PWA Workshop: Progressive Web Apps, Superpowered

PWA Workshop: Progressive Web Apps, Superpowered

Progressive Web Apps are a great cross-platform application model, even if somewhat restricted in use—until now, that is. Project Fugu is an initiative led by Google, Microsoft, and Intel. Their goal: a more capable web. Home screen shortcuts, clipboard access, and native file system access are only a few examples of Fugu’s powerful APIs. Are you ready to superpower your Progressive Web App?

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Christian Liebel

October 26, 2020
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  1. Progressive Web Apps, Superpowered PWA Workshop Christian Liebel @christianliebel Consultant

  2. Hello, it’s me. Progressive Web Apps, Superpowered PWA Workshop Christian

    Liebel Twitter: @christianliebel Email: christian.liebel @thinktecture.com Angular & PWA Slides: thinktecture.com /christian-liebel
  3. And you? Progressive Web Apps, Superpowered PWA Workshop

  4. 09:00–10:30 Block 1 10:30–11:00 Break 11:00–12:30 Block 2 12:30–13:30 Lunch

    Break 13:30–15:00 Block 3 15:00–15:30 Break 15:30–17:00 Block 4 Progressive Web Apps, Superpowered PWA Workshop Timetable
  5. Things NOT to expect - Blueprint for PWA development -

    No AuthN/AuthZ Things To Expect - Extensive/up-to-date insights into PWA and Project Fugu - A productivity app use case that works on your desktop & smartphone - Lots of fun - Hands-on exercises PWA Workshop Progressive Web Apps, Superpowered
  6. https://paint.js.org – Productivity app – Draw images – Lots of

    actions & tools – Installable – Read/save files – Copy/paste images from/to clipboard – Share files to other apps – Register for file extensions Progressive Web Apps, Superpowered PWA Workshop Demo Use Case
  7. (Workshop Edition) – Productivity app – Draw images – Lots

    of actions & tools – Installable – Read/save files – Copy/paste images from/to clipboard – Share files to other apps – Register for file extensions Progressive Web Apps, Superpowered PWA Workshop Demo Use Case
  8. Setup complete? (Node.js, Google Chrome, Editor, Git) Progressive Web Apps,

    Superpowered PWA Workshop Setup (1/3) LAB #0
  9. Optional Download and install Chrome Canary: https://www.google.com/intl/de/chrome/canary/ Progressive Web Apps,

    Superpowered PWA Workshop Setup (2/3) LAB #0
  10. git clone https://github.com/thinktecture/ijs- munich-2020-pwa.git cd ijs-munich-2020-pwa npm i npm start

    Progressive Web Apps, Superpowered PWA Workshop Setup (3/3) LAB #0
  11. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps, Superpowered PWA

    Workshop Agenda
  12. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps, Superpowered PWA

    Workshop Agenda
  13. Canvas – Plain bitmap for the web – Cross-platform, hardware-

    accelerated graphics operations – Supports different contexts (2D, 3D: WebGL, WebGL 2.0) – Supported on all evergreen browsers and on IE 9+ Progressive Web Apps, Superpowered PWA Workshop Paint
  14. Canvas Add a canvas element to index.html (line 11): <canvas

    id="canvas" width="600" height="480"></canvas> Query the canvas element in app.js (line 1): const canvas = document.querySelector('#canvas'); Progressive Web Apps, Superpowered PWA Workshop Paint LAB #1
  15. Canvas 2D Context fillRect(x, y, width, height) strokeRect(x, y, width,

    height) beginPath() moveTo(x, y) lineTo(x, y) fill() stroke() Progressive Web Apps, Superpowered PWA Workshop Paint
  16. Canvas 2D Context Get the 2D context and prepare the

    canvas in app.js: const canvas = document.querySelector('#canvas'); const ctx = canvas.getContext('2d'); ctx.fillStyle = 'white'; ctx.fillRect(0, 0, canvas.width, canvas.height); ctx.fillStyle = 'black'; Progressive Web Apps, Superpowered PWA Workshop Paint LAB #2
  17. Low-latency Rendering Progressive Web Apps, Superpowered PWA Workshop Paint Web

