List of topics in channel

[gnprice]

In the legacy app, if you're looking at the messages in a topic, we have a button in the app bar (a "list" icon) that gets you a list of all the topics in that channel. It's sorted by recency, and shows the number of unreads, whether you have an @-mention, and whether the topic is muted etc.

Basically it's similar to what you get in the web left sidebar after hitting "Show all topics" under a given channel.

We should offer the same thing in the new app. I wasn't sure people really use that feature; but it came up in user feedback after yesterday's beta announcement, so that's a sign that people do.

Design

Design is in Figma:
https://www.figma.com/design/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?node-id=6819-35869&m=dev

For this issue, differences from the design there:

• The design shows a "pinned topics" feature, which is a possible future Zulip feature but doesn't currently exist. Pending that feature, we'll leave out the "pinned" icon, and avoid using up horizontal space for it.
• For this first version, let's leave out the "filter" feature. I'll file a post-launch followup issue for that. → Filter topics in topic-list screen #1384
• For this issue, we'll leave out the "New topic" button and the modal it leads to. I'll file a separate, post-launch issue for that. → "New topic" modal from list of topics in channel #1385

Implementation

The list of topics will come from making a request to the server, after opening the page.

As a follow-up task, after getting the list for a given channel we might store it (on ChannelStore), and keep it up to date when handling events, so that coming back a second time to this topic-list page for a given channel is fast. For this PR, though, that's out of scope. Instead the list of topics can just live on a StatefulWidget for the page.

References

• Design thread: #mobile-design > Topic list in channel
• A different feature serving some of the same use cases: Show topics on channels page #412

[chrisbobbe]

Tim and others propose featuring this page more prominently than the interleaved channel view:

Tim said:

I've never been happy with the legacy app's approach of having the channel feed be what clicking on a channel takes you to by default. We've been moving towards it being a secondary action on channels in the web app, and I think it'd be wise to just make the default click be the list of topics, and channel feed be the thing that's a smaller tap target button.

[chrisbobbe]

And another long-time Zulip user said:

In the old app, opening a channel from the channel view shows a feed of all the messages in the channel, but it has a button in the upper right that looks like a list, which opens a view of all topics with a single line for each topic.

In the new app, there doesn't seem to be any way to show all the topics in a channel without showing the messages within those topics.

(In an ideal world, that would be the default view I get when opening a channel.)

[chrisbobbe]

Another user said:

[…] it feels unnatural to always browse all messages in all topics. Topics can be really long like folks talking about Haiku operating system.

And browsing all of them to cherry pick something is also a pain.

[chrisbobbe]

From a review in the Google Play Console:

It is nice, but the absence of a search bar (at least to search for topics) makes it frustrating to use.

I assume we'll want this list of topics to be searchable, like in zulip-mobile.