Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on)

Progressive Web Apps sind ein plattformübergreifend einsetzbares Anwendungsmodell auf Web-Basis. Dank Project Fugu, einer Initiative der Chrome-Contributors Google, Microsoft und Intel, wird das Web um noch mächtigere Features erweitert. Damit können Entwickler endlich auch Produktivitäts-Apps wie Büro- und Bearbeitungsprogramme oder IDEs sinnvoll ins Web bringen.

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1. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Christian Liebel @christianliebel Consultant
2. Hello, it’s me. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Christian Liebel X: @christianliebel Email: christian.liebel @thinktecture.com Angular & PWA Slides: thinktecture.com /christian-liebel
3. 13:30–15:00 Block 1 15:00–15:30 Coffee Break 15:30–17:00 Block 2 Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Timetable
4. 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 für Desktop und Mobile mit Angular (Hands-on) Progressive Web Apps
5. 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 für Desktop und Mobile mit Angular (Hands-on) Demo Use Case
6. (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 für Desktop und Mobile mit Angular (Hands-on) Demo Use Case
7. Setup complete? (Node.js, Google Chrome, Editor, Git) Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Setup (1/3) LAB #0
8. git clone https://github.com/thinktecture/angular- days-2024-spring-pwa.git cd angular-days-2024-spring-pwa npm i npm start -- --open Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Setup (3/3) LAB #0
9. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Agenda
10. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Agenda
11. 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 für Desktop und Mobile mit Angular (Hands-on) Paint
12. Canvas Add a canvas element to app.component.html: <canvas #canvas width="600" height="480"></canvas> Query the canvas element in app.component.ts: @ViewChild('canvas') canvas!: ElementRef<HTMLCanvasElement>; Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #1
13. 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 für Desktop und Mobile mit Angular (Hands-on) Paint
14. Canvas 2D Context 1. Introduce a new field at the top of app.component.ts: context!: CanvasRenderingContext2D; 2. Get the 2D context in ngAfterViewInit(): const canvas = this.canvas.nativeElement; const ctx = canvas.getContext('2d')!; this.context = ctx; 3. Prepare the canvas: ctx.fillStyle = 'white'; ctx.fillRect(0, 0, canvas.width, canvas.height); ctx.fillStyle = 'black'; Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #2
15. Low-latency Rendering Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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)
16. Low-latency Rendering Opt-in to low-latency rendering (app.component.ts): const ctx = canvas.getContext('2d', { desynchronized: true })!; Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #3
17. Pointer Events Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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
18. Pointer Events 1. In app.component.html, add event bindings for the pointer events: <canvas #canvas width="600" height="480" (pointerdown)="onPointerDown($event)" (pointermove)="onPointerMove($event)" (pointerup)="onPointerUp()" ></canvas> 2. In app.component.ts (onPointerMove()), draw the user input: this.context.fillRect(event.offsetX, event.offsetY, 2, 2); Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #4
19. 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 für Desktop und Mobile mit Angular (Hands-on) Paint
20. Bresenham Line Algorithm 1. At the top of app.component.ts, a field called previousPoint to store the previous point: previousPoint?: { x: number, y: number }; 2. In onPointerDown(), set the current point as the previous point: this.previousPoint = { x: event.offsetX, y: event.offsetY }; 3. In onPointerUp(), set this.previousPoint to undefined. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #5
21. Bresenham Line Algorithm 4. In onPointerMove(), call the Bresenham line algorithm with the points: if (this.previousPoint) { const currentPoint = { x: event.offsetX, y: event.offsetY }; for (const point of this.paintService.bresenhamLine(this.previousPoint, currentPoint)) { this.context.fillRect(point.x, point.y, 2, 2); } this.previousPoint = currentPoint; } Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #5
22. 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 für Desktop und Mobile mit Angular (Hands-on) Paint
23. Color Selection 1. In app.component.html, replace the content of the <nav> node with: <input type="color" #color (change)="onColorChange(color)"> 2. In app.component.ts (onColorChange()), update the context’s fill style accordingly: this.context.fillStyle = color.value; Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Paint LAB #6
24. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Agenda
25. für Desktop und Mobile mit Angular (Hands-on) Progressive Web Apps Responsive Linkable Discoverable Installable App-like Connectivity Independent Fresh Safe Re-engageable Progressive
26. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Web App Manifest Service Worker
27. 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 für Desktop und Mobile mit Angular (Hands-on) PWA
28. 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 für Desktop und Mobile mit Angular (Hands-on) PWA Names Icons Display Mode Shortcuts Start URL Theme color (status bar/window bar)
29. Manifest Display Modes Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA browser minimal-ui standalone fullscreen
30. Manifest Icon Purposes (any) any context (e.g. app icon) monochrome different color requirements maskable user agent masks icon as required Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA Safe Zone Windows iOS Android
31. Web App Manifest 1. Stop the npm start command, then run the following command to add PWA support to the current project: npm run ng add @angular/pwa 2. In manifest.webmanifest, a) set name and short_name to values of your choice b) change the theme_color to #000080 c) change the background_color to #808080 3. In index.html, change the theme-color to #000080. 4. Run npm start again. 5. Test manifest in DevTools: F12 > Application > Manifest Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA LAB #7
32. Manifest Shortcuts Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA Secondary entrypoints for your application (e.g., home screen quick actions, jump lists, …) Static definition in Web App Manifest Supported by Google Chrome for Android, macOS and Windows Supported by Safari 17.4+ on macOS
33. 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": "./", "icons": [{ "src": "assets/icons/icon-512x512.png", "sizes": "512x512" }] }] 2. Test in DevTools: F12 > Application > Manifest Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA LAB #8
34. Web App Manifest – Chromium Install Criteria 1. Web App is not already installed 2. Meets a user engagement heuristic (user has interacted with origin or viewed the page for at least 30 seconds) 3. 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 4. Served over HTTPS 5. Service workers Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA https://web.dev/articles/install-criteria
35. Service Worker JavaScript 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 für Desktop und Mobile mit Angular (Hands-on) PWA
36. Service Worker Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA Service Worker Internet Website HTML/JS Cache fetch
37. NgServiceWorker Angular CLI supports Service Worker generation by simply adding PWA support: ng add @angular/pwa One-size-fits-all Service Worker Pre-defined functionality, limited customizability PWA für Desktop und Mobile mit Angular (Hands-on) Progressive Web Apps
38. 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 für Desktop und Mobile mit Angular (Hands-on) PWA
39. Service Worker 1. In your console, run: npm run pwa 2. Test in DevTools: F12 > Application > Service Worker 3. Install the app: Address Bar > Install Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA LAB #9
40. Push Notifications Just as native apps, PWAs can receive push notifications Combination of two technologies: Web Notifications and Push API Supported by Chrome, Edge, Firefox, Safari Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA
41. Service Worker Debugging More information on installed service workers can be found on • about://serviceworker- internals (Chromium-based browsers) • about:serviceworkers (Mozilla Firefox) Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA
42. Service Worker Debugging Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA
43. Lighthouse Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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 “Analyze page load” Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) PWA LAB #10
45. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Agenda
46. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on)
47. Project Fugu Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities »Let’s bring the web back – API by API« Thomas Steiner, Google
48. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities Contacts Picker Screen Wake Lock API File System Access API Shape Detection API
49. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities https://goo.gle/fugu-api-tracker
50. Browser Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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 Supported by Chrome, Edge Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities
52. File System Access API 1. Add the following buttons to the <nav> bar in app.component.html (before the color input): <button (click)="open()">Open</button> <button (click)="save()">Save</button> <button (click)="copy()">Copy</button> <button (click)="paste()">Paste</button> <button (click)="share()">Share</button> Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #11
