From 44b9f2ba55e6412af3114a12322d5613e5e2289e Mon Sep 17 00:00:00 2001
From: SleepWalker <mybox@udf.su>
Date: Sat, 28 Oct 2017 16:38:07 +0300
Subject: [PATCH] #305: scroll to meaningful content on multistep forms on
 devices with smalls screen resolution

---
 package-lock.json                             |   8 +-
 package.json                                  |   1 +
 src/components/MeasureHeight.js               |   4 +-
 .../profile/changeEmail/ChangeEmail.js        |   3 +
 .../profile/multiFactorAuth/MfaEnable.js      |   3 +
 .../multiFactorAuth/status/MfaStatus.js       |   3 +
 src/components/ui/bsod/BoxesField.js          |   2 -
 src/components/ui/scroll/ScrollIntoView.js    |  35 +++++
 src/components/ui/scroll/index.js             |   3 +
 src/components/ui/scroll/scroll.js            | 147 ++++++++++++++++++
 src/functions.js                              | 105 -------------
 src/pages/root/RootPage.js                    |   6 +-
 src/polyfills.js                              |   2 +
 13 files changed, 207 insertions(+), 115 deletions(-)
 create mode 100644 src/components/ui/scroll/ScrollIntoView.js
 create mode 100644 src/components/ui/scroll/index.js
 create mode 100644 src/components/ui/scroll/scroll.js

diff --git a/package-lock.json b/package-lock.json
index 0a4838e..de39884 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8749,9 +8749,9 @@
       "dev": true
     },
     "raf": {
-      "version": "3.3.2",
-      "resolved": "https://registry.npmjs.org/raf/-/raf-3.3.2.tgz",
-      "integrity": "sha1-DBO+C1tJtG921maSSNUnzysC/ic=",
+      "version": "3.4.0",
+      "resolved": "https://registry.npmjs.org/raf/-/raf-3.4.0.tgz",
+      "integrity": "sha512-pDP/NMRAXoTfrhCfyfSEwJAKLaxBU9eApMeBPB1TkDouZmvPerIClV8lTAd+uF8ZiTaVl69e1FCxQrAd/VTjGw==",
       "requires": {
         "performance-now": "2.1.0"
       },
@@ -8924,7 +8924,7 @@
       "requires": {
         "performance-now": "0.2.0",
         "prop-types": "15.5.10",
-        "raf": "3.3.2"
+        "raf": "3.4.0"
       }
     },
     "react-proxy": {
diff --git a/package.json b/package.json
index def47a9..5fdb614 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,7 @@
     "intl-format-cache": "^2.0.4",
     "intl-messageformat": "^2.1.0",
     "promise.prototype.finally": "3.0.1",
+    "raf": "^3.4.0",
     "raven-js": "^3.8.1",
     "react": "^15.0.0",
     "react-dom": "^15.0.0",
diff --git a/src/components/MeasureHeight.js b/src/components/MeasureHeight.js
index e685064..44a5212 100644
--- a/src/components/MeasureHeight.js
+++ b/src/components/MeasureHeight.js
@@ -1,7 +1,7 @@
 // @flow
 import React, { PureComponent } from 'react';
 
-import { omit, rAF, debounce } from 'functions';
+import { omit, debounce } from 'functions';
 
 /**
  * MeasureHeight is a component that allows you to measure the height of elements wrapped.
@@ -61,6 +61,6 @@ export default class MeasureHeight extends PureComponent<{
     }
 
     measure = debounce(() => {
-        rAF(() => this.el && this.props.onMeasure(this.el.offsetHeight));
+        requestAnimationFrame(() => this.el && this.props.onMeasure(this.el.offsetHeight));
     });
 }
diff --git a/src/components/profile/changeEmail/ChangeEmail.js b/src/components/profile/changeEmail/ChangeEmail.js
index 8b18623..f89dc21 100644
--- a/src/components/profile/changeEmail/ChangeEmail.js
+++ b/src/components/profile/changeEmail/ChangeEmail.js
@@ -5,6 +5,7 @@ import { FormattedMessage as Message } from 'react-intl';
 import Helmet from 'react-helmet';
 
 import { ScrollMotion } from 'components/ui/motion';
+import { ScrollIntoView } from 'components/ui/scroll';
 import { Input, Button, Form, FormModel, FormError } from 'components/ui/form';
 import { BackButton } from 'components/profile/ProfileForm';
 import styles from 'components/profile/profileForm.scss';
@@ -98,6 +99,8 @@ export default class ChangeEmail extends Component {
                     </div>
 
                     <div className={styles.form}>
+                        {activeStep > 0 ? <ScrollIntoView /> : null}
+
                         {this.renderStepForms()}
 
