feat(scroll): smarter scroll behavior

Author: Mate Solymosi

src/core/event/index.js

@@ -1,11 +1,26 @@
 import {isMobile} from '../util/env'
 import {body, on} from '../util/dom'
 import * as sidebar from './sidebar'
-import {scrollIntoView} from './scroll'
+import {scrollIntoView, scroll2Top} from './scroll'
 
 export function eventMixin(proto) {
-  proto.$resetEvents = function () {
-    scrollIntoView(this.route.path, this.route.query.id)
+  proto.$resetEvents = function (source) {
+    const {auto2top} = this.config
+
+    ;(() => {
+      // Rely on the browser's scroll auto-restoration when going back or forward
+      if (source === 'history') {
+        return
+      }
+      // Scroll to ID if specified
+      if (this.route.query.id) {
+        scrollIntoView(this.route.path, this.route.query.id)
+      }
+      // Scroll to top if a link was clicked and auto2top is enabled
+      if (source === 'navigate') {
+        auto2top && scroll2Top(auto2top)
+      }
+    })();
 
     if (this.config.loadNavbar) {
       sidebar.getAndActive(this.router, 'nav')

src/core/fetch/index.js

@@ -144,7 +144,7 @@ export function fetchMixin(proto) {
     }
   }
 
-  proto.$fetch = function (cb = noop) {
+  proto.$fetch = function (cb = noop, $resetEvents = this.$resetEvents.bind(this)) {
     const done = () => {
       callHook(this, 'doneEach')
       cb()
@@ -156,7 +156,7 @@ export function fetchMixin(proto) {
       done()
     } else {
       this._fetch(() => {
-        this.$resetEvents()
+        $resetEvents();
         done()
       })
     }

src/core/render/index.js

@@ -8,7 +8,7 @@ import {getAndActive, sticky} from '../event/sidebar'
 import {getPath, isAbsolutePath} from '../router/util'
 import {isMobile, inBrowser} from '../util/env'
 import {isPrimitive} from '../util/core'
-import {scrollActiveSidebar, scroll2Top} from '../event/scroll'
+import {scrollActiveSidebar} from '../event/scroll'
 import {prerenderEmbed} from './embed'
 
 function executeScript() {
@@ -107,7 +107,7 @@ export function renderMixin(proto) {
   }
 
   proto._bindEventOnRendered = function (activeEl) {
-    const {autoHeader, auto2top} = this.config
+    const {autoHeader} = this.config
 
     scrollActiveSidebar(this.router)
 
@@ -120,8 +120,6 @@ export function renderMixin(proto) {
         dom.before(main, h1)
       }
     }
-
-    auto2top && scroll2Top(auto2top)
   }
 
   proto._renderNav = function (text) {

src/core/router/history/hash.js

@@ -30,7 +30,25 @@ export class HashHistory extends History {
   }
 
   onchange(cb = noop) {
-    on('hashchange', cb)
+    // The hashchange event does not tell us if it originated from
+    // a clicked link or by moving back/forward in the history;
+    // therefore we set a `navigating` flag when a link is clicked
+    // to be able to tell these two scenarios apart
+    let navigating = false
+
+    on('click', e => {
+      const el = e.target.tagName === 'A' ? e.target : e.target.parentNode
+
+      if (el.tagName === 'A' && !/_blank/.test(el.target)) {
+        navigating = true
+      }
+    })
+
+    on('hashchange', e => {
+      const source = navigating ? 'navigate' : 'history'
+      navigating = false
+      cb({event: e, source})
+    })
   }
 
   normalize() {

src/core/router/history/html5.js

@@ -28,11 +28,13 @@ export class HTML5History extends History {
         e.preventDefault()
         const url = el.href
         window.history.pushState({key: url}, '', url)
-        cb()
+        cb({event: e, source: 'navigate'})
       }
     })
 
-    on('popstate', cb)
+    on('popstate', e => {
+      cb({event: e, source: 'history'})
+    })
   }
 
   /**

src/core/router/index.js

@@ -1,6 +1,7 @@
 import {HashHistory} from './history/hash'
 import {HTML5History} from './history/html5'
 import {supportsPushState} from '../util/env'
+import {noop} from '../util/core'
 import * as dom from '../util/dom'
 
 export function routerMixin(proto) {
@@ -30,16 +31,16 @@ export function initRouter(vm) {
   updateRender(vm)
   lastRoute = vm.route
 
-  router.onchange(_ => {
+  router.onchange(params => {
     updateRender(vm)
     vm._updateRender()
 
     if (lastRoute.path === vm.route.path) {
-      vm.$resetEvents()
+      vm.$resetEvents(params.source)
       return
     }
 
-    vm.$fetch()
+    vm.$fetch(noop, vm.$resetEvents.bind(vm, params.source))
     lastRoute = vm.route
   })
 }