d3#88 an optional "level" property for sankey nodes

If present, this will override the x-position/stack for this node
(otherwise computed during layout in computeNodeBreadths)

sankey/README.md

@@ -15,3 +15,13 @@ var sankey = d3.sankey()
 ```
 var path = sankey.link();
 ```
+
+### Node attributes
+
+Some attributes influence how sankey does its layout (anything else is just passed through).
+
+  * `level` can be set to an integer to specify how far right a node is pushed, starting with 0
+     for the left-most position (a "source"). If unspecified, the default layout position is 
+     "sources" left, "sinks" right, everything else to the right of their "inputs".
+
+

sankey/sankey.js

@@ -107,34 +107,36 @@ d3.sankey = function() {
   // Nodes are assigned the maximum breadth of incoming neighbors plus one;
   // nodes with no incoming links are assigned breadth zero, while
   // nodes with no outgoing links are assigned the maximum breadth.
+  // This can be overridden by a "level" property of the node 
   function computeNodeBreadths() {
     var remainingNodes = nodes,
         nextNodes,
-        x = 0;
+        x = 0, maxX = 0;
 
     while (remainingNodes.length) {
       nextNodes = [];
       remainingNodes.forEach(function(node) {
-        node.x = x;
+        node.x = ('level' in node) ? node.level : x;
         node.dx = nodeWidth;
+        if (node.x > maxX){ maxX = node.x; }
         node.sourceLinks.forEach(function(link) {
           if (nextNodes.indexOf(link.target) < 0) {
             nextNodes.push(link.target);
           }
         });
       });
       remainingNodes = nextNodes;
-      ++x;
+      x++;
     }
 
-    moveSinksRight(x);
-    scaleNodeBreadths((size[0] - nodeWidth) / (x - 1));
+    moveSinksRight(maxX);
+    scaleNodeBreadths((size[0] - nodeWidth) / maxX);
   }
 
   function moveSinksRight(x) {
     nodes.forEach(function(node) {
-      if (!node.sourceLinks.length) {
-        node.x = x - 1;
+      if (!node.level && !node.sourceLinks.length) {
+        node.x = x;
       }
     });
   }