save

d2graph/cyclediagram.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.ShapeCycleDiagram
+}

d2layouts/d2cycle/layout.go

@@ -0,0 +1,241 @@
+package d2cycle
+
+import (
+	"context"
+	"math"
+
+	"oss.terrastruct.com/d2/d2graph"
+	"oss.terrastruct.com/d2/lib/geo"
+	"oss.terrastruct.com/d2/lib/label"
+	"oss.terrastruct.com/util-go/go2"
+)
+
+const (
+	MIN_RADIUS      = 200
+	PADDING         = 20
+	MIN_SEGMENT_LEN = 10
+	ARC_STEPS       = 30 // high resolution for smooth arcs
+
+)
+
+// Layout arranges nodes in a circle, ensures label/icon positions are set,
+// then routes edges with arcs that get clipped at node borders.
+func Layout(ctx context.Context, g *d2graph.Graph, layout d2graph.LayoutGraph) error {
+	objects := g.Root.ChildrenArray
+	if len(objects) == 0 {
+		return nil
+	}
+
+	// Make sure every object that has label/icon also has a default position
+	for _, obj := range g.Objects {
+		positionLabelsIcons(obj)
+	}
+
+	// Arrange objects in a circle
+	radius := calculateRadius(objects)
+	positionObjects(objects, radius)
+
+	// Create arcs
+	for _, edge := range g.Edges {
+		createCircularArc(edge)
+	}
+
+	return nil
+}
+
+func calculateRadius(objects []*d2graph.Object) float64 {
+	numObjects := float64(len(objects))
+	maxSize := 0.0
+	for _, obj := range objects {
+		size := math.Max(obj.Box.Width, obj.Box.Height)
+		maxSize = math.Max(maxSize, size)
+	}
+	// ensure enough radius to fit all objects
+	minRadius := (maxSize/2.0 + PADDING) / math.Sin(math.Pi/numObjects)
+	return math.Max(minRadius, MIN_RADIUS)
+}
+
+func positionObjects(objects []*d2graph.Object, radius float64) {
+	numObjects := float64(len(objects))
+	// Offset so i=0 is top-center
+	angleOffset := -math.Pi / 2
+
+	for i, obj := range objects {
+		angle := angleOffset + (2 * math.Pi * float64(i) / numObjects)
+
+		x := radius * math.Cos(angle)
+		y := radius * math.Sin(angle)
+
+		// center the box at (x, y)
+		obj.TopLeft = geo.NewPoint(
+			x-obj.Box.Width/2,
+			y-obj.Box.Height/2,
+		)
+	}
+}
+
+// createCircularArc samples a smooth arc from center to center, then
+// forces the endpoints onto each shape's border, and finally calls
+// TraceToShape to clip any additional overrun.
+func createCircularArc(edge *d2graph.Edge) {
+	if edge.Src == nil || edge.Dst == nil {
+		return
+	}
+
+	srcCenter := edge.Src.Center()
+	dstCenter := edge.Dst.Center()
+
+	// angles from origin
+	srcAngle := math.Atan2(srcCenter.Y, srcCenter.X)
+	dstAngle := math.Atan2(dstCenter.Y, dstCenter.X)
+	if dstAngle < srcAngle {
+		dstAngle += 2 * math.Pi
+	}
+
+	arcRadius := math.Hypot(srcCenter.X, srcCenter.Y)
+
+	// Sample points along the arc
+	path := make([]*geo.Point, 0, ARC_STEPS+1)
+	for i := 0; i <= ARC_STEPS; i++ {
+		t := float64(i) / float64(ARC_STEPS)
+		angle := srcAngle + t*(dstAngle-srcAngle)
+		x := arcRadius * math.Cos(angle)
+		y := arcRadius * math.Sin(angle)
+		path = append(path, geo.NewPoint(x, y))
+	}
+	// Set start/end to exact centers
+	path[0] = srcCenter
+	path[len(path)-1] = dstCenter
+
+	// Use TraceToShape to clip route to node borders
+	edge.Route = path
+	startIndex, endIndex := edge.TraceToShape(edge.Route, 0, len(edge.Route)-1)
+	if startIndex < endIndex {
+		edge.Route = edge.Route[startIndex : endIndex+1]
+	}
+	edge.IsCurve = true
+}
+
+// clampPointOutsideBox walks forward from 'startIdx' until the path segment
+// leaves the bounding box. Then it sets path[startIdx] to the intersection.
+// If we never find it, we return (startIdx, path[startIdx]) meaning we can't clamp.
+func clampPointOutsideBox(box *geo.Box, path []*geo.Point, startIdx int) (int, *geo.Point) {
+	if startIdx >= len(path)-1 {
+		return startIdx, path[startIdx]
+	}
+	// If path[startIdx] is outside, no clamp needed
+	if !boxContains(box, path[startIdx]) {
+		return startIdx, path[startIdx]
+	}
+
+	// Walk forward looking for outside
