d2render: support gradient values

d2graph/d2graph.go

@@ -253,16 +253,16 @@ func (s *Style) Apply(key, value string) error {
 		if s.Stroke == nil {
 			break
 		}
-		if !go2.Contains(color.NamedColors, strings.ToLower(value)) && !color.ColorHexRegex.MatchString(value) {
-			return errors.New(`expected "stroke" to be a valid named color ("orange") or a hex code ("#f0ff3a")`)
+		if !color.ValidColor(value) {
+			return errors.New(`expected "stroke" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
 		}
 		s.Stroke.Value = value
 	case "fill":
 		if s.Fill == nil {
 			break
 		}
-		if !go2.Contains(color.NamedColors, strings.ToLower(value)) && !color.ColorHexRegex.MatchString(value) {
-			return errors.New(`expected "fill" to be a valid named color ("orange") or a hex code ("#f0ff3a")`)
+		if !color.ValidColor(value) {
+			return errors.New(`expected "fill" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
 		}
 		s.Fill.Value = value
 	case "fill-pattern":
@@ -348,8 +348,8 @@ func (s *Style) Apply(key, value string) error {
 		if s.FontColor == nil {
 			break
 		}
-		if !go2.Contains(color.NamedColors, strings.ToLower(value)) && !color.ColorHexRegex.MatchString(value) {
-			return errors.New(`expected "font-color" to be a valid named color ("orange") or a hex code ("#f0ff3a")`)
+		if !color.ValidColor(value) {
+			return errors.New(`expected "font-color" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
 		}
 		s.FontColor.Value = value
 	case "animated":

d2renderers/d2svg/d2svg.go

@@ -706,6 +706,11 @@ func renderDoubleOval(tl *geo.Point, width, height float64, fill, fillStroke, st
 	return renderOval(tl, width, height, fill, fillStroke, stroke, style) + renderOval(innerTL, width-10, height-10, fill, "", stroke, style)
 }
 
+func defineGradients(writer io.Writer, cssGradient string) {
+	gradient, _ := color.ParseGradient(cssGradient)
+	fmt.Fprint(writer, fmt.Sprintf(`<defs>%s</defs>`, color.GradientToSVG(gradient)))
+}
+
 func defineShadowFilter(writer io.Writer) {
 	fmt.Fprint(writer, `<defs>
 	<filter id="shadow-filter" width="200%" height="200%" x="-50%" y="-50%">
@@ -1824,6 +1829,29 @@ func Render(diagram *d2target.Diagram, opts *RenderOpts) ([]byte, error) {
 		}
 	}
 
+	if color.IsGradient(diagram.Root.Fill) {
+		defineGradients(buf, diagram.Root.Fill)
+	}
+	if color.IsGradient(diagram.Root.Stroke) {
+		defineGradients(buf, diagram.Root.Stroke)
+	}
+	for _, s := range diagram.Shapes {
+		if color.IsGradient(s.Fill) {
+			defineGradients(buf, s.Fill)
+		}
+		if color.IsGradient(s.Stroke) {
+			defineGradients(buf, s.Stroke)
+		}
+		if color.IsGradient(s.Color) {
+			defineGradients(buf, s.Color)
+		}
+	}
+	for _, c := range diagram.Connections {
+		if color.IsGradient(c.Stroke) {
+			defineGradients(buf, c.Stroke)
+		}
+	}
+
 	// Apply hash on IDs for targeting, to be specific for this diagram
 	diagramHash, err := diagram.HashID()
 	if err != nil {

d2themes/element.go

@@ -178,11 +178,17 @@ func (el *ThemableElement) Render() string {
 	if color.IsThemeColor(el.Stroke) {
 		class += fmt.Sprintf(" stroke-%s", el.Stroke)
 	} else if len(el.Stroke) > 0 {
+		if color.IsGradient(el.Stroke) {
+			el.Stroke = fmt.Sprintf("url('#%s')", color.UniqueGradientID(el.Stroke))
+		}
 		out += fmt.Sprintf(` stroke="%s"`, el.Stroke)
 	}
 	if color.IsThemeColor(el.Fill) {
 		class += fmt.Sprintf(" fill-%s", el.Fill)
 	} else if len(el.Fill) > 0 {
+		if color.IsGradient(el.Fill) {
+			el.Fill = fmt.Sprintf("url('#%s')", color.UniqueGradientID(el.Fill))
+		}
 		out += fmt.Sprintf(` fill="%s"`, el.Fill)
 	}
 	if color.IsThemeColor(el.BackgroundColor) {