Found in

• Beta 105.0b3

Affected versions

• Release 104.0
• Beta 105.0b3
• Nightly 106.0a1

Tested platforms

• Affected platforms: Windows 10 x64, macOS 11
• Unaffected platforms: Ubuntu 20.04 x64

Steps to reproduce

1. Launch Firefox.
2. Navigate to http://www.pdf995.com/samples/pdf.pdf.
3. Enter into presentation mode, and start scrolling via space bar, page up/down or home/end keys from the keyboard.

Expected result

• The scrolling is working in every case.

Actual result

• The scrolling is not working at all.

Regression range

• This seems to be a regression as I cannot reproduce the problem on Release 103.0. I'll investigate further in order to find a regression range.

mozregression gives the following pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=5da16396fa22b03b190b7d87f597ab11fa810b1d&tochange=cfcf61dedb350b96952a742d0466de479c17aa4e

Setting dom.fullscreen.modal = false in about:config also "fixes" things, which thus confirms the regressing bug found above.

Note that the PDF Viewer uses "keydown" events to handle page-switching in Fullscreen-mode, and it appears that those events are no longer being dispatched after bug 1771150.
:emilio, can you please help out here?

Set release status flags based on info from the regressing bug 1771150

When entering in fullscreen mode in using the button, this one is "stealing" the focus, hence a way to fix this issue is to add an evt.preventDefault():
https://github.com/mozilla/pdf.js/blob/76f665d57fab7da08445a56c1b36fd746887ee75/web/toolbar.js#L158
but in a mousedown listener.

(In reply to Calixte Denizet (:calixte) from comment #3)

When entering in fullscreen mode in using the button, this one is "stealing" the focus, hence a way to fix this issue is to add an evt.preventDefault():
https://github.com/mozilla/pdf.js/blob/76f665d57fab7da08445a56c1b36fd746887ee75/web/toolbar.js#L158
but in a mousedown listener.

If in the end we need to work-around this on the PDF.js side of things, which isn't entirely clear to me (hopefully Emilio can chime in here), then a much smaller/simpler way to fix this would probably be to have the PresentationMode-code invoke this method instead.

Yeah, so this is technically bug 1740989 (we should blur the element when it becomes non-focusable). I took a quick look and it seems https://github.com/whatwg/html/issues/8225 would be great to get sorted out at least before implementing that.

The workaround being trivial seems worth landing / uplifting for now tho. Can anyone test Safari? My understanding is that they don't implement this either and should behave the same way we do...

Backport of upstream commit:
https://github.com/mozilla/pdf.js/pull/15355

The patch landed in nightly and beta is affected.
:Snuffleupagus, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox105 to wontfix.

For more information, please visit auto_nag documentation.

A patch has been attached on this bug, which was already closed. Filing a separate bug will ensure better tracking. If this was not by mistake and further action is needed, please alert the appropriate party. (Or: if the patch doesn't change behavior -- e.g. landing a test case, or fixing a typo -- then feel free to disregard this message)

Comment on attachment 9292765 [details]
Bug 1787456 - Always focus the viewerContainer when entering PresentationMode. r?#release-managers!

Beta/Release Uplift Approval Request

• User impact if declined: Keyboard scrolling is broken in PresentationMode in the PDF Viewer.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: Please see https://bugzilla.mozilla.org/show_bug.cgi?id=1787456#c0
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): It's a single line of added JS-code, inside of a try-catch block. The function being called is also used elsewhere in the PDF Viewer and has existed for many years.
• String changes made/needed: N/A
• Is Android affected?: No

Comment on attachment 9292765 [details]
Bug 1787456 - Always focus the viewerContainer when entering PresentationMode. r?#release-managers!

Approved for 105.0b7.

https://hg.mozilla.org/releases/mozilla-beta/rev/fafbc87cd7a4

Verified as fixed in Beta 105.0b7 and our latest Nightly build 106.0a1 (2022-09-04) on both platforms.