Windows isn't the only OS that cares about pens

But it might be the only OS with the patent to do pens the right way…

One of the highlights of Adobe's MAX developer conference this year was Photoshop Touch; a tablet application, initially for Android but coming soon for iPad, that's a real application with powerful features. Equally interesting was the device Adobe was demonstrating it on - a prototype Samsung Galaxy Tab with the kind of pressure-sensitive Wacom pen that's been in Tablet PCs for years.

That works really well for drawing on screen; the harder you press, the thicker the line you draw. You can use the pen anywhere in Android, so you can take handwritten notes as well as drawing in Photoshop Touch. But you can't rest your hand anywhere on the screen while you do that, because Android treats that as a valid touch - even when the pen is resting on the screen and you're almost certain to want the tablet to detect the pen rather than your hand.

That might be great if you want to draw with one hand and blend the paint with the other; we saw an artist using the Microsoft Research Project Gustav natural painting system draw on screen with a pen and his hand to produce really impressive art. But most of the time you're only resting your hand on screen to steady the pen (try writing on a piece of paper without ever touching it with the hand holding the pen to see the difference it makes). Why wouldn't Samsung put that into its Android tablet when it's already in the slate PCs it makes (the Series 7 as well the Windows 8 prototype slate handed out at the Build conference)?

Microsoft certainly thinks rejecting the touch of your palm when the pen is around - palm rejection or blunt touch blocking - is a key feature of Windows for tablets, as VP Mike Angiulo explained when showing off Windows 8 slate prototypes at CES this year. "When I have the pen down on the screen, can you see how my hand is not moving the spreadsheet around? This is one of the reasons that it's hard to do ink on touch-only devices, and why Tablet PCs are so good for ink, is because it's implementing palm rejection here. It actually knows what my hand is and knows what the pen is, and doesn't get the two confused."

And Steven Sinofsky, the head of Windows, went even further. "It's really important for when you want to develop a touch surface you can also write on," he told us, adding that "no other operating system has that when you're using a stylus."

In the past, Sinofsky has also pointed out that having had tablet devices for years means Microsoft has plenty of patents around tablets and pens. Check the US Patent Office, and yes, Microsoft has a 2005 patent for 'unintentional touch rejection' based on determining how certain the system is that you meant to touch the screen with your hand.

The introduction reads "A method for rejecting an unintentional palm touch is disclosed. In at least some embodiments, a touch is detected by a touch-sensitive surface associated with a display. Characteristics of the touch may be used to generate a set of parameters related to the touch. In an embodiment, firmware is used to determine a reliability value for the touch. The reliability value and the location of the touch is provided to a software module. The software module uses the reliability value and an activity context to determine a confidence level of the touch. In an embodiment, the confidence level may include an evaluation of changes in the reliability value over time. If the confidence level for the touch is too low, it may be rejected.")

Samsung did recently make a cross-licencing deal with Microsoft for its Android tablets, but it's not clear that this would give them the rights to block accidental touch on Android. The Australian lawsuit has revealed that Apple suggested to Samsung that it might license some "some 'lower level patents'" but Apple would protect the user experience and features of the iPad. The patent infringements Microsoft is suing Motorola over do include user experience features like selecting and annotating text as well as system-level options like notifying applications of changes in signal strength and battery power, but they're not as crucial a part of the user experience of using a tablet with a dual-touch screen as being able to lean your hand on screen while using a pen. If active pens become common on the Galaxy Tab, that will certainly help to distinguish them from the iPad - but if it's awkward and frustrating to use the pen, that will give Windows tablets an advantage.

Mary Branscombe