Document `get_chat_securejoin_qr_code()`, `check_qr()`, `set_config_from_qr()` (particularly, QR code withdrawal)

[milad2golnia]

Hello,

I am building automation around Delta Chat broadcast channels using the core library and/or RPC server, and I need to reset/revoke SecureJoin invite links programmatically.

In the official Delta Chat clients (deltachat android application), there is a “Reset QR Code” button in channel settings. When this is used:

• a new SecureJoin QR/link is generated
• previous invite links stop working

However, when using the core programmatically, I can only find the method:

get_chat_securejoin_qr_code(account_id, chat_id)

This generates a the same QR code every time and does not revoke previously generated invites.

Questions

1. Is there an RPC method that exposes this functionality?
2. If not, would it be possible to expose such a method in deltachat-rpc-server?

Use Case

I am implementing automated invite management for channels, I want to reset SecureJoin QR/Links automatically so that publicly exposed links don't work anymore. I need to:

• rotate invite links
• revoke previously shared links
• generate a new SecureJoin QR

Expected API (example)

Something like:

resetSecurejoinQr(chat_id)

or

rotateSecurejoinToken(chat_id)

which would invalidate all previously generated invite links.

Thanks for your work on Delta Chat and the core library!

[iequidoo]

You should use check_qr() which is undocumented however. If you pass an existing QR code to it, and the QR code is still "alive", the function will return another one which you can use to withdraw/revoke the passed QR code, you should use set_config_from_qr() to do that. If the QR code is already withdrawn, check_qr() returns another one which you can use to "revive" the passed QR code, again, using set_config_from_qr(). This issue should be closed after documenting these functions.

[r10s]

You should use check_qr() which is undocumented however.

it is documented at cffi documentation

(jsonrpc documentation is worse than cffi in general still, however, many function names are identical so cffi is often helpful)

[iequidoo]

CFFI docs also should be improved, dc_get_securejoin_qr() tells what the scanning device can do with the QR code, but it doesn't tell what the issuer device can do, i.e. withdraw/revive it. I.e. docs mention dc_check_qr() only in the context of "scanning device".