pdf.js: PDFs with form fields crash in Safari

The following PDFs from the test/pdfs/ directory crash the viewer in Safari:

test/pdfs/160F-2019.pdf
test/pdfs/annotation-text-widget.pdf
test/pdfs/issue12963.pdf
test/pdfs/issue6127.pdf
test/pdfs/prefilled_f1040.pdf

Affected version

Commit: a17bd1302
Date: 2021-07-13

pdfjs.config:

  {
    "betaVersion": "2.9.359",
    "stableVersion": "2.8.335",
    "baseVersion": "e667c8cbcf8a8368dfab5eccb6b6f7999f1ae275",
    "versionPrefix": "2.10."
  }

Affected platforms

Safari on the following OS’s:

MacOS 11.4 Big Sur (Safari 14.1.1)
iPadOS 14.6
iOS 14.6

Steps to reproduce

Install and then run web server:

 $ git clone https://github.com/mozilla/pdf.js.git
 $ cd pdf.js
 $ npm install
 $ gulp server

Open http://localhost:8888/test/pdfs/?frame in Safari.
Click on top link in list, for 160F-2019.pdf

Expected result

File 160F-2019.pdf is rendered correctly.

Actual result

The web page crashes with the error:

A problem repeatedly occurred with "localhost:8888/test/pdfs/?frame"

There are no errors logged in the JavaScript console.

Additional notes

Here is a .gif showing the issue:
These PDFs load properly and also have (some) form fields:
- test/pdfs/annotation-tx.pdf
- test/pdfs/annotation-tx2.pdf
- test/pdfs/annotation-tx3.pdf
- test/pdfs/bug1669099.pdf
- test/pdfs/doc_actions.pdf
- test/pdfs/evaljs.pdf
- test/pdfs/issue12504.pdf
- test/pdfs/issue12706.pdf
- test/pdfs/issue12750.pdf
- test/pdfs/issue13269.pdf
- test/pdfs/issue13271.pdf
- test/pdfs/issue9972-1.pdf
- test/pdfs/issue9972-2.pdf
- test/pdfs/issue9972-3.pdf
- test/pdfs/js-authors.pdf
- test/pdfs/js-buttons.pdf
- test/pdfs/js-colors.pdf
- test/pdfs/listbox_actions.pdf
- test/pdfs/pr12828.pdf

About this issue

Original URL
State: closed
Created 3 years ago
Comments: 15 (2 by maintainers)

Most upvoted comments

I tracked down the cause of the crash to this line:

https://github.com/mozilla/pdf.js/blob/51f0a810851c311598748f637fb583b20b7dce03/src/display/annotation_layer.js#L900

The following PDFs from the test/pdfs/ directory will no longer crash the viewer in Safari with that line commented out (although letter spacing is now messed up in certain cases):

test/pdfs/160F-2019.pdf
test/pdfs/annotation-text-widget.pdf
test/pdfs/issue12963.pdf
test/pdfs/issue6127.pdf
test/pdfs/prefilled_f1040.pdf

It seems that Safari’s CSS calc function can’t handle ch units in letter-spacing.

I created a minimum test for this, in case anyone with access to Safari wants to try it out:

<!doctype html>
<html>
    <head>
        <title>CSS calc() with ch units</title>
        <style>
         #fail {letter-spacing: calc(1ch);}
        </style>
    </head>
    <body>
        <h1 id="fail">This will cause a crash</h1>
    </body>
</html>

I installed the Safari Technology Preview for Big Sur from here: https://developer.apple.com/safari/download/ and the bug is fixed there. For reference, I think this WebKit bug report and patch might be related to the crashing behavior:

I have no idea when Safari will actually see this fix. In the meantime, the crashing behavior is present across MacOS, iOS and iPadOS.

jhacksworth on Jul 24, 2021

Given https://github.com/mozilla/pdf.js/issues/13726#issuecomment-929517624 let’s close this issue here, since:

This was clearly a browser bug, which has now been fixed. Given that a single line of very simple CSS was enough to “crash” the browser, you’d really hope that previous versions of Safari will be patched as well.
Historically, in the PDF.js project, we’ve always been reluctant to add browser-specific compatibility hacks in the main code-base for reasons of readability/maintainability/performance.
This only affects a small number of PDF documents, when Safari is used, since the document needs to contain forms and also have “comb”-fields.

Snuffleupagus on Sep 29, 2021

I have no idea when Safari will actually see this fix. In the meantime, the crashing behavior is present across MacOS, iOS and iPadOS.

I can confirm that the CSS bug is now fixed in Safari 15 on:

macOS (available for Big Sur & Catalina)
iPadOS 15
iOS 15

I put up a page for people to easily check if their browser version has this bug:

https://jhacksworth.github.io/safari-css-bug-test.html

That page won’t load properly for browser versions with the bug.

jhacksworth on Sep 28, 2021

Can’t we just replace 1ch by 0.5em ? (see https://developer.mozilla.org/en-US/docs/Web/CSS/length#ch)

calixteman on Jul 26, 2021