support font

alias.go

@@ -332,6 +332,7 @@ var (
 
 // functions from gvc package.
 var (
+	SetFontLoader   = gvc.SetFontLoader
 	DefaultPlugins  = gvc.DefaultPlugins
 	DeviceQuality   = gvc.WithDeviceQuality
 	DeviceFeatures  = gvc.WithDeviceFeatures

cgraph/attribute.go

@@ -1071,6 +1071,11 @@ func (g *Graph) SetInputScale(v float64) *Graph {
 	return g
 }
 
+// Label returns label attribute.
+func (g *Graph) Label() (string, error) {
+	return g.GetStr(string(labelAttr))
+}
+
 // SetLabel
 // Text label attached to objects.
 // If a node's shape is record, then the label can have a special format which describes the record layout.
@@ -1080,10 +1085,15 @@ func (g *Graph) SetInputScale(v float64) *Graph {
 // To get an HTML-like label, the label attribute value itself must be an HTML string.
 // https://graphviz.gitlab.io/_pages/doc/info/attrs.html#a:label
 func (g *Graph) SetLabel(v string) *Graph {
-	g.SafeSet(string(labelAttr), v, "")
+	g.SafeSet(string(labelAttr), v, "\\G")
 	return g
 }
 
+// Label returns label attribute.
+func (n *Node) Label() (string, error) {
+	return n.GetStr(string(labelAttr))
+}
+
 // SetLabel
 // Text label attached to objects.
 // If a node's shape is record, then the label can have a special format which describes the record layout.
@@ -1097,6 +1107,11 @@ func (n *Node) SetLabel(v string) *Node {
 	return n
 }
 
+// Label returns label attribute.
+func (e *Edge) Label() (string, error) {
+	return e.GetStr(string(labelAttr))
+}
+
 // SetLabel
 // Text label attached to objects.
 // If a node's shape is record, then the label can have a special format which describes the record layout.
@@ -1106,7 +1121,7 @@ func (n *Node) SetLabel(v string) *Node {
 // To get an HTML-like label, the label attribute value itself must be an HTML string.
 // https://graphviz.gitlab.io/_pages/doc/info/attrs.html#a:label
 func (e *Edge) SetLabel(v string) *Edge {
-	e.SafeSet(string(labelAttr), v, "")
+	e.SafeSet(string(labelAttr), v, "\\E")
 	return e
 }
 

cmd/dot/go.mod

@@ -11,9 +11,11 @@ require (
 )
 
 require (
+	github.com/flopp/go-findfont v0.1.0 // indirect
 	github.com/fogleman/gg v1.3.0 // indirect
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect
 	github.com/tetratelabs/wazero v1.8.1 // indirect
 	golang.org/x/image v0.21.0 // indirect
 	golang.org/x/sys v0.26.0 // indirect
+	golang.org/x/text v0.19.0 // indirect
 )

cmd/dot/go.sum

@@ -1,5 +1,7 @@
 github.com/corona10/goimagehash v1.1.0 h1:teNMX/1e+Wn/AYSbLHX8mj+mF9r60R1kBeqE9MkoYwI=
 github.com/corona10/goimagehash v1.1.0/go.mod h1:VkvE0mLn84L4aF8vCb6mafVajEb6QYMHl2ZJLn0mOGI=
+github.com/flopp/go-findfont v0.1.0 h1:lPn0BymDUtJo+ZkV01VS3661HL6F4qFlkhcJN55u6mU=
+github.com/flopp/go-findfont v0.1.0/go.mod h1:wKKxRDjD024Rh7VMwoU90i6ikQRCr+JTHB5n4Ejkqvw=
 github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
 github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
@@ -16,3 +18,5 @@ golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
 golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.25.0 h1:WtHI/ltw4NvSUig5KARz9h521QvRC8RmF/cuYqifU24=
 golang.org/x/term v0.25.0/go.mod h1:RPyXicDX+6vLxogjjRxjgD2TKtmAO6NZBsBRfrOLu7M=
+golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
+golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=

go.mod

@@ -4,10 +4,14 @@ go 1.22.0
 
 require (
 	github.com/corona10/goimagehash v1.1.0
+	github.com/flopp/go-findfont v0.1.0
 	github.com/fogleman/gg v1.3.0
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/tetratelabs/wazero v1.8.1
 	golang.org/x/image v0.21.0
 )
 
