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RE: Some comments about Pointer Events

From: François REMY <francois.remy.dev@outlook.com>
Date: Wed, 14 Nov 2012 17:04:13 +0100
Message-ID: <SNT002-W11748A2BCDCA393E9B9F5ACA5530@phx.gbl>
To: Jacob Rossi <jacob.rossi@microsoft.com>, Pointer Events WG <public-pointer-events@w3.org>
> From: Jacob.Rossi@microsoft.com
> To: francois.remy.dev@outlook.com; public-pointer-events@w3.org
> I think you misunderstand "height." Height (along with 
> width) refers to the contact geometry of the touch. It's 
> not the distance from the touchscreen, but the vertical 
> length of the physical contact your finger makes with the 
> screen.

Indeed, I misinterpreted "height" as a kind of depht. Nevermind. If there's no specification for the depht, we should just report this discussion until someone feels the need to implement it, as the final form will indeed depends on the use we intend to make out of it.

> Since it's normalized, I usually think of pressure as a modifier. For example, in the line drawing scenario, I would do something like: lineWidth = pressure * MAX_LINE_WIDTH. 

I think about it, too. However, if you do so, you'll get no line at all using a mouse (pressure=0) and as far as I can tell, there's no way to know if the input device supports pressure or not.

> So while, yes, it might require different amounts of pressure to produce the same effect across devices, at least every device is interoperable in the sense that it can produce the same *range* of values. In the line drawing scenario, I'm not sure that I want one device to not be able to draw as thick of a line as another simply because it cannot register that much pressure.

So, basically, you propose a model where an user using a better stylus has to press harder to get the same effect as someone which has a very simple one which only handles small pressure levels? To me, this seems a deal breaker, and it would lead to the impossibility for a stylus vendor to expose publicly the higher range if he want to keep the user's habit of a normal stylus.

By the way, you're already limited in the set of actions you can do using your input device because of its other limitations. If your stylus as no erase button, you can't erase. If it has no secondary button, you can't use it either. On a mouse, you can't support pressure at all. I don't see why it's a problem to say that on a device A you can achive a [0-3] range while on device B you can achieve a [0-5] range.

Also, some mouses allow to "adjust" sensibility. Similarily, my model would allow pressure-enabled sensors to "shift" the normal value they report (or their internal scale) to allow higher or lower returned values for the same physical pressure, as an user accomodation measure, and without any range clamping. If you keep using a [0-1] scale, you can only decrease precision, not increase it (or else, you reduce the pression range where you can work without clamping).

> I'm also not confident that devices report consistent pressure values (e.g. if you place a 10kg weight on a stylus then it produces the exact same pressure value on any device you put it on). So I don't think you could standardize around "standard pressure" (meaning a fixed physical amount of pressure).

It's up to each device to specify its "normal" value, not to this specification. In the absence of any information, then it's possible to try to guess the normal value using the available data (reasonable default), but it's just an error-recovery situation. 		 	   		  
Received on Wednesday, 14 November 2012 16:04:40 UTC

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