table: Read and write the selection as one TableSelection value

[violetpurpleish]

Description

After selecting a cell and then a row or column, selected_cell() still returned the old cell, contrary to its documentation. The other getters also exposed cached selections from inactive modes, and render_row read the raw row field, so a row left behind by a cell or column selection kept aria_selected, its forced bottom border and hover suppression while looking unselected.

The selection is one fact with four shapes, so this PR exposes it that way:

• TableSelection mirrors the three select events, and selection() / set_selection() read and write it as one value.
• selected_row(), selected_col() and selected_cell() are Some only when their own kind of thing is selected. A selected cell does not surface through selected_row(); callers that want its row map it from selected_cell() or match on selection().
• Every internal "is this selected" check goes through the getters, so the rule lives in one place. Row and column highlighting stay gated on their own mode.
• The internal cached positions are unchanged and keep serving keyboard navigation across mode changes.

The native DataTable story no longer displays a stale cell 5:3 footer after selecting a row or column.

Public API

gpui-component:

• pub enum TableSelection { None, Row(usize), Column(usize), Cell(usize, usize) } (new): the current selection as one value, mirroring TableEvent::SelectRow / SelectColumn / SelectCell.
• TableState<D>::selection(&self) -> TableSelection (new): reads the selection as one value; match on it instead of combining the three positional getters.
• TableState<D>::set_selection(&mut self, selection: TableSelection, cx: &mut Context<Self>) (new): writes the selection as one value; dispatches to the matching set_selected_* or clear_selection call so scrolling and events are unchanged.
• TableState<D>::selected_row(&self) -> Option<usize> (corrected): Some only when a row itself is selected.
• TableState<D>::selected_col(&self) -> Option<usize> (corrected): Some only when a column itself is selected.
• TableState<D>::selected_cell(&self) -> Option<(usize, usize)> (corrected): Some only when a cell is selected, as documented.

Breaking Changes

Each positional getter now answers only for its own kind of selection, so a selected cell no longer surfaces through selected_row() or selected_col(), and a row or column selection no longer leaves a stale selected_cell(). Callers that used the getters as a history of inactive selections must retain that history themselves. Signatures and internal navigation caches are unchanged.

 table.set_selected_cell(5, 3, cx);
-let row = table.selected_row();
+let row = table.selected_cell().map(|(row_ix, _)| row_ix);
 table.set_selected_row(2, cx);
-assert_eq!(table.selected_cell(), Some((5, 3)));
+assert_eq!(table.selected_cell(), None);
+assert_eq!(table.selection(), TableSelection::Row(2));

How to Test

• cargo test -p gpui-kit --features test-support --test collections --locked: 5 passed. table_selection_getters_follow_the_active_mode asserts selection() and the three getters after every mode transition, clear_selection, and a set_selection round trip through every variant; table_retains_navigation_positions_when_selection_mode_changes covers resuming row/column keyboard navigation from the retained positions. Both regressions failed on main before the fix.
• Story, DataTable: Options > Cell Selectable; Go To > Cell 5:3; select row 5; select cell 5:3 again; select the Name column. The footer displays the cell only during cell selection, and a selected cell highlights neither its row nor its column.
• cargo clippy -- --deny warnings and cargo fmt --check pass.

AI-assisted implementation with Codex and Claude Code; diff reviewed and regression/native checks run.

🤖 Generated with Claude Code

[huacnlee]

Thank you.