Commit f493006847
Verified · cmc
internal/web/tokens_test.go added +133
| @@ -0,0 +1,133 @@ | ||
| 1 | package web | |
| 2 | ||
| 3 | import ( | |
| 4 | "math" | |
| 5 | "regexp" | |
| 6 | "strconv" | |
| 7 | "strings" | |
| 8 | "testing" | |
| 9 | ) | |
| 10 | ||
| 11 | // parseTokens returns the --name: value pairs of the light :root block | |
| 12 | // and of the :root block inside the dark media query. A value that is | |
| 13 | // itself a var() is resolved one level deep within the same scheme. | |
| 14 | func parseTokens(css []byte) (light, dark map[string]string) { | |
| 15 | s := string(css) | |
| 16 | rootRe := regexp.MustCompile(`(?s):root\s*\{(.*?)\}`) | |
| 17 | darkIdx := strings.Index(s, "@media (prefers-color-scheme: dark)") | |
| 18 | if darkIdx < 0 { | |
| 19 | return nil, nil | |
| 20 | } | |
| 21 | parse := func(block string) map[string]string { | |
| 22 | m := map[string]string{} | |
| 23 | lineRe := regexp.MustCompile(`--([a-z0-9-]+)\s*:\s*([^;]+);`) | |
| 24 | for _, mm := range lineRe.FindAllStringSubmatch(block, -1) { | |
| 25 | v := strings.TrimSpace(mm[2]) | |
| 26 | if i := strings.Index(v, "/*"); i >= 0 { | |
| 27 | v = strings.TrimSpace(v[:i]) | |
| 28 | } | |
| 29 | m[mm[1]] = v | |
| 30 | } | |
| 31 | for k, v := range m { | |
| 32 | if strings.HasPrefix(v, "var(--") { | |
| 33 | ref := strings.TrimSuffix(strings.TrimPrefix(v, "var(--"), ")") | |
| 34 | if rv, ok := m[ref]; ok { | |
| 35 | m[k] = rv | |
| 36 | } | |
| 37 | } | |
| 38 | } | |
| 39 | return m | |
| 40 | } | |
| 41 | lm := rootRe.FindStringSubmatch(s[:darkIdx]) | |
| 42 | dm := rootRe.FindStringSubmatch(s[darkIdx:]) | |
| 43 | if lm == nil || dm == nil { | |
| 44 | return nil, nil | |
| 45 | } | |
| 46 | light = parse(lm[1]) | |
| 47 | dark = parse(dm[1]) | |
| 48 | for k, v := range light { | |
| 49 | if _, ok := dark[k]; !ok && strings.HasPrefix(v, "#") { | |
| 50 | dark[k] = v // a light-only colour is a bug; keep it visible below | |
| 51 | } | |
| 52 | } | |
| 53 | return light, dark | |
| 54 | } | |
| 55 | ||
| 56 | func hexChannel(h string) float64 { | |
| 57 | n, _ := strconv.ParseUint(h, 16, 8) | |
| 58 | c := float64(n) / 255 | |
| 59 | if c <= 0.03928 { | |
| 60 | return c / 12.92 | |
| 61 | } | |
| 62 | return math.Pow((c+0.055)/1.055, 2.4) | |
| 63 | } | |
| 64 | ||
| 65 | func luminanceHex(hex string) float64 { | |
| 66 | hex = strings.TrimPrefix(hex, "#") | |
| 67 | if len(hex) == 3 { | |
| 68 | hex = string([]byte{hex[0], hex[0], hex[1], hex[1], hex[2], hex[2]}) | |
| 69 | } | |
| 70 | return 0.2126*hexChannel(hex[0:2]) + 0.7152*hexChannel(hex[2:4]) + 0.0722*hexChannel(hex[4:6]) | |
| 71 | } | |
| 72 | ||
| 73 | func contrastHex(a, b string) float64 { | |
| 74 | la, lb := luminanceHex(a), luminanceHex(b) | |
| 75 | if la < lb { | |
| 76 | la, lb = lb, la | |
| 77 | } | |
| 78 | return (la + 0.05) / (lb + 0.05) | |
| 79 | } | |
| 80 | ||
