Estimation for mutter HiDPI thresholds

hidpu.py

#!/usr/bin/env python3

import sys
import numpy as np

def area(d, a, b):
    return (a*b)/(a**2+b**2) * d**2

def dpi(d, res, ratio):
    a, b = ratio
    x, y = res
    A = area(d, a, b)
    px = x*y
    return np.sqrt(px/A), d, res, ratio

res = [(3840, 2048)]
sizes = [22, 23, 23.4, 24, 25]
ratio = [(4,3), (16, 9), (16,10), (21,9)]

def main():
    ts = 192 if len(sys.argv) < 2 else int(sys.argv[1])
    dpis = [dpi(s, r, q) for s in sizes for r in res for q in ratio]

    print('Using threashold %d' % ts)
    for d, s, r, q in dpis:
        scale = 2 if d > ts else 1
        scale_5p = 2 if d > ts-(ts*0.05) else 1
        change = '!' if  scale != scale_5p else ''
        print('%2.1f", %dx%d, %2d:%2d  => %3.1f -> %d, %d %s' %
              (s, r[0], r[1], q[0], q[1], d, scale, scale_5p, change))

if __name__ == '__main__':
    main()