Fix concave hull having holes.

src/libslic3r/SLA/ConcaveHull.hpp

@@ -0,0 +1,53 @@
+#ifndef CONCAVEHULL_HPP
+#define CONCAVEHULL_HPP
+
+#include <libslic3r/ExPolygon.hpp>
+
+namespace Slic3r {
+namespace sla {
+
+inline Polygons get_contours(const ExPolygons &poly)
+{
+    Polygons ret; ret.reserve(poly.size());
+    for (const ExPolygon &p : poly) ret.emplace_back(p.contour);
+
+    return ret;
+}
+
+using ThrowOnCancel = std::function<void()>;
+
+/// A fake concave hull that is constructed by connecting separate shapes
+/// with explicit bridges. Bridges are generated from each shape's centroid
+/// to the center of the "scene" which is the centroid calculated from the shape
+/// centroids (a star is created...)
+class ConcaveHull {
+    Polygons m_polys;
+
+    static Point centroid(const Points& pp);
+
+    static inline Point centroid(const Polygon &poly) { return poly.centroid(); }
+
+    Points calculate_centroids() const;
+
+    void merge_polygons();
+
+    void add_connector_rectangles(const Points &centroids,
+                                  coord_t       max_dist,
+                                  ThrowOnCancel thr);
+public:
+
+    ConcaveHull(const ExPolygons& polys, double merge_dist, ThrowOnCancel thr)
+        : ConcaveHull{to_polygons(polys), merge_dist, thr} {}
+
+    ConcaveHull(const Polygons& polys, double mergedist, ThrowOnCancel thr);
+
+    const Polygons & polygons() const { return m_polys; }
+
+    ExPolygons to_expolygons() const;
+};
+
+ExPolygons offset_waffle_style_ex(const ConcaveHull &ccvhull, coord_t delta);
+Polygons   offset_waffle_style(const ConcaveHull &polys, coord_t delta);
+
+}}     // namespace Slic3r::sla
+#endif // CONCAVEHULL_HPP