msglist: Use directional positioning for unread marker in RTL

[yash-agarwa-l]

Fixes #1245

This PR corrects the unread-marker alignment in RTL layouts.

Problem:
_UnreadMarker used LTR-specific properties (left: 0, Border(left: …)), causing the unread marker to always appear on the left, even for RTL languages like Arabic.

Fix
Therefore Replaced LTR-specific properties with directional equivalents:
PositionedDirectional(start: 0)
BorderDirectional(start: BorderSide(...))

This ensures the unread marker appears on the correct “start” side based on text direction.

Manually tested by setting:
locale: Locale('ar')

Verified correct behavior in both LTR and RTL layouts (screenshots included).

Before

LTR

RTL

After

LTR

RTL

[chrisbobbe]

Thanks! Small comments below.

Also:

• Please say Fixes #1245. in the commit message. For examples, use Greg's "secret" to using git log -p.
• Please also post screenshots of what it looks like before this change, so we can see clearly the improvement being made. 🙂

[chrisbobbe]

Same here.

[chrisbobbe]

This code-style change is unrelated and unhelpful; please remove it.

[yash-agarwa-l]

Thank you for the feedback.
I’ve cleaned up the commit and added the before screenshots as requested.
Please let me know if there’s anything else I should adjust.

[chrisbobbe]

Bump on this part:

• Please say Fixes #1245. in the commit message. For examples, use Greg's "secret" to using git log -p.

[yash-agarwa-l]

Thank You, I've updated the commit and pushed the revision.

[chrisbobbe]

Please write it according to the project style; the Fixes #1245. line belongs in the commit-message body, not in the summary line.

[yash-agarwa-l]

Thanks for the clarification, updated.

[chrisbobbe]

Thanks! Marked for Greg's review.

[gnprice]

Thanks @yash-agarwa-l for taking care of this, and thanks @chrisbobbe for the previous reviews!

Those before/after screenshots in particular are very helpful, thanks. It's especially helpful that they're very clean — the before and after differ only in the one way that's relevant.

This looks good; merging. One commit-message nit which I'll fix up:

-    msglist: Use directional positioning for unread marker in RTL.
+    msglist: Use directional positioning for unread marker in RTL

In this repo we don't use a trailing period on the summary line of a commit message.

[gnprice]

I also just did a quick audit with git grep left: and git grep right: to look for other similar places to be fixed. (More precisely: git grep -iP 'left:|right:' lib/. Some matches for that query treat left and right symmetrically already, so those are fine.)

I found 4 of them:

• The formatting on block quotations (the Quotation widget).

• The display of images and video thumbnails in the message list. That's the MessageMediaContainer, here:

      child: UnconstrainedBox(
        alignment: Alignment.centerLeft,
        child: Padding(
          // TODO clean up this padding by imitating web less precisely;
          //   in particular, avoid adding loose whitespace at end of message.
          padding: const EdgeInsets.only(right: 5, bottom: 5),

• In ReactionButtons, there are two references to BorderRadius.only which use topLeft and topRight respectively. I suspect those are wrong in RTL locales.

• We have an icon chevron_right. Probably each place that's used is an example of this bug. … I guess this one is tracked as RTL: Flip directional icons, like chevron_right and send, in RTL mode #1907.

@yash-agarwa-l if you're looking for more issues to work on for contributing to Zulip, I think those would be a good list to pick up while this area is fresh in your mind from doing this issue.

I'd suggest going in the order listed above — the quotes in particular I would guess look pretty wrong right now. And then a key element in a PR for any of these will be to post good before/after screenshots that clearly show the change, just like you did on this PR.

[yash-agarwa-l]

Thanks so much for the review, the merge, and especially for auditing the code for these related RTL issues!

I'm really happy contributing to Zulip. I'll start working through that list, beginning with the block quotations (Quotation widget), and will keep all your feedback in mind for the new PR.