fix: use smooth scroll polyfill in Chrome for scroll-to-top (#1601)

* fix: use smooth scroll polyfill in Chrome for scroll-to-top

* rename thunk to __thunk__ for safety

bin/build-inline-script.js

@@ -8,6 +8,7 @@ import replace from 'rollup-plugin-replace'
 import fromPairs from 'lodash-es/fromPairs'
 import babel from 'rollup-plugin-babel'
 import { themes } from '../src/routes/_static/themes'
+import terserOptions from './terserOptions'
 
 const writeFile = promisify(fs.writeFile)
 
@@ -28,11 +29,7 @@ export async function buildInlineScript () {
         runtimeHelpers: true,
         presets: ['@babel/preset-env']
       }),
-      !process.env.DEBUG && terser({
+      !process.env.DEBUG && terser(terserOptions)
-        mangle: true,
-        compress: true,
-        ecma: 8
-      })
     ]
   })
   const { output } = await bundle.generate({

bin/terserOptions.js

@@ -0,0 +1,14 @@
+module.exports = {
+  ecma: 8,
+  mangle: true,
+  compress: {
+    pure_funcs: [
+      'console.log', // remove console logs in production
+      '__thunk__' // see thunk.js
+    ]
+  },
+  output: {
+    comments: false
+  },
+  safari10: true
+}

src/routes/_components/dialog/components/MediaDialog.html

@@ -333,7 +333,7 @@
             // smooth scroll, so disable smooth scrolling
             scroller.scrollLeft = scrollLeft
           } else {
-            smoothScroll(scroller, scrollLeft, true)
+            smoothScroll(scroller, scrollLeft, /* horizontal */ true, /* preferFast */ false)
           }
         } else {
           console.log('setting scrollLeft', scrollLeft)

src/routes/_components/shortcut/ScrollListShortcuts.html

@@ -72,7 +72,7 @@
         if (index === 0 && movement === -1) {
           activeItemKey = null
           this.set({ activeItemKey })
-          smoothScroll(getScrollContainer(), 0)
+          smoothScroll(getScrollContainer(), 0, /* horizontal */ false, /* preferFast */ false)
           return
         }
         if (index === -1) {

src/routes/_utils/emojiRegex.js

@@ -1,4 +1,4 @@
 import emojiRegex from 'emoji-regex/es2015/text'
-import { thunk } from './thunk'
+import { __thunk__ } from './thunk'
 
-export const getEmojiRegex = thunk(emojiRegex)
+export const getEmojiRegex = __thunk__(emojiRegex)

src/routes/_utils/handleRegex.js

@@ -1,5 +1,5 @@
 /* eslint-disable */
-import { thunk } from './thunk'
+import { __thunk__ } from './thunk'
 
-export const handleRegex = thunk(() => /(^|[^\/\w])@(([a-z0-9_]+)@[a-z0-9\.\-]+[a-z0-9]+)/ig)
+export const handleRegex = __thunk__(() => /(^|[^\/\w])@(([a-z0-9_]+)@[a-z0-9\.\-]+[a-z0-9]+)/ig)
 /* eslint-enable */

src/routes/_utils/scrollIntoView.js

@@ -66,5 +66,5 @@ export function scrollIntoViewIfNeeded (element) {
   }
   const scrollContainer = getScrollContainer()
   const scrollTop = scrollContainer.scrollTop
-  smoothScroll(scrollContainer, scrollTop + rect.top - scrollY)
+  smoothScroll(scrollContainer, scrollTop + rect.top - scrollY, /* horizontal */ false, /* preferFast */ false)
 }

src/routes/_utils/scrollToTop.js

@@ -8,7 +8,7 @@ export function scrollToTop (smooth) {
     return false
   }
   if (smooth) {
-    smoothScroll(scroller, 0)
+    smoothScroll(scroller, 0, /* horizontal */ false, /* preferFast */ true)
   } else {
     scroller.scrollTop = 0
   }

src/routes/_utils/smoothScroll.js

@@ -1,4 +1,5 @@
 import { store } from '../_store/store'
+import { isChrome } from './userAgent'
 
