Cross-Plattform-Workshop: Progressive Web Apps mit Angular – in Action

Progressive Web Apps mit Angular
In Action!
Christian Liebel
@christianliebel
Consultant

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Hello, it’s me.
In Action!
Christian Liebel
Twitter:
@christianliebel
Email:
christian.liebel
@thinktecture.com
Angular & PWA
Slides:
thinktecture.com
/christian-liebel

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09:00–10:30 Block 1
10:30–10:45 Break
10:45–12:15 Block 2
12:15–13:15 Lunch Break
13:15–14:45 Block 3
14:45–15:00 Break
15:00–16:30 Block 4
In Action!
Timetable

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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
In Action!

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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
In Action!
Demo Use Case

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(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
In Action!
Demo Use Case

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Setup complete?
(Node.js, Google Chrome, Editor, Git)
In Action!
Setup (1/3)
LAB #0

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git clone https://github.com/thinktecture/
md-devdays-2023-pwa.git
cd md-devdays-2023-pwa
npm i
npm start -- --open
In Action!
Setup (3/3)
LAB #0

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Paint PWA Capabilities
Progressive
Enhancement
In Action!
Agenda

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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+
In Action!
Paint

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Canvas
Add a canvas element to app.component.html:

Query the canvas element in app.component.ts:
@ViewChild('canvas') canvas?: ElementRef;
In Action!
Paint
LAB #1

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Canvas 2D Context
fillRect(x, y, width, height)
strokeRect(x, y, width, height)
beginPath()
moveTo(x, y)
lineTo(x, y)
fill()
stroke()
In Action!
Paint

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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';
In Action!
Paint LAB #2

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Low-latency Rendering
In Action!
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)

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Low-latency Rendering
Opt-in to low-latency rendering (app.component.ts):
const ctx = canvas.getContext('2d', {
desynchronized: true
})!;
In Action!
Paint
LAB #3

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Pointer Events
In Action!
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

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Pointer Events
1. In app.component.html, add event bindings for the pointer events:
(pointerdown)="onPointerDown($event)"
(pointermove)="onPointerMove($event)"
(pointerup)="onPointerUp()"
>
2. In app.component.ts (onPointerMove()), draw the user input:
this.context!.fillRect(event.offsetX, event.offsetY, 2, 2);
In Action!
Paint LAB #4

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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
In Action!
Paint

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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.
In Action!
Paint LAB #5

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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;
}
In Action!
Paint LAB #5

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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:

In Action!
Paint

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Color Selection
1. In app.component.html, replace the content of the node with:

2. In app.component.ts (onColorChange()), update the context’s fill style
accordingly:
this.context!.fillStyle = color.value;
In Action!
Paint
LAB #6

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Progressive
Enhancement
In Action!
Agenda

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In Action!
Responsive Linkable Discoverable Installable App-like
Connectivity
Independent
Fresh Safe Re-engageable Progressive

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In Action!
Web App
Manifest
Service
Worker

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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.
In Action!
PWA

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manifest.webmanifest
{
"short_name": "Paint",
"name": "Paint Workshop",
"theme_color": "white",
"icons": [{
"src": "icon.png",
"sizes": "512x512"
}],
"start_url": "/index.html",
"display": "standalone",
"shortcuts": [/* … */]
}
In Action!
PWA
Names
Icons
Display Mode
Shortcuts
Start URL
Theme color (status bar/window bar)

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Manifest Display Modes
In Action!
PWA
browser minimal-ui standalone fullscreen

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Manifest Icon Purposes
(any)
any context (e.g. app icon)
monochrome
different color requirements
(at risk)
maskable
user agent masks icon as required
In Action!
PWA
Safe Zone
Windows iOS Android

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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
In Action!
PWA LAB #7

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Manifest Shortcuts
In Action!
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, macOS and
Windows

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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
In Action!
PWA
LAB #8

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Web App Manifest – Chromium Install Criteria
1. Web App is not already installed
2. Meets a user engagement heuristic (user has interacted and clicked
with origin 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. Edge: Has a registered service worker with a fetch event handler
In Action!
PWA
https://web.dev/install-criteria/

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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)
In Action!
PWA

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Service Worker
In Action!
PWA
Service
Worker
Internet
Website
HTML/JS
Cache
fetch

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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
In Action!

