I would like to see a per widget (or per frame?) configurable click
threshold for table pressure clicks on my wacom tablet.

Currently, the wacom driver has a value, called the "Threshold" which is
the pressure threshold which causes a "click" event to be sent.  This is
good, because it means I can rest the stylus on my pad and control the
mouse.  (like a touch pad).  (fyi, wacom tablets can sense the stylus above
the pad, so the threshold can be basiclly zero and you can still move the
mouse, but it is easier if I can rest the stylus on the pad most of the time).

However, the current implementation is bad for the gimp because if someone
has a click threshold set (or is using the default of about 1/3 of tablet
max pressure) then the pressure range reported to the button_event signal
is (threshold,1.0], which basically breaks pressure sensitivity of our brushes.

Sven argues that this is a driver bug.  That the driver should map it's
pressure values from 0 to MAX during a button press, regardless of threshold.

I would rather see something else happen.

It would be nice if I could have the click threshold adjustable on a per
widget basis.  Basically, you would set the pre-mapping threshold, and GDK
would take care to ensure that the button_event pressures range from 0.0 to
1.0 instead of threshold to 1.0.  The driver threshold, then, would be a
reasonable default value.  bug #127784 is our (the gimp's) discussion of
this topic.

This is a reasonble feature because it uses the drivers default so it won't
alter the behavior of existing applications, while providing extra
functionality for apps that know about it (or need it).