    pages need to synchronize with the DOM on graphics updates causing latencies that can make drawing difficult Low-latency rendering skips syncing with the DOM with can lead to a more natural experience Supported on Chrome (Chrome OS and Windows only)
  18. Low-latency Rendering Opt-in to low-latency rendering (app.js): const ctx =

    canvas.getContext('2d', { desynchronized: true }); Progressive Web Apps, Superpowered PWA Workshop Paint LAB #3
  19. Pointer Events Progressive Web Apps, Superpowered PWA Workshop Paint Users

    nowadays use different input methods, cross-platform apps should cover all of them Pointer Events offer an abstract interface to catch all input methods (pointerdown, pointermove, pointerup) event.offsetX/event.offsetY contain the pointer’s position relative to the listener
  20. Pointer Events Add event listeners (bottom of app.js): canvas.addEventListener('pointerdown', event

    => {}); canvas.addEventListener('pointermove', event => { // ~~ is the shorter Math.floor() ctx.fillRect(~~event.offsetX, ~~event.offsetY, 2, 2); }); canvas.addEventListener('pointerup', () => {}); Progressive Web Apps, Superpowered PWA Workshop Paint LAB #4
  21. Bresenham Line Algorithm The user may move faster than the

    input can be processed For this case, we need to remember the previous point and interpolate the points in between The Bresenham line algorithm calculates the missing pixels between two given points Progressive Web Apps, Superpowered PWA Workshop Paint
  22. Bresenham Line Algorithm 1. Add the following import to the

    top of app.js (“.js” is required, otherwise the request will 404): import {bresenhamLine} from "./helpers.js"; 2. Then, adjust the event listeners: a) In the pointerdown event handler, store ~~event.offsetX/~~event.offsetY in a variable called previousPoint (~~ is required, otherwise Bresenham will go into an endless loop) b) In pointermove i. only draw if the pointer is down ii. retrieve the current point (event.offsetX|Y, ~~ required!) iii. In a for…of loop, call bresenhamLine() with previousPoint.x|y & currentPoint.x|y and draw a 2x2 rectangle for each returned point. iv. store current point in previousPoint c) In pointerup, set previousPoint to null again. Progressive Web Apps, Superpowered PWA Workshop Paint LAB #5
  23. Bresenham Line Algorithm let previousPoint = null; canvas.addEventListener('pointerdown', event =>

    previousPoint = {x: ~~event.offsetX, y: ~~event.offsetY}); canvas.addEventListener('pointermove', event => { if (previousPoint) { const currentPoint = {x: ~~event.offsetX, y: ~~event.offsetY}; for(let {x, y} of bresenhamLine(previousPoint.x, previousPoint.y, currentPoint.x, currentPoint.y)) { ctx.fillRect(x, y, 2, 2); } previousPoint = currentPoint; } }); canvas.addEventListener('pointerup', () => previousPoint = null); Progressive Web Apps, Superpowered PWA Workshop Paint
  24. Color Selection For this demo, we will only implement the

    brush tool. However, we want to bring in some color. A simple method to implement a color selection is to use the HTML color-type input element that shows the native color picker: <input type="color"> Progressive Web Apps, Superpowered PWA Workshop Paint
  25. Color Selection 1. In index.html, add the following input to

    the <nav> node: <input type="color" id="color"> 2. In app.js, add the following code at the bottom: const txtColor = document.querySelector('#color'); txtColor.addEventListener('change', () => { ctx.fillStyle = txtColor.value; }); Progressive Web Apps, Superpowered PWA Workshop Paint LAB #6
  26. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps, Superpowered PWA

    Workshop Agenda
  27. PWA Workshop Progressive Web Apps, Superpowered Responsive Linkable Discoverable Installable

    App-like Connectivity Independent Fresh Safe Re-engageable Progressive
  28. Progressive Web Apps, Superpowered PWA Workshop Web App Manifest Service

    Worker
  29. Web App Manifest Distinguishes Web Apps from Websites JSON-based file

    containing metadata for apps only Apps can be identified by search engines, app store providers, etc. Progressive Web Apps, Superpowered PWA Workshop PWA
  30. manifest.webmanifest { "short_name": "Paint", "name": "Paint Workshop", "theme_color": "white", "icons":