-require github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 // indirect
+require (
+	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 // indirect
+	golang.org/x/text v0.19.0 // indirect
+)

go.sum

@@ -1,5 +1,7 @@
 github.com/corona10/goimagehash v1.1.0 h1:teNMX/1e+Wn/AYSbLHX8mj+mF9r60R1kBeqE9MkoYwI=
 github.com/corona10/goimagehash v1.1.0/go.mod h1:VkvE0mLn84L4aF8vCb6mafVajEb6QYMHl2ZJLn0mOGI=
+github.com/flopp/go-findfont v0.1.0 h1:lPn0BymDUtJo+ZkV01VS3661HL6F4qFlkhcJN55u6mU=
+github.com/flopp/go-findfont v0.1.0/go.mod h1:wKKxRDjD024Rh7VMwoU90i6ikQRCr+JTHB5n4Ejkqvw=
 github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
 github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
@@ -10,3 +12,5 @@ github.com/tetratelabs/wazero v1.8.1 h1:NrcgVbWfkWvVc4UtT4LRLDf91PsOzDzefMdwhLfA
 github.com/tetratelabs/wazero v1.8.1/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
 golang.org/x/image v0.21.0 h1:c5qV36ajHpdj4Qi0GnE0jUc/yuo33OLFaa0d+crTD5s=
 golang.org/x/image v0.21.0/go.mod h1:vUbsLavqK/W303ZroQQVKQ+Af3Yl6Uz1Ppu5J/cLz78=
+golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
+golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=

graphviz.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/goccy/go-graphviz/cgraph"
 	"github.com/goccy/go-graphviz/gvc"
-	"golang.org/x/image/font"
 )
 
 type Graphviz struct {
@@ -75,10 +74,6 @@ func (g *Graphviz) SetLayout(layout Layout) *Graphviz {
 	return g
 }
 
-func (g *Graphviz) SetFontFace(callback func(size float64) (font.Face, error)) {
-	gvc.SetFontFace(callback)
-}
-
 func (g *Graphviz) Render(ctx context.Context, graph *Graph, format Format, w io.Writer) (e error) {
 	defer func() {
 		if err := g.ctx.FreeLayout(ctx, graph); err != nil {

gvc/gvc.go

@@ -50,6 +50,9 @@ func (c *Context) Close() error {
 }
 
 func (c *Context) Layout(ctx context.Context, g *cgraph.Graph, engine string) error {
+	if err := c.setupNodeLabelIfEmpty(g); err != nil {
+		return err
+	}
 	res, err := c.gvc.Layout(ctx, toGraphWasm(g), engine)
 	if err != nil {
 		return err
@@ -111,6 +114,40 @@ func (c *Context) FreeClonedContext(ctx context.Context) error {
 	return c.gvc.FreeClonedContext(ctx)
 }
 
+func (c *Context) setupNodeLabelIfEmpty(g *cgraph.Graph) error {
+	n, err := g.FirstNode()
+	if err != nil {
+		return err
+	}
+	if err := c.setLabelIfEmpty(n); err != nil {
+		return err
+	}
+	for {
+		n, err = g.NextNode(n)
+		if err != nil {
+			return err
+		}
+		if n == nil {
+			break
+		}
+		if err := c.setLabelIfEmpty(n); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *Context) setLabelIfEmpty(n *cgraph.Node) error {
+	label, err := n.Label()
+	if err != nil {
+		return err
+	}
+	if label == "" {
+		n.SetLabel("\\N")
+	}
+	return nil
+}
+
 func newPlugins(ctx context.Context, plugins ...Plugin) ([]*wasm.SymList, error) {
 	defaults, err := wasm.DefaultSymList(ctx)
 	if err != nil {