+	for i := startIdx + 1; i < len(path); i++ {
+		insideNext := boxContains(box, path[i])
+		if insideNext {
+			// still inside -> keep going
+			continue
+		}
+		// crossing from inside to outside between path[i-1], path[i]
+		seg := geo.NewSegment(path[i-1], path[i])
+		inters := boxIntersections(box, *seg)
+		if len(inters) > 0 {
+			// use first intersection
+			return i, inters[0]
+		}
+		// fallback => no intersection found
+		return i, path[i]
+	}
+	// entire remainder is inside, so we can't clamp
+	// Just return the end
+	last := len(path) - 1
+	return last, path[last]
+}
+
+// clampPointOutsideBoxReverse scans backward from endIdx while path[j] is in the box.
+// Once we find crossing (outside→inside), we return (j, intersection).
+func clampPointOutsideBoxReverse(box *geo.Box, path []*geo.Point, endIdx int) (int, *geo.Point) {
+	if endIdx <= 0 {
+		return endIdx, path[endIdx]
+	}
+	if !boxContains(box, path[endIdx]) {
+		// already outside
+		return endIdx, path[endIdx]
+	}
+
+	for j := endIdx - 1; j >= 0; j-- {
+		if boxContains(box, path[j]) {
+			continue
+		}
+		// crossing from outside -> inside between path[j], path[j+1]
+		seg := geo.NewSegment(path[j], path[j+1])
+		inters := boxIntersections(box, *seg)
+		if len(inters) > 0 {
+			return j, inters[0]
+		}
+		return j, path[j]
+	}
+
+	// entire path inside
+	return 0, path[0]
+}
+
+// Helper if your geo.Box doesn’t implement Contains()
+func boxContains(b *geo.Box, p *geo.Point) bool {
+	// typical bounding-box check
+	return p.X >= b.TopLeft.X &&
+		p.X <= b.TopLeft.X+b.Width &&
+		p.Y >= b.TopLeft.Y &&
+		p.Y <= b.TopLeft.Y+b.Height
+}
+
+// Helper if your geo.Box doesn’t implement Intersections(geo.Segment) yet
+func boxIntersections(b *geo.Box, seg geo.Segment) []*geo.Point {
+	// We'll assume d2's standard geo.Box has a built-in Intersections(*Segment) method.
+	// If not, implement manually. For example, checking each of the 4 edges:
+	//   left, right, top, bottom
+	// For simplicity, if you do have b.Intersections(...) you can just do:
+	//     return b.Intersections(seg)
+	return b.Intersections(seg)
+	// If you don't have that, you'd code the line-rect intersection yourself.
+}
+
+// positionLabelsIcons is basically your logic that sets default label/icon positions if needed
+func positionLabelsIcons(obj *d2graph.Object) {
+	// If there's an icon but no icon position, give it a default
+	if obj.Icon != nil && obj.IconPosition == nil {
+		if len(obj.ChildrenArray) > 0 {
+			obj.IconPosition = go2.Pointer(label.OutsideTopLeft.String())
+			if obj.LabelPosition == nil {
+				obj.LabelPosition = go2.Pointer(label.OutsideTopRight.String())
+				return
+			}
+		} else if obj.SQLTable != nil || obj.Class != nil || obj.Language != "" {
+			obj.IconPosition = go2.Pointer(label.OutsideTopLeft.String())
+		} else {
+			obj.IconPosition = go2.Pointer(label.InsideMiddleCenter.String())
+		}
+	}
+
+	// If there's a label but no label position, give it a default
+	if obj.HasLabel() && obj.LabelPosition == nil {
+		if len(obj.ChildrenArray) > 0 {
+			obj.LabelPosition = go2.Pointer(label.OutsideTopCenter.String())
+		} else if obj.HasOutsideBottomLabel() {
+			obj.LabelPosition = go2.Pointer(label.OutsideBottomCenter.String())
+		} else if obj.Icon != nil {
+			obj.LabelPosition = go2.Pointer(label.InsideTopCenter.String())
+		} else {
+			obj.LabelPosition = go2.Pointer(label.InsideMiddleCenter.String())
+		}
+
+		// If the label is bigger than the shape, fallback to outside positions
+		if float64(obj.LabelDimensions.Width) > obj.Width ||
+			float64(obj.LabelDimensions.Height) > obj.Height {
+			if len(obj.ChildrenArray) > 0 {
+				obj.LabelPosition = go2.Pointer(label.OutsideTopCenter.String())
+			} else {
+				obj.LabelPosition = go2.Pointer(label.OutsideBottomCenter.String())
+			}
+		}
+	}
+}

