@netless/app-pdfjs
v0.1.5
Published
Netless App for viewing raw PDF files, using PDF.js
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@netless/app-pdfjs
A Netless App that renders PDF files with PDF.js.
Install
Usage
[!IMPORTANT] This app only implements viewing PDF files.
It does not supportdispatchDocsEvent()
nor export PDF.
Get a static URL pointing to the PDF file.
This package only synces the URL for each client to download the PDF. You have to obtain a static URL to the file first to continue. For example, you can use an OSS to achieve this.
Convert this PDF file using the Agora File Conversion service. Remember to set
outputFormat: "qpdf"
.You will get a
taskId
andprefix
URL in the response of Query Task Status API.Register this app before joinning room.
import { register } from "@netless/fastboard" import { install } from "@netless/app-pdfjs" install(register, options) // the app is named 'PDFjs'
Add this app after joinning room.
fastboard.manager.addApp({ kind: 'PDFjs', options: { title: 'a.pdf', // ! Required for window title. scenePath: '/pdf/paper' // ! Required for displaying whiteboard on it. }, attributes: { prefix, // ! Required. taskId, // ! Required. } })
- Make sure
scenePath
starts with/
and not ends with/
. - The
prefix
will be like"https://white-cover.oss-cn-hangzhou.aliyuncs.com/flat/"
. - The
taskId
will be like"b444a180c2f44a409a4d081e8f1a6d5f"
.
You can get the
prefix
andtaskId
from the conversion response JSON.- Make sure
Troubleshooting
Failed to fetch pdf.min.mjs
This package downloads the latest PDF.js release from jsDelivr:
https://cdn.jsdelivr.net/npm/pdfjs-dist@latest/build/
To alter this URL or choose a different version, set the app option:
install(register, {
appOptions: {
pdfjsLib: 'https://cdn.jsdelivr.net/npm/pdfjs-dist@latest/build/pdf.min.mjs',
workerSrc: 'https://cdn.jsdelivr.net/npm/pdfjs-dist@latest/build/pdf.worker.min.mjs'
}
})
If the URL is blocked by your CSP,
you have to add them to your script-src
policy:
Content-Security-Policy: script-src https://cdn.jsdelivr.net/
Note: If you want to load PDFs on demand (without having to download the entire PDF before rendering), you need to expose the 'Accept-Ranges' headers on your stored OSS. If our library cannot obtain this header, it will not make segmented requests.
TypeError: Promise.withResolvers is not a function
PDF.js uses Promise.withResolvers()
, which is a brand new feature in JavaScript.
In case your target environment does not support this, you need to add the following code to the first line of
pdf.min.mjs
and pdf.worker.min.mjs
to resolve this issue.
if (typeof Promise.withResolvers === 'undefined') {
Promise.withResolvers = function () {
let resolve, reject
const promise = new Promise((res, rej) => {
resolve = res
reject = rej
})
return { promise, resolve, reject }
}
}
For convenience, you can run node ./scripts/patch.mjs
in this repo to generate patched pdf.min.mjs
and pdf.worker.min.mjs
.
The 2 files will be placed at the dist
folder.
Uncaught SyntaxError / Uncaught ReferenceError
This package only targets modern browsers that support native ES modules.
A certain PDF file opens exceptionally slowly, even several times slower than smaller PDFs.
Most PDF files are designed for easy transmission, allowing us to render a single page by requesting a portion of the file through Range requests. However, a few PDF files require a complete download before they can be rendered. You can check the browser's requests to confirm if the slow rendering of the first page is due to the complete download of a PDF file. If so, you need to use qpdf to convert the PDF into a structure that is easier to transmit.
What should I do if the OSS I entered in the Agora Console
is private?
You can add a new property urlInterrupter to the second parameter options when calling register. This property is a function that returns a publicly accessible address by passing in the URL.
PDF Rendering Issue
As the package name implies, it uses PDF.js to render the file. It is possible that PDF.js has a bug when rendering some files. Please raise an issue there to ask for help.
Changelog
License
MIT @ netless