Mouse Pressure Support in Mozilla

A few months back, I prototyped a device feature that would allow the MouseEvent to also carry an attribute of how hard you were pushing down on the screen. This evening, Oleg Romashin, pushed an implementation into the mozilla-central. With this new addition, you can build a new class of interactions. For example, you could imagine a painting web application that varies the size of the pen’s stroke depending on how hard the user is pressing down on the screen. Or the web browser itself could scroll faster or slower depending on how hard you are pressing down.

To use this feature, simply register to listen to mouse events how you normally would, and then check the value of the new attribute mozPressure.

target.addEventListener(“click”, listenerForClick, true);

function listenerForClick(event) {
if (event.mozPressure != undefined)
alert(event.mozPressure);
}

The value is defined between 0 and 1. The harder you press, the closer the number gets to 1. You can also use this to determine if the user is using a stylus, or if the user is using their thumb. Oleg has pointed out that, at least on the Nokia N-series devices, different values are grouped in such a manner:

0.0 – light touch with stylus
0.1-0.2 – normal stylus touch
0.2-0.5 – normal finger press
0.5-0.75 – Fat thumb press
0.75 – 0.99 – palm press

This feature will most likely be in Mozilla Fennec, as well as future version of Firefox. It is a mozilla-only feature (notice the “moz” prefix on the attribute name), but i would think this would be something Mozilla would be interested in standardizing (maybe not this exact behavior, but something similar).

Currently, it is only supported on Gtk, but I do not see any reason why this wouldn’t also be supported on other platforms that expose this functionality. We would love to have feedback on this new attribute.

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