83352c4571
Replace the physical ekp-region renderer with ekp-buffer text-property projection backed by shared semantic layout plans and stable live-edit transactions. Optimize the C-backed resize hot path, and add deterministic performance, ERT, GUI, fuzz, release, and documentation coverage for task017 through task032. BREAKING CHANGE: require ekp-buffer instead of ekp-region and rename module-owned ekp-region-* settings to ekp-buffer-*.
105 lines
4.4 KiB
Markdown
105 lines
4.4 KiB
Markdown
# Let Source Edits Own the Live Editing Frontier
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> Superseded note (2026-07-29): point-only motion remains a zero-work
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> invariant. `20260729-stable-live-transaction.md` replaces the frontier's
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> natural-suffix and immediate-publication ownership with a saved committed
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> projection and a local dirty edit transaction.
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## Context
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`task028` fixed the planning boundary: all projected rows in one hard line
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now come from one complete `ekp-layout-plan`. It nevertheless used current
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point to choose the natural suffix whenever `post-command-hook` ran.
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That conflated two independent facts:
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- point is transient navigation state;
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- the editing frontier records which semantic line is currently unfinished.
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As a result, cursor motion alone removed and reinstalled projection
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properties. It did no DP work, but it still changed the visual document.
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Worse, a later width or font reflow could read the cursor's temporary
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position and silently move the natural suffix boundary.
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## Decision
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The latest real source edit owns the editing frontier.
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1. A live hard line keeps a source marker for the changed region's new end.
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2. Before a real edit, the existing prefix line containing the edit is
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returned to native display together with its suffix.
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3. After the edit, the frontier marker moves to the changed region's new
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end and the whole-hard-line plan is recomputed or reused once.
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4. The active semantic index is derived from that marker, never from
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transient point.
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5. Point-only motion within the active hard line does nothing.
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6. Width, font, and layout-context changes preserve the marker and map it
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into the new plan.
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7. Leaving the hard line still completes the old hard line with the
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existing static KP path.
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The core DP remains unaware of point, markers, buffers, and editing state.
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## Why This Is Simpler
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`active-index` is derived plan state; the frontier marker is the one stable
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source fact. There is no point-motion state machine and no attempt to infer
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editing intent from navigation. One owner event—source mutation—moves the
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frontier.
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The change deletes the point-boundary publication path instead of adding
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another condition to it.
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## Superseded Decision
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This record supersedes only the point-driven boundary statements in
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`20260729-whole-hard-line-live-prefix.md`. That record's main decisions
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remain valid:
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- one complete hard line is the planning unit;
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- all projected prefix lines come from the same core plan;
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- the frontier line and suffix stay natural;
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- prior breaks may change together after later source edits.
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## Consequences
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- Moving point cannot cause visual reflow or text-property writes.
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- Editing an earlier projected line still makes that actual edit line and
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its suffix natural before mutation, then republishes from the updated
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whole-hard-line plan.
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- Resizing can change breaks and glue, but not because point happened to be
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elsewhere inside the hard line.
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- The frontier remains display-layer state. Core DP, the C ABI, and the
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source-clean representation are unchanged.
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## Verification
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The regression gate compares the complete owned-property projection,
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frontier marker, active index, signatures, spans, source characters,
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modified tick, undo state, plan calls, cache calls, and property writes
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before and after backward/forward point motion. It failed before the change
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and now passes; reflow and deferred IME completion also preserve the
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frontier instead of reading transient point.
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Default, seed-`20260729`, and isolated full ERT pass 182/182; buffer ERT
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passes 93/93 and C/Elisp fuzz passes 300/300. Point-motion p99 is
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0.033 ms on the C backend with zero plan/cache calls.
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Reviewed dynamic GUI evidence at
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`/private/tmp/ekp-frontier-live-v3-66WYRW` contains a 26.6-second screen
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recording and 39 manifest lines. Backward/forward commands preserve the
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projection hash, plan, generation, cache size, active index, and frontier
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through every required checkpoint. Delete, yank, real undo, resize,
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restore, and hard-newline transitions also pass; source text remains exact,
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overlays and horizontal scroll remain zero, and the final report is PASS.
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Independent architecture review is CLEAR. Independent code review finds
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zero task029 blockers; the separate unique-append performance debt is
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recorded as `issue018`/`task030`.
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## Rollback
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Revert this editing-frontier change as one unit if a public editing or GUI
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gate fails. Do not restore point-driven projection changes as a fallback;
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navigation is not a layout invalidation event.
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