☂️ Upstream Flutter issues affecting Zulip

[gnprice]

This tracking issue collects notes on potential work in Flutter upstream that would benefit the (new) Zulip mobile app. See also:

• ☂️ Upstream Dart issues affecting Zulip #1079

Some of these are much more important to us than others. They're organized by where the work would happen, not by importance.

Many of these have corresponding issues in our tracker with the "upstream" label. Conversely, all issues with that label should appear either below or in the sibling issue #1079.

Framework

• WidgetSpan double-applies text scaling: Global text scaling shouldn't be automatically applied on WidgetSpans as scale transforms flutter/flutter#126962
  In Zulip the main symptom is on @-mentions: content: @-mentions and global times are scaled too much by system text-size setting #735
  Especially affects a11y, at large font size: one @-mention can easily occupy 1/3 of the screen.

• (TODO upstream issue)
  RawAutocomplete should gain a "controller" for customizability.
  autocomplete: Options list can persistently lag behind query #226

• (TODO upstream issue)
  Richer Flex (aka Row and Column), with more CSS flexbox features like flex-basis vs flex-grow vs flex-shrink. (This is one of the few things we miss from React Native: its Yoga layout engine has those features.)
  We probably need something like this for:
  Long stream name can overflow recipient header #282
  reactions: Label text can linebreak sooner than necessary #433

• Back gesture on Android 12+ kills app rather than backgrounding it flutter/flutter#117061
  Android "back" quits the app completely #638

• Let iOS keyboard dismissal synchronize with scroll flutter/flutter#57609

• ListView: Poor performance with many variable-extent items + jumpTo (scroll bar, trackpad, mouse wheels) flutter/flutter#52207
  The Zulip impact is that if you try the "scroll to end" button when scrolled a long way back in history, the result is very choppy — like ~1fps — until it reaches the end.

• (TODO upstream issue)
  Flywheel/momentum scrolling #69

• (TODO upstream issue)
  InputDecoration should gain a helper field, to generalize helperText in the same way as error vs. errorText and label vs. labelText.
  We'd use this on the "server URL" field in the login flow.
  login: Link to doc to help users understand what a "server URL" is and how to find theirs #109 (comment)
  login: Link to doc to help users understand what a "server URL" is and how to find theirs #109 (comment)

Engine

• The Color API is in flux; to accommodate it, we're currently (since 2024-08) relying on versions of package:color_models and package:flutter_color_models from a branch maintained by a member of the Flutter engine team, instead of released versions.
  This isn't a stable situation and we hope the API settles soon.
  deps: Await/take flutter_color_models release that accommodates wide-gamut adjustments to Flutter's Color #918

• (TODO upstream issue)
  We want to have scripts that run as a CLI (at dev time) and import our model code.

  • E.g., Systematically survey message content for unimplemented features #190
    where we wound up with a real hack of putting the logic in a "test", run with flutter test, and having a wrapper script around that to accept a more reasonable CLI and run flutter test. (flutter test has a fine CLI for its actual job; but a terrible one for running an arbitrary tool as a script, which it's not intended for.)
    Potentially also: content test: Record URLs of sample messages, and validate them #617
  • This is a well-known problem in the community. The trouble is our model code imports package:flutter/foundation.dart for things like ChangeNotifier and dart:ui for things like Color; the former imports the latter; and dart:ui is available only in the Flutter SDK, not dart run.
  • One existing proposal is to move some definitions to a package outside the Flutter SDK. Not sure if that will succeed in solving the problem.

• FontWeight should subsume wght in FontVariation flutter/flutter#148026
  Has a proposed API from Hixie which would solve it; needs implementation.
  The symptom in Zulip is:
  text: Bold text is sometimes way bolder than intended #500

Skia / SkParagraph

• Emoji small on iOS: Emoji size is off on iOS flutter/flutter#28894

• (TODO upstream issue)
  Padding for text spans, to let us match Zulip web's styling for code spans.
  (For Zulip's pre-2023 visual design we would have needed borders too: chat thread.)
  An overlapping issue: Space between text and underline flutter/flutter#30541

Flutter on Android

• [Android] Autofill from saved credentials doesn't work flutter/flutter#137760
  Symptoms in Zulip:
  Login autofill doesn't work right on username/password login screen, on Android #546
  (There might be another upstream issue underlying that Zulip issue thread, too.)

Flutter on iOS

• (TODO upstream issue)
  ios: Keyboard can briefly reappear after "Share" is tapped and before the share sheet appears #591

Packages (first-party)

• package:video_player bugs on iOS:
  [video_player] iOS seems to downloads entire file before playing flutter/flutter#126760
  First Frame of Video Once VideoPlayer Controller doesn't show in iOS Safari/Chrome flutter/flutter#139107
  Because of these, for now we don't try to play video in the message list; we only play if the user opens in lightbox.
  Details here: Preview inline videos directly in message list #656

Tool

• We want to specify in our tree what Flutter version to use:
  [flutter_tools] pubspec.yaml environment.flutter constraint not respected by pub get flutter/flutter#95472
  Pin a precise version of Flutter #15
  The design space here is a bit tricky: we want the pinned version to be automatic, but also preserve our low friction for developing upstream changes in tandem with changes in our tree.

• (TODO upstream issue)
  After upgrading a package, running its CLI with flutter pub run still gets the old version. Running with dart run gets the new version, and works around the problem.
  For Zulip this shows up when running pigeon:
  tools/check: pigeon runs old/cached version of Pigeon after Pigeon dependency is upgraded #622

• Tool snapshot gets rebuilt on each unrelated Git commit flutter/flutter#123977
  Greg, for one, finds this a pretty substantial source of friction in developing changes to the Flutter tree.

flutter_test

• Make addTearDown and testWidgets interoperate properly, for invariants checked by testWidgets flutter/flutter#123189
  This is the reason many of our tests have to end with debugNetworkImageHttpClientProvider = null; — even tests that don't otherwise mention that variable. With this issue fixed, a line setting a variable like that one to some non-default value could be paired immediately with an addTearDown to reset it.

Integration tests

• We'll want to write some integration tests. The current state of writing those seems challenging:
  Difficult state of flutter_driver v integration_test flutter/flutter#142021
  though happily it looks like there's active work going on right now.
  In the future once we actually sit down to writing these, we may have more specific thoughts on what we want to see.
  ☂️ Integration tests to run on-device #757

[gnprice]

(Posting a first comment, to have the option to edit it as a home for related information in the future.)