[devmobasa]

Summary

On newer GTK, changing the interface language while a shortcut is being
recorded or text-edited cancels the edit. The configurator is meant to carry
open edits across the language rebuild. That works on GTK 4.14, which CI
uses, but not on GTK 4.24.

app::component::tests::language_changes_rebuild_the_window_in_place shows
this with GTK 4.24 and Weston 15.

Cause

GTK 4.24 closes a popover it cannot place. gtk_popover_native_layout calls
gtk_popover_popdown when the compositor gives the popup less than its
minimum size, which is what happens once the anchor row is outside the view.
GTK 4.14 does not have that check. field_canceled then reports the close
as the user canceling the edit.

A language change hit this path in two ways:

1. Reopening too early. The first refresh after
   rebuild_if_language_changed reopened the edit's popover on the new row.
   At that moment the new page has no layout and is at scroll 0, so the row
   is off screen. The saved scroll is restored only after the first
   allocation.
2. The restored scroll is not enough. Translated rows above the edited
   row can be taller. In the test, the Undo row ends up 560 px down a 446 px
   view at the restored offset after switching to Chinese.

The test also started recording on a row far below the visible part of the
page. A real recording starts from a click on its row, so that row is always
on screen.

Changes

• pages/mod.rs: a settle ticket per rebuild. A newer rebuild makes an older
  ticket stale.

• component/rebuild.rs: the rebuild takes a ticket before its first
  refresh. A new settle step:

  1. waits for the visible page to be laid out
  2. restores the scroll
  3. waits one more frame
  4. ends settling and sends Message::PagesLaidOut

  Focus that was inside a popover that has not reopened yet is restored, with
  its caret and selection, right after the popover opens. If the edit ends
  before the popover reopens, the saved focus is dropped. A rebuild that
  starts before the previous one settled carries over that rebuild's scroll
  for the same page, unless the page has a scroll of its own.

• pages/keybindings/widgets.rs: PopoverPresenter opens the recorder and
  text-editor popovers only when all of these hold:

  • the pages have settled
  • no Leave confirmation is pending, because the popover's focus would
    select its row and that withdraws the confirmation
  • the row is mapped and laid out

  If the row is outside the view, it scrolls the row into view and opens the
  popover after the next layout. A row that is not showing, on another page
  or in a hidden category, opens once it is shown and laid out.

• messages.rs and update/mod.rs: PagesLaidOut changes no state. It is
  allowed while a document replacement is in flight and does not withdraw a
  pending Leave confirmation.

Tests

The GTK scenario, with existing assertions unchanged:

• Recording now starts on a row that is on screen. After every language
  switch the test waits for the rebuilt page to reopen the open edit, and
  asserts that each popover opened with its row on screen. The listeners
  attach when the rebuilt page becomes visible, before its first refresh.
  Without the production changes this check fails with [false] on GTK 4.24.
• The reopened text editor keeps its selection.
• A cancel made while the pages settle stays canceled, and nothing reopens.
• If a text edit is canceled before its editor reopens, the next edit opened
  on that row does not get the old selection.
• A Reload Leave confirmation asked while the pages settle survives. The
  recorder reopens once, on screen, after the confirmation is canceled.
• Two language changes before the text editor reopens keep its selection.
• A recording whose category is hidden while the pages settle stays active
  and closed, and reopens when the category is shown again.
• The reload scenario asserts that the recording is active before Reload.

The Leave, old-selection, two-change and hidden-category checks each fail
when the production change they cover is removed.

A unit test covers the settle ticket.

Validation

• ./tools/test-gtk-widgets.sh and ./tools/lint-and-test.sh pass with
  GTK 4.24.1 and Weston 15.
• cargo clippy with --all-features and with --no-default-features, and
  cargo fmt --check, pass.
• CI runs the same scenario on Ubuntu 24.04.

Not changed

• The compact-mode shortcut editor is still not reopened after a rebuild. The
  model does not track it, which was already the case before this change.
• Focus is still restored by widget path rather than by shortcut field.
• The GTK widget job pin to ubuntu-24.04 (ci: build the Nix flake and check the minimum Rust version #436) can be removed once this
  scenario passes on a newer runner image.