| 81 | // TestTokenContrast is the contract for the colour tokens in style.css: | |
| 82 | // every text colour clears WCAG AA on every ground it lands on, in both | |
| 83 | // schemes. The hex values in the stylesheet are free to move as long as | |
| 84 | // this passes. | |
| 85 | func TestTokenContrast(t *testing.T) { | |
| 86 | light, dark := parseTokens(StyleCSS) | |
| 87 | if light == nil || dark == nil { | |
| 88 | t.Fatal("could not find the light and dark :root blocks in style.css") | |
| 89 | } | |
| 90 | type check struct { | |
| 91 | fg, bg string | |
| 92 | floor float64 | |
| 93 | } | |
| 94 | checks := []check{ | |
| 95 | {"fg", "canvas", 7}, {"fg", "surface", 7}, | |
| 96 | {"muted", "canvas", 4.5}, {"muted", "surface", 4.5}, | |
| 97 | {"link", "canvas", 4.5}, {"link", "surface", 4.5}, {"link", "hover", 4.5}, | |
| 98 | {"fill-fg", "fill", 4.5}, {"fill", "surface", 3}, | |
| 99 | {"line", "canvas", 3}, | |
| 100 | {"mark", "canvas", 3}, | |
| 101 | {"warn", "canvas", 4.5}, {"warn", "surface", 4.5}, | |
| 102 | {"ok", "canvas", 4.5}, {"ok", "surface", 4.5}, | |
| 103 | {"bad", "canvas", 4.5}, {"bad", "surface", 4.5}, | |
| 104 | {"done", "canvas", 4.5}, {"done", "surface", 4.5}, | |
| 105 | {"focus", "canvas", 3}, | |
| 106 | {"shell-fg", "shell-bg", 7}, {"shell-muted", "shell-bg", 4.5}, {"shell-mark", "shell-bg", 3}, | |
| 107 | } | |
| 108 | for name, scheme := range map[string]map[string]string{"light": light, "dark": dark} { | |
| 109 | for _, tok := range []string{"canvas", "surface", "inset", "hover", "line", "faint", "fg", "muted", "link", "fill", "fill-fg", "mark", "warn", "ok", "bad", "done", "neutral", "focus", "shell-bg", "shell-fg", "shell-muted", "shell-mark"} { | |
| 110 | v, ok := scheme[tok] | |
| 111 | if !ok || !strings.HasPrefix(v, "#") { | |
| 112 | t.Errorf("%s: --%s is missing or not a hex colour (%q)", name, tok, v) | |
| 113 | } | |
| 114 | } | |
| 115 | if t.Failed() { | |
| 116 | continue | |
| 117 | } | |
| 118 | for _, c := range checks { | |
| 119 | if got := contrastHex(scheme[c.fg], scheme[c.bg]); got < c.floor { | |
| 120 | t.Errorf("%s: --%s (%s) on --%s (%s) is %.2f:1, want >= %.1f", name, c.fg, scheme[c.fg], c.bg, scheme[c.bg], got, c.floor) | |
| 121 | } | |
| 122 | } | |
| 123 | // The surface ladder must be visible: canvas, surface and inset | |
| 124 | // are three grounds, not one. | |
| 125 | lc, ls, _ := luminanceHex(scheme["canvas"]), luminanceHex(scheme["surface"]), luminanceHex(scheme["inset"]) | |
| 126 | if r := (math.Max(lc, ls) + 0.05) / (math.Min(lc, ls) + 0.05); r < 1.15 { | |
| 127 | t.Errorf("%s: canvas %s and surface %s are %.2f apart, want >= 1.15", name, scheme["canvas"], scheme["surface"], r) | |
| 128 | } | |
| 129 | if scheme["inset"] == scheme["surface"] { | |
| 130 | t.Errorf("%s: inset and surface are the same colour %s", name, scheme["inset"]) | |
| 131 | } | |
| 132 | } | |
| 133 | } | |