Make branching tree algorithm cancellable

src/libslic3r/BranchingTree/BranchingTree.cpp

@@ -20,7 +20,7 @@ void build_tree(PointCloud &nodes, Builder &builder)
     auto distances = reserve_vector<NodeDistance>(ReachablesToExamine);
     double prev_dist_max = 0.;
 
-    while (!ptsqueue.empty()) {
+    while (!ptsqueue.empty() && builder.is_valid()) {
         size_t node_id = ptsqueue.top();
 
         Node node = nodes.get(node_id);
@@ -49,7 +49,7 @@ void build_tree(PointCloud &nodes, Builder &builder)
 
         auto closest_it = distances.begin();
         bool routed = false;
-        while (closest_it != distances.end() && !routed) {
+        while (closest_it != distances.end() && !routed && builder.is_valid()) {
             size_t closest_node_id = closest_it->node_id;
             Node closest_node = nodes.get(closest_node_id);
 

src/libslic3r/BranchingTree/BranchingTree.hpp

@@ -102,6 +102,9 @@ public:
 
     // Report nodes that can not be routed to an endpoint (model or ground)
     virtual void report_unroutable(const Node &j) = 0;
+
+    // If returns false, the tree building process shall stop
+    virtual bool is_valid() const { return true; }
 };
 
 // Build the actual tree.

src/libslic3r/SLA/BranchingTreeSLA.cpp

@@ -111,6 +111,8 @@ public:
     {
         return m_unroutable_pinheads;
     }
+
+    bool is_valid() const override { return !m_builder.ctl().stopcondition(); }
 };
 
 bool BranchingTreeBuilder::add_bridge(const branchingtree::Node &from,