xf86-input-joystick: Changes to 'master'

[Sascha Hlusiak]

 src/backend_evdev.c |   26 +++++++++++++++++++++--
 src/jstk_axis.c     |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 79 insertions(+), 4 deletions(-)

New commits:
commit 819ba33c9d7440cd40e1e54a9b1e073ed89353a7
Author: Sascha Hlusiak <saschahlusiak at arcor.de>
Date:   Sat Oct 6 18:28:53 2012 +0200

    jast_axis: tune accelerated axis transformation to better work with circular axis fields
    
    reference: https://bugs.freedesktop.org/show_bug.cgi?id=42399
    
    joysticks with a rectangular field have a
    corner position of (32768,32768), joysticks with a
    circular field have (23170,23170).
    
    make sure that diagonal movement feels fast. either:
    1) linear
    
      f(32768) ~= f(23170) + f(23170)
      f(32768) ~= a * f(23170)
             a  = 2.0
    
      on circular joysticks, the time needed for xy movement is
      exactly the time needed for x + the time for y separately.
      absolute diagonal travel speed (in cm/s) is 0.707 times as fast,
      which feels pretty slow.
    
      on square joysticks, diagonal travel speed is always 1.41 times
      faster than orthogonal travel speed. time needed for diagonal
      movement is always 0.5 times as long as for orthogonal movement.
    
      the value of a = 2.0 results in a nice, non-linear acceleration.
    
    or
    2) trigonometric
    
      f(32768) ~= sqrt(f(23170)^2 + f(23170)^2))
      f(32768) ~= a * f(23170)
      a = 1.414
    
    on circular joysticks, the absolute pointer travel speed
    (in cm/s) is now the same for both linear and diagonal movement,
    which feels natural. moving diagonally takes 0.707 times the time
    of moving orthogonally.
    
    on square joysticks, values are as in 1)
    
    the value of a = 1.414 results in linear acceleration, which feels
    too slow.
    
    to maintain non-linear acceleration, make sure that:
    
    a >>= 1.414
    
    the following formula achieves results inbetween,
    so it should feel natural on both devices while maintaining a
    nice acceleration:
    
    f(32768) ~= 1.620 * f(23170)

commit 342057bf38e2da46609ed2fa0d3f5fb46c8ed215
Author: Sascha Hlusiak <saschahlusiak at arcor.de>
Date:   Sat Oct 6 16:18:24 2012 +0200

    backend_evdev: fix scaling overflow for high resolution axes
    
    The module scales all axis values from the kernel to the range of
    -32768 .. 32768, for compatibility with the old joystick kernel module.
    
    The current implementation had an integer overflow, if the axis had a high
    resolution of > 16384, like the popular XBox 360 controller.
    
    This commitmakes the scaling use float instead to fix erratic behaviour
    on high resolution joysticks. The joystick backend was not affected.
    
    Fixes bug: https://bugs.freedesktop.org/show_bug.cgi?id=42399