Layout algorithm is now applied to each connected component in the

selection separately.  Previously, behaviour of layout on disconnected 
graphs was... undefined!

(bzr r1421)

1 files changed, 67 insertions, 0 deletions

diff --git a/src/libcola/connected_components.cpp b/src/libcola/connected_components.cpp
new file mode 100644
index 000000000..8450e4874
--- /dev/null
+++ b/src/libcola/connected_components.cpp
@@ -0,0 +1,67 @@
+#include <map>
+#include "cola.h"
+using namespace std;
+
+namespace cola {
+    namespace ccomponents {
+        struct Node {
+            unsigned id;
+            bool visited;
+            vector<Node*> neighbours;
+            Rectangle* r;
+        };
+        // Depth first search traversal of graph to find connected component
+        void dfs(Node* v,
+                set<Node*>& remaining,
+                Component* component,
+                map<unsigned,pair<Component*,unsigned> > &cmap) {
+            v->visited=true;
+            remaining.erase(v);
+            cmap[v->id]=make_pair(component,component->node_ids.size());
+            component->node_ids.push_back(v->id);
+            component->rects.push_back(v->r);
+            for(unsigned i=0;i<v->neighbours.size();i++) {
+                Node* u=v->neighbours[i];
+                if(!u->visited) {
+                    dfs(u,remaining,component,cmap);
+                }
+            }
+        }
+    }
+
+    using namespace ccomponents;
+
+    // for a graph of n nodes, return connected components
+    void connectedComponents(
+            vector<Rectangle*> &rs,
+            vector<Edge> &es, 
+            vector<Component*> &components) {
+        unsigned n=rs.size();
+        vector<Node> vs(n);
+        set<Node*> remaining;
+        for(unsigned i=0;i<n;i++) {
+            vs[i].id=i;
+            vs[i].visited=false;
+            vs[i].r=rs[i];
+            remaining.insert(&vs[i]);
+        }
+        for(vector<Edge>::iterator e=es.begin();e!=es.end();e++) {
+            vs[e->first].neighbours.push_back(&vs[e->second]);
+            vs[e->second].neighbours.push_back(&vs[e->first]);
+        }
+        map<unsigned,pair<Component*,unsigned> > cmap;
+        while(!remaining.empty()) {
+            Component* component=new Component;
+            Node* v=*remaining.begin();
+            dfs(v,remaining,component,cmap);
+            components.push_back(component);
+        }
+        for(vector<Edge>::iterator e=es.begin();e!=es.end();e++) {
+            pair<Component*,unsigned> u=cmap[e->first],
+                                      v=cmap[e->second];
+            assert(u.first==v.first);
+            u.first->edges.push_back(make_pair(u.second,v.second));
+        }
+    }
+}
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=4:softtabstop=4