such that they behave exactly the same, no matter the source: touch, mouse, stylus, skull implant, etc. To do this right, this normalized event system needs to be available for all the web platform to use.
Thus, Pointer Events!
Polyfill Limitations
touch-action
According to the spec, the touch-action CSS property controls whether an element will perform a "default action" such as scrolling, or receive a continuous stream of pointer events.
Due to the difficult nature of polyfilling new CSS properties, this library uses a touch-action attribute instead. For PEP to work correctly, you will therefore need to include touch-action="..." attributes in your HTML that mirror any touch-action:... properties you have in your CSS.
<style>
div#foo { touch-action: none; }
</style>
...
<div id="foo" touch-action="none"> ... </div>
Run time changes involving the touch-action attribute are monitored using Mutation Observers for maximum flexibility.
Touches will not generate events unless inside of an area that has a valid touch-action attribute defined. This is to maintain composition scrolling optimizations where possible.
Capturing Phase
PEP does not currently polyfill the capturing phase for pointer events.
navigator.maxTouchPoints
As the information necessary to populate navigator.maxTouchPoints is not available in browsers that do not natively implement pointer events, PEP sets the value to 0, which is "the minimum number guaranteed to be recognized" as required by the specification.
Browser Compatibility
PEP should work on IE 10+ and the latest versions of Chrome, Safari, Firefox, and Opera. In any browser implementing pointer events natively (detected by checking for window.PointerEvent), PEP won't do anything.
Building PEP
If you want to build PEP yourself from source, you'll need to install Node.js and run the following commands:
# Install all dependencies
npm install
# Build PEP
npm run build
When the build completes, the generated files will be available in the dist/ directory.
NOTE: Running the demos requires building PEP.
