Fix edge padding

d2layouts/d2sequence/constants.go

@@ -20,6 +20,8 @@ const SPAN_DEPTH_GROWTH_FACTOR = 8.
 // when a span has a single messages
 const MIN_SPAN_HEIGHT = 80.
 
+const SPAN_MESSAGE_PAD = 16.
+
 const LIFELINE_STROKE_WIDTH int = 2
 
 const LIFELINE_STROKE_DASH int = 8

d2layouts/d2sequence/layout_test.go

@@ -246,7 +246,7 @@ func TestSpansSequenceDiagram(t *testing.T) {
 	}
 
 	// Y diff of the 2 first edges
-	expectedHeight := g.Edges[1].Route[0].Y - g.Edges[0].Route[0].Y
+	expectedHeight := g.Edges[1].Route[0].Y - g.Edges[0].Route[0].Y + (2 * SPAN_MESSAGE_PAD)
 	if a_t1.Height != expectedHeight {
 		t.Fatalf("expected a.t1 height to be %.5f, got %.5f", expectedHeight, a_t1.Height)
 	}
@@ -268,7 +268,7 @@ func TestSpansSequenceDiagram(t *testing.T) {
 	if a_t1.TopLeft.Y != b_t1.TopLeft.Y {
 		t.Fatal("expected a.t1 and b.t1 to be placed at the same Y")
 	}
-	if a_t1.TopLeft.Y != g.Edges[0].Route[0].Y {
+	if a_t1.TopLeft.Y-SPAN_MESSAGE_PAD != g.Edges[0].Route[0].Y {
 		t.Fatal("expected a.t1 to be placed at the same Y of the first message")
 	}
 

d2layouts/d2sequence/sequence_diagram.go

@@ -210,12 +210,12 @@ func (sd *sequenceDiagram) placeSpans() {
 
 		// if it is the same as the child top left, add some padding
 		minY := math.Min(minMessageY, minChildY)
-		if minY == minChildY {
-			minY -= SPAN_DEPTH_GROWTH_FACTOR
+		if minY == minChildY || minY == minMessageY {
+			minY -= SPAN_MESSAGE_PAD
 		}
 		maxY := math.Max(maxMessageY, maxChildY)
-		if maxY == maxChildY {
-			maxY += SPAN_DEPTH_GROWTH_FACTOR
+		if maxY == maxChildY || maxY == maxMessageY {
+			maxY += SPAN_MESSAGE_PAD
 		}
 
 		height := math.Max(maxY-minY, MIN_SPAN_HEIGHT)