四维阅读增强

修改页面字体为 Lato，添加较强的文字阴影，阅读进度指示器，移动端回到顶部按钮，和阅读位置记忆功能。
换行
// ==UserScript==
// @name         四维阅读增强
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  修改页面字体为 Lato，添加较强的文字阴影，阅读进度指示器，移动端回到顶部按钮，和阅读位置记忆功能。
// @author       You
// @match        *://*/*
// @grant        GM_addStyle
// ==/UserScript==

(function() {
    'use strict';

    // Add Lato font from Google Fonts
    const fontURL = 'https://fonts.googleapis.com/css2?family=Lato:wght@400;700&display=swap';
    const link = document.createElement('link');
    link.rel = 'stylesheet';
    link.href = fontURL;
    document.head.appendChild(link);

    // Apply font and stronger text shadow styles
    GM_addStyle(`
        body {
            font-family: 'Lato', sans-serif !important;
            text-shadow: 2px 2px 6px rgba(0, 0, 0, 0.2); /* Set a stronger text shadow */
        }
        #reading-progress-bar {
            position: fixed;
            top: 0;
            left: 0;
            width: 0;
            height: 5px;
            background-color: #3b82f6;
            z-index: 9999;
            transition: width 0.25s ease;
        }
        #back-to-top-btn {
            position: fixed;
            left: 6px; /* Adjusted: 6px from the left edge */
            bottom: 100px; /* Adjusted: 100px from the bottom */
            padding: 10px;
            background-color: #000;
            color: #fff;
            border: none;
            border-radius: 50%;
            z-index: 9999;
            display: none;
            cursor: pointer;
        }
    `);

    // Create and insert the progress bar
    let progressBar = document.createElement('div');
    progressBar.id = 'reading-progress-bar';
    document.body.appendChild(progressBar);

    // Calculate scroll percentage and update the progress bar
    function updateProgressBar() {
        let scrollTop = window.scrollY || document.documentElement.scrollTop;
        let documentHeight = document.documentElement.scrollHeight - document.documentElement.clientHeight;
        let progress = (scrollTop / documentHeight) * 100;
        progressBar.style.width = progress + '%';
    }

    // Update progress bar on scroll
    window.addEventListener('scroll', updateProgressBar);

    // Execute after page loads
    window.onload = function() {
        updateProgressBar();  // Initialize progress bar
    };

    // Create a back-to-top button
    const backToTopButton = document.createElement('button');
    backToTopButton.id = 'back-to-top-btn';
    backToTopButton.textContent = '↑';  // Button content
    document.body.appendChild(backToTopButton);

    let lastScrollTop = 0;  // Save previous scroll position

    // Smoothly scroll to top when button is clicked
    backToTopButton.addEventListener('click', () => {
        window.scrollTo({ top: 0, behavior: 'smooth' });
    });

    // Show/hide button based on scroll, and control display based on scroll direction
    window.addEventListener('scroll', () => {
        let currentScrollTop = window.scrollY;  // Current scroll position

        if (currentScrollTop > 200) {
            // Show button when scrolling up
            if (currentScrollTop < lastScrollTop) {
                backToTopButton.style.display = 'block';
            } else {
                backToTopButton.style.display = 'none';  // Hide button when scrolling down
            }
        } else {
            backToTopButton.style.display = 'none';  // Hide button if scroll is less than 200px
        }

        lastScrollTop = currentScrollTop;  // Update previous scroll position
    });

    // Reading position memory
    const currentUrl = window.location.href;

    // Check local storage for saved reading progress
    const savedScrollPosition = localStorage.getItem(currentUrl);

    // If progress is saved, restore to that position
    if (savedScrollPosition) {
        window.scrollTo(0, savedScrollPosition);
    }

    // Save current scroll position on every scroll
    window.addEventListener('scroll', function() {
        localStorage.setItem(currentUrl, window.scrollY);
    });

})();