solidcraft-smlib: Brep::merge_faces, SMLib's removal of topological edges and vertices

The wrapper of the fork's smlib_merge_faces (SmBrep::RemoveTopologicalEdgesAndVertices): faces
on one surface meeting along an edge become one, edges on one curve meeting at a vertex nothing
else uses become one, and the edges under the given points stay. SMLIB_REV moves to the fork
commit that adds it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt

crates/smlib/SMLIB_REV

@@ -1 +1 @@
-e7522f4e7917fe817643ff691f2860c310038c27
+c899502f2bdd0e8e21c25e69eca423f659c9da8f

crates/smlib/src/ffi/ops.rs

@@ -1,6 +1,6 @@
 //! The operations block of `capi/include/smlib.h` (`smlib_boolean`, `smlib_fillet`,
 //! `smlib_chamfer`, `smlib_blend`, `smlib_fillet_variable`, `smlib_chamfer_sides`, `smlib_shell`, `smlib_offset_faces`,
-//! `smlib_thicken`, `smlib_draft`, `smlib_brep_solid_count`, `smlib_imprint`; the fork's `capi/src/smlib_ops.cpp`), declared by
+//! `smlib_thicken`, `smlib_draft`, `smlib_merge_faces`, `smlib_brep_solid_count`, `smlib_imprint`; the fork's `capi/src/smlib_ops.cpp`), declared by
 //! hand. Part of the FFI boundary, like its parent: called only through
 //! [`crate::ops`].
 
@@ -121,6 +121,14 @@ unsafe extern "C" {
         out_failed_point: *mut i64,
     ) -> i32;
     fn smlib_thicken(brep: *const RawBrep, thickness: f64, symmetric: i32, out: *mut *mut RawBrep) -> i32;
+    fn smlib_merge_faces(
+        brep: *const RawBrep,
+        keep: *const f64,
+        n_keep: i64,
+        tolerance: f64,
+        out: *mut *mut RawBrep,
+        out_failed_point: *mut i64,
+    ) -> i32;
     fn smlib_draft(
         brep: *const RawBrep,
         points: *const f64,
@@ -209,6 +217,24 @@ pub fn draft(_: &Handle, _: &[[f64; 3]], _: f64, _: &[f64; 3], _: &[f64; 3], _:
     Err((NOT_BUILT, None))
 }
 
+/// `smlib_merge_faces`: the body's topological edges and vertices removed, the edges under
+/// `keep` kept.
+#[cfg(feature = "native")]
+pub fn merge_faces(b: &Handle, keep: &[[f64; 3]], tolerance: f64) -> Result<Handle, PickError> {
+    let n = i64::try_from(keep.len()).map_err(|_| (ERR_ARG, None))?;
+    let flat = keep.as_ptr().cast::<f64>();
+    let mut failed = -1i64;
+    new_brep(|out| unsafe { smlib_merge_faces(b.raw(), flat, n, tolerance, out, &mut failed) }).map_err(|s| {
+        let at = (s == ERR_PICK_NONE || s == ERR_PICK_AMBIGUOUS).then(|| usize::try_from(failed).ok()).flatten();
+        (s, at)
+    })
+}
+
+#[cfg(not(feature = "native"))]
+pub fn merge_faces(_: &Handle, _: &[[f64; 3]], _: f64) -> Result<Handle, PickError> {
+    Err((NOT_BUILT, None))
+}
+
 /// `smlib_blend`: `sizes` holds one size per point (the caller checks the lengths match).
 #[cfg(feature = "native")]
 pub fn blend(kind: i32, b: &Handle, points: &[[f64; 3]], sizes: &[f64], tolerance: f64) -> Result<Handle, PickError> {

crates/smlib/src/ops.rs

@@ -170,6 +170,19 @@ impl Brep {
         ffi::ops::thicken(&self.0, thickness, symmetric).map(Brep).map_err(error)
     }
 
+    /// This body with its topological edges and vertices removed (SMLib's
+    /// `SmBrep::RemoveTopologicalEdgesAndVertices`): faces on one surface meeting along an edge
+    /// become one, and two edges on one curve meeting at a vertex nothing else uses become one.
+    /// The edges nearest to `keep` (each within `tolerance`) stay. The shape is unchanged, and
+    /// SMLib's history tags follow the merge.
+    pub fn merge_faces(&self, keep: &[[f64; 3]], tolerance: f64) -> Result<Brep> {
+        init()?;
+        if keep.len() > MAX_POINTS {
+            return Err(Error::Argument);
+        }
+        ffi::ops::merge_faces(&self.0, keep, tolerance).map(Brep).map_err(pick_error)
+    }
+
     /// The flat faces nearest to `faces` (each within `tolerance`) tilted by `angle` radians
     /// (0 < |angle| < 89.94 degrees) about the line where each meets the neutral plane through
     /// `neutral_origin` with normal `neutral_normal`, a positive angle leaning them in going along