d2layouts/d2layouts.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"oss.terrastruct.com/d2/d2graph"
+	"oss.terrastruct.com/d2/d2layouts/d2cycle"
 	"oss.terrastruct.com/d2/d2layouts/d2grid"
 	"oss.terrastruct.com/d2/d2layouts/d2near"
 	"oss.terrastruct.com/d2/d2layouts/d2sequence"
@@ -20,12 +21,12 @@ import (
 
 type DiagramType string
 
-// a grid diagram at a constant near is
 const (
 	DefaultGraphType  DiagramType = ""
 	ConstantNearGraph DiagramType = "constant-near"
 	GridDiagram       DiagramType = "grid-diagram"
 	SequenceDiagram   DiagramType = "sequence-diagram"
+	CycleDiagram      DiagramType = "cycle-diagram"
 )
 
 type GraphInfo struct {
@@ -260,6 +261,12 @@ func LayoutNested(ctx context.Context, g *d2graph.Graph, graphInfo GraphInfo, co
 			if err != nil {
 				return err
 			}
+		case CycleDiagram:
+			log.Debug(ctx, "layout sequence", slog.Any("rootlevel", g.RootLevel), slog.Any("shapes", g.PrintString()))
+			err = d2cycle.Layout(ctx, g, coreLayout)
+			if err != nil {
+				return err
+			}
 		default:
 			log.Debug(ctx, "default layout", slog.Any("rootlevel", g.RootLevel), slog.Any("shapes", g.PrintString()))
 			err := coreLayout(ctx, g)
@@ -360,6 +367,8 @@ func NestedGraphInfo(obj *d2graph.Object) (gi GraphInfo) {
 		gi.DiagramType = SequenceDiagram
 	} else if obj.IsGridDiagram() {
 		gi.DiagramType = GridDiagram
+	} else if obj.IsCycleDiagram() {
+		gi.DiagramType = CycleDiagram
 	}
 	return gi
 }

d2renderers/d2svg/d2svg.go

@@ -452,37 +452,78 @@ func getArrowheadAdjustments(connection d2target.Connection, idToShape map[strin
 func pathData(connection d2target.Connection, srcAdj, dstAdj *geo.Point) string {
 	var path []string
 	route := connection.Route
+	if len(route) == 0 {
+		return ""
+	}
 