                         <Button
diff --git a/src/components/profile/multiFactorAuth/MfaEnable.js b/src/components/profile/multiFactorAuth/MfaEnable.js
index 0dff363..6a7bab7 100644
--- a/src/components/profile/multiFactorAuth/MfaEnable.js
+++ b/src/components/profile/multiFactorAuth/MfaEnable.js
@@ -5,6 +5,7 @@ import { Button, FormModel } from 'components/ui/form';
 import styles from 'components/profile/profileForm.scss';
 import Stepper from 'components/ui/stepper';
 import { ScrollMotion } from 'components/ui/motion';
+import { ScrollIntoView } from 'components/ui/scroll';
 import logger from 'services/logger';
 import mfa from 'services/api/mfa';
 
@@ -81,6 +82,8 @@ export default class MfaEnable extends Component<Props, {
                 </div>
 
                 <div className={styles.form}>
+                    {activeStep > 0 ? <ScrollIntoView /> : null}
+
                     {this.renderStepForms()}
 
                     <Button
diff --git a/src/components/profile/multiFactorAuth/status/MfaStatus.js b/src/components/profile/multiFactorAuth/status/MfaStatus.js
index 3fea65e..56cf07c 100644
--- a/src/components/profile/multiFactorAuth/status/MfaStatus.js
+++ b/src/components/profile/multiFactorAuth/status/MfaStatus.js
@@ -3,6 +3,7 @@ import React from 'react';
 import { FormattedMessage as Message } from 'react-intl';
 
 import styles from 'components/profile/profileForm.scss';
+import { ScrollIntoView } from 'components/ui/scroll';
 import icons from 'components/ui/icons.scss';
 
 import messages from '../MultiFactorAuth.intl.json';
@@ -13,6 +14,8 @@ export default function MfaStatus({onProceed}: {
 }) {
     return (
         <div className={styles.formBody}>
+            <ScrollIntoView />
+
             <div className={styles.formRow}>
                 <div className={mfaStyles.bigIcon}>
                     <span className={icons.lock} />
diff --git a/src/components/ui/bsod/BoxesField.js b/src/components/ui/bsod/BoxesField.js
index a94c0e6..e45ba95 100644
--- a/src/components/ui/bsod/BoxesField.js
+++ b/src/components/ui/bsod/BoxesField.js
@@ -1,5 +1,3 @@
-import { rAF as requestAnimationFrame } from 'functions';
-
 import Box from './Box';
 
