* [Completer] Highlight popup rows without rewriting the line edit
Selecting a popup row with ClearAndSelect emits selectionChanged, which
QCompleter turns into highlighted() and QLineEdit turns into setText().
Since be2c16eca5 (#7466) that rewrites the typed text on every completion
reset / arrow-key press (e.g. typing "A" becomes "Axe" and cannot be
edited), regressing the 514014dc00 (#7447) fix that used NoUpdate.
Add selectWithoutRewrite(), which blocks the selection-model signals while
applying ClearAndSelect so the highlight stays visible without touching
the line edit, then syncs the preview manually. Route both the
above-popup auto-select and Up/Down navigation through it, and handle
Up/Down for below-popups too instead of falling through to Qt's
rewriting default. Enter/click acceptance via activated() is unchanged.
* [Completer] Repaint popup highlight after silent selection change
Blocking the selection model's signals also suppresses the view's own
selectionChanged/currentChanged repaints, so force a viewport update
after restoring signals. Use EnsureVisible to match Qt's normal scroll
behaviour.
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Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>
bbe438b09a