Add warning for low contrast and equal colors #86
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -1372,6 +1372,104 @@ const RandomTips = (function () {// eslint-disable-line no-unused-vars | |
| return me; | ||
| })(); | ||
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| const Colors = (() => { // eslint-disable-line no-unused-vars | ||
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There was a problem hiding this comment. Yeah, this module looks great! So for doing #20 later, everything is set. |
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| const me = {}; | ||
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| /** | ||
| * Calculates the contrast between two colors | ||
| * | ||
| * @name Colors.contrastRatio | ||
| * @function | ||
| * @param {Array} rgb1 | ||
| * @param {Array} rgb2 | ||
| * @returns {int} | ||
| */ | ||
| me.contrastRatio = function(rgb1, rgb2) { | ||
| const l1 = luminance(rgb1); | ||
| const l2 = luminance(rgb2); | ||
| // Formula: https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef | ||
| return (Math.max(l1, l2) + 0.05) / (Math.min(l1, l2) + 0.05); | ||
| }; | ||
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| /** | ||
| * Calculates the luminance of a given RGB color. | ||
| * | ||
| * @name Colors.luminance | ||
| * @function | ||
| * @private | ||
| * @param {Array} rgb | ||
| * @returns {Array|null} | ||
| */ | ||
| function luminance(rgb) { | ||
| // Formula: https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef | ||
| let r = rgb[0] / 255; | ||
| let g = rgb[1] / 255; | ||
| let b = rgb[2] / 255; | ||
| // Note: I'm using 0.04045 here (instead of 0.03928) because 0.04045 is the | ||
| // number used in the actual sRGB standard. | ||
| // See also: https://github.com/w3c/wcag21/issues/815 | ||
| r = r < 0.04045 ? r / 12.92 : Math.pow((r + 0.055) / 1.055, 2.4); | ||
| g = g < 0.04045 ? g / 12.92 : Math.pow((g + 0.055) / 1.055, 2.4); | ||
| b = b < 0.04045 ? b / 12.92 : Math.pow((b + 0.055) / 1.055, 2.4); | ||
| return 0.2126 * r + 0.7152 * g + 0.0722 * b; | ||
| } | ||
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| /** | ||
| * Returns the complementary color of a given RGB array. | ||
| * | ||
| * @name Colors.invertColor | ||
| * @function | ||
| * @param {Array} rgb | ||
| * @returns {string} | ||
| */ | ||
| me.invertColor = function(rgb) { | ||
| // invert color components | ||
| const r = (255 - rgb[0]).toString(16); | ||
| const g = (255 - rgb[1]).toString(16); | ||
| const b = (255 - rgb[2]).toString(16); | ||
| // pad each with zeros and return | ||
| return `#${padZero(r)}${padZero(g)}${padZero(b)}`; | ||
| }; | ||
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| /** | ||
| * Adds missing zeros in front of a string. | ||
| * | ||
| * @name Colors.padZero | ||
| * @function | ||
| * @private | ||
| * @param {string} string | ||
| * @param {int} length | ||
| * @returns {string} | ||
| */ | ||
| function padZero(string, length) { | ||
| length = length || 2; | ||
| const zeros = new Array(length).join("0"); | ||
| return (zeros + string).slice(-length); | ||
| } | ||
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| /** | ||
| * Converts a hex color string to RGB. | ||
| * | ||
| * @name Colors.hexToRgb | ||
| * @function | ||
| * @param {string} hex | ||
| * @returns {Array|null} | ||
| */ | ||
| me.hexToRgb = function(hex) { | ||
| const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex); | ||
| if (result) { | ||
| return [ | ||
| parseInt(result[1], 16), | ||
| parseInt(result[2], 16), | ||
| parseInt(result[3], 16) | ||
| ]; | ||
| } | ||
| return null; | ||
| }; | ||
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| return me; | ||
| })(); | ||
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| // init modules | ||
| AddonSettings.loadOptions(); | ||
| Logger.init(); | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -4,6 +4,7 @@ | |
| /* globals AddonSettings */ | ||
| /* globals MESSAGE_LEVEL, MessageHandler */ | ||
| /* globals RandomTips */ | ||
| /* globals Colors */ | ||
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| const OptionHandler = (function () { | ||
| const me = {}; | ||
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@@ -19,7 +20,7 @@ const OptionHandler = (function () { | |
| /** | ||
| * Applies option to element. | ||
| * | ||
| * @name OptionHandler.applyOptionToElement | ||
| * @function | ||
| * @private | ||
| * @param {string} option string ob object ID | ||
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@@ -151,6 +152,8 @@ const OptionHandler = (function () { | |
| // run for each option, which we know to handle | ||
| applyOptionLive("popupIconColored", res.popupIconColored); | ||
