try

d2layouts/d2cycle/layout.go

@@ -65,46 +65,6 @@ func positionObjects(objects []*d2graph.Object, radius float64) {
 	}
 }
 
-// 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
-// }
 func createCircularArc(edge *d2graph.Edge) {
 	if edge.Src == nil || edge.Dst == nil {
 		return
@@ -115,14 +75,9 @@ func createCircularArc(edge *d2graph.Edge) {
 
 	srcAngle := math.Atan2(srcCenter.Y, srcCenter.X)
 	dstAngle := math.Atan2(dstCenter.Y, dstCenter.X)
-	diff := dstAngle - srcAngle
-	if math.Abs(diff) > math.Pi {
-		if diff > 0 {
-			dstAngle -= 2 * math.Pi
-		} else {
+	if dstAngle < srcAngle {
 		dstAngle += 2 * math.Pi
 	}
-	}
 
 	arcRadius := math.Hypot(srcCenter.X, srcCenter.Y)
 
@@ -144,11 +99,36 @@ func createCircularArc(edge *d2graph.Edge) {
 	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)
+// 	path = trimPathPoints(path, edge.Src.Box)
+// 	path = trimPathPoints(path, edge.Dst.Box)
 
-	edge.Route = path
-	edge.IsCurve = true
+// 	edge.Route = path
+// 	edge.IsCurve = true
+// }
+path = trimPathPoints(path, edge.Src.Box)
+path = trimPathPoints(path, edge.Dst.Box)
+
+// Adjust the last two points to align the arrow direction with the arc's tangent at the destination.
+if len(path) >= 2 {
+	dstPoint := path[len(path)-1]
+	// Calculate the tangent direction at the destination point (counter-clockwise)
+	tangentX := -dstPoint.Y
+	tangentY := dstPoint.X
+	// Normalize the tangent vector
+	length := math.Hypot(tangentX, tangentY)
+	if length > 0 {
+		tangentX /= length
+		tangentY /= length
+	}
+	// Adjust the penultimate point to be a small step back along the tangent direction
+	step := 10.0
+	prevX := dstPoint.X - tangentX*step
+	prevY := dstPoint.Y - tangentY*step
+	path[len(path)-2] = geo.NewPoint(prevX, prevY)
+}
+
+edge.Route = path
+edge.IsCurve = true
 }
 
 // clampPointOutsideBox walks forward along the path until it finds a point outside the box,

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

@@ -864,8 +864,8 @@
           "y": -37.47600173950195
         },
         {
-          "x": 197.02099609375,
-          "y": -34.3849983215332
+          "x": 195.6020050048828,
+          "y": -42.86199951171875
         },
         {
           "x": 197.2519989013672,
@@ -1228,8 +1228,8 @@
           "y": 197.53700256347656
         },
         {
-          "x": 28.18000030517578,
-          "y": 198.00399780273438
+          "x": 36.4109992980957,
+          "y": 196.90499877929688
         },
         {
           "x": 26.5,
@@ -1592,8 +1592,8 @@
           "y": 37.47600173950195
         },
         {
-          "x": -197.02099609375,
-          "y": 34.3849983215332
+          "x": -195.6020050048828,
+          "y": 42.86199951171875
         },
         {
           "x": -197.2519989013672,
@@ -1972,8 +1972,8 @@
           "y": 111.8030014038086
         },
         {
-          "x": 701.875,
-          "y": 115.77300262451172
+          "x": 704.7830200195312,
+          "y": 107.5770034790039
         },
         {
           "x": 701.4329833984375,
@@ -2336,8 +2336,8 @@
           "y": 186.90899658203125
         },
         {
-          "x": 364.3710021972656,
-          "y": 183.8260040283203
+          "x": 370.2919921875,
+          "y": 190.46800231933594
         },
         {
           "x": 363.6419982910156,
@@ -2740,8 +2740,8 @@
           "y": 196.45700073242188
         },
         {
-          "x": 1003.2860107421875,
-          "y": 197.53700256347656
+          "x": 1008.4110107421875,
+          "y": 196.89300537109375
         },
         {
           "x": 998.5,

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

@@ -864,8 +864,8 @@
           "y": -25.47599983215332
         },
         {
-          "x": 209.02099609375,
-          "y": -22.385000228881836
+          "x": 207.6020050048828,
+          "y": -30.86199951171875
         },
         {
           "x": 209.2519989013672,
@@ -1228,8 +1228,8 @@
           "y": 209.53700256347656
         },
         {
-          "x": 40.18000030517578,
-          "y": 210.00399780273438
+          "x": 48.4109992980957,
+          "y": 208.90499877929688
         },
         {
           "x": 38.5,
@@ -1592,8 +1592,8 @@
           "y": 49.47600173950195
         },
         {
-          "x": -185.02099609375,
-          "y": 46.3849983215332
+          "x": -183.6020050048828,
+          "y": 54.86199951171875
         },
         {
           "x": -185.2519989013672,
@@ -1972,8 +1972,8 @@
           "y": 123.8030014038086
         },
         {
-          "x": 674.375,
-          "y": 127.77300262451172
+          "x": 677.2830200195312,
+          "y": 119.5770034790039
         },
         {
           "x": 673.9329833984375,
@@ -2336,8 +2336,8 @@
           "y": 198.90899658203125
         },
         {
-          "x": 336.8710021972656,
-          "y": 195.8260040283203
+          "x": 342.7919921875,
+          "y": 202.46800231933594
         },
         {
           "x": 336.1419982910156,
@@ -2740,8 +2740,8 @@
           "y": 208.45700073242188
         },
         {
-          "x": 936.197021484375,
-          "y": 209.53700256347656
+          "x": 941.3209838867188,
+          "y": 208.89300537109375
         },
         {
           "x": 931.4099731445312,