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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)
In Action!
PWA

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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
In Action!
PWA
LAB #9

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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
In Action!
PWA

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Service Worker Debugging
More information on installed
service workers can be found on
• about://serviceworker-
internals (Chromium-based
browsers)
• about:serviceworkers
(Mozilla Firefox)
In Action!
PWA

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Service Worker Debugging
In Action!
PWA

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Lighthouse
In Action!
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

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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”
In Action!
PWA
LAB #10

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Progressive
Enhancement
In Action!
Agenda

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In Action!

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Project Fugu
In Action!
Capabilities
»Let’s bring the web
back – API by API«
Thomas Steiner, Google

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In Action!
Capabilities
Contacts
Picker
Screen Wake
Lock API
File System
Access API
Shape
Detection API

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In Action!
Capabilities
https://goo.gle/fugu-api-tracker

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Browser
In Action!
Capabilities
navigator.share({ url: 'http://example.com' });
ShareIntent DataTransferManager
…
NSSharingServicePicker

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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
In Action!
Capabilities

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1. Add the following buttons to the bar in app.component.html
(before the color input):
Open
Save
Copy
Paste
Share
In Action!
Capabilities
LAB #11

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2. Add the following lines at the top of app.component.ts:
readonly fileOptions = {
types: [{
description: 'PNG files',
accept: {'image/png': ['.png']}
}]
};
In Action!
Capabilities
LAB #11

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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();
In Action!
Capabilities
LAB #11

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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);
In Action!
Capabilities
LAB #12

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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)
In Action!
Capabilities

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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) }),
]);
In Action!
Capabilities
LAB #13

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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);
}
}
}
In Action!
Capabilities
LAB #14

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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)
In Action!
Capabilities

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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);
}
In Action!
Capabilities
LAB #15

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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
In Action!
Capabilities

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File Handling API
1. Add the following property to your manifest (manifest.webmanifest):
"file_handlers": [{
"action": "/index.html",
"accept": {
"image/png": [".png"]
}
}]
In Action!
Capabilities
LAB #16

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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);
}
});
}
In Action!
Capabilities
LAB #16

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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.
about://apps
In Action!
Capabilities
LAB #16

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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
In Action!
Capabilities

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Progressive
Enhancement
In Action!
Agenda

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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
In Action!
Progressive Enhancement

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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)
In Action!
Progressive Enhancement

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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:

Open
In Action!
Progressive Enhancement LAB #17

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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
In Action!

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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.
In Action!

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Deployment
In Action!
Electron/Capacitor
JS
HTML
CSS
.ipa
.exe .app ELF
.apk .appx
Single-Page
Application
Capacitor
Electron

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(Simplified)
In Action!
Store Deployments
https://example.com
.appx
.apk
Server
Microsoft
Store
Play
Store
Source
Files

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Run app on your device
npm run pwa
https://ngrok.com/download
ngrok http 3000
In Action!
LAB #19

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Q&A
In Action!

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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!
In Action!
Summary

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Thank you
for your kind attention!
Christian Liebel
@christianliebel
[email protected]

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Cross-Plattform-Workshop: Progressive Web Apps mit Angular – in Action

Cross-Plattform-Workshop: Progressive Web Apps mit Angular – in Action

Christian Liebel
PRO

More Decks by Christian Liebel

Other Decks in Programming

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Transcript

Cross-Plattform-Workshop: Progressive Web Apps mit Angular – in Action

Cross-Plattform-Workshop: Progressive Web Apps mit Angular – in Action

Christian Liebel PRO

More Decks by Christian Liebel

Other Decks in Programming

Featured

Transcript

Christian Liebel
PRO