Restyle the Keys panel, make it focusable, and bind it to F7

[tconbeer]

Closes #753

What are the key elements of this solution?

• New harlequin.components.keys_panel with Harlequin subclasses of Textual's HelpPanel and KeyPanel:
  • KeysPanel(HelpPanel) has BORDER_TITLE = "Keys" and takes the same rounded border/focus colors as the Data Catalog, Query Editor and Results Viewer (app.tcss). Keys are $secondary (green) and descriptions $primary, matching the footer.
  • KeysList(KeyPanel, can_focus=True) can be focused by clicking it or with Tab, and scrolled with the arrow keys or PgUp/PgDn.
  • Both drop Textual's -textual-system class. With that class, the app's * { scrollbar-* } rules don't match (that's where the pink scrollbar came from), and the screen won't focus the widget on click.
• Focusing the list would normally swap the listed keys for the list's own (empty) bindings. KeysList.recompose() skips while it is focused, and KeysTable.render() reuses its last table while its list is focused, so the panel keeps showing the keys of the widget you came from. Both check screen.focused rather than has_focus, which is set a render later.
• Harlequin.action_show_help_panel is overridden, so the command palette's "Keys" command opens the new panel too. On the main screen it mounts into the main row (self.main_row) as a column above the footer, not as a screen split over it.
• New bindable toggle_keys_panel action, bound to F7 in the default (vscode) keymap, to make the panel easier to find.
• The Help screen (F1) has a line at the top, above the docs, naming the key that toggles the Keys panel. The key is read from the active keymap. If nothing is bound, the line points to the command palette instead.

Why did you design your solution this way? Did you assess any alternatives? Are there tradeoffs?

Subclassing HelpPanel, rather than writing a new widget, keeps the palette's show/hide command (screen.query("HelpPanel")) working. Freezing the table while focused is a small override of Textual internals (textual.widgets._key_panel.BindingsTable). An upstream can_focus option on KeyPanel would be cleaner, but Textual isn't one of ours. F7 was the free function key between the focus keys (F2/F5/F6) and History (F8); F11 is usually taken by the terminal emulator. It isn't in the footer, because adding it there would change every app snapshot; the Help screen names it instead.

Does this PR require a change to Harlequin's docs?

• No.
• Yes, and I have opened a PR at tconbeer/harlequin-web.
• Yes; I haven't opened a PR, but the gist of the change is: the default keymap's app-level bindings gain F7: toggle_keys_panel (show/hide the Keys panel), and the keymap docs' action list gains toggle_keys_panel.

Did you add or update tests for this change?

• Yes. test_layout.py::test_toggle_keys_panel covers F7 show/hide, the command palette's Keys command, mounting in the main row, focusing by click, and the keys staying those of the Query Editor after focus and scrolling, with two new snapshots. test_help_screen.py checks the Help screen's key line, including the version shown when nothing is bound. The test_keys_app and Help screen snapshots are regenerated.

Please complete the following checklist:

• I have added an entry to CHANGELOG.md, under the [Unreleased] section heading. That entry references the issue closed by this PR.
• I acknowledge Harlequin's MIT license. I do not own my contribution.

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[tconbeer]

Review: #1169, Keys panel restyle, focus and F7

What I looked at: correctness and edge cases of the new keys_panel.py overrides and of action_show_help_panel / action_toggle_keys_panel; reuse and whether this is the simplest way to build it; comments and changelog against AGENTS.md. I skipped a security pass because the diff touches no I/O, config or adapter code.

Findings: 2 inline comments, both non-blocking.

• Low: the command-palette path is untested. It is the reason action_show_help_panel is overridden, and it only works because Textual dismisses the palette before it runs the command (app.py L1336–1344).
• Nit: the CHANGELOG entry is three sentences; the rule asks for one or two.

Checked with no problems found

• Both overrides are needed, and the test catches the loss of either one. I disabled each in a scratch script, focused the list and pressed PgDn, then checked whether Format Query was still listed:

  • baseline: True rows 61 scroll_y 33
  • KeysList.recompose → KeyPanel.recompose: False rows 26 scroll_y 0.0
  • KeysTable.render → BindingsTable.render: False rows 26 scroll_y 33

  So test_toggle_keys_panel's "Format Query" in listed_descriptions() assertion fails if either override is removed. That also limits the risk of importing the private textual.widgets._key_panel: if a Textual bump changes how KeyPanel refreshes, the test will fail rather than the panel silently going stale.

• Dropping -textual-system does what the PR says. css/model.py stops the universal * rule from matching nodes with that class, and Screen.get_focusable_widget_at refuses to focus them on click. Tab order with the panel open: ResultsViewer → KeysList → DatabaseTree → editor.

• Pressing F7 while the list is focused removes the panel, and focus lands on ResultsViewer. F10 (full screen) with the list focused goes up the ancestors and returns without error.

• Layout: at 120×36 the panel is 39 columns wide, and at 80×24 it is 30 wide (its min-width), which leaves the editor column 38 wide.

• f7 is not bound anywhere else in src/, textual_textarea or textual_fastdatatable.

• The test_keys_app snapshot churn is only the new "Toggle Keys Panel f7" row, plus the rows below it shifting down. I compared the text extracted from the SVGs on origin/main and on this branch.

• uv run mypy, uv run ruff check . and uv run lint-imports all pass. pytest -m "not online" tests/functional_tests: 199 passed, 3 skipped.

• CI: the one red job (MacOs-latest 3.11) is test_hsql_serve.py::test_a_client_that_gives_up_while_it_waits_runs_nothing timing out, and this PR does not touch hsql.

Design questions, not findings

• While the list is focused it keeps showing the previous widget's keys, such as f4 Format Query. Those keys do nothing until focus goes back to that widget. That is the intended behavior per the PR body; I'm raising it only so the choice is deliberate.
• In full-screen mode (F10) the panel stays open next to the full-screen widget and fills the row the hidden footer used. That seems reasonable, since the user opened it.

Not checked

• I did not run the py12 snapshot pass, and I did not run the suite on Windows or macOS. I relied on CI for those.
• I did not look at the snapshots with an SVG renderer. I only compared their text, so colors ($secondary keys, $primary descriptions, the scrollbar) were not checked visually.
• I did not check ANSI or light themes, or what happens when the theme changes while the list is focused (the cached Table keeps the old theme's styles until focus leaves).
• I did not check the palette "Keys" command opened from a modal screen (the else: self.screen.mount(...) branch). F7 does nothing on HistoryScreen and HelpScreen.
• I did not review the harlequin-web docs, since no PR has been opened there yet.

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