Add Precise Seam placement feature (#12974)

Co-authored-by: Ioannis Giannakas <59056762+igiannakas@users.noreply.github.com>
Co-authored-by: Rodrigo Faselli <162915171+RF47@users.noreply.github.com>
Co-authored-by: Ian Bassi <ian.bassi@outlook.com>

tests/slic3rutils/test_precise_seam_plugin.cpp

@@ -0,0 +1,61 @@
+#include <catch2/catch_all.hpp>
+
+#include "libslic3r/Model.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+#include "python_test_support.hpp"
+
+#include <pybind11/embed.h>
+#include <array>
+
+namespace py = pybind11;
+using namespace Slic3r;
+
+TEST_CASE("Python exposes every seam mode and distinguishes strong weak and ordinary volumes", "[PreciseSeamPlugin][Python]")
+{
+    struct Mode {
+        const char *name;
+        ModelVolumeType type;
+        bool strong;
+        bool weak;
+    };
+    // Explicit expectations protect enum registration and both predicate groups independently.
+    const std::array<Mode, 11> modes = {{
+        {"PreciseSeamCenter", ModelVolumeType::PRECISE_SEAM_CENTER, true, false},
+        {"PreciseSeamLeft", ModelVolumeType::PRECISE_SEAM_LEFT, true, false},
+        {"PreciseSeamRight", ModelVolumeType::PRECISE_SEAM_RIGHT, true, false},
+        {"PreciseSeamEnforced", ModelVolumeType::PRECISE_SEAM_ENFORCED, false, true},
+        {"PreciseSeamBlocked", ModelVolumeType::PRECISE_SEAM_BLOCKED, false, true},
+        {"PreciseSeamNeutral", ModelVolumeType::PRECISE_SEAM_NEUTRAL, false, true},
+        {"ModelPart", ModelVolumeType::MODEL_PART, false, false},
+        {"NegativeVolume", ModelVolumeType::NEGATIVE_VOLUME, false, false},
+        {"ParameterModifier", ModelVolumeType::PARAMETER_MODIFIER, false, false},
+        {"SupportEnforcer", ModelVolumeType::SUPPORT_ENFORCER, false, false},
+        {"SupportBlocker", ModelVolumeType::SUPPORT_BLOCKER, false, false}
+    }};
+
+    // Bootstrap holds the GIL on first initialization; acquire explicitly for an already-running interpreter too.
+    ensure_python_initialized();
+    py::gil_scoped_acquire gil;
+    py::object host = import_orca_module().attr("host");
+    REQUIRE(py::hasattr(host, "ModelVolumeType"));
+    py::object enumeration = host.attr("ModelVolumeType");
+    for (const Mode &mode : modes) {
+        DYNAMIC_SECTION(mode.name) {
+            REQUIRE(py::hasattr(enumeration, mode.name));
+            CHECK(enumeration.attr(mode.name).cast<ModelVolumeType>() == mode.type);
+            Model model;
+            auto *volume = model.add_object()->add_volume(make_cube(1, 1, 1));
+            volume->set_type(mode.type);
+            // Borrow the volume: the Python reference is destroyed before its owning Model.
+            py::object py_volume = py::cast(volume, py::return_value_policy::reference);
+            REQUIRE(py::hasattr(py_volume, "is_precise_seam"));
+            REQUIRE(py::hasattr(py_volume, "is_precise_seam_strong"));
+            REQUIRE(py::hasattr(py_volume, "is_precise_seam_weak"));
+            CHECK(py_volume.attr("type")().cast<ModelVolumeType>() == mode.type);
+            const bool precise = mode.strong || mode.weak;
+            CHECK(py_volume.attr("is_precise_seam")().cast<bool>() == precise);
+            CHECK(py_volume.attr("is_precise_seam_strong")().cast<bool>() == mode.strong);
+            CHECK(py_volume.attr("is_precise_seam_weak")().cast<bool>() == mode.weak);
+        }
+    }
+}