brep-app — the BREP CAD application

The BREP CAD application (on crates.io as BREP_app, live at 0.1.0, this tree 0.2.0; lib brep_app): an eframe (egui + wgpu) app hosting the brep-render engine on the BREP kernel — one codebase for web and desktop, no DOM, the 3D drawn by the engine and the UI drawn by egui, sharing one wgpu frame. Build the wasm app with ./build.sh app at the repository root; the generated docs site lands in web/help/.

Dependency chain: BREP_app → BREP_render → { BREP_kernel, BREP_gizmos, BREP_reconstruction }.

Architecture

• EngineState (brep-render) stays the windowing-agnostic brain — scene, camera, controls, settings, selection, sketch mode, history, widgets, pointer/wheel/ViewCube/pick. Not forked; panels borrow &mut EngineState.
• RenderCore::render_to_view draws the 3D into an app-owned offscreen texture (its own 4× MSAA + full-target clear + submit) on eframe's shared wgpu device/queue — the render core is built via RenderCore::new(device, queue, format) from eframe's RenderState.
• That offscreen texture is composited into egui's own frame by an egui_wgpu paint callback — a fullscreen-triangle blit into egui's render pass at the viewport rect egui scissors for the callback. The engine's native Rgba8Unorm output is linearized in the blit when egui's target is sRGB so colors round-trip exactly.
• The toolbar + 3D ViewCube drive EngineState live (zoom-to-fit, projection toggle, standard views); camera_state_json() is published for the verifiers. Pointer/wheel/ViewCube over the viewport route into EngineState (mirroring the engine's own desktop shell).

Module layout (one module per panel)

src/app.rs is a thin shell: it owns Documents (every open model — see below), the Viewport, the Store, and one small state value per panel, and its eframe::App::ui just lays the panels out. The heavy code lives in focused modules:

• src/document.rs — the OPEN MODELS. Each Document is one EngineState (still the single brain, per model) plus its file identity; Documents is the open list + the active index, and docs.engine_mut() is how every panel reaches the active brain. Panels are shared, not per-document: the shell resets their transient state when the active document changes.
• src/panels/document_tabs.rs — the seam the document tabs report through (click / close / verifier rects). The tabs themselves are egui_tiles' own: each open model is a PaneKind::Document pane and they share one Tabs container, so the 3D pane's tab bar IS the model switcher. dock.rs keeps that bar exclusive (nothing else may be dropped in, no model tab may be dragged out).
• src/viewport.rs + src/viewport/ — the 3D viewport: the engine render core, the app-owned offscreen texture, the egui_wgpu blit callback + shader, viewport input routing, and in-viewport labels.
• src/panels/ — one file per UI surface, all following one pattern:
  • toolbar.rs — the top action strip (undo/redo, wireframe, zoom-to-fit, standard views, the file-action seam); toolbar_button.rs is the single source of truth for toolbar-button styling, shared by every toolbar.
  • history.rs — the history feature tree + the schema-driven feature dialogs.
  • scene.rs — the Scene tree; tree.rs is the reusable custom-painted tree-node widget both trees are built on.
  • settings.rs — the Settings window: one tab per section (Display, the schema-driven display settings; Assemblies, the BOM columns), each drawn as a tree.rs tree, persisted via the Store. Model colours are NOT set here — they are a durable color metadata attribute edited in the Info window; Display ▸ Faces ▸ Override model colors is only the display switch that makes the viewport ignore them.
  • selection.rs — the selection filter (which entity kinds a click picks).
  • sketch.rs — the 2D sketcher's side-panel entry point + in-sketch bars.
  • expressions.rs — the variable sheet (name = expr;) feature params resolve against.
  • file.rs — the model-document modal: New / Open / Save / Save As, plus Import, Export, flat-pattern export, and Insert-Component (one FileAction per mode).
  • file_explorer.rs — the reusable, embeddable file explorer shared by Open, Save As, Import, and Insert Component. A single click SELECTS a file (highlight + footer preview); a double-click, Enter, or the footer confirm button opens it; ↑/↓ move the selection; folders enter on a single click. Everything is driven through the ModelStore seam, identical on web and desktop.
  • info_windows.rs — pinned per-entity inspector windows.
  • context_bar.rs / action_rail.rs / mode_bar.rs — the selection-driven context actions, the shared right-side action rail that renders them, and the pinned Finish/Cancel controls for special modes.
  • toasts.rs — transient notices queued by the engine.
• src/form.rs — the generic, schema-driven form engine: one field_input renderer per field kind (Color, Bool, Enum, Number/Range, Text, Vec3, references, and the expression-capable Scalar), used by both the settings tree and the feature dialogs — the structure of the schema drives the UI; no hand-coded widget per field.
• src/store.rs — the unified persistence seam, the one platform exception: ModelStore handles settings, dock layout, and model documents through the same read / write API, with a native filesystem implementation and a wasm in-memory mirror backed asynchronously by IndexedDB.
• src/palette.rs — a generic searchable command-palette modal (used for "pick one of N named things", e.g. add-feature).
• src/worker.rs — the wasm history runner: executes the history in a dedicated web worker behind the same HistoryRunner trait as the engine's native thread runner, so the UI stays responsive during a run.
• src/fonts.rs — the bundled UI fonts (assets/, embedded at compile time).