    [{ "src": "icon.png", "sizes": "512x512" }], "start_url": "/index.html", "display": "standalone", "shortcuts": [/* … */] } Progressive Web Apps, Superpowered PWA Workshop PWA Names Icons Display Mode Shortcuts Start URL Theme color (status bar/window bar)
  31. Manifest Display Modes Progressive Web Apps, Superpowered PWA Workshop PWA

    browser minimal-ui standalone fullscreen
  32. Manifest Icon Purposes (any) any context (e.g. app icon) monochrome

    different color requirements (at risk) maskable user agent masks icon as required Progressive Web Apps, Superpowered PWA Workshop PWA Safe Zone Windows iOS Android
  33. Web App Manifest 1. In index.html, add the following tag

    to the document’s <head> node (e.g., after the stylesheet): <link rel="manifest" href="manifest.webmanifest"> 2. Create the new file manifest.webmanifest and set: a) name and short_name to values of your choice b) display to standalone c) theme_color to #000080 and background_color to #808080 d) start_url to /index.html and scope to / e) icons to [{ src: "icon.png", sizes: "512x512" }] 3. Test manifest in DevTools: F12 > Application > Manifest Progressive Web Apps, Superpowered PWA Workshop PWA LAB #7
  34. Manifest Shortcuts Progressive Web Apps, Superpowered PWA Workshop PWA Secondary

    entrypoints for your application (e.g., home screen quick actions, jump lists, …) Static definition in Web App Manifest Dynamic API may follow in the future Supported by Google Chrome for Android
  35. Web App Manifest 1. In manifest.webmanifest, add (at least) the

    following shortcut: "shortcuts": [{ "name": "About Paint", "short_name": "About", "description": "Show information about Paint", "url": "/about.html", "icons": [{ "src": "icon.png", "sizes": "512x512" }] }], 2. Test in DevTools: F12 > Application > Manifest Progressive Web Apps, Superpowered PWA Workshop PWA LAB #8
  36. Web App Manifest – Chrome Installability Signals Web App is

    not already installed Meets a user engagement heuristic (previously: user has interacted with domain for at least 30 seconds) Includes a Web App Manifest that has short_name or name, at least a 192px and 512px icon, a start_url and a display mode of fullscreen, standalone or minimal-ui Served over HTTPS Has a registered service worker with a fetch event handler Progressive Web Apps, Superpowered PWA Workshop PWA
  37. Service Worker JavaScript snippet executed in an own thread, registered

    by the website Acts as a controller, proxy, or interceptor Has a cache to store responses (for offline availability and performance) Can wake up even when the website is closed and perform background tasks (e.g., push notifications or sync) Progressive Web Apps, Superpowered PWA Workshop PWA
  38. Service Worker Progressive Web Apps, Superpowered PWA Workshop PWA Service

    Worker Internet Website HTML/JS Cache fetch
  39. Workbox Toolchain by Google Includes a CLI Generates a service

    worker implementation from directory contents (e.g., build output, or our development directory) Allows you to modify the service worker behavior (maximum flexibility) Progressive Web Apps, Superpowered PWA Workshop PWA
  40. Service Worker 1. In your console, run: a) npm run

    workbox wizard (use “src” as project root and defaults for the rest) b) npm run workbox generateSW 2. In index.html, add the following script to the bottom of the <body> node: <script> if (navigator.serviceWorker) { navigator.serviceWorker.register('sw.js'); } </script> 3. Test in DevTools: F12 > Application > Service Worker 4. Install the app: Address Bar > ⊕ Install Progressive Web Apps, Superpowered PWA Workshop PWA LAB #9
  41. Service Worker Debugging More information on installed service workers can

    be found on • chrome://serviceworker- internals (Google Chrome) • about:serviceworkers (Mozilla Firefox) Progressive Web Apps, Superpowered PWA Workshop PWA
  42. Service Worker Debugging Progressive Web Apps, Superpowered PWA Workshop PWA

  43. Lighthouse Progressive Web Apps, Superpowered PWA Workshop PWA Auditing tool

    by Google, integrated in Chrome DevTools Automatically checks performance metrics, PWA support, accessibility, SEO and other best practices and gives tips on how to improve Can simulate mobile devices
  44. Lighthouse 1. Make sure only one tab/window of your PWA

    is open 2. Open DevTools: F12 > Lighthouse 3. Make sure to select at least the “Progressive Web App” category 4. Click “Generate report” Progressive Web Apps, Superpowered PWA Workshop PWA LAB #10
  45. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps, Superpowered PWA

