Add the possibility to change some pdfjs preferences from the viewer (bug 1908483)

[calixteman]

No description provided.

[Snuffleupagus]

Would it not be more appropriate to restore (some of) the code removed in 1f9d1f3 instead?

[calixteman]

Would it not be more appropriate to restore (some of) the code removed in 1f9d1f3 instead?

I didn't know the removed code existed and I forgot I reviewed this patch...

With an allow-list, I've the feeling that my code is slightly better because the change in m-c is limited to pdf.js.
That said, I could add an allow-list too, to make sure we avoid a change for an unexpected pref.

EDIT: I'm mostly talking about my patch in m-c... I can updated this PR for using preferences stuff.

[calixteman]

@Snuffleupagus, I don't understand why we're writing all the prefs:

pdf.js/web/preferences.js

Lines 117 to 118 in 15b71b8

	const prefs = AppOptions.getAll(OptionKind.PREFERENCE);
	await this._writeToStorage(prefs);

I'd have expected to only write the changed ones, wdyt ?

[Snuffleupagus]

EDIT: I'm mostly talking about my patch in m-c... I can updated this PR for using preferences stuff.

Yes, for the viewer-side of things I believe it'd make sense to mostly revert that commit; however I think we can probably keep the reset-method disabled in MOZCENTRAL builds.

I'd have expected to only write the changed ones, wdyt ?

In the GENERIC viewer the prefs are stored as a string in localStorage, hence why all are written. (Perhaps we could special-case things for MOZCENTRAL builds, if that's helpful...)

[Snuffleupagus]

r=me, with https://github.com/mozilla/pdf.js/pull/18449/files#r1681726885 fixed; thank you.