cycle diagram #1

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 +1,337 @@
+package d2cycle
+
+import (
+    "context"
+    "math"
+    "sort"
+
+    "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       = 100
+)
+
+// Layout lays out the graph and computes curved edge routes.
+func Layout(ctx context.Context, g *d2graph.Graph, layout d2graph.LayoutGraph) error {
+    objects := g.Root.ChildrenArray
+    if len(objects) == 0 {
+        return nil
+    }
+
+    for _, obj := range g.Objects {
+        positionLabelsIcons(obj)
+    }
+
+    radius := calculateRadius(objects)
+    positionObjects(objects, radius)
+
+    for _, edge := range g.Edges {
+        createCircularArc(edge)
+    }
+
+    return nil
+}
+
+// calculateRadius computes a radius ensuring that the circular layout does not overlap.
+// For each object we compute the half-diagonal (i.e. the radius of the minimal enclosing circle),
+// then ensure the chord between two adjacent centers (2*radius*sin(π/n)) is at least
+// 2*(maxHalfDiag + PADDING). We also add a safety factor (1.2) to avoid floating-point issues.
+func calculateRadius(objects []*d2graph.Object) float64 {
+    if len(objects) < 2 {
+        return MIN_RADIUS
+    }
+    numObjects := float64(len(objects))
+    maxHalfDiag := 0.0
+    for _, obj := range objects {
+        halfDiag := math.Hypot(obj.Box.Width/2, obj.Box.Height/2)
+        if halfDiag > maxHalfDiag {
+            maxHalfDiag = halfDiag
+        }
+    }
+    // We need the chord (distance between adjacent centers) to be at least:
+    //    2*(maxHalfDiag + PADDING)
+    // and since chord = 2*radius*sin(π/n), we require:
+    //    radius >= (maxHalfDiag + PADDING) / sin(π/n)
+    minRadius := (maxHalfDiag + PADDING) / math.Sin(math.Pi/numObjects)
+    // Apply a safety factor of 1.2 and ensure it doesn't fall below MIN_RADIUS.
+    return math.Max(minRadius*1.2, MIN_RADIUS)
+}
+
+func positionObjects(objects []*d2graph.Object, radius float64) {
+    numObjects := float64(len(objects))
+    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)
+        obj.TopLeft = geo.NewPoint(
+            x-obj.Box.Width/2,
+            y-obj.Box.Height/2,
+        )
+    }
+}
+
+func createCircularArc(edge *d2graph.Edge) {
+    if edge.Src == nil || edge.Dst == nil {
+        return
+    }
+
+    srcCenter := edge.Src.Center()
+    dstCenter := edge.Dst.Center()
+
+    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)
+
+    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))
+    }
+    path[0] = srcCenter
+    path[len(path)-1] = dstCenter
+
+    // Clamp endpoints to the boundaries of the source and destination boxes.
+    _, newSrc := clampPointOutsideBox(edge.Src.Box, path, 0)
+    _, newDst := clampPointOutsideBoxReverse(edge.Dst.Box, path, len(path)-1)
+    path[0] = newSrc
+    path[len(path)-1] = newDst
+
+    // Trim redundant path points that fall inside node boundaries.
+    path = trimPathPoints(path, edge.Src.Box)
+    path = trimPathPoints(path, edge.Dst.Box)
+
+    edge.Route = path
+    edge.IsCurve = true
+
+    if len(edge.Route) >= 2 {
+        lastIndex := len(edge.Route) - 1
+        lastPoint := edge.Route[lastIndex]
+        secondLastPoint := edge.Route[lastIndex-1]
+
+        tangentX := -lastPoint.Y
+        tangentY := lastPoint.X
+        mag := math.Hypot(tangentX, tangentY)
+        if mag > 0 {
+            tangentX /= mag
+            tangentY /= mag
+        }
+        const MIN_SEGMENT_LEN = 4.159
+
+        dx := lastPoint.X - secondLastPoint.X
+        dy := lastPoint.Y - secondLastPoint.Y
+        segLength := math.Hypot(dx, dy)
+        if segLength > 0 {
+            currentDirX := dx / segLength
+            currentDirY := dy / segLength
+
+            // Check if we need to adjust the direction
+            if segLength < MIN_SEGMENT_LEN || (currentDirX*tangentX+currentDirY*tangentY) < 0.999 {
+                adjustLength := MIN_SEGMENT_LEN
+                if segLength >= MIN_SEGMENT_LEN {
+                    adjustLength = segLength
+                }
+                newSecondLastX := lastPoint.X - tangentX*adjustLength
+                newSecondLastY := lastPoint.Y - tangentY*adjustLength
+                edge.Route[lastIndex-1] = geo.NewPoint(newSecondLastX, newSecondLastY)
+            }
+        }
+    }
+}
+
+// clampPointOutsideBox walks forward along the path until it finds a point outside the box,
+// then replaces the point with a precise intersection.
