msglist: Have content pad bottom inset when the compose box isn't shown

[chrisbobbe]

This takes advantage of some of StickyHeaderListView's default behavior (inherited from ListView). From the doc on ListView:

https://api.flutter.dev/flutter/widgets/ListView-class.html

By default, ListView will automatically pad the list's scrollable
extremities to avoid partial obstructions indicated by
MediaQuery's padding. To avoid this behavior, override with a zero
padding property.

The code changes here are just to arrange for that default behavior to help us out: we let the real height of the bottom inset propagate down to the StickyHeaderListView, with the MediaQuery mechanism.

Fixes: #263

[chrisbobbe]

Before	After

[chrisbobbe]

Also, the layout is unchanged when the compose box is shown:

Before	After

[gnprice]

Thanks for this fix! This had been bugging me occasionally before the mark-as-read button, too.

Does #263 correspond to what this fixes?

One small code comment below.

[gnprice]

Suggested change

	removeBottom: widget.narrow != const AllMessagesNarrow(),
	removeBottom: widget.narrow is! AllMessagesNarrow,

Because we override ==, the two forms are actually exactly equivalent. But the is form is what appears in the ComposeBox logic, and I think is also the right conceptual framing of it. (For example if we somehow had two variants of AllMessagesNarrow — perhaps a boolean for whether to exclude muted? — then they'd still presumably both skip the compose box.)

[chrisbobbe]

Makes sense.

[chrisbobbe]

(For example if we somehow had two variants of AllMessagesNarrow — perhaps a boolean for whether to exclude muted? — then they'd still presumably both skip the compose box.)

Yeah. Incidentally, I've become a little wary that AllMessagesNarrow might not always mean what we think it means. Here's its dartdoc:

/// The narrow called "All messages" in the UI.
///
/// This does not literally mean all messages, or even all messages
/// that the user has access to: in particular it excludes muted streams
/// and topics.

And yet:

1. Doesn't the "All messages" message list include even muted messages?
2. When we .apiEncode() this narrow and send it to the server for mark-all-as-read, it's taken to mean all messages, including muted ones.

[gnprice]

1. Doesn't the "All messages" message list include even muted messages?

It does, but that's because we haven't implemented muting yet. When we implement #346, one piece of it is to have the muting control

which messages are shown in stream narrows and the all-messages narrow.

2. When we .apiEncode() this narrow and send it to the server for mark-all-as-read, it's taken to mean all messages, including muted ones.

Hmm true. And that's intended behavior: it's the same as the specialized endpoint https://zulip.com/api/mark-all-as-read does, and the same as the web UI does.

So possibly the better way to conceptualize this narrow (vs. what the quoted doc comment says) is that the narrow does include muted messages, but the message list only shows a subset of the messages in the narrow, namely those that aren't muted.

I'll think more about that when I take up #346.

[chrisbobbe]

It does, but that's because we haven't implemented muting yet.

Huh, TIL (or today I reminded myself) that zulip-mobile's "All messages" view also seems to filter out messages in muted conversations. 😅 (I almost never use that view myself.)

[chrisbobbe]

Does #263 correspond to what this fixes?

…Er, now it does! 😂 Thanks for making that connection! Revision pushed.

Updated to get the scroll-to-bottom button out of the inset, and to add TODOs about how we'd do things differently if we do a bottom nav, which would pad the bottom inset. Quoting myself from #263:

This will be naturally solved if we put some surface down there that pads the bottom inset, with the message list abutting that surface in the y-direction. That surface is likely to be the bottom nav bar in Vlad's design, I think.

[gnprice]

Ah yes, I see.

[gnprice]

Great, thanks! Looks good; merging.