From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 toolkit/modules/Color.sys.mjs | 109 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 toolkit/modules/Color.sys.mjs

(limited to 'toolkit/modules/Color.sys.mjs')

diff --git a/toolkit/modules/Color.sys.mjs b/toolkit/modules/Color.sys.mjs
new file mode 100644
index 0000000000..d00902ef6b
--- /dev/null
+++ b/toolkit/modules/Color.sys.mjs
@@ -0,0 +1,109 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * A list of minimum contrast ratio's per WCAG 2.0 conformance level.
+ * Please refer to section 1.4.3 of the WCAG 2.0 spec at http://www.w3.org/TR/WCAG20/.
+ * Simply put:
+ * A = Large text only.
+ * AA = Regular sized text or large text in enhanced contrast mode.
+ * AAA = Regular sized text in enhanced contrast mode.
+ *
+ * @type {Object}
+ */
+const CONTRAST_RATIO_LEVELS = {
+  A: 3,
+  AA: 4.5,
+  AAA: 7,
+};
+
+/**
+ * For text legibility on any background color, you need to determine which text
+ * color - black or white - will yield the highest contrast ratio.
+ * Since you're always comparing `contrastRatio(bgcolor, black) >
+ * contrastRatio(bgcolor, white) ? <use black> : <use white>`, we can greatly
+ * simplify the calculation to the following constant.
+ *
+ * @type {Number}
+ */
+const CONTRAST_BRIGHTTEXT_THRESHOLD = Math.sqrt(1.05 * 0.05) - 0.05;
+
+/**
+ * Color class, which describes a color.
+ * In the future, this object may be extended to allow for conversions between
+ * different color formats and notations, support transparency.
+ *
+ * @param {Number} r Red color component
+ * @param {Number} g Green color component
+ * @param {Number} b Blue color component
+ */
+export class Color {
+  constructor(r, g, b) {
+    this.r = r;
+    this.g = g;
+    this.b = b;
+  }
+
+  /**
+   * Formula from W3C's WCAG 2.0 spec's relative luminance, section 1.4.1,
+   * http://www.w3.org/TR/WCAG20/.
+   *
+   * @return {Number} Relative luminance, represented as number between 0 and 1.
+   */
+  get relativeLuminance() {
+    let colorArr = [this.r, this.g, this.b].map(color => {
+      color = parseInt(color, 10);
+      if (color <= 10) {
+        return color / 255 / 12.92;
+      }
+      return Math.pow((color / 255 + 0.055) / 1.055, 2.4);
+    });
+    return colorArr[0] * 0.2126 + colorArr[1] * 0.7152 + colorArr[2] * 0.0722;
+  }
+
+  /**
+   * @return {Boolean} TRUE if you need to use a bright color (e.g. 'white'), when
+   *                   this color is set as the background.
+   */
+  get useBrightText() {
+    return this.relativeLuminance <= CONTRAST_BRIGHTTEXT_THRESHOLD;
+  }
+
+  /**
+   * Get the contrast ratio between the current color and a second other color.
+   * A common use case is to express the difference between a foreground and a
+   * background color in numbers.
+   * Formula from W3C's WCAG 2.0 spec's contrast ratio, section 1.4.1,
+   * http://www.w3.org/TR/WCAG20/.
+   *
+   * @param  {Color}  otherColor Color instance to calculate the contrast with
+   * @return {Number} Contrast ratios can range from 1 to 21, commonly written
+   *                  as 1:1 to 21:1.
+   */
+  contrastRatio(otherColor) {
+    if (!(otherColor instanceof Color)) {
+      throw new TypeError("The first argument should be an instance of Color");
+    }
+
+    let luminance = this.relativeLuminance;
+    let otherLuminance = otherColor.relativeLuminance;
+    return (
+      (Math.max(luminance, otherLuminance) + 0.05) /
+      (Math.min(luminance, otherLuminance) + 0.05)
+    );
+  }
+
+  /**
+   * Method to check if the contrast ratio between two colors is high enough to
+   * be discernable.
+   *
+   * @param  {Color}  otherColor Color instance to calculate the contrast with
+   * @param  {String} [level]    WCAG conformance level that maps to the minimum
+   *                             required contrast ratio. Defaults to 'AA'
+   * @return {Boolean}
+   */
+  isContrastRatioAcceptable(otherColor, level = "AA") {
+    return this.contrastRatio(otherColor) > CONTRAST_RATIO_LEVELS[level];
+  }
+}
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