autorouter: treat (layer, net) pairs like separate nets for ratsnest

Most likely we won't be having via placement anytime soon, so let's
narrow our routing capabilities to single layer at a time.

src/autorouter/ratsnest.rs

@@ -70,27 +70,27 @@ impl Ratsnest {
 
         let mut triangulations = HashMap::new();
 
-        for node in layout.drawing().primitive_nodes() {
+        for layer in 0..layout.drawing().layer_count() {
+            for node in layout.drawing().layer_primitive_nodes(layer) {
                 match node {
                     PrimitiveIndex::FixedDot(dot) => {
                         if layout.compounds(dot).next().is_none() {
                             if let Some(net) = layout.drawing().primitive(dot).maybe_net() {
-                            if !triangulations.contains_key(&net) {
+                                if !triangulations.contains_key(&(layer, net)) {
                                     triangulations.insert(
-                                    net,
+                                        (layer, net),
                                         Triangulation::new(
                                             layout.drawing().geometry().graph().node_bound(),
                                         ),
                                     );
                                 }
 
-                            triangulations
-                                .get_mut(&net)
-                                .unwrap()
-                                .add_vertex(VertexWeight {
+                                triangulations.get_mut(&(layer, net)).unwrap().add_vertex(
+                                    VertexWeight {
                                         vertex: RatsnestVertexIndex::FixedDot(dot),
                                         pos: node.primitive(layout.drawing()).shape().center(),
-                                })?;
+                                    },
+                                )?;
                             }
                         }
                     }
@@ -98,17 +98,17 @@ impl Ratsnest {
                 }
             }
 
-        for zone in layout.zone_nodes() {
+            for zone in layout.layer_zone_nodes(layer) {
                 if let Some(net) = layout.drawing().compound_weight(zone).maybe_net() {
-                if !triangulations.contains_key(&net) {
+                    if !triangulations.contains_key(&(layer, net)) {
                         triangulations.insert(
-                        net,
+                            (layer, net),
                             Triangulation::new(layout.drawing().geometry().graph().node_bound()),
                         );
                     }
 
                     triangulations
-                    .get_mut(&net)
+                        .get_mut(&(layer, net))
                         .unwrap()
                         .add_vertex(VertexWeight {
                             vertex: RatsnestVertexIndex::Zone(zone),
@@ -116,8 +116,9 @@ impl Ratsnest {
                         })?
                 }
             }
+        }
 
-        for (net, triangulation) in triangulations {
+        for ((_layer, _net), triangulation) in triangulations {
             let mut map = Vec::new();
 
             for element in petgraph::algo::min_spanning_tree(&triangulation) {

src/drawing/drawing.rs

@@ -838,6 +838,12 @@ impl<CW: Copy, R: RulesTrait> Drawing<CW, R> {
         self.geometry_with_rtree.rtree()
     }
 
+    #[debug_ensures(self.geometry_with_rtree.graph().node_count() == old(self.geometry_with_rtree.graph().node_count()))]
+    #[debug_ensures(self.geometry_with_rtree.graph().edge_count() == old(self.geometry_with_rtree.graph().edge_count()))]
+    pub fn layer_count(&self) -> u64 {
+        self.geometry_with_rtree.layer_count()
+    }
+
     #[debug_ensures(self.geometry_with_rtree.graph().node_count() == old(self.geometry_with_rtree.graph().node_count()))]
     #[debug_ensures(self.geometry_with_rtree.graph().edge_count() == old(self.geometry_with_rtree.graph().edge_count()))]
     pub fn rules(&self) -> &R {

src/geometry/with_rtree.rs

@@ -347,6 +347,10 @@ impl<
         }
     }
 
+    pub fn layer_count(&self) -> u64 {
+        self.layer_count
+    }
+
     pub fn geometry(&self) -> &Geometry<PW, DW, SW, BW, CW, PI, DI, SI, BI> {
         &self.geometry
     }