Implements docs/folding-stage2-framing.md rev 4. The daemon grid
renderer now consults the fold store: hidden lines are omitted, rows
below shift up, and every consumer that assumed
`display_row = source_line - view_top` routes through one shared
projection. No wire schema change and no protocol bump (Bet B6) — the
collapse is entirely daemon-side; the GPU path is Stage 3.
The spine (Q#FD12) is `src/fold_view.rs`: a `VisibleLineMap` derived
from `FoldRegistry::folds` plus a window's line offsets and never
stored. Its unit is a merged **hidden component** — overlapping OR
adjacent hidden intervals unioned, each keeping the one visible
`head_line` and that line's exact `head_position`. Adjacent intervals
merge because the later fold's head is itself hidden, which is what
makes nesting, shared heads, and crossing overlap all resolve to a
head that can actually render (round-3 F2).
Instances are short-lived and built **per rendered window** and **per
command/event operation**, never once per frame: `paint_frame` renders
several windows that may show different buffers, so a singleton would
leak one pane's folds into another (round-2 F2). The render instance
rides on a lifetime-bearing `Viewport<'a>` as `Option<&'a
VisibleLineMap>` — a shared ref is `Copy`, so `Viewport` stays `Copy`
(Bet B7).
Rendering:
- `TextView::render` walks visible lines; the head line gets a
trailing content-area ellipsis (Q#FD13).
- The gutter walks visible lines too: Absolute keeps the raw `line+1`,
Relative/Hybrid measure VISIBLE distance anchored on the cursor's
visible head (Q#FD14). The fold glyph takes the col-0 sign cell only
when a gutter exists — line numbers default to Off, so with no gutter
the ellipsis is the sole marker (Q#FD20, round-1 F3). A diagnostic
clamped onto the head wins that cell by paint order.
- A diagnostic on a hidden line clamps its SIGN to the outermost
visible head (most-severe merge); the squiggle needs a real row, so
only the sign clamps (Q#FD15).
- Caret, local selection endpoints, and peer cursors project via
`visible_position_of` — the head row AND the head's end-of-content
column, never an arbitrary column (round-2 F3). Peer presence derives
the RECIPIENT window's map.
- Style/search/completion overlays route through
`Viewport::row_offset_of`; the mode-line indicator reckons in
visible-line space.
Command/event time is scoped per frontend (Q#FD21): a
`fold_projection` flag on `FrontendView`, set at attach from the
negotiated `semantic_render` bit (grid ⇒ true, semantic ⇒ false until
Stage 3, LOCAL ⇒ true) and never inferred from a `FrontendId` (Bet
B8). Without it, shared `EditorCore` motion would make a simultaneous
unfolded GPU session's cursor skip lines it still displays. The map's
two axes stay separate (round-3 F1): the acting frontend supplies the
policy, the operation's TARGET window supplies the buffer — a wheel
event names a pane without activating it.
Motion (Q#FD17, ruled: include), paging, wheel, the click inverse, and
the auto-scroll clamp all step by visible lines under that gate;
motion from a hidden logical cursor normalizes to the visible head
first. `view_top` stays a source-line index (Bet B5), set only via
`clamp_view_top` so it never rests hidden.
Unfold widening (Q#FD19): the pre-edit unfold moves to the top of
`apply_active_edit` — one funnel that subsumes the six primitives'
calls and covers yank + query-replace, both of which place point at
the edit site first. Interactive Lua mutators hook the common
`run_buffer_edit`, above the managed/bypass split, gated on
`InteractiveCommandOrigin` AND the edit targeting that frontend's
active-window buffer. The remote/optimistic-CRDT path stays excluded
(Stage 3); undo/redo unfold stays deferred.
Acceptance: `tests/folding_stage2_acceptance.rs`, 35 tests asserting
on the real `paint_frame` cell grid, covering framing items 1–14
including crossing folds, a nested deeply-hidden cursor, a split of
two different buffers with an inactive-pane wheel, and simultaneous
grid+semantic motion.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Q5BkezMppbpCgGAYk2ftxV
Levi Neuwirth
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