Raft layers cause SeamPlacer crash - fix

src/libslic3r/GCode.cpp

@@ -2586,7 +2586,7 @@ std::string GCode::extrude_loop(ExtrusionLoop loop, std::string description, dou
         loop.split_at(last_pos, false);
     }
     else
-        m_seam_placer.place_seam(m_layer->object(), loop, m_layer->slice_z, m_layer_index, m_config.external_perimeters_first);
+        m_seam_placer.place_seam(m_layer, loop, m_config.external_perimeters_first);
 
     // clip the path to avoid the extruder to get exactly on the first point of the loop;
     // if polyline was shorter than the clipping distance we'd get a null polyline, so

src/libslic3r/GCode/SeamPlacerNG.cpp

@@ -703,12 +703,12 @@ void SeamPlacer::init(const Print &print) {
     }
 }
 
-void SeamPlacer::place_seam(const PrintObject *po, ExtrusionLoop &loop, coordf_t unscaled_z, int layer_index,
-        bool external_first) {
-    assert(m_perimeter_points_trees_per_object.find(po) != nullptr);
-    assert(m_perimeter_points_per_object.find(po) != nullptr);
+void SeamPlacer::place_seam(const Layer* layer, ExtrusionLoop &loop, bool external_first) {
+    const PrintObject* po = layer->object();
+    //NOTE this is necessary, since layer->id() is quite unreliable
+    size_t layer_index = std::max(0,int(layer->id()) - int(po->slicing_parameters().raft_layers()));
+    double unscaled_z = layer->slice_z;
 
-    assert(layer_index >= 0);
     const auto &perimeter_points_tree = *m_perimeter_points_trees_per_object[po][layer_index];
     const auto &perimeter_points = m_perimeter_points_per_object[po][layer_index];
 

src/libslic3r/GCode/SeamPlacerNG.hpp

@@ -97,8 +97,7 @@ public:
 
     void init(const Print &print);
 
-    void place_seam(const PrintObject *po, ExtrusionLoop &loop, coordf_t unscaled_z, int layer_index,
-            bool external_first);
+    void place_seam(const Layer* layer, ExtrusionLoop &loop, bool external_first);
 
 private:
     void gather_seam_candidates(const PrintObject* po, const SeamPlacerImpl::GlobalModelInfo& global_model_info);