Update arrowhead label positioning and use label dimensions

ci/release/changelogs/next.md

@@ -8,6 +8,7 @@
 
 - Markdown text can now be adjusted with `font-size` [#1191](https://github.com/terrastruct/d2/issues/1191)
 - SVG outputs for internal links use relative paths instead of absolute [#1197](https://github.com/terrastruct/d2/pull/1197)
+- Improves arrowhead label positioning [#1207](https://github.com/terrastruct/d2/pull/1207)
 
 #### Bugfixes ⛑️
 

d2exporter/export.go

@@ -213,7 +213,11 @@ func toConnection(edge *d2graph.Edge, theme *d2themes.Theme) d2target.Connection
 	}
 	if edge.SrcArrowhead != nil {
 		if edge.SrcArrowhead.Label.Value != "" {
-			connection.SrcLabel = edge.SrcArrowhead.Label.Value
+			connection.SrcLabel = &d2target.Text{
+				Label:       edge.SrcArrowhead.Label.Value,
+				LabelWidth:  edge.SrcArrowhead.LabelDimensions.Width,
+				LabelHeight: edge.SrcArrowhead.LabelDimensions.Height,
+			}
 		}
 	}
 	if edge.DstArrow {
@@ -230,7 +234,11 @@ func toConnection(edge *d2graph.Edge, theme *d2themes.Theme) d2target.Connection
 	}
 	if edge.DstArrowhead != nil {
 		if edge.DstArrowhead.Label.Value != "" {
-			connection.DstLabel = edge.DstArrowhead.Label.Value
+			connection.DstLabel = &d2target.Text{
+				Label:       edge.DstArrowhead.Label.Value,
+				LabelWidth:  edge.DstArrowhead.LabelDimensions.Width,
+				LabelHeight: edge.DstArrowhead.LabelDimensions.Height,
+			}
 		}
 	}
 	if theme != nil && theme.SpecialRules.NoCornerRadius {

d2graph/d2graph.go

@@ -1042,9 +1042,6 @@ func (obj *Object) OuterNearContainer() *Object {
 type Edge struct {
 	Index int `json:"index"`
 
-	MinWidth  int `json:"minWidth"`
-	MinHeight int `json:"minHeight"`
-
 	SrcTableColumnIndex *int `json:"srcTableColumnIndex,omitempty"`
 	DstTableColumnIndex *int `json:"dstTableColumnIndex,omitempty"`
 
@@ -1471,21 +1468,23 @@ func (g *Graph) SetDimensions(mtexts []*d2target.MText, ruler *textmeasure.Ruler
 		}
 	}
 	for _, edge := range g.Edges {
-		endpointLabels := []string{}
+		usedFont := fontFamily
+		if edge.Style.Font != nil {
+			f := d2fonts.D2_FONT_TO_FAMILY[edge.Style.Font.Value]
+			usedFont = &f
+		}
+
 		if edge.SrcArrowhead != nil && edge.SrcArrowhead.Label.Value != "" {
-			endpointLabels = append(endpointLabels, edge.SrcArrowhead.Label.Value)
+			t := edge.Text()
+			t.Text = edge.SrcArrowhead.Label.Value
+			dims := GetTextDimensions(mtexts, ruler, t, usedFont)
+			edge.SrcArrowhead.LabelDimensions = *dims
 		}
 		if edge.DstArrowhead != nil && edge.DstArrowhead.Label.Value != "" {
-			endpointLabels = append(endpointLabels, edge.DstArrowhead.Label.Value)
-		}
-
-		for _, label := range endpointLabels {
 			t := edge.Text()
-			t.Text = label
-			dims := GetTextDimensions(mtexts, ruler, t, fontFamily)
-			edge.MinWidth += dims.Width
-			// Some padding as it's not totally near the end
-			edge.MinHeight += dims.Height + 5
+			t.Text = edge.DstArrowhead.Label.Value
+			dims := GetTextDimensions(mtexts, ruler, t, usedFont)
+			edge.DstArrowhead.LabelDimensions = *dims
 		}
 
 		if edge.Label.Value == "" {
@@ -1497,20 +1496,12 @@ func (g *Graph) SetDimensions(mtexts []*d2target.MText, ruler *textmeasure.Ruler
 		}
 		edge.ApplyTextTransform()
 
