Add support for "share_target" property

[tomayac]

Since according to @PaulKinlan's post Chrome started supporting the Web Share Target API (implementing the Draft Community Group Report 27 February 2018), and since no other than Twitter added the proposed syntax in their manifest, it might be a great point in time to consider adding the "share_target" property to the Web App Manifest spec. Here is the relevant extract of Twitter's manifest, showcasing the proposed syntax with the three URL placeholders {title}, {text}, and {url}:

"share_target": {
    "url_template": "compose/tweet?title={title}&text={text}&url={url}"
}

I reckon this is a bit of a 🐔 and 🥚 problem, as they both depend on each other. Happy to help with either.

[kenchris]

I believe Matt originally wrote this as an extension spec to Web App Manifest - but I wouldn't mind having it in the web app manifest spec itself

[kenchris]

https://wicg.github.io/web-share-target/#extension-to-the-web-app-manifest

[tomayac]

Yepp, it feels more "at home" in the Web App Manifest spec.

[kenchris]

I really hope we can get people from Microsoft involved with this @boyofgreen @patrickkettner @kirupa

[tomayac]

I'd say $MSFT are pretty invested here 👏: https://www.windowsobserver.com/2018/04/11/twitter-pwa-on-windows-10-now-a-share-target/

[kenchris]

TAG review yielded some new suggestions: w3ctag/design-reviews#221 (comment)

[kenchris]

Some comments from MS @boyofgreen https://twitter.com/boyofgreen/status/986075414685626368?s=20

we find a number of scenerios where launch events make a lot of sense. We can tell you how you were luanched (from a tile or from a toast or from another app), payload, etc. it would be messy to put that all in the URI

[mgiuca]

I only just saw this. (Lots of people have been @-mentioned in this thread but not me #sad).

This was always intended to be incorporated into the manifest spec once complete, but it isn't finalized yet. I didn't want to work in a branch off the manifest spec so I created a separate repo.

it might be a great point in time to consider adding the "share_target" property to the Web App Manifest spec

Note that the TAG review is ongoing and major changes to the syntax are being proposed. The API is not available in Chrome Stable (only on Dev and Canary channel on Android). We are not ready to land this in any spec that is being implemented by real browsers. Please keep discussion of this on the WICG issue tracker for web-share-target: https://github.com/WICG/web-share-target/issues

[tomayac]

SGTM, closing the issue for now.

[mgiuca]

I think it's helpful to keep this open as a top-level tracking issue for the Manifest standard to incorporate WST once that goes ahead. Re-opening for now, but still, discuss details on the WST issue tracker.