+	// Move command to start
 	path = append(path, fmt.Sprintf("M %f %f",
 		route[0].X+srcAdj.X,
 		route[0].Y+srcAdj.Y,
 	))
 
 	if connection.IsCurve {
+		// If we don't have enough points to do triple-step, handle small fallback
+		if len(route) < 3 {
+			// If only 1 or 2 points in route, just draw lines
+			for _, p := range route[1:] {
+				path = append(path, fmt.Sprintf("L %f %f",
+					p.X+dstAdj.X, p.Y+dstAdj.Y,
+				))
+			}
+			return strings.Join(path, " ")
+		}
+
 		i := 1
-		for ; i < len(route)-3; i += 3 {
+		// Process triple curves in steps of 3
+		for ; i+2 < len(route)-1; i += 3 {
 			path = append(path, fmt.Sprintf("C %f %f %f %f %f %f",
 				route[i].X, route[i].Y,
 				route[i+1].X, route[i+1].Y,
 				route[i+2].X, route[i+2].Y,
 			))
 		}
-		// final curve target adjustment
+
-		path = append(path, fmt.Sprintf("C %f %f %f %f %f %f",
+		// Now handle the “final” curve to last point
-			route[i].X, route[i].Y,
+		// Make sure i+2 is still within range
-			route[i+1].X, route[i+1].Y,
+		if i+2 < len(route) {
-			route[i+2].X+dstAdj.X,
+			// last triple
-			route[i+2].Y+dstAdj.Y,
+			path = append(path, fmt.Sprintf("C %f %f %f %f %f %f",
-		))
+				route[i].X, route[i].Y,
+				route[i+1].X, route[i+1].Y,
+				route[i+2].X+dstAdj.X, // final point plus dst adjustment
+				route[i+2].Y+dstAdj.Y,
+			))
+		} else if i+1 < len(route) {
+			// We have i+1 but not i+2 => do a simpler final curve or line
+			path = append(path, fmt.Sprintf("C %f %f %f %f %f %f",
+				route[i].X, route[i].Y,
+				route[i].X, route[i].Y, // repeated for control
+				route[i+1].X+dstAdj.X,
+				route[i+1].Y+dstAdj.Y,
+			))
+		} else {
+			// We have no final triple => do nothing or fallback line
+		}
 	} else {
+		// Not a curve => the "rounded corner" logic
 		for i := 1; i < len(route)-1; i++ {
 			prevSource := route[i-1]
 			prevTarget := route[i]
 			currTarget := route[i+1]
+
+			// Make sure i+1 is valid
+			if i+1 >= len(route) {
+				break
+			}
+
 			prevVector := prevSource.VectorTo(prevTarget)
 			currVector := prevTarget.VectorTo(currTarget)
 
-			dist := geo.EuclideanDistance(prevTarget.X, prevTarget.Y, currTarget.X, currTarget.Y)
+			dist := geo.EuclideanDistance(
+				prevTarget.X, prevTarget.Y,
+				currTarget.X, currTarget.Y,
+			)
 
 			connectionBorderRadius := connection.BorderRadius
 			units := math.Min(connectionBorderRadius, dist/2)
@@ -490,20 +531,26 @@ func pathData(connection d2target.Connection, srcAdj, dstAdj *geo.Point) string
 			prevTranslations := prevVector.Unit().Multiply(units).ToPoint()
 			currTranslations := currVector.Unit().Multiply(units).ToPoint()
 
+			// Move to corner with "L"
 			path = append(path, fmt.Sprintf("L %f %f",
 				prevTarget.X-prevTranslations.X,
 				prevTarget.Y-prevTranslations.Y,
 			))
 
-			// If the segment length is too small, instead of drawing 2 arcs, just skip this segment and bezier curve to the next one
 			if units < connectionBorderRadius && i < len(route)-2 {
+				// Next checks i+2 => ensure it’s in range
+				if i+2 >= len(route) {
+					// can't do nextTarget => break or do fallback
+					continue
+				}
 				nextTarget := route[i+2]
-				nextVector := geo.NewVector(nextTarget.X-currTarget.X, nextTarget.Y-currTarget.Y)
+				nextVector := geo.NewVector(
-				i++
+					nextTarget.X-currTarget.X,
+					nextTarget.Y-currTarget.Y,
+				)
+				i++ // skip next point
 				nextTranslations := nextVector.Unit().Multiply(units).ToPoint()
 