Adding a panel

EngineState (brep-render) is the single brain; a panel is just a small state struct + a show method that borrows &mut EngineState. To add one — nothing else changes:

1. Add src/panels/<name>.rs with a state struct and a show method:

   use brep_render::engine_state::EngineState;
   use eframe::egui;
   
   #[derive(Default)]
   pub struct MyPanel { /* the panel's OWN editing buffers only */ }
   
   impl MyPanel {
       pub fn new() -> Self { Self::default() }
   
       // Pass the unified store too if the panel persists:
       // (…, store: &dyn ModelStore).
       pub fn show(&mut self, ui: &mut egui::Ui, state: &mut EngineState) {
           egui::CollapsingHeader::new("My panel")
               .id_salt("my-panel")
               .default_open(false)
               .show(ui, |ui| { /* widgets; read/write via `state.*` */ });
       }
   }
   

2. Register it: add pub mod <name>; to src/panels/mod.rs.

3. Add one field to BrepApp in src/app.rs (<name>: MyPanel) and construct it in BrepApp::new (<name>: MyPanel::new()).

4. Add one self.<name>.show(ui, self.docs.engine_mut()); call in eframe::App::ui (or a PaneKind arm in panels/dock.rs), where you want it. Use self.docs.engine_mut() rather than an accessor on BrepApp: it borrows one FIELD, so it still composes with the disjoint &mut self.<panel> borrow beside it.

Keep the model state in EngineState — panels own only transient editing buffers. That keeps parallel panel work conflict-free (different files, one field

• one call each in the shell).

Schema-driven UI

There is deliberately no hand-written dialog code per feature or setting:

• Display settings come from the engine: brep_render::style::settings_schema() returns the ordered field list and RenderSettings::to_json()/apply_json() are a round-trip identity, so adding a field to the engine schema grows a widget with zero UI code changes. Edits are applied to EngineState (which marks the GPU state dirty) and persisted through the Store.
• Feature dialogs come from the kernel: brep_render::features::feature_form_fields maps each feature's inputParamsSchema (the kernel's feature_schema_catalogue) to the same FormField shape, rendered by the same src/form.rs engine. Editing a param calls EngineState::update_feature_params → the engine mutates its history and re-runs → the viewport updates live. Numeric fields accept expressions resolved against the expressions panel's variable sheet.
• History is engine-owned (brep_render::history::History, held by EngineState): the ordered features + rollback index are the single source of truth with undo/redo; the UI keeps no copy and mutates only through EngineState methods.

Version alignment (the crux)

brep-render is on wgpu 29. eframe 0.35 → egui 0.35 → egui-wgpu 0.35 → wgpu ^29.0, so all three unify on wgpu 29 — the paint callback can hand eframe's device/queue/renderpass straight to the wgpu-29 RenderCore. No wgpu bump to brep-render.

eframe 0.35 requires Rust ≥ 1.92. The repo's root rust-toolchain.toml pins the whole crate family — kernel, render engine, and this crate — to 1.92, so plain cargo and wasm-pack already use it; no +toolchain needed.

Build & run

./build.sh at the repository root is the front door — see the root README for prerequisites and the full matrix.

Web (wasm)

./build.sh              # wasm-pack build BREP_app --target web --out-dir pkg --release
./build.sh serve        # serve; open http://localhost:8080/web/

or manually, from BREP_app/:

wasm-pack build --target web --out-dir pkg --release       # add --no-opt for a faster dev build
python3 -m http.server 8099 --bind 127.0.0.1               # serve the crate root
# open http://127.0.0.1:8099/web/index.html

web/index.html loads pkg/brep_app.js and calls the exported start("brep_canvas"). eframe uses WebGPU when available and falls back to WebGL2.

