Merge pull request #20 from nulab/dev-19/empty-nodes

autolayout.go

@@ -1,6 +1,8 @@
 package autog
 
 import (
+	"slices"
+
 	"github.com/nulab/autog/graph"
 	ig "github.com/nulab/autog/internal/graph"
 	imonitor "github.com/nulab/autog/internal/monitor"
@@ -27,8 +29,7 @@ func Layout(source graph.Source, opts ...Option) graph.Layout {
 	}
 
 	// populate the graph struct from the graph source
-	g := &ig.DGraph{}
-	source.Populate(g)
+	g := from(source)
 
 	if layoutOpts.params.NodeFixedSizeFunc != nil {
 		for _, n := range g.Nodes {
@@ -43,20 +44,43 @@ func Layout(source graph.Source, opts ...Option) graph.Layout {
 
 	// return only relevant data to the caller
 	out := graph.Layout{
-		Nodes: make([]graph.Node, len(g.Nodes)),
-		Edges: make([]graph.Edge, len(g.Edges)),
+		Nodes: make([]graph.Node, 0, len(g.Nodes)),
+		Edges: make([]graph.Edge, 0, len(g.Edges)),
 	}
-	for i, n := range g.Nodes {
-		if n.IsVirtual {
+	for _, n := range g.Nodes {
+		if n.IsVirtual && !layoutOpts.output.keepVirtualNodes {
 			continue
 		}
-		out.Nodes[i] = graph.Node{ID: n.ID, Size: n.Size}
+		out.Nodes = append(out.Nodes, graph.Node{
+			ID:   n.ID,
+			Size: n.Size,
+		})
+		// todo: clients can't reliably tell virtual nodes from concrete nodes
+	}
+	if !layoutOpts.output.keepVirtualNodes {
+		out.Nodes = slices.Clip(out.Nodes)
 	}
-	for i, e := range g.Edges {
-		out.Edges[i] = graph.Edge{
+
+	for _, e := range g.Edges {
+		out.Edges = append(out.Edges, graph.Edge{
+			FromID:         e.From.ID,
+			ToID:           e.To.ID,
 			Points:         e.Points,
 			ArrowHeadStart: e.ArrowHeadStart,
-		}
+		})
 	}
 	return out
 }
+
+func from(source graph.Source) *ig.DGraph {
+	switch t := source.(type) {
+	case *ig.DGraph:
+		// special case for when the graph source is already a DGraph
+		// this happens only during unit testing
+		return t
+	default:
+		g := &ig.DGraph{}
+		source.Populate(g)
+		return g
+	}
+}

autolayout_options.go

@@ -17,9 +17,14 @@ type options struct {
 	p4      positioning.Alg
 	p5      routing.Alg
 	params  graph.Params
+	output  output
 	monitor imonitor.Monitor
 }
 
+type output struct {
+	keepVirtualNodes bool
+}
+
 var defaultOptions = options{
 	p1: cbreaking.Greedy,
 	p2: layering.NetworkSimplex,
@@ -37,6 +42,11 @@ var defaultOptions = options{
 		BrandesKoepfLayout:                       -1,
 	},
 	monitor: nil,
+	output:  defaultOutputOptions,
+}
+
+var defaultOutputOptions = output{
+	keepVirtualNodes: false,
 }
 
 type Option func(*options)

autolayout_options_params.go → autolayout_options_funcs.go

@@ -43,3 +43,9 @@ func WithMonitor(monitor imonitor.Monitor) Option {
 		o.monitor = monitor
 	}
 }
+
+func WithKeepVirtualNodes(keep bool) Option {
+	return func(o *options) {
+		o.output.keepVirtualNodes = keep
+	}
+}

graph/edge.go

@@ -1,14 +1,16 @@
 package graph
 
 type Edge struct {
-	ID string
-
+	// Identifier of this edge's source node
+	FromID string
+	// Identifier of this edge's target node
+	ToID string
 	// Slice of points required to draw this edge.
 	// Depending on the routing algorithm, the slice can be interpreted differently:
 	//
-	// in case of edges made of straight segments (options autog.WithEdgeRoutingStraight, autog.WithEdgeRoutingPieceWise, autog.WithEdgeRoutingOrtho),
+	// in case of edges made of straight segments (options EdgeRoutingStraight, EdgeRoutingPieceWise, EdgeRoutingOrtho),
 	// the slice contains the start point, any number of intermediate bend points and the end point.
-	// If the option autog.WithEdgeRoutingStraight was chosen, the slice will have length 2 and include only the start and end points;
+	// If the option EdgeRoutingStraight was chosen, the slice will have length 2 and include only the start and end points;
 	//
 	// in case of curved edges, the slice contains the control points of a piece-wise cubic bezier spline, i.e. its length
 	// is a multiple of 4, and it must be processed in chunks of 4 points each.

internal/graph/dgraph.go

@@ -10,9 +10,11 @@ type DGraph struct {
 	Layers Layers
 }
 
-// Generate implements graph.Source by returning itself as a compatibility step
-func (g *DGraph) Populate(dst *DGraph) {
-	*dst = *g
+func (g *DGraph) Populate(*DGraph) {
+	// DGraph implements graph.Source to facilitate unit testing.
+	// It is not meant to do anything because *DGraph can be obtained from graph.Source
+	// via type assertion.
+	// todo: instead of having a dummy implementation, a wrapper could be used instead in unit tests
 }
 
 func (g *DGraph) GetNodes() []*Node {

internal/testfiles/adjacency_lists.go

@@ -15,6 +15,12 @@ var issues1and4 = [][]string{
 	{"N2", "Nd"},
 }
 
+var simpleVirtualNodes = [][]string{
+	{"N1", "N2"},
+	{"N2", "N3"},
+	{"N1", "N3"},
+}
+
 var cacooArch = [][]string{
 	{"gql", "acc"},
 	{"gql", "dia"},

internal/testfiles/bugfix_test.go

@@ -70,4 +70,15 @@ func TestCrashers(t *testing.T) {
 			}
 		}
 	})
+
+	t.Run("output layout empty nodes", func(t *testing.T) {
+		src := graph.EdgeSlice(simpleVirtualNodes)
+		layout := autog.Layout(
+			src,
+			autog.WithPositioning(autog.PositioningVAlign),
+			autog.WithEdgeRouting(autog.EdgeRoutingNoop),
+		)
+		assert.Len(t, layout.Nodes, 3)
+		assert.Len(t, layout.Edges, 3)
+	})
 }