scroll-button

scroll-button (Mobile Optimized: Smaller & Auto-Fade)
当前为 2025-12-17 提交的版本，查看最新版本。
换行
// ==UserScript==
// @name         scroll-button
// @namespace    https://github.com/livinginpurple
// @version      20251217.03
// @description  scroll-button (Mobile Optimized: Smaller & Auto-Fade)
// @license      WTFPL
// @author       livinginpurple
// @include      *
// @run-at       document-end
// @grant        none
// ==/UserScript==

(() => {
    'use strict';

    const init = () => {
        const btnId = 'gamma-scroll-btn';
        if (document.getElementById(btnId)) return;

        // SVG 圖示 (保持不變)
        const icons = {
            up: `<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" fill="white" viewBox="0 0 16 16"><path fill-rule="evenodd" d="M8 12a.5.5 0 0 0 .5-.5V5.707l2.146 2.147a.5.5 0 0 0 .708-.708l-3-3a.5.5 0 0 0-.708 0l-3 3a.5.5 0 1 0 .708.708L7.5 5.707V11.5a.5.5 0 0 0 .5.5z"/></svg>`,
            down: `<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" fill="white" viewBox="0 0 16 16"><path fill-rule="evenodd" d="M8 4a.5.5 0 0 1 .5.5v5.793l2.146-2.147a.5.5 0 0 1 .708.708l-3 3a.5.5 0 0 1-.708 0l-3-3a.5.5 0 1 1 .708-.708L7.5 10.293V4.5A.5.5 0 0 1 8 4z"/></svg>`
        };

        const btn = document.createElement('button');
        btn.id = btnId;
        btn.type = 'button';
        btn.setAttribute('aria-label', 'Scroll navigation');

        // 定義樣式 (調整大小與加入透明度過渡)
        const styles = {
            position: 'fixed',
            bottom: '20px',
            right: '20px',
            width: '40px',     // 縮小尺寸
            height: '40px',    // 縮小尺寸
            borderRadius: '50%',
            backgroundColor: '#0d6efd',
            border: 'none',
            boxShadow: '0 0.2rem 0.5rem rgba(0,0,0,0.3)',
            zIndex: '10000',
            cursor: 'pointer',
            display: 'flex',
            justifyContent: 'center',
            alignItems: 'center',
            // 增加 opacity 的過渡效果
            transition: 'transform 0.2s, background-color 0.2s, opacity 0.5s ease-in-out',
            touchAction: 'manipulation',
            padding: '0',
            opacity: '0.3' // 預設為半透明 (腳本啟動時)
        };

        Object.assign(btn.style, styles);

        // Hover & Active 互動
        btn.onmouseenter = () => { btn.style.transform = 'scale(1.1)'; activeHandler(); };
        btn.onmouseleave = () => { btn.style.transform = 'scale(1)'; };
        btn.onmousedown = () => { btn.style.backgroundColor = '#0b5ed7'; activeHandler(); };
        btn.onmouseup = () => { btn.style.backgroundColor = '#0d6efd'; };
        // 針對手機觸摸也視為「活躍」
        btn.ontouchstart = () => { activeHandler(); };

        document.body.appendChild(btn);

        const State = { TOP: 'top', SCROLLED: 'scrolled' };

        // --- 透明度控制邏輯 ---
        let idleTimer = null;
        const activeHandler = () => {
            // 1. 動作時：顯示按鈕 (不透明)
            btn.style.opacity = '1';
            
            // 2. 重置計時器
            if (idleTimer) clearTimeout(idleTimer);

            // 3. 設定閒置 2 秒後變淡
            idleTimer = setTimeout(() => {
                btn.style.opacity = '0.3'; // 淡出目標透明度
            }, 2000);
        };

        const updateButtonState = () => {
            activeHandler(); // 捲動視為活躍動作

            const scrollTop = window.scrollY || document.documentElement.scrollTop;
            const isAtTop = scrollTop < 50;

            const nextState = isAtTop ? State.TOP : State.SCROLLED;
            if (btn.dataset.state === nextState) return;

            if (isAtTop) {
                btn.innerHTML = icons.down;
                btn.dataset.state = State.TOP;
            } else {
                btn.innerHTML = icons.up;
                btn.dataset.state = State.SCROLLED;
            }
        };

        const handleScrollAction = (e) => {
            e.preventDefault();
            activeHandler(); // 點擊視為活躍動作
            
            if (btn.dataset.state === State.TOP) {
                window.scrollTo({ top: document.body.scrollHeight, behavior: 'smooth' });
            } else {
                window.scrollTo({ top: 0, behavior: 'smooth' });
            }
        };

        btn.addEventListener('click', handleScrollAction);
        window.addEventListener('scroll', updateButtonState, { passive: true });
        
        // 初始執行
        updateButtonState();
    };

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', init);
    } else {
        init();
    }
})();