53. File System Access API 2. Add the following lines at the top of app.component.ts: readonly fileOptions: FilePickerOptions = { types: [{ description: 'PNG files', accept: {'image/png': ['.png']} }] }; Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #11
54. File System Access API 3. Add the following lines to the save() function: const blob = await this.paintService.toBlob(this.canvas.nativeElement); const handle = await window.showSaveFilePicker(this.fileOptions); const writable = await handle.createWritable(); await writable.write(blob); await writable.close(); Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #11
55. File System Access API Add the following code to the open() function: const [handle] = await window.showOpenFilePicker(this.fileOptions); const file = await handle.getFile(); const image = await this.paintService.getImage(file); this.context.drawImage(image, 0, 0); Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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 and Firefox (plain- text only) Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities
57. Async Clipboard API Add the following code to the copy() function: await navigator.clipboard.write([ new ClipboardItem({ "image/png": this.paintService.toBlob(this.canvas.nativeElement) }), ]); Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #13
58. Async Clipboard API 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 this.paintService.getImage(blob); this.context.drawImage(image, 0, 0); } } } Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) 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) Supported by Chrome, Edge, Safari and Firefox (Android only) Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities
60. Web Share API const blob = await this.paintService.toBlob(this.canvas.nativeElement); const file = new File([blob], 'untitled.png', {type: 'image/png'}); const item = { files: [file] }; if (navigator.canShare(item)) { await navigator.share(item); } Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #15
61. File 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 für Desktop und Mobile mit Angular (Hands-on) Capabilities
62. File Handling API 1. Add the following property to your manifest (manifest.webmanifest): "file_handlers": [{ "action": "/index.html", "accept": { "image/png": [".png"] } }] Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #16
63. File Handling API 2. Add the following code to ngAfterViewInit() in app.component.ts: if ('launchQueue' in window) { window.launchQueue.setConsumer(async params => { const [handle] = params.files; if (handle) { const file = await handle.getFile(); const image = await this.paintService.getImage(file); ctx.drawImage(image, 0, 0); } }); } Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #16
64. File Handling API 3. Rebuild PWA: npm run pwa Note: Wait for a few seconds and reload the application after opening, as the PWA needs to fetch the new files first. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Capabilities LAB #16
65. 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 für Desktop und Mobile mit Angular (Hands-on) Capabilities
66. Paint PWA Capabilities Progressive Enhancement Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Agenda
67. 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 für Desktop und Mobile mit Angular (Hands-on) Progressive Enhancement
68. 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 für Desktop und Mobile mit Angular (Hands-on) Progressive Enhancement
69. Disabling unsupported features In app.component.ts, introduce the following check object: readonly supported = { open: 'showOpenFilePicker' in window, } as const; In app.component.html, disable the open button if the API is unsupported: <button (click)="open()" [disabled]="!supported.open"> Open</button> Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Progressive Enhancement LAB #17
70. Disabling unsupported features Introduce checks for the remaining APIs: 1. Save: 'showSaveFilePicker' in window 2. Copy: navigator.clipboard && 'write' in navigator.clipboard 3. Paste: navigator.clipboard && 'read' in navigator.clipboard 4. Share: 'canShare' in navigator Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Progressive Enhancement LAB #17
71. Providing an alternative implementation 1. In the save() method of app.component.ts, test for the existence of the showSaveFilePicker() method on the window 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); 3. Remove the compatibility check to always enable the button. Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Progressive Enhancement LAB #18
72. PWAs are now installable, offline-capable and can receive push notifications on all relevant platforms Google, Microsoft and Apple are aligned on installable web applications Project Fugu unlocks more and more capabilities for the web in a secure, privacy-preserving manner Big apps like Photoshop and Visual Studio Code prove that the application model works Write your apps once, run them anywhere! Progressive Web Apps für Desktop und Mobile mit Angular (Hands-on) Summary
73. Thank you for your kind attention! Christian Liebel @christianliebel christian.liebel@thinktecture.com