| applyOptionLive("qrCodeSize", res.qrCodeSize); | ||
| applyOptionLive("qrColor", res.qrColor); | ||
| applyOptionLive("qrBackgroundColor", res.qrBackgroundColor); | ||
| }); | ||
| } | ||
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@@ -200,6 +203,50 @@ const OptionHandler = (function () { | |
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| case "debugMode": | ||
| Logger.setDebugMode(optionValue); | ||
| break; | ||
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| case "qrColor": | ||
| case "qrBackgroundColor": { | ||
| const elQrColor = document.getElementById("qrColor"); | ||
| const elQrBackgroundColor = document.getElementById("qrBackgroundColor"); | ||
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| const qrCodeColor = Colors.hexToRgb(elQrColor.value); | ||
| const qrCodeBackgroundColor = Colors.hexToRgb(elQrBackgroundColor.value); | ||
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| const colorContrast = Colors.contrastRatio(qrCodeColor, qrCodeBackgroundColor); | ||
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| const actionButton = { | ||
| text: "messageAutoSelectColorButton", | ||
| action: () => { | ||
| const invertedColor = Colors.invertColor(qrCodeColor); | ||
| browser.storage.sync.set({ | ||
| "qrBackgroundColor": invertedColor | ||
| }).catch((error) => { | ||
| Logger.logError("could not save option", option, ":", error); | ||
| MessageHandler.showError("couldNotSaveOption", true); | ||
| }).finally(() => { | ||
| applyOptionLive(); | ||
| elQrBackgroundColor.value = invertedColor; | ||
| }); | ||
| } | ||
| }; | ||
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| // breakpoints: https://github.com/rugk/offline-qr-code/pull/86#issuecomment-390426286 | ||
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There was a problem hiding this comment. Oh and once we are at it. You can link to my comment, yes, but please still add comments for the colors, i.e. the accessibility guidelines I mentioned. Or even better remember the "no magic numbers" rules. So put these numbers into constants. As they are color stuff not (only) related to the options handler, the best would be to use these as constants in the |
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| if (colorContrast <= 2) { | ||
| // show an error when nearly no QR code scanner can read it | ||
| MessageHandler.showError("lowContrastRatioError", false, actionButton); | ||
| } else if (colorContrast <= 3) { | ||
| // show a warning when approx. 50% of the QR code scanners can read it | ||
| MessageHandler.showWarning("lowContrastRatioWarning", false, actionButton); | ||
| } else if (colorContrast <= 4.5) { | ||
| // show only an info when the contrast is low but most of the scanners can still read it | ||
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There was a problem hiding this comment. Okay, I rather thought about "WCAG 2.0 level AA" (so please add that), but this information is also good. Still prefer them as constants though. 😄 |
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| MessageHandler.showInfo("lowContrastRatioInfo", false, actionButton); | ||
| } else { | ||
| MessageHandler.hideInfo(); | ||
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There was a problem hiding this comment. Hmm, this could get problematic, because we also show a permanent "managed setting" info message when this is used (see What we could do about this:
So I can do the second version after your PR is merged. |
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| MessageHandler.hideWarning(); | ||
| MessageHandler.hideError(); | ||
| } | ||
| } | ||
| } | ||
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| return null; | ||
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@@ -263,7 +310,7 @@ const OptionHandler = (function () { | |
| browser.storage.sync.set({ | ||
| [option]: optionValue | ||
| }).catch((error) => { | ||
| Logger.logError("could not save option", option, ":", error); | ||
| MessageHandler.showError("couldNotSaveOption", true); | ||
| }); | ||
| } | ||
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@@ -475,9 +522,9 @@ const OptionHandler = (function () { | |
| } | ||
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| /** | ||
| * Initializes the options. | ||
| * | ||
| * @name OptionHandler.init | ||
| * @function | ||
| * @returns {void} | ||
| */ | ||
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shorter:
das Kontrastverhältnis -> der Kontrast
is "wahrscheinlich" neccessary? Maybe just use subjunctive ("Konjunktiv") here, too (as in the English version).
grammar:
dem Hintergrund -> dessen Hintergrund
In general you may reword it. Keep the fact that it may not be scanned by many QR code readers.