Level 2 — Detail view¶

Level 2 is the per-pair alignment workspace. It shows a single MIDI file and a single camera clip side-by-side, plus supporting widgets for navigation, probing, and anchor management.

Level 2 detail view showing the MIDI piano roll, camera panel, overlap indicator, intensity plot, and anchor table

Layout¶

┌─────────────────────────────────────────────────────────────────────┐
│ [< Back] MIDI:[combo▾] Camera:[combo▾] [Mode: Independent]          │ ← top bar
│                                            [ Compute Global Shift ] │
├─────────────────────────────────────────────────────────────────────┤
│ Independent Mode | Active: Camera (Tab to switch) | Arrows: …       │ ← status hint line
├─────────────────────────────────────────────────────────────────────┤
│ ═══════════ Overlap indicator (30 px dual-track) ═══════════════════│ ← clickable nav bar
├─────────────────────────────┬───────────────────────────────────────┤
│                             │                                       │
│      MIDI panel             │         Camera panel                  │
│   (falling keys)            │     (video frame)                     │
│                             │                                       │
│   MIDI mark: (none)         │      Camera mark: (none)              │ ← marker labels
├─────────────────────────────┴───────────────────────────────────────┤
│ Intensity plot (fixed 120 px) — shows ±120 frames around probe dot  │
├─────────────────────────────────────────────────────────────────────┤
│ [Alignment Anchors] [Add Anchor (A)]           [Delete Selected]    │
│ # | MIDI File | MIDI Time | Camera Frame | Derived Shift | Label |* │ ← anchor table
└─────────────────────────────────────────────────────────────────────┘

Top bar¶

Widget	Behaviour
< Back	Returns to Level 1. Clears the active anchor, drops the probe dot, and emits `back_requested`. Also bound to `Esc`.
MIDI: [combo]	Lists every MIDI file in the session. Changing the selection reloads the MIDI panel, clears the active anchor, and re-syncs if in Locked mode.
Camera: [combo]	Symmetric to the MIDI combo. Changing the selection reloads the camera panel, closes the old video, opens the intensity worker on the new clip, clears the active anchor, and re-syncs if in Locked mode.
Mode: Independent / Mode: Locked	Checkable button. Toggle behaviour is detailed in §5.9 Modes. Bound to `L`.
Compute Global Shift	Disabled until both markers are set. On click, runs the controller's `compute_shift_from_markers`, shows a `Yes/No` confirmation with the computed value, and applies it through `AlignmentService.set_global_shift`. If existing anchors would be invalidated, a second warning asks for confirmation.

Tooltips on Compute Global Shift and Add Anchor (A) read "Set markers first: press M on MIDI panel, C on camera panel" when either button is disabled.

Status hint line¶

Single grey line below the top bar, refreshed on every mode change and active-panel switch:

Locked Mode  |  Active: MIDI (Tab to switch)  |  Arrows: navigate  |  L: toggle mode  |  M: mark MIDI  |  C: mark camera  |  A: add anchor  |  O: jump to overlap

Overlap indicator¶

Full-width, 30 px tall; see §5.6 Overlap indicator.

Main splitter¶

Horizontal QSplitter set to [500, 500] initially. Left column: MIDI panel with a "MIDI mark: …" label below. Right column: camera panel with a "Camera mark: …" label below.

An active panel indicator is drawn as a 2 px border around the currently-active panel:

MIDI panel active → blue border (#4488ff).
Camera panel active → orange border (#ff8844).
Inactive panels get a grey (#555) border.

A panel becomes "active" when the user clicks, wheels, or double-clicks within it, or via Tab, or when jumping to that panel via an anchor or overlap click. "Active" determines which panel the Left / Right / Shift+Left / Shift+Right arrow keys drive.

Marker labels¶

State	Label text
No marker set	`MIDI mark: (none)` / `Camera mark: (none)`
Marker set	`MIDI mark: trial_001.mid @ 12.456s` / `Camera mark: frame 2987 (12.467s)`

Pressing M / C replaces the current marker and triggers a 400 ms dark-blue flash on the label to confirm the keystroke registered.

Intensity plot¶

Fixed-height 120 px widget below the splitter; see §5.7 Intensity plot.

Anchor table¶

Fixed-max-height 200 px widget at the bottom; see §5.8 Anchor table. The header row includes an Add Anchor (A) button injected from Level 2 and a Delete Selected button.

Dialogs raised by Level 2¶

Dialog	Trigger	Buttons
"Markers not set" warning	Computing shift or adding anchor with `MarkersNotSetError`	OK
"Apply Global Shift: Computed X.XXXX s"	Clicking Compute Global Shift	Yes / No
"This will remove all N anchor(s). Continue?"	Computing a new shift when anchors exist	Yes / No (default No)
"Anchor Label" text input	Clicking Add Anchor (A)	OK / Cancel
"Unknown MIDI file" warning	Adding an anchor whose MIDI can't be found (should be unreachable in practice)	OK
"No Overlap" info	Pressing `O` when the clip pair doesn't overlap at the current shift	OK

Cleanup¶

On Back, Esc, or closing the window, the Level 2 view:

Clears the active anchor across all camera clips.
Clears the probe dot (emitting dot_cleared to clear the plot).
On full shutdown, closes the video capture and the intensity worker, then joins the intensity thread (up to 2 s).

A late intensity sample arriving after the clip has been swapped is discarded by a tuple-match filter (center_frame, src_x, src_y must still match the latest dropped dot), so a stale trace cannot overwrite the current plot.