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glebm / Render Whitespace on GitHub

/**
The MIT License (MIT)

Copyright (c) 2017-2018 Gleb Mazovetskiy

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
**/
// ==UserScript==
// @id              RenderWhitespace
// @name            Render Whitespace on GitHub
// @description     Renders spaces as · and tabs as → in all the code on GitHub.
// @namespace       https://github.com/glebm
// @version         1.3.12
// @author          Gleb Mazovetskiy <glex.spb@gmail.com>
// @license         MIT
// @domain          github.com
// @domain          gist.github.com
// @match           https://gist.github.com/*
// @match           https://github.com/*
// @homepageUrl     https://github.com/glebm/render-whitespace-on-github
// @run-at          document-end
// @contributionURL https://etherchain.org/account/0x962644db6d8735446c1af84a2c1f16143f780184
// ==/UserScript==

// Settings
let settings;
const DEFAULTS = {
    whitespaceOpacity: 0.4,
    copyableWhitespace: false,
    space: '·',
    tab: '→',
};

// Constants
const WS_CLASS = 'glebm-ws';
const ROOT_SELECTOR = 'table[data-tab-size],div[data-tab-size],table.diff-table';
const NODE_FILTER = {
    acceptNode(node) {
        let parent = node.parentNode;
        if (parent.classList.contains(WS_CLASS)) return NodeFilter.FILTER_SKIP;
        while (!parent.matches(ROOT_SELECTOR)) {
            if ( /* mobile code */
                parent.classList.contains('js-file-line') ||
                 /* desktop code, diff; mobile diff */
                parent.classList.contains('blob-code-inner')) {
                return !(parent.firstChild === node && node.nodeValue === ' ') ?
                    NodeFilter.FILTER_ACCEPT : NodeFilter.FILTER_SKIP;
            }
            parent = parent.parentNode;
        }
        return NodeFilter.FILTER_SKIP;
    }
};

function main() {
    const styleNode = document.createElement('style');
    styleNode.textContent = settings.copyableWhitespaceIndicators ?
        `.${WS_CLASS} { opacity: ${settings.whitespaceOpacity}; }` :
        `.${WS_CLASS}::before {
  opacity: ${settings.whitespaceOpacity};
  position: absolute;
  text-indent: 0;
}
/* desktop non-diff, mobile diff */
.blob-code .${WS_CLASS}::before {
  line-height: 20px;
}
/* horizontal scroll */
.blob-file-content pre,
.diff-view .file .highlight,
.blob-wrapper {
  position: relative;
}`;
    document.head.appendChild(styleNode);

    // github/legacy/pages/diffs/expander
    const diffTableObserver = new MutationObserver((records) => {
        for (const record of records) {
            showWhitespaceIn(record.target.parentElement);
        }
    });
    const initDiffExpanders = () => {
        for (const node of document.querySelectorAll('.diff-table > tbody')) {
            diffTableObserver.observe(node, { childList: true });
        }
    };
    document.addEventListener('pjax:success', () => {
        diffTableObserver.disconnect();
    });

    // https://github.com/github/include-fragment-element
    const registeredFragments = new WeakSet();
    const onFragmentLoadEnd = (node) => {
        return () => {
            setTimeout(() => {
                for (const root of node.querySelectorAll(ROOT_SELECTOR)) {
                    showWhitespaceIn(root);
                }
            }, 0);
        };
    }
    const initFragments = () => {
        for (const node of document.querySelectorAll('include-fragment')) {
            if (registeredFragments.has(node)) continue;
            registeredFragments.add(node);
            node.addEventListener('loadend', onFragmentLoadEnd(node.parentElement));
        }
    }

    const initDOM = () => {
        for (const root of document.querySelectorAll(ROOT_SELECTOR)) {
            showWhitespaceIn(root);
        }
        initDiffExpanders();
        initFragments();
    };
    document.addEventListener('pjax:success', initDOM);
    initDOM();
}

