Function iconSizeDistance
Distance between desired size and minimum or maximum size value supported by icon theme subdirectory.
Example
auto fixed = IconSubDir(32, IconSubDir .Type .Fixed);
assert(iconSizeDistance(fixed, fixed .size()) == 0);
assert(iconSizeDistance(fixed, 30) == 2);
assert(iconSizeDistance(fixed, 35) == 3);
auto threshold = IconSubDir(32, IconSubDir .Type .Threshold, "", 0, 0, 5);
assert(iconSizeDistance(threshold, threshold .size()) == 0);
assert(iconSizeDistance(threshold, threshold .size() - threshold .threshold()) == 0);
assert(iconSizeDistance(threshold, threshold .size() + threshold .threshold()) == 0);
assert(iconSizeDistance(threshold, 26) == 1);
assert(iconSizeDistance(threshold, 39) == 2);
auto scalable = IconSubDir(32, IconSubDir .Type .Scalable, "", 24, 48);
assert(iconSizeDistance(scalable, scalable .size()) == 0);
assert(iconSizeDistance(scalable, scalable .minSize()) == 0);
assert(iconSizeDistance(scalable, scalable .maxSize()) == 0);
assert(iconSizeDistance(scalable, 20) == 4);
assert(iconSizeDistance(scalable, 50) == 2);