-				// These 2 bezier control points aren't just at the corner -- they are reflected at the corner, which causes the curve to be ~tangent to the corner,
-				// which matches how the two arcs look
 				path = append(path, fmt.Sprintf("C %f %f %f %f %f %f",
 					// Control point
 					prevTarget.X+prevTranslations.X,
@@ -511,7 +558,7 @@ func pathData(connection d2target.Connection, srcAdj, dstAdj *geo.Point) string
 					// Control point
 					currTarget.X-nextTranslations.X,
 					currTarget.Y-nextTranslations.Y,
-					// Where curve ends
+					// End
 					currTarget.X+nextTranslations.X,
 					currTarget.Y+nextTranslations.Y,
 				))
@@ -525,11 +572,14 @@ func pathData(connection d2target.Connection, srcAdj, dstAdj *geo.Point) string
 			}
 		}
 
-		lastPoint := route[len(route)-1]
+		// Finally, draw a line to the last route point + dst offset
-		path = append(path, fmt.Sprintf("L %f %f",
+		if len(route) > 1 {
-			lastPoint.X+dstAdj.X,
+			lastPoint := route[len(route)-1]
-			lastPoint.Y+dstAdj.Y,
+			path = append(path, fmt.Sprintf("L %f %f",
-		))
+				lastPoint.X+dstAdj.X,
+				lastPoint.Y+dstAdj.Y,
+			))
+		}
 	}
 
 	return strings.Join(path, " ")

d2target/d2target.go

@@ -942,6 +942,7 @@ const (
 	ShapeSQLTable        = "sql_table"
 	ShapeImage           = "image"
 	ShapeSequenceDiagram = "sequence_diagram"
+	ShapeCycleDiagram    = "cycle"
 	ShapeHierarchy       = "hierarchy"
 )
 
@@ -969,6 +970,7 @@ var Shapes = []string{
 	ShapeSQLTable,
 	ShapeImage,
 	ShapeSequenceDiagram,
+	ShapeCycleDiagram,
 	ShapeHierarchy,
 }
 
@@ -1037,6 +1039,7 @@ var DSL_SHAPE_TO_SHAPE_TYPE = map[string]string{
 	ShapeSQLTable:        shape.TABLE_TYPE,
 	ShapeImage:           shape.IMAGE_TYPE,
 	ShapeSequenceDiagram: shape.SQUARE_TYPE,
+	ShapeCycleDiagram:    shape.SQUARE_TYPE,
 	ShapeHierarchy:       shape.SQUARE_TYPE,
 }
 