 /**
diff --git a/src/components/ui/scroll/ScrollIntoView.js b/src/components/ui/scroll/ScrollIntoView.js
new file mode 100644
index 0000000..88ca9c3
--- /dev/null
+++ b/src/components/ui/scroll/ScrollIntoView.js
@@ -0,0 +1,35 @@
+// @flow
+import React from 'react';
+import { withRouter } from 'react-router-dom';
+import { restoreScroll } from './scroll';
+
+class ScrollIntoView extends React.Component<{
+    location: string,
+    top?: bool, // do not touch any DOM and simply scroll to top on location change
+}> {
+    componentDidMount() {
+        this.onPageUpdate();
+    }
+
+    componentDidUpdate(prevProps) {
+        if (this.props.location !== prevProps.location) {
+            this.onPageUpdate();
+        }
+    }
+
+    onPageUpdate() {
+        if (this.props.top) {
+            restoreScroll();
+        }
+    }
+
+    render() {
+        if (this.props.top) {
+            return null;
+        }
+
+        return <span ref={(el) => el && restoreScroll(el)} />;
+    }
+}
+
+export default withRouter(ScrollIntoView);
diff --git a/src/components/ui/scroll/index.js b/src/components/ui/scroll/index.js
new file mode 100644
index 0000000..2f17421
--- /dev/null
+++ b/src/components/ui/scroll/index.js
@@ -0,0 +1,3 @@
+// @flow
+
+export { default as ScrollIntoView } from './ScrollIntoView';
diff --git a/src/components/ui/scroll/scroll.js b/src/components/ui/scroll/scroll.js
new file mode 100644
index 0000000..17995d7
--- /dev/null
+++ b/src/components/ui/scroll/scroll.js
@@ -0,0 +1,147 @@
+// @flow
+/**
+ * Implements scroll to animation with momentum effect
+ *
+ * @see http://ariya.ofilabs.com/2013/11/javascript-kinetic-scrolling-part-2.html
+ */
+
+const TIME_CONSTANT = 100; // higher numbers - slower animation
+const SCROLL_ANCHOR_OFFSET = 80; // 50 + 30 (header height + some spacing)
+// Первый скролл выполняется сразу после загрузки страницы, так что чтобы снизить
+// нагрузку на рендеринг мы откладываем первый скрол на 200ms
+let isFirstScroll = true;
+let scrollJob = null;
+
+export function scrollTo(y: number) {
+    if (scrollJob) {
+        // we already scrolling, so simply change the coordinates we are scrolling to
+        if (scrollJob.hasAmplitude) {
+            const delta = y - scrollJob.y;
+            scrollJob.amplitude += delta;
+        }
+
+        scrollJob.y = y;
+        return;
+    }
+
+    const start = Date.now();
+    let scrollWasTouched = false;
+    scrollJob = {
+        // NOTE: we may use some sort of debounce to wait till we catch all the
+        // scroll requests after app state changes, but the way with hasAmplitude
+        // seems to be more reliable
+        hasAmplitude: false,
+        start,
+        y,
+        amplitude: 0
+    };
+
+    requestAnimationFrame(() => { // wrap in requestAnimationFrame to optimize initial reading of scrollTop
+        if (!scrollJob) {
+            return;
+        }
+
+        const y = normalizeScrollPosition(scrollJob.y);
+
+        scrollJob.hasAmplitude = true;
+        scrollJob.y = y;
+        scrollJob.amplitude = y - getScrollTop();
+
+        (function animateScroll() {
+            if (!scrollJob) {
+                return;
+            }
+
+            const { start, y, amplitude } = scrollJob;
+            const elapsed = Date.now() - start;
+
+            let delta = -amplitude * Math.exp(-elapsed / TIME_CONSTANT);
+
+            if (Math.abs(delta) > 0.5 && !scrollWasTouched) {
+                requestAnimationFrame(animateScroll);
+            } else {
+                // the last animation frame
+                delta = 0;
+                scrollJob = null;
+                document.removeEventListener('mousewheel', markScrollTouched);
+                document.removeEventListener('touchstart', markScrollTouched);
+            }
+
+            if (scrollWasTouched) {
+                // block any animation visualisation in case, when user touched scroll
+                return;
+            }
+
+            const newScrollTop = y + delta;
+            window.scrollTo(0, newScrollTop);
+        }());
+    });
+
+    document.addEventListener('mousewheel', markScrollTouched);
+    document.addEventListener('touchstart', markScrollTouched);
+    function markScrollTouched() {
+        scrollWasTouched = true;
+    }
+}
+
+/**
+ * Ensures, that `y` is the coordinate, that can be physically scrolled to
+ *
+ * @param  {number} y
+ *
+ * @return {number}
+ */
+function normalizeScrollPosition(y: number): number {
+    const contentHeight = (document.documentElement
+        && document.documentElement.scrollHeight) || 0;
+    const windowHeight: number = window.innerHeight;
+    const maxY = contentHeight - windowHeight;
+
+    return Math.min(y, maxY);
+}
+
+/**
+ * Scrolls to page's top or #anchor link, if any
+ *
+ * @param {?HTMLElement} targetEl - the element to scroll to
+ */
+export function restoreScroll(targetEl: ?HTMLElement = null) {
+    const {hash} = location;
+
+    setTimeout(() => {
+        isFirstScroll = false;
+        const id = hash.replace('#', '');
+        const el = id ? document.getElementById(id) : targetEl;
+        const viewPort = document.body;
+
+        if (!viewPort) {
+            console.log('Can not find viewPort element'); // eslint-disable-line
+            return;
+        }
+
+        let y = 0;
+
+        if (el) {
+            const {top} = el.getBoundingClientRect();
+
+            y = getScrollTop() + top - SCROLL_ANCHOR_OFFSET;
+        }
+
+        scrollTo(y);
+    }, isFirstScroll ? 200 : 0);
+}
+
+/**
+ * http://stackoverflow.com/a/3464890/5184751
+ *
+ * @return {number}
+ */
+export function getScrollTop(): number {
+    const doc = document.documentElement;
+
+    if (doc) {
+        return (window.pageYOffset || doc.scrollTop) - (doc.clientTop || 0);
+    }
+
+    return 0;
+}
diff --git a/src/functions.js b/src/functions.js
index 3441e73..0c37edf 100644
--- a/src/functions.js
+++ b/src/functions.js
@@ -44,12 +44,6 @@ export function loadScript(src: string): Promise<*> {
     });
 }
 