+func clampPointOutsideBox(box *geo.Box, path []*geo.Point, startIdx int) (int, *geo.Point) {
+    if startIdx >= len(path)-1 {
+        return startIdx, path[startIdx]
+    }
+    if !boxContains(box, path[startIdx]) {
+        return startIdx, path[startIdx]
+    }
+
+    for i := startIdx + 1; i < len(path); i++ {
+        if boxContains(box, path[i]) {
+            continue
+        }
+        seg := geo.NewSegment(path[i-1], path[i])
+        inter := findPreciseIntersection(box, *seg)
+        if inter != nil {
+            return i, inter
+        }
+        return i, path[i]
+    }
+    return len(path)-1, path[len(path)-1]
+}
+
+// clampPointOutsideBoxReverse works similarly but in reverse order.
+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]) {
+        return endIdx, path[endIdx]
+    }
+
+    for j := endIdx - 1; j >= 0; j-- {
+        if boxContains(box, path[j]) {
+            continue
+        }
+        seg := geo.NewSegment(path[j], path[j+1])
+        inter := findPreciseIntersection(box, *seg)
+        if inter != nil {
+            return j, inter
+        }
+        return j, path[j]
+    }
+    return 0, path[0]
+}
+
+// findPreciseIntersection calculates intersection points between seg and all four sides of the box,
+// then returns the intersection closest to seg.Start.
+func findPreciseIntersection(box *geo.Box, seg geo.Segment) *geo.Point {
+    intersections := []struct {
+        point *geo.Point
+        t     float64
+    }{}
+
+    left := box.TopLeft.X
+    right := box.TopLeft.X + box.Width
+    top := box.TopLeft.Y
+    bottom := box.TopLeft.Y + box.Height
+
+    dx := seg.End.X - seg.Start.X
+    dy := seg.End.Y - seg.Start.Y
+
+    // Check vertical boundaries.
+    if dx != 0 {
+        t := (left - seg.Start.X) / dx
+        if t >= 0 && t <= 1 {
+            y := seg.Start.Y + t*dy
+            if y >= top && y <= bottom {
+                intersections = append(intersections, struct {
+                    point *geo.Point
+                    t     float64
+                }{geo.NewPoint(left, y), t})
+            }
+        }
+        t = (right - seg.Start.X) / dx
+        if t >= 0 && t <= 1 {
+            y := seg.Start.Y + t*dy
+            if y >= top && y <= bottom {
+                intersections = append(intersections, struct {
+                    point *geo.Point
+                    t     float64
+                }{geo.NewPoint(right, y), t})
+            }
+        }
+    }
+
+    // Check horizontal boundaries.
+    if dy != 0 {
+        t := (top - seg.Start.Y) / dy
+        if t >= 0 && t <= 1 {
+            x := seg.Start.X + t*dx
+            if x >= left && x <= right {
+                intersections = append(intersections, struct {
+                    point *geo.Point
+                    t     float64
+                }{geo.NewPoint(x, top), t})
+            }
+        }
+        t = (bottom - seg.Start.Y) / dy
+        if t >= 0 && t <= 1 {
+            x := seg.Start.X + t*dx
+            if x >= left && x <= right {
+                intersections = append(intersections, struct {
+                    point *geo.Point
+                    t     float64
+                }{geo.NewPoint(x, bottom), t})
+            }
+        }
+    }
+
+    if len(intersections) == 0 {
+        return nil
+    }
+
+    // Sort intersections by t (distance from seg.Start) and return the closest.
+    sort.Slice(intersections, func(i, j int) bool {
+        return intersections[i].t < intersections[j].t
+    })
+    return intersections[0].point
+}
+
+// trimPathPoints removes intermediate points that fall inside the given box while preserving endpoints.
+func trimPathPoints(path []*geo.Point, box *geo.Box) []*geo.Point {
+    if len(path) <= 2 {
+        return path
+    }
+    trimmed := []*geo.Point{path[0]}
+    for i := 1; i < len(path)-1; i++ {
+        if !boxContains(box, path[i]) {
+            trimmed = append(trimmed, path[i])
+        }
+    }
+    trimmed = append(trimmed, path[len(path)-1])
+    return trimmed
+}
+
+// boxContains uses strict inequalities so that points exactly on the boundary are considered outside.
+func boxContains(b *geo.Box, p *geo.Point) bool {
+    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
+}
+
+func positionLabelsIcons(obj *d2graph.Object) {
+    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 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 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"
@@ -26,6 +27,7 @@ const (
 	ConstantNearGraph DiagramType = "constant-near"
 	GridDiagram       DiagramType = "grid-diagram"
 	SequenceDiagram   DiagramType = "sequence-diagram"
+	CycleDiagram      DiagramType = "cycle-diagram"
 )
 
 type GraphInfo struct {
@@ -260,6 +262,12 @@ 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 +368,8 @@ 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
 }