forked from 1b-agent/opencadstudio-upstream
104 lines
5.3 KiB
Markdown
104 lines
5.3 KiB
Markdown
# Native vs. Web (WebAssembly)
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Open CAD Studio ships as a native desktop app and as a WebAssembly build that
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runs in the browser (https://hakanseven12.github.io/OpenCADStudio/). Both are
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built from the same source; the web target drops or shims the pieces that a
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browser can't provide. This page lists the differences.
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## At a glance
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| Area | Native (desktop) | Web (wasm) |
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|------|------------------|------------|
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| Windowing | Multi-window (`iced::daemon`) | Single window (`iced::application`); dialogs are in-canvas modals |
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| 3D solid modeling | Yes | **No** — `solid3d` feature off |
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| Hatch rendering | Yes | **No** — WebGL2 has no vertex-stage storage |
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| Fonts | Embedded stroke fonts + system TrueType + shaping + fallback | Embedded stroke fonts only |
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| File open | Native file dialog → path | Browser picker → bytes |
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| File save | Path / Save dialog → write to disk | Save dialog → direct browser download |
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| Parallelism | Multi-threaded (rayon) | Single-threaded |
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| GPU backend | Vulkan / DX12 / Metal (wgpu) | WebGL2 (WebGPU where available) |
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| Update check / external links | `ureq`, `open` | skipped / `window.open` |
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| External plugins | Native packages + Plugin Manager | **No** — native libraries cannot run in a browser |
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## Details
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### 3D solid modeling — web: disabled
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The `solid3d` Cargo feature (default on) gates `truck-meshalgo` and
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`truck-shapeops`, which pull `vtkio → xz2 → lzma-sys`, a C library that can't
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cross-compile to `wasm32`. The web build compiles with `--no-default-features`,
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so on the web:
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- The Model tab's solid primitives and boolean operations are no-ops.
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- Solid tessellation and ACIS (SAT) import produce no geometry.
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2-D CAD is unaffected.
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### Hatch rendering — web: not drawn
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The batched hatch pipeline binds a read-only storage buffer in the vertex
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stage. WebGL2 lacks `VERTEX_STORAGE`, so that pipeline is skipped on wasm and
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hatches simply don't render. Everything else (lines, arcs, polylines, text,
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images) draws normally.
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### Fonts — web: bundled stroke fonts only
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- **Native** discovers installed system fonts (fontdb), extracts TrueType
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outlines (ttf-parser), shapes runs with cosmic-text (ligatures, Arabic
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joining, kerning, bidi), and falls back to a system font for glyphs a stroke
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font lacks.
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- **Web** has no system fonts, and cosmic-text panics with "no default font
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found" on an empty font set, so shaping and fallback are disabled. Only the
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embedded LFF stroke fonts render; a glyph missing from them is skipped.
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(A future option is to fetch a font file from the server at startup.)
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### File I/O — web: bytes and downloads
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- **Open**: the desktop returns a filesystem path and reads it (streaming).
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The web reads the picked file's bytes via the browser and parses them in
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memory (`io::load_bytes`).
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- **Save**: both show the in-app Save dialog (filename + format). The desktop
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writes to the chosen path; the web serializes to bytes and triggers a direct
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browser download (a Blob + a programmatic `<a download>` click — no
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intermediate "click to download" link). The unsaved-changes prompt's *Save*
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routes through the same dialog on the web.
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- There is no persistent filesystem path on the web, so a name-only path stands
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in for document tracking.
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### Windowing — web: single window, in-canvas modals
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The desktop uses `iced::daemon` and opens secondary OS windows for every
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manager and style dialog. The browser has only the canvas, so the web uses
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`iced::application` and renders all dialogs (layer/layout/plot managers, the
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style editors, the colour picker, Save / unsaved prompts, About, shortcuts,
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plugins, …) as in-canvas modal overlays. As of the Plan-B work this path is
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shared: native renders the same modals too, so the desktop is effectively
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single-window now. A modal's backdrop dims and blocks clicks but does not
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dismiss; the ✕ button closes it.
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### Parallelism — web: single-threaded
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`wasm32` has no threads without SharedArrayBuffer (which needs COOP/COEP
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headers GitHub Pages can't set). `crate::par::prelude` re-exports `rayon` on
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native and sequential `std` iterators on wasm, so the same call sites run in
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parallel on the desktop and serially in the browser. Large drawings are slower
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on the web.
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### External plugins — web: unavailable
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Marketplace plugins are native `.dll`, `.so`, or `.dylib` packages launched in
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an isolated child process. Browsers cannot load those libraries or spawn the
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plugin runner, so the web build does not show the Plugin Manager or register
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its commands. Installed desktop plugins remain in the per-user plugins folder
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and load again on the next desktop launch.
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### Platform shims (`src/sys.rs`)
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- `open_url`: `open::that` on native, `window.open(_blank)` on web.
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- `download_bytes`: web only (Blob + anchor download).
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- `handle_path`: real path on native, a name-only `PathBuf` on web.
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- `platform_info`: OS + arch on native, the browser user-agent on web (used to
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pre-fill the Send Feedback issue).
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- The self-update check (`ureq`) is a no-op on the web.
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## Build & deploy
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- Native: `cargo build --release --bin OpenCADStudio`.
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- Web: `trunk build --release --public-url /OpenCADStudio/` (the rust `<link>`
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in `index.html` sets `data-cargo-no-default-features`, dropping `solid3d`).
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`.github/workflows/pages.yml` builds and deploys to GitHub Pages on every
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release. No COOP/COEP headers are needed because the web build is
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single-threaded.
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