ebox/docs/maintainer/ebox-current-implementation-reference.en.md

Ebox current implementation reference

This is the maintainer entry point for the standalone Ebox repository. It describes the package boundary, active files, runtime model, invariants, and verification commands. The historical emacs-box checkout is a separate legacy source tree; it is not a dependency of this package. ETAF is the sibling higher-level package.

Reading order

1. Read AGENTS.md for repository rules.
2. Read README.md for installation and the public boundary.
3. Read docs/user/ebox-user-guide.en.md for public construction patterns.
4. Read this document for ownership and verification.
5. Read docs/maintainer/ebox-incremental-update-contract.en.md before changing publication or patch planning.

Active source map

File	Owns
ebox.el	Public facade, construction helpers, rendering, buffer entry points, scrolling, commit, and byte compilation.
ebox-cache.el	Measurement/render cache records, invalidation, and cache reports.
ebox-style.el	Property registration, aliases, shorthand expansion, computed style, colors, borders, and dirty effects.
ebox-tree.el	Node traversal, child access, identity, parent paths, keys, and tree snapshots.
ebox-measure.el	Display-sensitive character/face/pixel measurement and measurement caches.
ebox-fragment.el	Layout fragments, signatures, snapshots, spans, and dirty-kind facts.
ebox-render-context.el	Render-local context and publication inputs.
ebox-layout.el	Box, row, column, stack, concatenation, spacer, wrapping, and common formatting context.
ebox-flex.el	Flex normalization, lines, free-space distribution, and flex rendering.
ebox-grid.el	Tracks, implicit tracks, fractions, minmax/repeat, gap, placement, span, and alignment.
ebox-surface.el	Candidate identity, projection to TP surface plans, retained mount/update, and the rollback-capable Ebox runtime-state participant.
ebox-buffer-backend.el	Text properties, display spaces/borders, markers, extents, and specialized local patch primitives.
ebox-incremental.el	Runtime state, snapshots, dirty planning, owner escalation, pure commit preparation, and reports.
ebox-dsl.el	Data-oriented .ebox forms and lowering to public nodes.
ebox-selector.el	CSS-like queries over trees and runtime handles.
ebox-native-reflow.el	Optional native module loading/build commands, ABI checks, bounded sessions, and Elisp fallback.

The package intentionally does not include application Components, UI controls, reactive data, or a playground implementation. Those are sibling-package responsibilities.

The active contract also covers Makefile, .github/workflows/ci.yml, tests/ebox-core-render-tests.el, tests/ebox-grid-tests.el, tests/ebox-commit-tests.el, tests/ebox-surface-tests.el, tests/ebox-dsl-tests.el, tests/ebox-flex-tests.el, tests/ebox-selector-tests.el, tests/ebox-package-tests.el, tests/ebox-visual-check-tests.el, tests/ebox-docs-contract-tests.el, tests/ebox-ci-contract-tests.el, native/Cargo.toml, native/Cargo.lock, native/build.rs, native/vendor/emacs-30/emacs-module.h, native/src/lib.rs, native/src/layout.rs, native/c/ebox_module.c, scripts/ebox-package-lint.el, and scripts/ebox-visual-check.el.

Runtime model

The normal data flow is:

Caller-owned Source Tree
  -> Surface-owned Runtime Copy
  -> TP Candidate Objects
  -> Element Tree
  -> Computed Style
  -> Box/Formatting Context
  -> Measurement + Render Context
  -> Layout Fragment/Snapshot
  -> Ebox Dirty/Patch Plan
  -> TP Surface Plan
  -> TP Atomic Publication
  -> Ebox Runtime-State Participant

Model	Owner	Must not own
Source/Element Tree	ebox-tree.el, ebox-dsl.el	Published buffer mutation.
Computed Style	ebox-style.el	Layout identity or patch execution.
Measurement	ebox-measure.el	Application state or dirty policy.
Formatting Context	ebox-layout.el, ebox-flex.el, ebox-grid.el	Buffer edits.
Fragment/Snapshot	ebox-fragment.el, ebox-incremental.el	Source parsing or identity allocation.
Surface Projection and Full-Root Publication	ebox-surface.el plus public TP surface APIs	Ebox layout decisions or generic diff execution.
Dirty/Patch Semantics	ebox-incremental.el	Raw measurement or TP buffer writes.
Generic Surface Diff/Commit	TP	Ebox geometry, dirty policy, or application state.
Specialized Local Backend	ebox-buffer-backend.el	Full-root mount/commit ownership, style semantics, or application state.

Invariants

• Public Ebox nodes are data; ebox--* names are private.
• A one-element horizontal list such as '(420) denotes pixels; ordinary horizontal numbers denote character columns.
• ebox-render uses an ephemeral TP surface and does not publish to a buffer; ebox-render-to-buffer mounts a retained TP surface; ebox-commit prepares Ebox semantics and updates that surface through TP.
• Declarative input remains caller-owned. Live mount/commit assigns identity only on a surface-owned copy, so the same source can back multiple buffers.
• Logical :id values resolve through ebox-region-resolve to opaque surface-scoped handles. Handles, not source-tree numeric ids, distinguish the same logical region mounted in different buffers.
• A failed candidate leaves the previous buffer, runtime identity, and report intact.
• Keys are local to siblings; visible strings are never used as identity.
• owner-rerender is broader than span-patch, which is broader than paint-patch.
• Buffer coordinates belong to the generation that produced them and must be refreshed after mutation.
• Grid uses the normal measurement and rendering pipeline. Native reflow may reject an ineligible tree and must fall back to Elisp without changing correctness.
• Loading Ebox never builds or installs the optional Rust module.
• Phase 8 is active: ebox-render-to-buffer and declarative ebox-commit use TP as their only live publication boundary, while Ebox runtime state joins the same rollback-capable transaction. Existing specialized numeric region, selector, viewport, and scroll update publishers remain until the local-update cutover; they must not become an alternate full-root path.
• Successful full-root reports preserve the Ebox semantic strategy and planned publication scope, then add :publication-scope tp-surface, TP operation counts, surface revision, and retained-object reconciliation counts.

Grid contract

Grid currently covers fixed and pixel tracks, auto, fractional tracks, minmax, repeat, implicit rows and columns, row/column gap, auto-flow, one-based placement, positive spans, item/content alignment, and ordinary buffer rendering and updates. CSS cascade, percentages, absolute positioning, z-index, border radius, shadows, full typography, and browser-level bidi are outside the contract.

Active examples and tests

The standalone package has no bundled playground fixtures. The migrated .ebox references and their file runner live in the sibling ebox-playground package; this repository tests the DSL and layout primitives directly. The regression boundary is the ERT files under tests/ listed in the repository's documentation contract. No test in this package should load the historical full-stack source tree or an application framework.

Verification matrix

make load
make compile
make check
make core-tests
make grid-tests
make ebox-commit-tests
make surface-tests
make visual-check-tests
make package-tests
make selector-tests
make dsl-tests
make flex-tests
make docs-contract-tests
make ci-contract-tests
make visual-check
make native-rust-tests
make native-build
make package-lint
make diff-check

Run focused tests first, then make check after changes to shared rendering, Grid, public constructors, or documentation. Native changes require the Rust checks and a native build.