[...]One reason is to make the behavior of all touchscreens as similar as possible, so that applications don't have to care.
But...you want to force software calibration just for consistency? Really?
Really :)
Think about it. What does the software have to do to use the touchscreen hardware calibration? At the very least it as to draw the markers the controller is expecting and instruct the user to press them.
Lets say that it is currently 2 markers or 21 markers. Then another manufacturer comes along and says "no, our touchscreen is much better because it uses a 5 point linear calibration or a 45 point non-linear calibration", and you'll have to change your software to cope with that.
More over, you will still need to provide software calibration for those touchscreens that don't support it. So you have all the extra work to support hardware calibration and it won't remove any work from the software calibration.
Bottom line, if we have the same raw information that is already available to the controller, do you think we can't do the same job the controller does, in software?
This way, if we decide to provide a 5x4 20 points non-linear super-duper mega hyper calibration algorithm, it will be available to *all* supported touchscreens at no extra cost.
We can also do a lot more stuff in software, like requesting a 3 point calibration and validating that they are somewhat orthogonal, and reject them and request a new calibration if they aren't.
The more touchscreen models and brands we support, the more painful it will be to support hardware calibration. Believe me, we don't want to go down that road.
This has been discussed recently in a "elo touchscreen..." thread. The conclusion was that we needed a nice user space library to provide this kind of services (calibration, filtering, etc.), so that applications that worked with touchscreens could have more specific API than the generic one provided by the input layer.
-- Paulo Marques - www.grupopie.com
All that is necessary for the triumph of evil is that good men do nothing. Edmund Burke (1729 - 1797)
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