# HANDOFF — 2026-10-08 (zoom rework)

## Branch
- main (no feature branch)

## Dirty files (NOT mine — the in-flight "pinned chat" work unit; do NOT commit or co-edit)
- `Models/YouTube.cs`
- `ViewModels/MainViewModel.Chat.cs`
- `Controls/LeftPanel.xaml` (pinned-message UI)
- Untracked: `Helpers/RelayCommandGeneric.cs`

## What just happened (2026-10-08, second zoom pass — creator correction)
The zoom box shipped in `4b3d82f` was a **loupe** (box follows its own content, built from the
backdrop only, slotted at z-index 1). The creator corrected it; the model is now:

- **Anchored capture, not a loupe.** Right-clicking the live preview fixes a **capture window** —
  the box/2 region centred on the click (`CaptureX/Y`, clamped to the master) — and parks a movable
  **2x magnifier** box. The box is a **live, always-on 2x view of that captured region**; dragging the
  box relocates it, **`UpdateZoomMove` never touches the capture** (creator ruling).
- **Content = every layer.** The zoom pass runs on the **already-composited frame** (backdrop + all
  elements), so the magnified webcam/square/layers all show in the box. `SceneCompositor` skips the
  active `ZoomSceneElement` in every layer loop and `BlitZoom`s it **LAST (layer n+1, on top of
  everything)** via the pure static `ZoomMagnifier` (2x bilinear, 8.8 fixed-point, temp snapshot via
  `ArrayPool` so a box overlapping its own source never recurses, optional round clip).
- **Rectangle = 4:3** ("more of a 640x480 aspect ratio"); Circle = square, Phone = 9:16 (kept).

Changes in this pass: new `Services/Compositor/ZoomMagnifier.cs`; `ZoomSceneElement`/`ZoomState`
gained `CaptureX`/`CaptureY`; `MainViewModel.Zoom.cs` rewritten (`BuildZoomFrame`/`ZoomFrameBuilder`
and the zoom-as-crop resolver case removed — no per-frame builder/cache anymore);
`PreviewPane.xaml`: `ZoomBox` hoisted OUT of `OverlayCanvas` to be a **sibling of `CanvasGrid`**
(renders above everything in the preview); `PreviewPane.xaml.cs` `UpdateZoomBox` samples `CanvasGrid`
(the whole composed preview) at the fixed capture, `Stretch=Fill`. `ZoomFrameBuilderTests.cs` deleted
(superseded); new `ZoomMagnifierTests.cs` (the "box over blue shows green capture, at 2x, all layers"
proof + round-clip); `ZoomBoxInteractionTests.cs` rewritten (per-shape 4:3/9:16/square + capture
anchor centred on the click + move-moves-only-the-box assertion + corner-clamp).

## Zoom feature state
- Models: `ZoomState.cs`, `ZoomShape.cs` (Circle/VerticalRectangle/HorizontalRectangle), `ZoomSceneElement.cs`.
- ViewModel (`MainViewModel.Zoom.cs`): `ActivateZoom`/`ToggleZoom`/`DismissZoom`/`StartZoomMove`/`UpdateZoomMove`/`EndZoomMove` + `RebuildDimRectsForZoom`; transient element healed/mirrored by `HealZoomLayers`/`EnsureZoomLayer`.
- Output: box composited last via `BlitZoom`/`ZoomMagnifier`; output crop = tier (box never the crop).
- Preview: `ZoomBox` = sibling above `CanvasGrid`, samples the full composite at the fixed capture, 2x; circle→ellipse clip, rect/square outline per shape; `LeftPanel` hides the placeholder row via `IsZoomLayer`.

## Tests
- Full suite: **404 passed / 2 failed** (both = known pre-existing environment flakes, unrelated to
  zoom): `AudioPipelineTests.Mix_HonorsProviderGains_AndGameMute_KillsTheLoopback` (audio timing)
  and `LayerReorderPersistenceTests.RealMouseDrag_OnTheLayerList_PersistsTheReorder` (needs
  interactive desktop). Zoom tests 3/3 green, 0 build warnings.

## Known issues / follow-ups
- **Background "Use default background" toggle still not working** (carried from 2026-10-07):
  binding exists (`UseDefaultBackground`), VM handler invalidates bake; investigate when time permits.
- Preview shows editing chrome (dim rects, selection) inside the zoom box — accepted preview
  artefact; the output only shows composed content.

## Next step
- User runs the app live to eyeball the corrected zoom: right-click preview → anchored capture stays
  fixed while the box is dragged; the box shows ALL layers at 2x on top of everything; rectangle box
  is 4:3. Then TASK 51 (webcam background Remove + Blur) per `TASKS/task-51-webcam-bg-effects.md`,
  and the background-toggle investigation if still open.