 // via https://github.com/tootsuite/mastodon/blob/f59ed3a4fafab776b4eeb92f805dfe1fecc17ee3/app/javascript/mastodon/scroll.js
 const easingOutQuint = (x, t, b, c, d) =>
@@ -63,16 +64,22 @@ function testSupportsSmoothScroll () {
 
 export const hasNativeSmoothScroll = process.browser && testSupportsSmoothScroll()
 
-export function smoothScroll (node, topOrLeft, horizontal) {
+export function smoothScroll (node, topOrLeft, horizontal, preferFast) {
   if (store.get().reduceMotion) {
-    // don't do smooth-scroll at all for users who prefer reduced motion
+    console.log('smooth scroll: disabled')
+    // Don't do smooth-scroll at all for users who prefer reduced motion.
     node[horizontal ? 'scrollLeft' : 'scrollTop'] = topOrLeft
-  } else if (hasNativeSmoothScroll) {
+  } else if (hasNativeSmoothScroll && !(preferFast && isChrome())) {
+    // In some cases (e.g. scrolling to the top of the timeline), Chrome can take a really long time
+    // in their native smooth scroll implementation. If preferFast is true, just use the polyfill
+    // so we can control how long it takes.
+    console.log('smooth scroll: using native')
     return node.scrollTo({
       [horizontal ? 'left' : 'top']: topOrLeft,
       behavior: 'smooth'
     })
   } else {
+    console.log('smooth scroll: using polyfill')
     return smoothScrollPolyfill(node, horizontal ? 'scrollLeft' : 'scrollTop', topOrLeft)
   }
 }

src/routes/_utils/testStorage.js

@@ -1,11 +1,11 @@
 // LocalStorage and IDB may be disabled in private mode, when "blocking cookies" in Safari,
 // or other cases
 
-import { thunk } from './thunk'
+import { __thunk__ } from './thunk'
 
 const testKey = '__test__'
 
-export const testHasLocalStorage = thunk(() => {
+export const testHasLocalStorage = __thunk__(() => {
   try {
     localStorage.setItem(testKey, testKey)
     if (!localStorage.length || localStorage.getItem(testKey) !== testKey) {
@@ -18,7 +18,7 @@ export const testHasLocalStorage = thunk(() => {
   return true
 })
 
-export const testHasIndexedDB = thunk(async () => {
+export const testHasIndexedDB = __thunk__(async () => {
   if (typeof indexedDB === 'undefined') {
     return false
   }

src/routes/_utils/thunk.js

@@ -1,4 +1,6 @@
-export function thunk (func) {
+// We name this __thunk__ so that we can tell terser that it's a pure function, without possibly
+// affecting third-party libraries that may also be using a function called "thunk".
+export function __thunk__ (func) {
   let cached
   let runOnce
   return () => {

src/routes/_utils/urlRegex.js

@@ -1,6 +1,6 @@
-import { thunk } from './thunk'
+import { __thunk__ } from './thunk'
 
-export const urlRegex = thunk(() => {
+export const urlRegex = __thunk__(() => {
   // this is provided at build time to avoid having a lot of runtime code just to build
   // a static regex
   return process.env.URL_REGEX

src/routes/_utils/userAgent.js

@@ -1,19 +1,24 @@
-import { thunk } from './thunk'
+import { __thunk__ } from './thunk'
 
-export const isKaiOS = thunk(() => process.browser && /KAIOS/.test(navigator.userAgent))
+export const isKaiOS = __thunk__(() => process.browser && /KAIOS/.test(navigator.userAgent))
 
-export const isIOS = thunk(() => process.browser && /iP(?:hone|ad|od)/.test(navigator.userAgent))
+export const isIOS = __thunk__(() => process.browser && /iP(?:hone|ad|od)/.test(navigator.userAgent))
 
-export const isMac = thunk(() => process.browser && /mac/i.test(navigator.platform))
+export const isMac = __thunk__(() => process.browser && /mac/i.test(navigator.platform))
 
 // IntersectionObserver introduced in iOS 12.2 https://caniuse.com/#feat=intersectionobserver
-export const isIOSPre12Point2 = thunk(() => process.browser && isIOS() &&
+export const isIOSPre12Point2 = __thunk__(() => process.browser && isIOS() &&
   !(typeof IntersectionObserver === 'function' &&
     IntersectionObserver.toString().includes('[native code]')))
 
