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fixup: deduce kernel from mesh point type instead of hard-coding it
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Removes the only architectural lock-in spotted in the MVP audit before
Phase 9a starts: the wrapper hard-coded Simple_cartesian<double> as the
kernel inside discrete_conformal_map_euclidean.  This would have broken
any Surface_mesh<P> where P came from a different kernel (e.g. EPIC).

Change
──────
* CGAL::Kernel_traits<typename TriangleMesh::Point>::Kernel is now used
  to deduce the kernel from the mesh's point type.
* The full Default_traits<...> instantiation is wrapped in
  internal_np::Lookup_named_param_def so a future `geom_traits(...)`
  named parameter can override the entire traits class without changes
  to the wrapper body (CGAL idiom, used by every CGAL package).
* New test `KernelIsDeducedFromMeshPointType` pins the contract
  explicitly with static_asserts.

Why now
───────
Phase 9a (Inversive-Distance) will copy this same template pattern.
Fixing the kernel deduction once here keeps the design free for any
user kernel; doing it after 9a would mean two parallel hard-coded
kernel sites to refactor.

Tests
─────
CGAL suite: 184/184 passed, 0 skipped  (was 183).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Tarik Moussa
2026-05-19 22:50:40 +02:00
parent a1e74c1370
commit 140f50f707
2 changed files with 48 additions and 3 deletions
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20
code/include/CGAL/Discrete_conformal_map.h
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@@ -52,8 +52,10 @@ auto result = CGAL::discrete_conformal_map_euclidean(
#include <CGAL/Conformal_map_traits.h>
#include <CGAL/Conformal_map/internal/parameters.h>
#include <CGAL/Kernel_traits.h>
#include <CGAL/Named_function_parameters.h>
#include <CGAL/boost/graph/named_params_helper.h>
#include <CGAL/property_map.h>
// Existing implementation headers (Layer 1 — unchanged).
#include "../euclidean_functional.hpp"
@@ -147,9 +149,21 @@ auto discrete_conformal_map_euclidean(
TriangleMesh& mesh,
const CGAL_NP_CLASS& np = parameters::default_values())
{
using Traits = Default_conformal_map_traits<TriangleMesh, Simple_cartesian<double>>;
using FT = typename Traits::FT;
using Vertex_descriptor = typename Traits::Vertex_descriptor;
// ── Type plumbing ──────────────────────────────────────────────────────
//
// Deduce the kernel from the mesh's Point_3 type rather than hard-coding
// Simple_cartesian<double>. This lets the wrapper work with any
// Surface_mesh<P> whose P is a CGAL kernel point. The user can override
// the entire traits class via the `geom_traits(...)` named parameter
// (Phase 8b.2 extension; default below covers the common case).
using Point_type = typename TriangleMesh::Point;
using Default_kernel = typename CGAL::Kernel_traits<Point_type>::Kernel;
using Default_traits = Default_conformal_map_traits<TriangleMesh, Default_kernel>;
using Traits = typename internal_np::Lookup_named_param_def<
internal_np::geom_traits_t,
CGAL_NP_CLASS,
Default_traits>::type;
using FT = typename Traits::FT;
Conformal_map_result<FT> result;