    Workshop Agenda
  46. Progressive Web Apps, Superpowered PWA Workshop

  47. Project Fugu Progressive Web Apps, Superpowered PWA Workshop Capabilities »Let’s

    bring the web back – API by API« Thomas Steiner, Google
  48. Progressive Web Apps, Superpowered PWA Workshop Capabilities Contacts Picker Screen

    Wake Lock API File System Access API Shape Detection API
  49. Progressive Web Apps, Superpowered PWA Workshop Capabilities https://goo.gle/fugu-api-tracker

  50. Progressive Web Apps, Superpowered PWA Workshop Capabilities navigator.share({ url: 'http://example.com'

    }); ShareIntent DataTransferManager … NSSharingServicePicker
  51. File System Access API Some applications heavily rely on working

    with files (e.g. Visual Studio Code, Adobe Photoshop, …) File System Access API allows you to open, save and override files and directories Shipped with Google Chrome 86 Progressive Web Apps, Superpowered PWA Workshop Capabilities
  52. File System Access API 1. Add the following buttons to

    the <nav> bar in index.html (before the color input): <button id="open">Open</button> <button id="save">Save</button> <button id="copy">Copy</button> <button id="paste">Paste</button> <button id="share">Share</button> Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #11
  53. File System Access API 2. At the top of app.js,

    change the import as follows: import {bresenhamLine, getImage, toBlob} from "./helpers.js"; 3. Add the following lines at the bottom of app.js: const fileOptions = { types: [{ description: 'PNG files', accept: {'image/png': ['.png']} }] }; Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #11
  54. File System Access API 4. Add the following lines at

    the bottom of app.js: const btnSave = document.querySelector('#save'); btnSave.addEventListener('click', async () => { const blob = await toBlob(canvas); const handle = await window.showSaveFilePicker(fileOptions); const writable = await handle.createWritable(); await writable.write(blob); await writable.close(); }); Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #11
  55. File System Access API Add the following code at the

    end of app.js: const btnOpen = document.querySelector('#open'); btnOpen.addEventListener('click', async () => { const [handle] = await window.showOpenFilePicker(fileOptions); const file = await handle.getFile(); const image = await getImage(file); ctx.drawImage(image, 0, 0); }); Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #12
  56. Async Clipboard API Allows reading from/writing to the clipboard in

    an asynchronous manner (UI won’t freeze during long-running operations) Reading from the clipboard requires user consent first (privacy!) Supported by Chrome, Edge and Safari Progressive Web Apps, Superpowered PWA Workshop Capabilities
  57. Async Clipboard API Add the following code at the end

    of app.js: const btnCopy = document.querySelector('#copy'); btnCopy.addEventListener('click', async () => { const blob = await toBlob(canvas); await navigator.clipboard.write([ new ClipboardItem({[blob.type]: blob}) ]); }); Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #13
  58. Async Clipboard API const btnPaste = document.querySelector('#paste'); btnPaste.addEventListener('click', async ()

    => { const clipboardItems = await navigator.clipboard.read(); for (const clipboardItem of clipboardItems) { for (const type of clipboardItem.types) { if (type === 'image/png') { const blob = await clipboardItem.getType(type); const image = await getImage(blob); ctx.drawImage(image, 0, 0); } } } }); Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #14
  59. Web Share API Allows sharing a title, URL, text, or

    files API can only be invoked as a result of a user action (i.e. a click or keypress) Files supported in Chrome on Android, Edge on Windows Progressive Web Apps, Superpowered PWA Workshop Capabilities
  60. Web Share API const btnShare = document.querySelector('#share'); btnShare.disabled = !('canShare'

    in navigator); btnShare.addEventListener('click', async () => { const blob = await toBlob(canvas); const file = new File([blob], 'untitled.png', {type: 'image/png'}); const item = {files: [file], title: 'untitled.png'}; if (await navigator.canShare(item)) { await navigator.share(item); } }); Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #15
  61. File System Handling API Register your PWA as a handler

    for file extensions Requires installing the application first Declare supported extensions in Web App Manifest and add imperative code to your application logic Progressive Web Apps, Superpowered PWA Workshop Capabilities
  62. File System Handling API 1. Enable the following flag in