e2etests/testdata/txtar/cycle-diagram/dagre/board.exp.json

@@ -0,0 +1,694 @@
+{
+  "name": "",
+  "config": {
+    "sketch": false,
+    "themeID": 0,
+    "darkThemeID": null,
+    "pad": null,
+    "center": null,
+    "layoutEngine": null
+  },
+  "isFolderOnly": false,
+  "fontFamily": "SourceSansPro",
+  "shapes": [
+    {
+      "id": "a",
+      "type": "rectangle",
+      "pos": {
+        "x": -26,
+        "y": -233
+      },
+      "width": 53,
+      "height": 66,
+      "opacity": 1,
+      "strokeDash": 0,
+      "strokeWidth": 2,
+      "borderRadius": 0,
+      "fill": "B6",
+      "stroke": "B1",
+      "animated": false,
+      "shadow": false,
+      "3d": false,
+      "multiple": false,
+      "double-border": false,
+      "tooltip": "",
+      "link": "",
+      "icon": null,
+      "iconPosition": "",
+      "blend": false,
+      "fields": null,
+      "methods": null,
+      "columns": null,
+      "label": "a",
+      "fontSize": 16,
+      "fontFamily": "DEFAULT",
+      "language": "",
+      "color": "N1",
+      "italic": false,
+      "bold": true,
+      "underline": false,
+      "labelWidth": 8,
+      "labelHeight": 21,
+      "labelPosition": "INSIDE_MIDDLE_CENTER",
+      "zIndex": 0,
+      "level": 1
+    },
+    {
+      "id": "b",
+      "type": "rectangle",
+      "pos": {
+        "x": 173,
+        "y": -33
+      },
+      "width": 53,
+      "height": 66,
+      "opacity": 1,
+      "strokeDash": 0,
+      "strokeWidth": 2,
+      "borderRadius": 0,
+      "fill": "B6",
+      "stroke": "B1",
+      "animated": false,
+      "shadow": false,
+      "3d": false,
+      "multiple": false,
+      "double-border": false,
+      "tooltip": "",
+      "link": "",
+      "icon": null,
+      "iconPosition": "",
+      "blend": false,
+      "fields": null,
+      "methods": null,
+      "columns": null,
+      "label": "b",
+      "fontSize": 16,
+      "fontFamily": "DEFAULT",
+      "language": "",
+      "color": "N1",
+      "italic": false,
+      "bold": true,
+      "underline": false,
+      "labelWidth": 8,
+      "labelHeight": 21,
+      "labelPosition": "INSIDE_MIDDLE_CENTER",
+      "zIndex": 0,
+      "level": 1
+    },
+    {
+      "id": "c",
+      "type": "rectangle",
+      "pos": {
+        "x": -26,
+        "y": 167
+      },
+      "width": 53,
+      "height": 66,
+      "opacity": 1,
+      "strokeDash": 0,
+      "strokeWidth": 2,
+      "borderRadius": 0,
+      "fill": "B6",
+      "stroke": "B1",
+      "animated": false,
+      "shadow": false,
+      "3d": false,
+      "multiple": false,
+      "double-border": false,
+      "tooltip": "",
+      "link": "",
+      "icon": null,
+      "iconPosition": "",
+      "blend": false,
+      "fields": null,
+      "methods": null,
+      "columns": null,
+      "label": "c",
+      "fontSize": 16,
+      "fontFamily": "DEFAULT",
+      "language": "",
+      "color": "N1",
+      "italic": false,
+      "bold": true,
+      "underline": false,
+      "labelWidth": 8,
+      "labelHeight": 21,
+      "labelPosition": "INSIDE_MIDDLE_CENTER",
+      "zIndex": 0,
+      "level": 1
+    },
+    {
+      "id": "d",
+      "type": "rectangle",
+      "pos": {
+        "x": -227,
+        "y": -32
+      },
+      "width": 54,
+      "height": 66,
+      "opacity": 1,
+      "strokeDash": 0,
+      "strokeWidth": 2,
+      "borderRadius": 0,
+      "fill": "B6",
+      "stroke": "B1",
+      "animated": false,
+      "shadow": false,
+      "3d": false,
+      "multiple": false,
+      "double-border": false,
+      "tooltip": "",
+      "link": "",
+      "icon": null,
+      "iconPosition": "",
+      "blend": false,
+      "fields": null,
+      "methods": null,
+      "columns": null,
+      "label": "d",
+      "fontSize": 16,
+      "fontFamily": "DEFAULT",
+      "language": "",
+      "color": "N1",
+      "italic": false,
+      "bold": true,
+      "underline": false,
+      "labelWidth": 9,
+      "labelHeight": 21,
+      "labelPosition": "INSIDE_MIDDLE_CENTER",
+      "zIndex": 0,
+      "level": 1
+    }
+  ],
+  "connections": [
+    {
+      "id": "(a -> b)[0]",
+      "src": "a",
+      "srcArrow": "none",
+      "dst": "b",
+      "dstArrow": "triangle",
+      "opacity": 1,
+      "strokeDash": 0,
+      "strokeWidth": 2,
+      "stroke": "B1",
+      "borderRadius": 10,
+      "label": "",
+      "fontSize": 16,
+      "fontFamily": "DEFAULT",
+      "language": "",
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+}

e2etests/txtar.txt

@@ -775,3 +775,7 @@ a -> b: hello {
 b -> c: {
   icon: https://icons.terrastruct.com/essentials%2F213-alarm.svg
 }
+
+-- cycle-diagram --
+shape: cycle
+a -> b -> c -> d

lib/geo/point.go

@@ -324,3 +324,12 @@ func RemovePoints(points Points, toRemove []bool) Points {
 	}
 	return without
 }
+
+func (v Vector) Normalize() Vector {
+	length := v.Length()
+	if length == 0 {
+		// avoid dividing by 0
+		return Vector{0, 0}
+	}
+	return Vector{v[0] / length, v[1] / length}
+}