Desktop (native)

cargo build --release
WGPU_POWER_PREF=high ./target/release/brep-app

Open, Save As, import, and export use the same in-app file explorer on desktop and web; no OS-native file-dialog dependency is used. On desktop the explorer can move to parent, home, and filesystem-root directories and browse the real filesystem. In the browser it navigates the application's persistent virtual folder tree under /models (stored in IndexedDB), because browser sandboxing does not expose the host filesystem. Both implementations support creating and navigating folders through the same explorer API.

The explorer follows a conventional file-dialog interaction model: a single click SELECTS a file (highlight + a footer selection preview), and a double-click, the Enter key, or the footer confirm button (Open / Import / Insert) commits it — so the destructive "open" gesture is deliberate, which matters most for Save As (pick a name to overwrite without immediately committing). Folders enter on a single click. ↑/↓ move the selection whenever a confirm action is offered; Save As leaves Enter to its own name field. A left sidebar offers quick-access places (Home / Documents / Downloads / Models / root on desktop; the /models root on web) plus user-pinned folders (persisted under the reserved @pinned key); the top bar is a clickable breadcrumb with an editable path field and back/forward history; and the whole browse area is a drag-resizable region capped to the viewport. Files list in a sortable Name / Type / Size / Date table (the primary layout) whose body scrolls; hidden dotfiles are off by default with a toggle to reveal them — which never blocks typing a hidden path directly. Size/date come from the filesystem on desktop; the browser reports size from stored length and leaves date blank (the IndexedDB records store no timestamps).

WGPU_POWER_PREF=high asks wgpu for the discrete GPU. cargo build is the compile-only gate on headless boxes.

Windows (cross-compiled from Linux)

See the root README's "Windows (cross-compiled from Linux)" section — the toolchain setup and linker config live there; the build itself is cargo build --release --target x86_64-pc-windows-gnu from this directory.

Verification

Browser-driven UI verification scripts live in web/verify_*.mjs (Playwright + system Chrome, resolved from the repo-root node_modules; override with PLAYWRIGHT_DIR). After building the wasm app:

node web/verify.mjs        # baseline: shaded render, camera controls, 0 console errors

plus the focused scripts (verify_settings.mjs, verify_history.mjs, verify_selection.mjs, verify_ref_select.mjs, verify_scene.mjs, …), each driving the real egui widgets and asserting on screenshots + the published camera/hit state.

node web/verify_recovery.mjs http://127.0.0.1:8099 proves an unsaved edit survives a reload as the boot-time recovery offer, restores as a dirty tab, and is gone after Discard. node web/verify_cancel_run.mjs http://127.0.0.1:8098 needs the REPO ROOT served (the slow fixture is loaded through ?loadModel=): it names the feature the worker is executing, cancels it mid-boolean, and rebuilds through the respawned worker.

node web/verify_mesh_import_worker.mjs http://127.0.0.1:8099 checks STL and OBJ reconstruction through the actual WASM worker, including invalid input and a subsequent successful import. Serve BREP_app/ at the supplied URL. This check does not require WebGPU or a rendered canvas.

node web/verify_stl_import_preview.mjs http://127.0.0.1:8099 drives the real STL picker, tolerance controls, preview camera, Cancel, Accept, and Undo. Run with a display (or xvfb-run -a). cargo run --example capture_stl_import_preview captures the same panel and 3D viewport for the file-format documentation.

Documentation

User docs live in the repo-root docs/ tree (docs/features/, docs/panels/). The brep-docs crate generates the in-app help site from those user-facing docs into BREP_app/web/help/ (gitignored, wiped each run); docs/developer/ is not included. ./build.sh app regenerates the help site when the generator crate is present.

Every feature page leads its heading with assets/glyphs/icon_<hex>.svg — the app's own artwork, referenced as an ordinary markdown image so it shows in any reader — and docs/features/index.md repeats it beside each link. The generator INLINES those files (and any catalogued glyph character in the prose) as <svg>, lifts a heading's image off the title so the sidebar can draw the icon beside the name, and rewrites monochrome ink to currentColor so it reads in both themes. tests/docs_feature_icons.rs holds each page to the icon features::feature_icon gives for the feature it documents.

The feature-dialog screenshots embedded in the docs are captured headlessly from the real schema-driven dialogs:

cargo run --example capture_dialogs    # writes docs/features/<name>_dialog.png (change-detected)

License and links

• License: the repository's Autodrop3d LICENSE.md (license-file in the manifest).
• Repository: https://github.com/mmiscool/NURBS_BREP_kernel (this crate lives in BREP_app/).
• Live on crates.io: BREP_app 0.1.0; this tree is 0.2.0. See the repository-root publishing guide for the crate-family order and validation.