Allow to set the subject

[Hocuri]

• [x] Add an API to Core to set the subject of a message #4057
• [x] Add an API to Core to get the subject of a message
• [ ] Experiment with it in the UI (esp. how does the user access the subject text-input line: adding a menu option / long-tap on the send button / long-tap on the input field / somehow make it accessible via the attachment menu)
• [ ] Decide whether and how we want to show the subject in incoming messages, and find a way to technically do it (maybe with an extra header, a flag on the Chat-Version header, or an invisible character in the subject - note that the latter could break classical email bots)
  • [ ] Maybe the subject should then also be shown in bold in the UIs
• [ ] Handle a mailto: with a subject line in the UIs, e.g. mailto:noreply@example.org?subject=unsubscribe

[hpk42]

long-tap on send button i am skeptical about -- how about long tap in input field?

[Hocuri]

On my phone, when I long-tap in the input field, I get the possibility to "paste" from clipboard (that's a feature not by Delta Chat, but by the system), and I regularly use this. Would seem weird to me if something else happens when pasting from the clipboard.

Prior art: Signal and Telegram allows you to "send later" when you long-tap on the send button since the latest update, which also falls under 'extra options about sending'. (TG also allows you to 'send without sound' there)

I still added it as a possibility to the issue description.

[iequidoo]

Long tap on the "send" button isn't good for anything because if it accidently not long enough then bad things happen. Maybe we can use the "add attachment" button for "attaching" the subject? So that the subject line appears above the message field (like in K-9 Mail) and it gets the current subject content available for editing.

Btw, i don't like that the "add attachment" button disappears (on Android) when i start typing a message and then i should go the menu above the chat to add an attachment if i forgot to. Better if this button would remain in its place as on Desktop. See WhatsApp f.e. And in general, more or less unified UI on different platforms would be good (and this is another "against" to long taps).

EDIT: Maybe i'm wrong about unifying long taps with Desktop -- the right click is an analogy, but anyway i'd prefer the "send" button to be for sending-related things (as in Telegram f.e.), not for setting subject. Half-written mails sent isn't a good thing. Moreover, if a user wants to set subject, it may be a business correspondence.

[Septias]

I don't think many people will accidentally not press long enough if they intend to open the advanced send menu. There is not much that can go wrong when you are only waiting for the ui-change.

[r10s]

nb, offtopic: we recently got praise for the disappearing attach button:

by the changed flow it does not happen in practise to forget adding an attachment refered to in the text

things are rarely simple :)

[iequidoo]

Decide whether and how we want to show the subject in incoming messages, and find a way to technically do it (maybe with an extra header, a flag on the Chat-Version header, or an invisible character in the subject - note that the latter could break classical email bots)

Now it can be seen in "Message Details", so i think there's no need to show it in all messages. But if it's changed, maybe show a system message "Subject changed to ... by ..."? EDIT: And also change the chat name of course (with stripped "Re: "?)