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filter: simplify speed_factor()

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The `speed_factor()` formula is unnecessarily complex, The behavior that is described in the comment can be achieved with a simple power function.

And adjust the comment to explicitly state that 0.05 is the minimum.
This commit is contained in:
Tobias Bengfort 2023-02-08 10:56:48 +00:00 • committed by Peter Hutterer
parent 74415b13fb
commit 9bb2136bab
1 changed files with 2 additions and 12 deletions
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14
src/filter-touchpad.c
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@ -113,26 +113,16 @@ accelerator_filter_touchpad(struct motion_filter *filter,
/* Maps the [-1, 1] speed setting into a constant acceleration /* Maps the [-1, 1] speed setting into a constant acceleration
* range. This isn't a linear scale, we keep 0 as the 'optimized' * range. This isn't a linear scale, we keep 0 as the 'optimized'
* mid-point and scale down to 0 for setting -1 and up to 5 for * mid-point and scale down to 0.05 for setting -1 and up to 5 for
* setting 1. On the premise that if you want a faster cursor, it * setting 1. On the premise that if you want a faster cursor, it
* doesn't matter as much whether you have 0.56789 or 0.56790, * doesn't matter as much whether you have 0.56789 or 0.56790,
* but for lower settings it does because you may lose movements. * but for lower settings it does because you may lose movements.
* *shrug*. * *shrug*.
*
* Magic numbers calculated by MyCurveFit.com, data points were
* 0.0 0.0
* 0.1 0.1 (because we need 4 points)
* 1 1
* 2 5
*
* This curve fits nicely into the range necessary.
*/ */
static inline double static inline double
speed_factor(double s) speed_factor(double s)
{ {
s += 1; /* map to [0, 2] */ return pow(s + 1, 2.38) * 0.95 + 0.05;
return 435837.2 + (0.04762636 - 435837.2)/(1 + pow(s/240.4549,
2.377168));
} }
static bool static bool