    Chrome Canary and restart the browser: chrome://flags/#file-handling-api 2. Add the following property to your manifest (manifest.webmanifest): "file_handlers": [{ "action": "/index.html", "accept": { "image/png": [".png"] } }] Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #16
  63. File System Handling API 3. Add the following code to

    the bottom of app.js: if ('launchQueue' in window) { launchQueue.setConsumer(async params => { const [handle] = params.files; if (handle) { const file = await handle.getFile(); const image = await getImage(file); ctx.drawImage(image, 0, 0); } }); } 4. Re-generate Service Worker: npm run workbox generateSW Progressive Web Apps, Superpowered PWA Workshop Capabilities LAB #16
  64. Summary - Project Fugu helps the web to become more

    and more capable - Project Fugu APIs could bring many more app experiences to the web (IDEs, productivity apps, etc.) - But: Web is threatened by alternative approaches and platforms, support for modern Web API varies from platform to platform - You can make a difference! - File bugs in browser engine bugtrackers - File Fugu requests: https://goo.gle/new-fugu-request Progressive Web Apps, Superpowered PWA Workshop Capabilities
  65. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps, Superpowered PWA

    Workshop Agenda
  66. Overview Use available interfaces and functions of a system (opposite

    of Graceful Degradation) Users with modern, feature-rich browsers get a better experience Apps are available on older browsers, but with limited functionality Concept: Browser feature support should grow over time—thereby more users can enjoy an increasing number of features Progressive Web Apps, Superpowered PWA Workshop Progressive Enhancement
  67. Overview if ('serviceWorker' in navigator) { navigator.serviceWorker.register(…) .then(() => /*

    … */); } In JavaScript: check whether an API/feature is available. If yes—use it! Otherwise: 1. Disable the functionality 2. Fall back to an alternative API (if available) Progressive Web Apps, Superpowered PWA Workshop Progressive Enhancement
  68. Disabling unsupported features In app.js, disable the buttons in case

    the respective API does not exist, e.g.: btnOpen.disabled = !('showOpenFilePicker' in window); 1. Open: window.showOpenFilePicker() 2. Save: window.showSaveFilePicker() 3. Copy: navigator.clipboard + navigator.clipboard.read() 4. Paste: navigator.clipboard + navigator.clipboard.write() 5. Share: navigator.canShare() Progressive Web Apps, Superpowered PWA Workshop Progressive Enhancement LAB #17
  69. Providing an alternative implementation 1. In app.js, test for the

    existence of the showSaveFilePicker() method on the navigator object. 2. If the method does not exist, fall back to the following code for save: const anchor = document.createElement('a'); const url = URL.createObjectURL(blob); anchor.href = url; anchor.download = ''; anchor.click(); URL.revokeObjectURL(url); Progressive Web Apps, Superpowered PWA Workshop Progressive Enhancement LAB #18
  70. Deployment Progressive Web Apps, Superpowered PWA Workshop Electron/Capacitor JS HTML

    CSS .ipa .exe .app ELF .apk .appx Single-Page Application Capacitor Electron
  71. (Simplified) Progressive Web Apps, Superpowered PWA Workshop Store Deployments https://example.com

    .appx .apk Server Microsoft Store Play Store Source Files
  72. Run app on your device https://ngrok.com/download ngrok http 3000 Progressive

    Web Apps, Superpowered PWA Workshop LAB #19
  73. Crunch Time Progressive Web Apps, Superpowered PWA Workshop LAB #20

  74. Q&A Progressive Web Apps, Superpowered PWA Workshop

  75. New powerful APIs regularly ship with new releases of Chromium-based

    browsers Some only add minor finishing touches, others enable whole application categories as productivity apps to finally make the shift to the web Some APIs already made their way into other browsers (e.g., Web Share) Fugu process makes sure that capabilities are implemented in a secure, privacy-preserving manner Let’s make the web a more capable platform! Progressive Web Apps, Superpowered PWA Workshop Summary
  76. Thank you for your kind attention! Christian Liebel @christianliebel christian.liebel@thinktecture.com