scale.go RawHistoryFolder

1package core
2
3import "math"
4
5// Scales are in 1/120 steps, the wp_fractional_scale_v1 unit.
6const scaleDen = 120
7
8// CleanScales lists scales between 1 and 3 where the output divides into whole
9// logical pixels, so window edges land on physical pixels. Scales below 1.1
10// are skipped: 1.067 on 5120 wide outputs is too close to 1 to be useful.
11func CleanScales(width, height int) []float64 {
12	out := []float64{1}
13	for n := scaleDen + 1; n <= 3*scaleDen; n++ {
14		if width*scaleDen%n != 0 || height*scaleDen%n != 0 {
15			continue
16		}
17		if s := float64(n) / scaleDen; s >= 1.1 {
18			out = append(out, s)
19		}
20	}
21	return out
22}
23
24// StepScale returns the next clean scale above (dir 1) or below (dir -1) cur,
25// or cur at the ends.
26func StepScale(width, height int, cur float64, dir int) float64 {
27	list := CleanScales(width, height)
28	if dir > 0 {
29		for _, s := range list {
30			if s > cur+1e-6 {
31				return s
32			}
33		}
34		return cur
35	}
36	for i := len(list) - 1; i >= 0; i-- {
37		if list[i] < cur-1e-6 {
38			return list[i]
39		}
40	}
41	return cur
42}
43
44// SnapScale rounds to the nearest 1/120 and clamps to [1, 4].
45func SnapScale(s float64) float64 {
46	if !(s >= 1) {
47		return 1
48	}
49	return math.Round(min(s, 4)*scaleDen) / scaleDen
50}
51
52// logical converts a physical size to logical pixels.
53func logical(v int, scale float64) int { return int(math.Round(float64(v) / scale)) }