scroll-button (Draggable without memory, Stability fix)
// ==UserScript==
// @name scroll-button
// @namespace https://github.com/livinginpurple
// @version 20251217.07
// @description scroll-button (Draggable without memory, Stability fix)
// @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
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');
// 定義初始樣式 (固定在右下角，無記憶)
Object.assign(btn.style, {
position: 'fixed',
right: '20px',
bottom: '20px',
width: '40px',
height: '40px',
borderRadius: '50%',
backgroundColor: '#0d6efd',
border: 'none',
boxShadow: '0 0.2rem 0.5rem rgba(0,0,0,0.3)',
zIndex: '10000',
cursor: 'grab',
display: 'flex',
justifyContent: 'center',
alignItems: 'center',
// 不對 left/top/right/bottom 設 transition，以免拖曳時產生延遲感
transition: 'opacity 0.5s ease-in-out, transform 0.1s, background-color 0.2s',
touchAction: 'none',
padding: '0',
opacity: '0.3'
});
// 互動視覺效果
btn.onmouseenter = () => { btn.style.transform = 'scale(1.1)'; };
btn.onmouseleave = () => { btn.style.transform = 'scale(1)'; };
document.body.appendChild(btn);
// --- 狀態與透明度控制 ---
const State = { TOP: 'top', SCROLLED: 'scrolled' };
let idleTimer = null;
const activeHandler = () => {
btn.style.opacity = '1';
if (idleTimer) clearTimeout(idleTimer);
idleTimer = setTimeout(() => {
btn.style.opacity = '0.3';
}, 2000);
};
const updateButtonState = () => {
activeHandler();
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;
}
};
// --- 拖曳邏輯優化 (Drag Logic) ---
let isPressed = false; // 是否按住
let isDragging = false; // 是否真的開始拖曳 (超過閾值)
let startX, startY; // 點擊起始點
let initialRect; // 按鈕原始位置
let dragOffsetX, dragOffsetY; // 游標相對於按鈕左上角的偏移
const onDragStart = (e) => {
const clientX = e.type.includes('touch') ? e.touches[0].clientX : e.clientX;
const clientY = e.type.includes('touch') ? e.touches[0].clientY : e.clientY;
isPressed = true;
isDragging = false; // 重置拖曳狀態
startX = clientX;
startY = clientY;
// 記錄按下去瞬間，滑鼠在按鈕內的相對位置
const rect = btn.getBoundingClientRect();
dragOffsetX = clientX - rect.left;
dragOffsetY = clientY - rect.top;
// 此時不改變 cursor，也不改變 position，直到移動超過閾值
btn.style.backgroundColor = '#0b5ed7';
activeHandler();
};
const onDragMove = (e) => {
if (!isPressed) return;
const clientX = e.type.includes('touch') ? e.touches[0].clientX : e.clientX;
const clientY = e.type.includes('touch') ? e.touches[0].clientY : e.clientY;
// 計算移動距離
const moveX = clientX - startX;
const moveY = clientY - startY;
const distance = Math.sqrt(moveX * moveX + moveY * moveY);
// 閾值檢查：如果還沒進入拖曳模式，且移動小於 10px，則視為手震/點擊，不動作
if (!isDragging && distance < 10) {
return;
}
// --- 正式進入拖曳模式 ---
if (!isDragging) {
isDragging = true;
btn.style.cursor = 'grabbing';
// 鎖定當前視覺位置，轉為 left/top 定位，避免跳動
const rect = btn.getBoundingClientRect();
btn.style.right = 'auto';
btn.style.bottom = 'auto';
// 這裡是一個關鍵技巧：直接將 left/top 設為當前位置，確保無縫接軌
btn.style.left = rect.left + 'px';
btn.style.top = rect.top + 'px';
}
// 計算新位置：滑鼠位置 - 原始偏移量
let newX = clientX - dragOffsetX;
let newY = clientY - dragOffsetY;
// 邊界限制
const maxX = window.innerWidth - 40;
const maxY = window.innerHeight - 40;
newX = Math.max(0, Math.min(newX, maxX));
newY = Math.max(0, Math.min(newY, maxY));
btn.style.left = newX + 'px';
btn.style.top = newY + 'px';
};
const onDragEnd = () => {
isPressed = false;
btn.style.cursor = 'grab';
btn.style.backgroundColor = '#0d6efd';
// 注意：這裡不重置 isDragging，因為 click 事件會在 mouseup/touchend 之後觸發
// 我們需要在 click 事件中判斷 isDragging 的值
activeHandler();
};
// 綁定事件
btn.addEventListener('mousedown', onDragStart);
window.addEventListener('mousemove', onDragMove);
window.addEventListener('mouseup', onDragEnd);
btn.addEventListener('touchstart', onDragStart, { passive: false });
window.addEventListener('touchmove', onDragMove, { passive: false });
window.addEventListener('touchend', onDragEnd);
// --- 點擊捲動邏輯 ---
btn.addEventListener('click', (e) => {
// 如果剛剛是拖曳狀態，則阻止捲動，並重置狀態
if (isDragging) {
e.preventDefault();
e.stopImmediatePropagation();
isDragging = false; // 重置標記
return;
}
// 純點擊邏輯
e.preventDefault();
activeHandler();
if (btn.dataset.state === State.TOP) {
window.scrollTo({ top: document.body.scrollHeight, behavior: 'smooth' });
} else {
window.scrollTo({ top: 0, behavior: 'smooth' });
}
});
window.addEventListener('scroll', updateButtonState, { passive: true });
updateButtonState();
};
if (document.readyState === 'loading') {
document.addEventListener('DOMContentLoaded', init);
} else {
init();
}
})();