Notification portal documentation is confusing

[ilya-fedin]

I wanted to try to implement notification portal API in an application, but I got a lot of questions and I can't get how to use it properly.

1. I see icon parameter, but I see no image parameter. Does this mean I should just pass application icon and I can't (shouldn't) pass some image representing the content, like a user's avatar?
2. I see no way to set custom sound for a notification.
3. How can I set an icon for a notification button (like I used to with the FD.o standard)?
4. How can I set notification category?
5. How it gets what application shown the notification? I see no parameter for desktop file.
6. How can I know whether HTML is supported by notification daemon or not?
7. How can I know when the notification is closed in order to free all the data allocated for it?
8. What's default-action-target and target in buttons for?

For me the API seems like a fatal regression from the FD.o API, there are no even basic things that present in the latter, even though notification APIs on other OSes have a way more rich notification APIs like quick reply, text columns, selection menus, mutiple image types, notification grouping and etc, etc.

[ilya-fedin]

Personally I don't use persistence features, but I can imagine one lacks them, too.

[WhyNotHugo]

Regarding the first item, it seems you can just use icon to pass a custom image:

For bytes icons, the string is "bytes", and the value is a bytestring containing the icon data in png, jpeg or svg form.

[ilya-fedin]

I can, but should I? How much is this intended? Maybe it's invented for icons sent as data rather than any image?