ENH: enable arachne for concentric pattern

Enable arachne for concentric pattern by
referring to PrusaSlicer

Also remove useless pattern we added.

Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: Ie2574f7fc4751ebdf1caab4de52013f3101e104f

src/libslic3r/Fill/FillBase.hpp

@@ -63,6 +63,9 @@ struct FillParams
     // in this case we don't try to make more continuous paths
     bool        complete 		{ false };
 
+    // For Concentric infill, to switch between Classic and Arachne.
+    bool        use_arachne{ false };
+
     // BBS
     Flow            flow;
     ExtrusionRole   extrusion_role{ ExtrusionRole(0) };
@@ -121,6 +124,7 @@ public:
 
     // Perform the fill.
     virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+    virtual ThickPolylines fill_surface_arachne(const Surface* surface, const FillParams& params);
 
     // BBS: this method is used to fill the ExtrusionEntityCollection.
     // It call fill_surface by default
@@ -149,6 +153,13 @@ protected:
         ExPolygon                         /* expolygon */,
         Polylines                       & /* polylines_out */) {};
 
+    // Used for concentric infill to generate ThickPolylines using Arachne.
+    virtual void _fill_surface_single(const FillParams& params,
+        unsigned int                   thickness_layers,
+        const std::pair<float, Point>& direction,
+        ExPolygon                      expolygon,
+        ThickPolylines& thick_polylines_out) {}
+
     virtual float _layer_angle(size_t idx) const { return (idx & 1) ? float(M_PI/2.) : 0; }
 
     virtual std::pair<float, Point> _infill_direction(const Surface *surface) const;