Re: [PATCH] Input: wacom - Add POINTER and DIRECT device properties

quoted

 * Pen interface without screen should have both POINTER and DIRECT to
indicate pointer needed and to treat absolute coordinates as absolute
movement.

No.  DIRECT should not be set because the Pen is not directly touching
the objects on a screen.  The motions must still be translated through
some indirect means (a mapping function) onto the plane of the screen.

Therefore should only specify POINTER.

This is wrong given the intended semantics. Regardless of if DIRECT
means "absolute coordinates" or "one-to-one with screen", the result
is the same.

quoted

 * Touch interfaces with screen should have DIRECT only to indicate no
pointer displayed and absolute coordinates as absolute movement.
 * Pen interface with screen should have DIRECT only to indicate no
pointer displayed and absolute coordinates as absolute movement.
* A Pen+Touch touchscreen (only the wacom_w8001.c), should have DIRECT
only to indicate no pointer displayed and absolute coordinates as
absolute movement.

Yes, but not for this reason.  Touch interfaces with screen should
have DIRECT to indicate that touches are directly upon objects on the
screen.

A one-to-one correspondence should suffice.

It happens that the absolute coordinates of a tablet are usually
mapped 1-1 with the screen, but that's not what is meant by a direct
input device.  It's the usage that matters, not the mapping function
itself.

Precisely - it is the usage that matters here.

Note that a tablet's mapping function need not be precisely 1-1.  It
could be constrained to part of a window on the display, or it could
be rotated or skewed with respect to the display.  This is a
fundamental difference between direct and indirect input devices.  The
mapping function for a direct input devices must be a natural mapping
based on what is actually seen and directly touches.  The mapping
function for an indirect input device can be almost anything because a
pointer is being used to provide visual feedback so it is not
constrained by the physical position of objects on screen.

The fundamental difference between a touchscreen and the mapping you
describe here is POINTER, not DIRECT. There is no reason why a device
physically separated from the screen, and guided by one or several
markers, cannot behave the same way as a touchscreen.

quoted

Assuming we all agree on those combination, then in the patch the
Graphire and Intuos tablets are missing a DIRECT, the touchscreens are
correct, and the Bamboo's need to add DIRECT for the PEN interface
only.

I disagree.

A touchscreen is DIRECT.
A tablet or trackpad is INDIRECT (and POINTER).

Based on your assmumptions on the semantics, you are of course
right. Given the actual intended semantics, this is wrong. It is as
far as we get.

Further absolute/relative distinctions need to be made by tool.
Finger / mouse on tablet uses relative motion.  Pen uses absolute
motion.  Essentially the tool types qualify the mapping function used
by indirect devices.

Aggred, the pen tablets we see today behave this way, and we do not
break anything by skipping the DIRECT property here.

Thanks,
Henrik
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