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Document the CAD subsystem's real dependency weight
Maintainers will ask what the Design tab costs before they will look at the diff, so measure it rather than assert it. The headline correction: the OCCT delta is THREE toolkits, not two. The comment in deps/OCCT/OCCT.cmake claimed "TKFillet + TKOffset (3.77 MiB, Windows only)". Walking OCCT's own adm/MODULES and each toolkit's EXTERNLIB shows ModelingAlgorithms holds twelve toolkits, that eight of them are built either way because DataExchange (the STEP path upstream already ships) depends on them, and that the true delta is TKFeat, TKFillet, TKOffset and TKXMesh — of which TKXMesh is never produced. So three archives are built: 7.40, 5.38 and 4.42 MiB. TKFeat is the interesting one. Nothing in the Design tab references it and it is absent from the TKFillet/TKOffset dependency closure, so it is built for nothing — OCCT's module flag is all-or-nothing per module. On static-link platforms that is build time and zero shipped bytes. Two numbers are deliberately absent, marked as absent, and not approximated: the Windows DLL delta needs a Windows build (snaporca-gix), and a clean-build time delta needs the deps prefix built twice on one machine. The old 3.77 MiB figure is withdrawn rather than reused — it covered two of the three toolkits. Also recorded: the vendored solver is 9,339 lines under GPLv3 with its LICENSE preserved, which combines into this AGPLv3 fork without difficulty (AGPLv3 §13), and it is live code driving every sketch constraint — not a carried corpse. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Tommaso Bianchi
co-authored by
Claude Opus 5
Claude Opus 5
parent
e2b58a17f7
commit
f347afd22e
Vendored
+14
-3
@@ -5,9 +5,20 @@ else()
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endif()
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# The parametric Design/CAD tab is the only consumer of OCCT's ModelingAlgorithms
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# module (fillet/offset/loft). With it OFF the deps prefix matches upstream exactly;
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# with it ON the delta is TKFillet + TKOffset (3.77 MiB, Windows only -- OCCT links
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# statically on macOS/Linux). Must match the SLIC3R_CAD passed to the main project.
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# module (fillet/offset/loft). With it OFF the deps prefix matches upstream exactly.
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#
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# With it ON the delta is THREE toolkits, not two: TKFillet (7.40 MiB archive, used via
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# BRepFilletAPI), TKOffset (5.38 MiB, used via BRepOffsetAPI) and TKFeat (4.42 MiB), which
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# nothing here references but which the module flag builds anyway -- it is all-or-nothing
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# per module. The module's other nine toolkits are built either way, because DataExchange
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# (the STEP path upstream already ships) depends on them.
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#
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# On macOS/Linux OCCT links statically, so an unreferenced toolkit costs build time and no
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# shipped bytes. The Windows figure is a real DLL cost and has NOT been measured -- an
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# earlier "3.77 MiB, Windows only" note here covered only two of the three toolkits and is
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# not a number to quote. See docs/cad_dependency_weight.md.
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#
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# Must match the SLIC3R_CAD passed to the main project.
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option(SLIC3R_CAD "Build OCCT's ModelingAlgorithms module (required by the Design/CAD tab)" ON)
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if (IN_GIT_REPO)
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@@ -0,0 +1,136 @@
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# Dependency weight of the Design/CAD subsystem
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What the Design tab actually costs a maintainer who merges it. Written to be checkable:
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every number below is reproducible with the command that produced it, and the places where
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a number is still missing say so instead of guessing.
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Measured on Linux x86_64, OCCT V7_6_0, in the `snaporca-deps` build image.
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## Summary
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| | Cost |
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|---|---|
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| New third-party dependencies | **none** |
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| OCCT build flag | `BUILD_MODULE_ModelingAlgorithms=ON` |
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| Extra OCCT toolkits *built* | 3 (TKFillet, TKOffset, TKFeat) |
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| Extra OCCT toolkits *linked* | 2 (TKFillet, TKOffset) |
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| Vendored code | `src/libslic3r/slvs`, 9,339 lines, 380 KiB, GPLv3 |
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| Own object code | 6.79 MiB unstripped `.o` (7.13 MiB with the solver) |
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OCCT is **already** an upstream dependency — Orca uses it for STEP import. The Design tab
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does not add a library; it turns on one more OCCT module.
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## The OCCT module flag
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`deps/OCCT/OCCT.cmake` gates the module on `SLIC3R_CAD`:
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```cmake
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-DBUILD_MODULE_ModelingAlgorithms=${SLIC3R_CAD} # was hard-coded OFF
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```
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With `SLIC3R_CAD=OFF` the deps prefix matches upstream exactly.
