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-*.
118 lines
5.2 KiB
Markdown
118 lines
5.2 KiB
Markdown
# Separate Stable Editing From Global KP Commitment
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## Context
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`task028` fixed the planning unit by consuming one whole-hard-line KP plan.
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`task029` then removed point-only invalidation by preserving a source-edit
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frontier. User testing exposed that the combined model still gives the
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frontier three jobs: latest edit position, natural-suffix boundary, and
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projection reuse boundary.
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That ownership cannot deliver stable editing. Replanning the complete hard
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line after every key permits the globally optimal breakpoint set to change
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after every key. Line-signature diffing can reduce property writes only after
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those new decisions exist; it cannot make the decisions stable. Clearing the
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touched line and its entire suffix before every edit also destroys anchors
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that were not causally affected.
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The narrow unique-append cost recorded by `issue018` is therefore downstream
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of the correctness model, not the first problem to optimize.
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## Decision
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Use two edit-time layers and one completed-layout owner:
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1. A committed projection owns the last published source, core plan, line
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signatures, projected spans, and break anchors.
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2. A dirty edit transaction snapshots that complete baseline and
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naturalizes only the affected local island.
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3. The existing core DP remains the sole owner of globally optimal committed
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and completed layout.
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Ordinary input inside the same native visual row does not run whole-hard-line
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DP and does not rewrite unaffected properties. Existing glue and native soft
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wrapping absorb small local changes. If the dirty row no longer fits, native
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wrapping moves the necessary local words while following committed break
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anchors remain fixed.
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A transaction commits only when:
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- input crosses a native soft-wrap boundary;
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- a hard newline/paragraph end is inserted or removed;
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- the next real source edit occurs outside the dirty island;
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- the user explicitly refills the paragraph; or
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- width, font, or layout context changes.
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Point motion is never a commit event. On a soft-wrap commit, the complete
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hard-line source may be replanned once and the completed prefix is updated as
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one silent publication; the new current row remains natural. On hard
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paragraph completion, the existing full-quality KP path remains unchanged.
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If an edit restores the baseline source, the transaction restores the saved
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owned projection and committed state directly. Exact restoration is a state
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transition, not a hope that recomputation happens to reproduce equivalent
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properties.
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## Superseded Decisions
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This record supersedes:
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- `20260729-whole-hard-line-live-prefix.md` where it permits earlier
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projected rows to change after every source edit;
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- `20260729-editing-frontier-not-point.md` where the edit frontier also owns
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the natural suffix and immediate post-edit publication.
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It preserves their valid decisions:
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- the core DP and layout-plan contract stay unchanged;
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- committed prefix lines come from one semantic hard-line plan;
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- the current unfinished row is natural;
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- point-only motion performs zero work;
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- hard-paragraph completion receives full-quality KP layout.
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It also restores the useful local-stability principle from the earlier
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bounded-flow work without restoring its core continuation API, helper stack,
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or per-key DP control flow.
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## Consequences
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- Editing stability and final optimality have different, explicit triggers.
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- Unaffected visual rows retain their break anchors during continuous local
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editing.
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- Reversible source edits restore the exact projection immediately.
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- Per-key unique-state planning disappears from ordinary same-row append; the
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remaining `task030` surface must be measured after this change.
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- The live buffer layer owns more baseline state, but the core algorithm,
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source-clean representation, and projection primitives remain unchanged.
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## Verification
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Public hook/command paths must prove ordinary same-row no-plan behavior,
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local dirty-island ownership, unaffected-anchor stability, exact
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`equal-including-properties` reversal, soft-wrap atomic commit, hard
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completion, next-edit-elsewhere commit, zero-work point motion, IME
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deferral, width/font/context commit, and fail-closed conflicts. Dynamic GUI
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evidence is required because batch tests cannot prove temporal stability or
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native word migration.
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## Outcome
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The implementation confirmed the ownership split. Ordinary same-row edits
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and point motion now make zero planner calls; the 291-edit narrow benchmark
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contains 15 plans, each tied to a real structural crossing. Middle-row edits
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retain unrelated span objects, and exact source reversal restores the saved
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projection `equal-including-properties` with the original plan, signatures,
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and spans.
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The final 48.95-second GUI run records 11 public actions at five phases each.
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All 55 checkpoints pass, the run completes in one fullscreen target window,
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and temporal review finds no black, blank, split, stale-buffer, or client-
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message frame. The surviving structural-commit latency is correctly left to
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`task030`; it is no longer evidence against the transaction model.
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## Rollback
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Revert the transaction change as one unit if the public-path or GUI gates
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fail. Do not fall back to debounce, idle whole-paragraph formatting, or the
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per-key frontier planner; all three retain the same trigger-ownership error.
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