-export const rAF = window.requestAnimationFrame
-    || window.mozRequestAnimationFrame
-    || window.webkitRequestAnimationFrame
-    || window.msRequestAnimationFrame
-    || ((cb: Function) => setTimeout(cb, 1000 / 60));
-
 /**
  * Returns a function, that, as long as it continues to be invoked, will not
  * be triggered. The function will be called after it stops being called for
@@ -85,102 +79,3 @@ export function getJwtPayload(jwt: string): Object {
         throw new Error('Can not decode jwt token');
     }
 }
-
-/**
- * http://stackoverflow.com/a/3464890/5184751
- *
- * @return {number}
- */
-export function getScrollTop(): number {
-    const doc = document.documentElement;
-
-    if (doc) {
-        return (window.pageYOffset || doc.scrollTop) - (doc.clientTop || 0);
-    }
-
-    return 0;
-}
-
-/**
- * Implements scroll to animation with momentum effect
- *
- * @see http://ariya.ofilabs.com/2013/11/javascript-kinetic-scrolling-part-2.html
- */
-
-const TIME_CONSTANT = 100; // higher numbers - slower animation
-export function scrollTo(y: number) {
-    const start = Date.now();
-    let scrollWasTouched = false;
-    rAF(() => { // wrap in rAF to optimize initial reading of scrollTop
-        if (!document.documentElement) {
-            return;
-        }
-
-        const contentHeight = document.documentElement.scrollHeight || 0;
-        const windowHeight: number = window.innerHeight;
-        if (contentHeight < y + windowHeight) {
-            y = contentHeight - windowHeight;
-        }
-
-        const amplitude = y - getScrollTop();
-
-        (function animateScroll() {
-            const elapsed = Date.now() - start;
-
-            let delta = -amplitude * Math.exp(-elapsed / TIME_CONSTANT);
-
-            if (Math.abs(delta) > 0.5 && !scrollWasTouched) {
-                rAF(animateScroll);
-            } else {
-                delta = 0;
-                document.removeEventListener('mousewheel', markScrollTouched);
-                document.removeEventListener('touchstart', markScrollTouched);
-            }
-
-            if (scrollWasTouched) {
-                return;
-            }
-
-            const newScrollTop = y + delta;
-            window.scrollTo(0, newScrollTop);
-        }());
-    });
-
-    document.addEventListener('mousewheel', markScrollTouched);
-    document.addEventListener('touchstart', markScrollTouched);
-    function markScrollTouched() {
-        scrollWasTouched = true;
-    }
-}
-
-const SCROLL_ANCHOR_OFFSET = 80; // 50 + 30 (header height + some spacing)
-// Первый скролл выполняется сразу после загрузки страницы, так что чтобы снизить
-// нагрузку на рендеринг мы откладываем первый скрол на 200ms
-let isFirstScroll = true;
-/**
- * Scrolls to page's top or #anchor link, if any
- */
-export function restoreScroll() {
-    const {hash} = location;
-
-    setTimeout(() => {
-        isFirstScroll = false;
-        const id = hash.replace('#', '');
-        const el = id ? document.getElementById(id) : null;
-        const viewPort = document.body;
-
-        if (!viewPort) {
-            console.log('Can not find viewPort element'); // eslint-disable-line
-            return;
-        }
-
-        let y = 0;
-        if (el) {
-            const {top} = el.getBoundingClientRect();
-
-            y = getScrollTop() + top - SCROLL_ANCHOR_OFFSET;
-        }
-
-        scrollTo(y);
-    }, isFirstScroll ? 200 : 0);
-}
diff --git a/src/pages/root/RootPage.js b/src/pages/root/RootPage.js
index 48ab7ec..f6449bd 100644
--- a/src/pages/root/RootPage.js
+++ b/src/pages/root/RootPage.js
@@ -13,7 +13,7 @@ import ProfilePage from 'pages/profile/ProfilePage';
 import RulesPage from 'pages/rules/RulesPage';
 import PageNotFound from 'pages/404/PageNotFound';
 
-import { restoreScroll } from 'functions';
+import { ScrollIntoView } from 'components/ui/scroll';
 import PrivateRoute from 'containers/PrivateRoute';
 import AuthFlowRoute from 'containers/AuthFlowRoute';
 import Userbar from 'components/userbar/Userbar';
@@ -42,7 +42,6 @@ class RootPage extends Component<{
 
     onPageUpdate() {
         loader.hide();
-        restoreScroll();
     }
 
     render() {
@@ -59,6 +58,9 @@ class RootPage extends Component<{
                 <Helmet>
                     <html lang={user.lang} />
                 </Helmet>
+
+                <ScrollIntoView top />
+
                 <div id="view-port" className={classNames(styles.viewPort, {
                     [styles.isPopupActive]: isPopupActive
                 })}>
diff --git a/src/polyfills.js b/src/polyfills.js
index cfbdab2..efc2bfe 100644
--- a/src/polyfills.js
+++ b/src/polyfills.js
@@ -2,7 +2,9 @@ import 'babel-polyfill';
 import 'url-search-params-polyfill';
 import 'whatwg-fetch';
 import { shim as shimPromiseFinaly } from 'promise.prototype.finally';
+import { polyfill as rafPolyfill } from 'raf';
 
+rafPolyfill();
 shimPromiseFinaly();
 
 // allow :active styles in mobile Safary