Wayland Relative Pointer API Progress

x414e54 x414e54 at linux.com
Mon Apr 20 05:49:37 PDT 2015

>> There is no sense in saying the sensor reading itself as absolute or
>> relative. Either gives you some number in unknown units which you
>> calibrate to get usable results. You have no idea where the stick is
>> from the numbers you get. And there is absolutely no point caring. It
>> may have some sense for a particular application and no sense for
>> other.
> One of my original points was that a user should be able to hot-swap a
> mouse and a gamepad thumbstick without a game caring and that games do
> not care about mice/joystick/touchpad they just want raw axis values
> that they can use, evdev makes this abstraction.
> But you certainly need to know if the axis is relative or absolute to
> convert it to what the application needs.

If you had an application wanting to move an object around and I gave
you the value 500 and then 10 seconds later 400.
Has the object moved 900 units or -100 units? You need to know this,
this is the difference between absolute and relative.

But there is nothing stopping me giving you the position 500 and then
measuring the next value relatively -100 and then calculating the last
position plus the relative distance and giving this value to you.
Hence the hot-swapping.

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