 // PointerEvent introduced in iOS 13 https://caniuse.com/#feat=pointer
-export const isIOSPre13 = thunk(() => process.browser && isIOS() &&
+export const isIOSPre13 = __thunk__(() => process.browser && isIOS() &&
   !(typeof PointerEvent === 'function' &&
     PointerEvent.toString().includes('[native code]')))
 
-export const isMobile = thunk(() => process.browser && navigator.userAgent.match(/(?:iPhone|iPod|iPad|Android|KAIOS)/))
+export const isMobile = __thunk__(() => process.browser && navigator.userAgent.match(/(?:iPhone|iPod|iPad|Android|KAIOS)/))
+
+export const isSafari = __thunk__(() => process.browser && /Safari/.test(navigator.userAgent) &&
+  !/Chrome/.test(navigator.userAgent))
+
+export const isChrome = __thunk__(() => process.browser && /Chrome/.test(navigator.userAgent))

src/routes/_workers/blurhash.js

@@ -1,12 +1,11 @@
 import { decode as decodeBlurHash } from 'blurhash'
 import registerPromiseWorker from 'promise-worker/register'
 import { BLURHASH_RESOLUTION as RESOLUTION } from '../_static/blurhash'
-
+import { isChrome } from '../_utils/userAgent'
-const isChrome = /Chrome/.test(navigator.userAgent)
 
 // Disabled in Chrome because convertToBlob() is slow
 // https://github.com/nolanlawson/pinafore/issues/1396
-const OFFSCREEN_CANVAS = !isChrome && typeof OffscreenCanvas === 'function'
+const OFFSCREEN_CANVAS = !isChrome() && typeof OffscreenCanvas === 'function'
   ? new OffscreenCanvas(RESOLUTION, RESOLUTION) : null
 const OFFSCREEN_CANVAS_CONTEXT_2D = OFFSCREEN_CANVAS
   ? OFFSCREEN_CANVAS.getContext('2d') : null

src/service-worker.js

@@ -3,11 +3,8 @@ import {
   shell as __shell__,
   routes as __routes__
 } from '../__sapper__/service-worker.js'
-
+import { get, post } from './routes/_utils/ajax'
-import {
+import { isSafari } from './routes/_utils/userAgent'
-  get,
-  post
-} from './routes/_utils/ajax'
 
 const timestamp = process.env.SAPPER_TIMESTAMP
 const ASSETS = `assets_${timestamp}`
@@ -24,8 +21,6 @@ const ON_DEMAND_CACHE = [
   }
 ]
 
-const isSafari = /Safari/.test(navigator.userAgent) && !/Chrom/.test(navigator.userAgent)
-
 // `static` is an array of everything in the `static` directory
 const assets = __assets__
   .map(file => file.startsWith('/') ? file : `/${file}`)
@@ -163,7 +158,7 @@ self.addEventListener('fetch', event => {
     // range request need to be be patched with a 206 response to satisfy
     // Safari (https://stackoverflow.com/questions/52087208)
     // Once this bug is fixed in WebKit we can remove this https://bugs.webkit.org/show_bug.cgi?id=186050
-    if (isSafari && event.request.headers.get('range')) {
+    if (isSafari() && event.request.headers.get('range')) {
       return returnRangeRequest(req)
     }
 

webpack/terser.config.js

@@ -1,19 +1,10 @@
 const TerserWebpackPlugin = require('terser-webpack-plugin')
+const terserOptions = require('../bin/terserOptions')
 
 module.exports = () => new TerserWebpackPlugin({
   exclude: /(tesseract-asset|page-lifecycle)/, // tesseract causes problems, page-lifecycle is pre-minified
   cache: !process.env.TERSER_DISABLE_CACHE,
   parallel: true,
   sourceMap: true,
-  terserOptions: {
+  terserOptions
-    ecma: 8,
-    mangle: true,
-    compress: {
-      pure_funcs: ['console.log']
-    },
-    output: {
-      comments: false
-    },
-    safari10: true
-  }
 })