Creator corrected the "loupe" zoom on 2026-10-08: the click anchors a fixed
capture region (box/2 centred on the click) and the box is a live 2x view of
that region — dragging the box never changes its content; it magnifies the
fully-composited frame (every layer, incl. webcam) and draws LAST (n+1).
Rectangle shape is 4:3 ("more of a 640x480 aspect").
- MainViewModel.Zoom.cs rewritten: ActivateZoom anchors CaptureX/CaptureY
(independently clamped); UpdateZoomMove relocates the box only; the per-frame
BuildZoomFrame/ZoomFrameBuilder path is gone.
- SceneCompositor: skips the active ZoomSceneElement in every layer loop and
BlitZooms it last via the new pure ZoomMagnifier (2x bilinear, temp snapshot
via ArrayPool, round clip).
- Preview: ZoomBox hoisted above CanvasGrid as a sibling; its brush samples the
whole composed preview at the fixed capture (2x).
- Tests: ZoomMagnifierTests (box-over-blue shows green capture at 2x incl. an
extra red "layer" — the loupe/backdrop-only regressions both fail it) +
round-clip; ZoomBoxInteractionTests rewritten (anchored capture, move-doesn't-
change-capture, 4:3/9:16/square). 404 pass, 2 known environment flakes.