function showWhitespaceIn(root) {
    const rootStyle = window.getComputedStyle(root);
    const tab = settings.tab.padEnd(
        +(rootStyle['tab-size'] || rootStyle['-moz-tab-size'] || root.dataset.tabSize));
    const treeWalker =
        document.createTreeWalker(root, NodeFilter.SHOW_TEXT, NODE_FILTER);
    const nodes = [];
    while (treeWalker.nextNode()) nodes.push(treeWalker.currentNode);

    const isDiff = /* desktop */ root.classList.contains('diff-table') ||
        /* mobile */ root.classList.contains('file-diff');
    for (const node of nodes) replaceWhitespace(node, tab, settings.space, isDiff);
}

function isSpace(char) {
    return /* desktop */ char === ' ' ||
        /* mobile */ char === '\xa0' /* &nbsp; */;
}

function replaceWhitespace(node, tab, space, isDiff) {
    let originalText = node.nodeValue;
    const parent = node.parentNode;
    const ignoreFirstSpace = isDiff &&
        isSpace(originalText.charAt(0)) &&
        parent.firstChild === node &&
        parent.classList.contains('blob-code-inner') &&
        parent.parentNode.classList.contains('blob-expanded') &&
        // "Refined Github" extension removes the extra first space:
        // https://github.com/sindresorhus/refined-github/blob/34f713a331bf7dbf65c2082d3d2c667e06f22021/src/features/remove-diff-signs.js#L20
        !parent.matches('.refined-github-diff-signs *');
    if (ignoreFirstSpace) {
        if (isSpace(originalText)) return;
        originalText = originalText.slice(1);
        parent.insertBefore(document.createTextNode(' '), node);
    }
    const tabParts = originalText.split('\t');
    const tabSpaceParts = tabParts.map(s => s.split(/[ \xa0]/));
    if (!ignoreFirstSpace && tabSpaceParts.length === 1 &&
        tabSpaceParts[0].length === 1) return;
    const insert = (newNode) => {
        parent.insertBefore(newNode, node);
    };
    insertParts(tabSpaceParts,
        spaceParts => spaceParts.length === 1 && spaceParts[0] === '',
        n => insert(createWhitespaceNode('t', '\t', tab, n)),
        spaceParts =>
            insertParts(spaceParts,
                text => text === '',
                n => insert(createWhitespaceNode('s', ' ', space, n)),
                text => insert(document.createTextNode(text))));
    parent.removeChild(node);
}


var WS_ADDED_STYLES = new Set();
function createWhitespaceNode(type, originalText, text, n) {
    const node = document.createElement('span');
    node.classList.add(WS_CLASS);
    if (settings.copyableWhitespace) {
        node.textContent = text.repeat(n);
    } else {
        const className = `${type}-${n}`;
        if (!WS_ADDED_STYLES.has(className)) {
            const styleNode = document.createElement('style');
            styleNode.textContent =
                `.${WS_CLASS}-${className}::before { content: '${text.repeat(n)}'; }`;
            document.head.appendChild(styleNode);
            WS_ADDED_STYLES.add(className);
        }
        node.classList.add(`${WS_CLASS}-${className}`);
        node.textContent = originalText.repeat(n);
    }
    return node;
}

function insertParts(parts, isConsecutiveFn, addInterFn, addPartFn) {
    const n = parts.length;
    parts.reduce((consecutive, part, i) => {
        const isConsecutive = isConsecutiveFn(part);
        if (isConsecutive && i !== n - 1) return consecutive + 1;
        if (consecutive > 0) addInterFn(consecutive);
        if (!isConsecutive) addPartFn(part);
        return 1;
    }, 0);
}

function onSettingsLoaded(result) {
    settings = result;
    main();
}

if (typeof browser !== 'undefined' && typeof browser.storage !== 'undefined') {
    browser.storage.sync.get(DEFAULTS).then(onSettingsLoaded);
} else if (typeof chrome !== 'undefined' && typeof chrome.storage !== 'undefined') {
    chrome.storage.sync.get(DEFAULTS, onSettingsLoaded);
} else {
    onSettingsLoaded(DEFAULTS);
}