-		usedFont := fontFamily
-		if edge.Style.Font != nil {
-			f := d2fonts.D2_FONT_TO_FAMILY[edge.Style.Font.Value]
-			usedFont = &f
-		}
-
 		dims := GetTextDimensions(mtexts, ruler, edge.Text(), usedFont)
 		if dims == nil {
 			return fmt.Errorf("dimensions for edge label %#v not found", edge.Text())
 		}
 
 		edge.LabelDimensions = *dims
-		edge.MinWidth += dims.Width
-		edge.MinHeight += dims.Height
 	}
 	return nil
 }

d2graph/serde.go

@@ -388,22 +388,6 @@ func CompareSerializedEdge(edge, other *Edge) error {
 		)
 	}
 
-	if edge.MinWidth != other.MinWidth {
-		return fmt.Errorf(
-			"min width differs: edge=%d, other=%d",
-			edge.MinWidth,
-			other.MinWidth,
-		)
-	}
-
-	if edge.MinHeight != other.MinHeight {
-		return fmt.Errorf(
-			"min height differs: edge=%d, other=%d",
-			edge.MinHeight,
-			other.MinHeight,
-		)
-	}
-
 	if edge.Label.Value != other.Label.Value {
 		return fmt.Errorf(
 			"labels differ: edge=%s, other=%s",

d2renderers/d2sketch/sketch_test.go

@@ -1293,6 +1293,14 @@ queue -> package -> step
 callout -> stored_data -> person
 diamond -> oval -> circle
 hexagon -> cloud
+`,
+		},
+		{
+			name: "long_arrowhead_label",
+			script: `
+a -> b: {
+	target-arrowhead: "a to b with unexpectedly long target arrowhead label"
+}
 `,
 		},
 	}

d2renderers/d2svg/d2svg.go

@@ -20,8 +20,6 @@ import (
 	"github.com/alecthomas/chroma/v2/lexers"
 	"github.com/alecthomas/chroma/v2/styles"
 
-	"oss.terrastruct.com/util-go/go2"
-
 	"oss.terrastruct.com/d2/d2graph"
 	"oss.terrastruct.com/d2/d2renderers/d2fonts"
 	"oss.terrastruct.com/d2/d2renderers/d2latex"
@@ -39,8 +37,7 @@ import (
 )
 
 const (
-	DEFAULT_PADDING            = 100
-	MIN_ARROWHEAD_STROKE_WIDTH = 2
+	DEFAULT_PADDING = 100
 
 	appendixIconRadius = 16
 )
@@ -109,56 +106,13 @@ func arrowheadMarkerID(isTarget bool, connection d2target.Connection) string {
 	)))
 }
 
-func arrowheadDimensions(arrowhead d2target.Arrowhead, strokeWidth float64) (width, height float64) {
-	var baseWidth, baseHeight float64
-	var widthMultiplier, heightMultiplier float64
-	switch arrowhead {
-	case d2target.ArrowArrowhead:
-		baseWidth = 4
-		baseHeight = 4
-		widthMultiplier = 4
-		heightMultiplier = 4
-	case d2target.TriangleArrowhead:
-		baseWidth = 4
-		baseHeight = 4
-		widthMultiplier = 3
-		heightMultiplier = 4
-	case d2target.LineArrowhead:
-		widthMultiplier = 5
-		heightMultiplier = 8
-	case d2target.FilledDiamondArrowhead:
-		baseWidth = 11
-		baseHeight = 7
-		widthMultiplier = 5.5
-		heightMultiplier = 3.5
-	case d2target.DiamondArrowhead:
-		baseWidth = 11
-		baseHeight = 9
-		widthMultiplier = 5.5
-		heightMultiplier = 4.5
-	case d2target.FilledCircleArrowhead, d2target.CircleArrowhead:
-		baseWidth = 8
-		baseHeight = 8
-		widthMultiplier = 5
-		heightMultiplier = 5
-	case d2target.CfOne, d2target.CfMany, d2target.CfOneRequired, d2target.CfManyRequired:
-		baseWidth = 9
-		baseHeight = 9
-		widthMultiplier = 4.5
-		heightMultiplier = 4.5
-	}
-
-	clippedStrokeWidth := go2.Max(MIN_ARROWHEAD_STROKE_WIDTH, strokeWidth)
-	return baseWidth + clippedStrokeWidth*widthMultiplier, baseHeight + clippedStrokeWidth*heightMultiplier
-}
-
 func arrowheadMarker(isTarget bool, id string, connection d2target.Connection) string {
 	arrowhead := connection.DstArrow
 	if !isTarget {
 		arrowhead = connection.SrcArrow
 	}
 	strokeWidth := float64(connection.StrokeWidth)
-	width, height := arrowheadDimensions(arrowhead, strokeWidth)
+	width, height := arrowhead.Dimensions(strokeWidth)
 
