Add and process reader view history entries

[csadilek]

After #2624 lands, we still need to add a history entry (about:reader...) when reader view is activated and add functionality to process it when navigating.

┆Issue is synchronized with this Jira Task

[csadilek]

We currently can't implement this without either new GV API or some web extension enhancements. Discussion continues in: https://bugzilla.mozilla.org/show_bug.cgi?id=1550144

[cpeterso]

We currently can't implement this without either new GV API or some web extension enhancements. Discussion continues in: https://bugzilla.mozilla.org/show_bug.cgi?id=1550144

@csadilek - snorp says you are working around this Reader View issue with an extension page. Is that correct or do you still need a new GV API or extension enhancements?

[csadilek]

@cpeterso Yes, using an extension page will improve reader view lot and also make navigation work. However, the link will be moz-extension://[id]/readerview.html?url= and not about:reader?url=. So, I wanted to leave that ticket open until I understand the implications of this for sync (desktop and fennec use about:reader). There's also a relevant discussion here about allowing to make those extension page URLs prettier but that seems to have stalled: https://bugzilla.mozilla.org/show_bug.cgi?id=1322304

[csadilek]

This is now also causing limitations in Fenix:

• Reader URLs can't be shared: [Bug] Incorrect URL when sharing page from the reader view fenix#11798 -- Fixed
• Cannot pin shortcut with reader mode: [Bug] Can't access shortcut sites from device's home screen when saved in reader mode fenix#11699

[mcarare]

Can / should this be fixed before release?

[csadilek]

@mcarare I think we can address the two Fenix issues by using the original URL instead, as you mentioned. We don't have to extract (or parse) it, as it's already available in the browser store via store.state.findTab(session.id)?.readerState.activeUrl. Example: https://github.com/mozilla-mobile/fenix/blob/fee09c3092d037315d4403cc98eabf3523a8e02c/app/src/main/java/org/mozilla/fenix/ext/Session.kt#L23

@agi90 and I talked through options how to implement support for about:reader, or URL mapping functionality for extensions in general. Theoretically, this can either be done in Gecko (https://bugzilla.mozilla.org/show_bug.cgi?id=1322304), GeckoView (https://bugzilla.mozilla.org/show_bug.cgi?id=1550144) or in A-C directly. I think we need to decide how to implement this first. So, we likely need the short-term fix above.

[csadilek]

@agi90 pointed me to protocol headers https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/protocol_handlers which should be able to provide what we want e.g. a ext+reader:// url.

For sharing in Fenix, we would still want to use the original URL, as the receiver might not have ext+reader.