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`ModelingAlgorithms` contains 12 toolkits, but **most were already being built**, because
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`DataExchange` — the STEP path upstream already ships — depends on them. The honest delta is
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only the toolkits that DataExchange's dependency closure does *not* reach:
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```
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ModelingAlgorithms = TKGeomAlgo TKTopAlgo TKPrim TKBO TKBool TKHLR
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TKFillet TKOffset TKFeat TKMesh TKXMesh TKShHealing
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already required by DataExchange: TKBO TKBool TKGeomAlgo TKHLR TKMesh
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TKPrim TKShHealing TKTopAlgo
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true delta: TKFeat TKFillet TKOffset TKXMesh
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```
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Reproduce by walking `adm/MODULES` and each toolkit's `src/<TK>/EXTERNLIB` in the OCCT
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source tree.
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### Sizes of the delta toolkits
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Static archives in the deps prefix. These are *build artifacts*, not shipped bytes — a
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static link pulls in only the objects it references:
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| Toolkit | Archive | Referenced by the Design tab? |
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|---|---|---|
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| TKFillet | 7.40 MiB | yes — `BRepFilletAPI` |
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| TKOffset | 5.38 MiB | yes — `BRepOffsetAPI`, `BRepOffset_` |
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| TKFeat | 4.42 MiB | **no** |
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| TKXMesh | — | not produced at all |
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TKFeat is worth calling out: nothing in the Design tab references it, and it is absent from
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the `TKFillet`/`TKOffset` dependency closure, so it is built for nothing. OCCT's module flag
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is all-or-nothing per module, which is why it comes along. It costs build time and zero
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shipped bytes on any platform that links OCCT statically.
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**A correction to the record.** The comment in `deps/OCCT/OCCT.cmake` and the earlier
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summary both said the delta was "TKFillet + TKOffset — 3.77 MiB, Windows only". The toolkit
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list was incomplete: TKFeat is built too. The 3.77 MiB figure covers 2 of the 3 built
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toolkits and has not been re-derived here — see the gap below.
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## What is not measured yet
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Two numbers a maintainer may reasonably ask for are **not** in this document, because
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producing them honestly needs a build this machine cannot do:
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1. **Windows DLL delta.** OCCT builds shared on Windows, so the shipped cost there is real
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DLL bytes rather than linker-selected objects. That needs a Windows build to size —
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tracked as the cross-platform build proof (`snaporca-gix`).
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2. **Clean-build time delta.** Measuring it means building the deps prefix twice, with the
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flag ON and OFF, on the same machine. The incremental figures from day-to-day work do not
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answer the question and are not offered as if they did.
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Do not quote a number for either until it has been measured.
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## Vendored solver
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`src/libslic3r/slvs` — the 2D sketch constraint solver extracted from SolveSpace.
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- 19 files: 8 `.cpp`, 11 `.h`, plus `LICENSE`
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- 9,339 lines, 380 KiB of source, 0.34 MiB of object code
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- **GPLv3**, `LICENSE` preserved verbatim in the vendored directory
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The fork is **AGPLv3**. GPLv3 code combines into an AGPLv3 work without difficulty: AGPLv3
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§13 provides explicit compatibility in that direction. No licence question to resolve.
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It is live code, not a carried corpse — `SketchSolver.cpp` is its only consumer and drives
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every sketch constraint in the Design tab.
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## Own code
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Object sizes from the release build (unstripped, so these include debug information and
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overstate the shipped contribution):
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| Object | Size |
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|---|---|
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| DesignPanel.o | 2.22 MiB |
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| McpControl.o | 1.69 MiB |
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| DesignSketchTool.o | 0.88 MiB |
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| CadDocument.o | 0.76 MiB |
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| SketchEngine.o | 0.40 MiB |
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| DesignCanvas.o | 0.37 MiB |
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| GeometryEngine.o | 0.32 MiB |
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| SketchSolver.o | 0.15 MiB |
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| slvs (all objects) | 0.34 MiB |
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| **total** | **7.13 MiB** |
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For scale, the linked binary is 137.1 MiB.
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## Reproducing
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```bash
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# toolkit membership and dependency closure
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R=<occt-source>
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cat $R/adm/MODULES # module -> toolkits
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cat $R/src/<TK>/EXTERNLIB # toolkit -> its dependencies
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# archive sizes
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ls -l <deps-prefix>/lib/libTK{Fillet,Offset,Feat}.a
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# what the Design tab actually references
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grep -rE 'BRepFilletAPI|BRepOffsetAPI|BRepOffset_|BRepFeat' src/libslic3r/
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# vendored solver
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wc -l src/libslic3r/slvs/*.cpp src/libslic3r/slvs/**/*.h
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head -3 src/libslic3r/slvs/LICENSE
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```
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