 	var path string
 	switch arrowhead {
@@ -620,38 +574,40 @@ func drawConnection(writer io.Writer, labelMaskID string, connection d2target.Co
 		fmt.Fprint(writer, textEl.Render())
 	}
 
-	length := geo.Route(connection.Route).Length()
-	if connection.SrcLabel != "" {
-		// TODO use arrowhead label dimensions https://github.com/terrastruct/d2/issues/183
-		size := float64(connection.FontSize)
-		position := 0.
-		if length > 0 {
-			position = size / length
-		}
-		fmt.Fprint(writer, renderArrowheadLabel(connection, connection.SrcLabel, position, size, size))
-	}
-	if connection.DstLabel != "" {
-		// TODO use arrowhead label dimensions https://github.com/terrastruct/d2/issues/183
-		size := float64(connection.FontSize)
-		position := 1.
-		if length > 0 {
-			position -= size / length
-		}
-		fmt.Fprint(writer, renderArrowheadLabel(connection, connection.DstLabel, position, size, size))
+	if connection.SrcLabel != nil && connection.SrcLabel.Label != "" {
+		fmt.Fprint(writer, renderArrowheadLabel(connection, connection.SrcLabel.Label, false))
+	}
+	if connection.DstLabel != nil && connection.DstLabel.Label != "" {
+		fmt.Fprint(writer, renderArrowheadLabel(connection, connection.DstLabel.Label, true))
 	}
 	fmt.Fprintf(writer, `</g>`)
 	return
 }
 
-func renderArrowheadLabel(connection d2target.Connection, text string, position, width, height float64) string {
-	labelTL := label.UnlockedTop.GetPointOnRoute(connection.Route, float64(connection.StrokeWidth), position, width, height)
+func renderArrowheadLabel(connection d2target.Connection, text string, isDst bool) string {
+	var width, height float64
+	if isDst {
+		width = float64(connection.DstLabel.LabelWidth)
+		height = float64(connection.DstLabel.LabelHeight)
+	} else {
+		width = float64(connection.SrcLabel.LabelWidth)
+		height = float64(connection.SrcLabel.LabelHeight)
+	}
+
+	labelTL := connection.GetArrowheadLabelPosition(isDst)
+
+	// svg text is positioned with the center of its baseline
+	baselineCenter := geo.Point{
+		X: labelTL.X + width/2.,
+		Y: labelTL.Y + float64(connection.FontSize),
+	}
 
 	textEl := d2themes.NewThemableElement("text")
-	textEl.X = labelTL.X + width/2
-	textEl.Y = labelTL.Y + float64(connection.FontSize)
+	textEl.X = baselineCenter.X
+	textEl.Y = baselineCenter.Y
 	textEl.Fill = d2target.FG_COLOR
 	textEl.ClassName = "text-italic"
-	textEl.Style = fmt.Sprintf("text-anchor:%s;font-size:%vpx", "middle", connection.FontSize)
+	textEl.Style = fmt.Sprintf("text-anchor:middle;font-size:%vpx", connection.FontSize)
 	textEl.Content = RenderText(text, textEl.X, height)
 	return textEl.Render()
 }