Open matrix.to link in existing browser tab I already have open with Element

[MadLittleMods]

Issue originally opened at https://github.com/matrix-org/matrix.to/issues/198

Is your feature request related to a problem? Please describe.

When I go through the matrix.to link flow for a permalink, it asks me whether I want to continue via browser or desktop app. I use Element in my browser and already have a tab open. When I press Continue in browser, it opens yet another tab of Element to show the message.

Describe the solution you'd like

Open the permalink in my existing tab of Element instead of a new one which takes forever to load.

When Matrix.to sends you off to app.element.io, we could use some of the cross-tab communication in browsers and have a script run at the very beginning of page-load which would communicate the permalink location to the other tab instance and close itself.

Describe alternatives you've considered

Copy paste the permalink and use the /goto https://matrix.to/#/!xxx:matrix.org/$oIfQnLVKFwRE_Rme0Z5AvqzaYvHTuTtxqBYnnbR1yN8 slash command in your Element instance.

Or just use the desktop app which will always point to one instance.

Dev notes

There are multiple ways we can communicate but I was thinking of using broadcast channels. Here is a nice concise video where I was introduced to it: https://www.youtube.com/watch?v=kBut8LqVgYE. To be clear, I was thinking of doing the communication on the app.element.io side. Matrix.to -> New app.element.io page that posts to the broadcast channel (BC) right when it starts up(before the main app loads at all) of where we need to go and closes -> my existing Element tab picks up that information from the BC goes to the place.

Other ways from a quick Google: https://blog.bitsrc.io/4-ways-to-communicate-across-browser-tabs-in-realtime-e4f5f6cbedca

[MadLittleMods]

Related to MSC1716

[t3chguy]

The proposed approach is likely going to be made redundant via the matrix:// scheme handler https://developer.mozilla.org/en-US/docs/Web/API/Navigator/registerProtocolHandler

[bkil]

Related #16393