Add support for OSC777 - send notification

[zadjii-msft]

This adds support for the OSC 777 ; notify ; title ; body ST sequence. This allows client applications to send a notification to the Terminal. When this notification is clicked, it summons the terminal window that sent it.

This can be used in PowerShell as follows:

Write-Output "`e]777;notify;Hello From the Terminal;This is a notification sent by the client application`a"
 
# but do it with a sleep, because notifications while the Terminal is the FG window won't do anything
sleep 2; write-Output "`e]777;notify;Hello From the Terminal;This is a notification sent by the client </text><text>application`a"

• closes Send Desktop Notification via VT Sequence (OSC777) #7718
• gifs in that thread

other details

• The notification is only sent if the tab is inactive, or the window is inactive.
• When a user clicks on a notification, it launches a new windowsterminal.exe. So we've got to be able to send a notification to the existing window, WITHOUT registering as the monarch. That's what WindowManager::SummonForNotification is all about.
• Future places we could use this:
  • Notification after a long running command finishes #6372
  • terminal activity indicator/alert when in background #7955

todo

• Elevated?
  • see Add support for OSC777 - send notification #14425 (comment)
  • This plain-old isn't possible.
• Unpackaged?
  • same as elevated, we're just ignoring this for now.

  • Do not use this overload when creating a toast notifier for a desktop app. Use CreateToastNotifier(appID) to supply the required AppUserModelID.

• XML injection?
  • Looks like they handled this for us
    
• Doesn't work on Windows 10? Add support for OSC777 - send notification #14425 (comment)

[lhecker]

Our notification system uses full blown XML instead of data transfer objects?
...and instead of making it use structured data we added a AppNotifications.Builder that still spits out XML?

[zadjii-msft]

Lemme tell you, it's a disaster. At least the sample has like, 25% c++winrt code these days. The original sample was "Well, the API it hard to use, so go get this third party nuget package, and do some C#" 🤦

[WSLUser]

Is there going to be an optional WinToast notification as well users can set in settings.json or Settings UI (Similar to BEL where we could have visual, audio or both) where here we have "only within the Terminal, only in the Action Center or both"?)

[zadjii-msft]

Is there going to be an optional WinToast notification as well users can set in settings.json or Settings UI (Similar to BEL where we could have visual, audio or both) where here we have "only within the Terminal, only in the Action Center or both"?)

I'd reckon probably not. Toasts have been harder to do right in the Terminal than it's been worth (see #8592).

[WSLUser]

The issue you linked sounds a bit different than the guide I provided within 7718 (which this PR would close) but maybe they're the same thing.

[zadjii-msft]

@WSLUser You linked to https://learn.microsoft.com/en-us/windows/apps/design/shell/tiles-and-notifications/scheduled-toast in #7718, which looks like a guide around using a C# wrapper around the same toast notification APIs I'm using here. Windows apparently just calls all these notifications "toast notifications", which kinda muddies the water when comparing to something like Android (where Toasts and Notifications are two very different concepts).

[zadjii-msft]

Elevated?

Oh hey, this is a problem. We might have to disable this entirely for elevated instances.

The notification is obviously running unelevated. When it calls back to our app, you guessed it, it calls into the unelevated instance. We can't trivially have a notification call back to an elevated instance. We'd need to have the unelevated ActivatedEventArgs handler take the args, then use them to invoke an elevated wt.exe with some commandline to try and summon the window. Something like wt summon -w {id} ala #13276. That's obviously a long way off - I'm just gonna disable this when elevated for now.

[zadjii-msft]

Note to self - pushed a merge of this with main to dev/migrie/fhl/7718-notifications-reboot. Still need to re-plumb the notification actually activating the window, but we're close. I'll merge that into here after I do that.

[zadjii-msft]

Further notes from 4ab628d:

• Testing this while debugging will not work. If you have a debugger attached to a process, Windows DNGAF about the FG rules and lets the terminal come to the FG. Without the debugger, this pretty much never works. At least, not on 26051.1000.amd64fre.ge_release_we_adept.240201-1823
• Test case: sleep 2; write-Output "`e]777..., then minimize, then click another app, then click the notification
  • Terminal gets restored, and activated, but not brought to FG or the top
  • When I ask what the FG window is, it's a "New notification" window from ShellExperienceHost. NOT the Terminal
  • I tried AllowSetForeground(monarch.GetPID()) but that did nothing, and the HR was E_ACCESSDENIED
  • I tried to create a message window in the emperor of the toast wt.exe, but that didn't give us FG

Does this just... not work ever?

[zadjii-msft]

At this point, I'm very tempted to stick this behind velocity and only enable for Dev & Canary builds, while we sort out the foreground issues

[DHowett]

I'm very on the fence about this, even checked in behind velocity.

• It doesn't work for unpackaged builds (it requires package identity)
• It's broken if Terminal isn't the foreground application, since it can't activate us
  • Much of the utility of notifications is that they bring you to the thing that notified you
• It doesn't work on Windows 10 ??
• It doesn't work when you're elevated?
• In the limited cases where it actually does work, it allows a text-mode application to spam users with system-wide toasts
  • However, there's no possible "action" response, so they can't gate actual complicated and meaningful features behind notifications (e.g. to perform a thing on click, or to receive a text response)

Frankly, I still don't see the value in offering this support! 😄

[DHowett]

(Stake in the ground)

[zadjii-msft]

• lemme look into this more. There's surely got to be other ways of doing this unpackaged, or this would be a good thing to send to our WASDK friends
• LMAO we have just discovered that this is a platform issue. We'll get that fixed internally. I don't think that's a reason to prevent it from merging.
• Almost certainly the same as the above
• I have an i d e a here which I'll be excited to talk about tomorrow
• Yep. That's... kinda the whole point. I believe semantically, the idea is to be used for after a long-running command completes. I wouldn't be opposed to a per-profile disableNotifications setting or something, for more granular control than just Windows Settings
  • The original spec doesn't support actions, it literally just sends a message. There's no existing spec for "send a notification with buttons", this was just supposed to implement the existing osc777.

fite-me.emoji

[DHowett]

we can come back to this if we ever want it

[zadjii-msft]

(there's more discussion over at #20012, but this is just the start of working on it, we'd be open to more feature requests and contributions once that merges 😉)