windows acceleration function

windows-acceleration-function.py

# calculation are based on http://www.esreality.com/index.php?a=post&id=1945096
# assuming windows 10 uses the same calculation as windows 7.
import struct

# set according to your device:
device_dpi = 304 # mouse/touchpad dpi
screen_dpi = 157
sample_point_count = 30
sensitivity_factor = 1.0
# sensitivity factor translation table: (windows slider notches)
# 1 = 0.1
# 2 = 0.2
# 3 = 0.4
# 4 = 0.6
# 5 = 0.8
# 6 = 1.0 default
# 7 = 1.2
# 8 = 1.4
# 9 = 1.6
# 10 = 1.8
# 11 = 2.0

# inch/s to native-device-units/us
scaling_factor = device_dpi / 1e6

def float16x16(num):
    return struct.unpack('<i', num[:-4])[0] / int(0xffff)

# windows registry values:
# HKEY_CURRENT_USER\Control Panel\Mouse\SmoothMouseXCurve
X = [
b'\x00\x00\x00\x00\x00\x00\x00\x00',
b'\x15\x6e\x00\x00\x00\x00\x00\x00',
b'\x00\x40\x01\x00\x00\x00\x00\x00',
b'\x29\xdc\x03\x00\x00\x00\x00\x00',
b'\x00\x00\x28\x00\x00\x00\x00\x00',
]
# HKEY_CURRENT_USER\Control Panel\Mouse\SmoothMouseYCurve
Y=[
b'\x00\x00\x00\x00\x00\x00\x00\x00',
b'\xfd\x11\x01\x00\x00\x00\x00\x00',
b'\x00\x24\x04\x00\x00\x00\x00\x00',
b'\x00\xfc\x12\x00\x00\x00\x00\x00',
b'\x00\xc0\xbb\x01\x00\x00\x00\x00',
]

points = []
for x,y in zip(X,Y):
    x = float16x16(x) * scaling_factor
    y = float16x16(y) * scaling_factor
    gain = 0 if x == 0 else (y / x) / (3.5 * 150 / screen_dpi)
    points.append((x, y, gain))



def find2points(x):
    i = 0
    while i < len(points) - 2 and x > points[i][0]:
        i +=1
    return points[i], points[i+1]


max_x = points[-1][0]
step = max_x / (sample_point_count - 1) # we need another point for 0
sample_points = []
pi = 0
for si in range(sample_point_count):
    x = si * step
    (x0, _, y0), (x1, _, y1) = find2points(x)
    interpolated_value = ((x-x0)*y1+(x1-x)*y0)/(x1-x0)
    sample_points.append(interpolated_value)

sample_points_str = ",".join(["%.2f" % number for number in sample_points])

print("device dpi: ", device_dpi)
print("screen dpi: ", screen_dpi)
print("sensitivity factor: ", sensitivity_factor)
print("windows points scaled to native-device-units/us (x, y, gain):")
for p in points:
    print("\t", p)

print(f"libinput delta-x: {step}")
print(f"libinput sample points ({sample_point_count}):")
print("\t", sample_points_str)

print("libinput test:")
print("\t", f"sudo ./builddir/libinput-debug-gui --verbose --set-profile=custom --set-custom-points={sample_points_str} --set-custom-step={step} --set-custom-type=1")