shape: add cycle diagram layout

d2compiler/compile.go

@@ -1254,6 +1254,9 @@ func (c *compiler) validatePositionsCompatibility(g *d2graph.Graph) {
 					if o.Parent.GridColumns != nil || o.Parent.GridRows != nil {
 						c.errorf(pos.MapKey, `position keywords cannot be used with grids`)
 					}
+					if o.Parent.IsCycleDiagram() {
+						c.errorf(pos.MapKey, `position keywords cannot be used inside shape "cycle"`)
+					}
 				}
 			}
 		}
@@ -1282,6 +1285,22 @@ func (c *compiler) validateEdges(g *d2graph.Graph) {
 			c.errorf(edge.GetAstEdge(), "edge from grid cell %#v cannot enter itself", edge.Dst.AbsID())
 			continue
 		}
+		if edge.Src.IsCycleDiagram() && edge.Dst.IsDescendantOf(edge.Src) {
+			c.errorf(edge.GetAstEdge(), "edge from cycle diagram %#v cannot enter itself", edge.Src.AbsID())
+			continue
+		}
+		if edge.Dst.IsCycleDiagram() && edge.Src.IsDescendantOf(edge.Dst) {
+			c.errorf(edge.GetAstEdge(), "edge from cycle diagram %#v cannot enter itself", edge.Dst.AbsID())
+			continue
+		}
+		if edge.Src.Parent.IsCycleDiagram() && edge.Dst.IsDescendantOf(edge.Src) {
+			c.errorf(edge.GetAstEdge(), "edge from cycle node %#v cannot enter itself", edge.Src.AbsID())
+			continue
+		}
+		if edge.Dst.Parent.IsCycleDiagram() && edge.Src.IsDescendantOf(edge.Dst) {
+			c.errorf(edge.GetAstEdge(), "edge from cycle node %#v cannot enter itself", edge.Dst.AbsID())
+			continue
+		}
 		if edge.Src.IsSequenceDiagram() && edge.Dst.IsDescendantOf(edge.Src) {
 			c.errorf(edge.GetAstEdge(), "edge from sequence diagram %#v cannot enter itself", edge.Src.AbsID())
 			continue

d2compiler/compile_test.go

@@ -4091,6 +4091,28 @@ svc_1.t2 -> b: do with B
 	}
 }
 
+func TestCompileCycleShape(t *testing.T) {
+	g, _, err := d2compiler.Compile("d2/testdata/d2compiler/TestCompileCycleShape.d2", strings.NewReader(`
+x: {
+  shape: cycle
+  a
+  b
+}
+`), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(g.Objects) != 3 {
+		t.Fatalf("expected 3 objects: %#v", g.Objects)
+	}
+	if g.Objects[0].Shape.Value != d2target.ShapeCycle {
+		t.Fatalf("expected g.Objects[0].Shape.Value to be cycle: %#v", g.Objects[0].Shape.Value)
+	}
+	if !g.Objects[0].IsCycleDiagram() {
+		t.Fatalf("expected x to be a cycle diagram")
+	}
+}
+
 func TestCompile2(t *testing.T) {
 	t.Parallel()
 

d2graph/cycle_diagram.go

@@ -0,0 +1,7 @@
+package d2graph
+
+import "oss.terrastruct.com/d2/d2target"
+
+func (obj *Object) IsCycleDiagram() bool {
+	return obj != nil && obj.Shape.Value == d2target.ShapeCycle
+}

d2graph/d2graph.go

@@ -545,7 +545,7 @@ func (obj *Object) GetFill() string {
 		return color.N7
 	}
 
-	if shape == "" || strings.EqualFold(shape, d2target.ShapeSquare) || strings.EqualFold(shape, d2target.ShapeCircle) || strings.EqualFold(shape, d2target.ShapeOval) || strings.EqualFold(shape, d2target.ShapeRectangle) || strings.EqualFold(shape, d2target.ShapeHierarchy) {
+	if shape == "" || strings.EqualFold(shape, d2target.ShapeSquare) || strings.EqualFold(shape, d2target.ShapeCircle) || strings.EqualFold(shape, d2target.ShapeOval) || strings.EqualFold(shape, d2target.ShapeRectangle) || strings.EqualFold(shape, d2target.ShapeCycle) || strings.EqualFold(shape, d2target.ShapeHierarchy) {
 		if level == 1 {
 			if !obj.IsContainer() {
 				return color.B6
@@ -675,7 +675,7 @@ func (obj *Object) Text() *d2target.MText {
 
 	if obj.OuterSequenceDiagram() == nil {
 		// Note: during grid layout when children are temporarily removed `IsContainer` is false
-		if (obj.IsContainer() || obj.IsGridDiagram()) && obj.Shape.Value != "text" {
+		if (obj.IsContainer() || obj.IsGridDiagram() || obj.IsCycleDiagram()) && obj.Shape.Value != "text" {
 			fontSize = obj.Level().LabelSize()
 		}
 	} else {

d2layouts/d2cycle/cycle_diagram.go

@@ -0,0 +1,35 @@
+package d2cycle
+
+import (
+	"oss.terrastruct.com/d2/d2graph"
+	"oss.terrastruct.com/d2/lib/geo"
+)
+
+type cycleDiagram struct {
+	objects []*d2graph.Object
+	edges   []*d2graph.Edge
+
+	width  float64
+	height float64
+}
+
+func newCycleDiagram(root *d2graph.Object) *cycleDiagram {
+	cd := &cycleDiagram{
+		objects: root.ChildrenArray,
+	}
+
+	for _, o := range cd.objects {
+		o.TopLeft = geo.NewPoint(0, 0)
+	}
+
+	return cd
+}
+
+func (cd *cycleDiagram) shift(dx, dy float64) {
+	for _, obj := range cd.objects {
+		obj.MoveWithDescendants(dx, dy)
+	}
+	for _, e := range cd.edges {
+		e.Move(dx, dy)
+	}
+}