ruler does not have entire mono font family %s loaded, is a

Error message

ruler does not have entire mono font family %s loaded, is a style missing?

What it means

Same guard as the regular font family check but for the mono font family (used by code/class/sql_table text). The ruler must have the entire mono family (default SourceCodePro, or the family set by the theme's Mono special rule or `mono` style) loaded, otherwise SetDimensions refuses to proceed.

Source

Thrown at d2graph/d2graph.go:1529

	return nil
}

func appendTextDedup(texts []*d2target.MText, t *d2target.MText) []*d2target.MText {
	if GetTextDimensions(texts, nil, t, nil) == nil {
		return append(texts, t)
	}
	return texts
}

func (g *Graph) SetDimensions(mtexts []*d2target.MText, ruler *textmeasure.Ruler, fontFamily *d2fonts.FontFamily, monoFontFamily *d2fonts.FontFamily) error {
	if ruler != nil && fontFamily != nil {
		if ok := ruler.HasFontFamilyLoaded(fontFamily); !ok {
			return fmt.Errorf("ruler does not have entire font family %s loaded, is a style missing?", *fontFamily)
		}
	}
	if ruler != nil && monoFontFamily != nil {
		if ok := ruler.HasFontFamilyLoaded(monoFontFamily); !ok {
			return fmt.Errorf("ruler does not have entire mono font family %s loaded, is a style missing?", *monoFontFamily)
		}
	}

	if g.Theme != nil && g.Theme.SpecialRules.Mono {
		tmp := d2fonts.SourceCodePro
		fontFamily = &tmp
	}

	for _, obj := range g.Objects {
		obj.Box = &geo.Box{}

		// user-specified label/icon positions
		if obj.HasLabel() && obj.Attributes.LabelPosition != nil {
			scalar := *obj.Attributes.LabelPosition
			position := d2ast.LabelPositionsMapping[scalar.Value]
			obj.LabelPosition = go2.Pointer(position.String())
		}
		if obj.Icon != nil && obj.Attributes.IconPosition != nil {

View on GitHub (pinned to 0d69dca6f5)

Solutions

Load the default mono font: after NewRuler(), call InitFonts with d2fonts.D2Fonts so SourceCodePro variants are present
If overriding monoFontFamily, register every style variant of that family in the ruler
Match the family name exactly (check `mono: <name>` in diagram code / theme Mono rules against registered names)
Pre-validate with ruler.HasFontFamilyLoaded(&d2fonts.SourceCodePro) before rendering

Example fix

// before
ruler, _ := textmeasure.NewRuler()
err := graph.SetDimensions(mtexts, ruler, fontFamily, &myMono) // myMono not registered
// after
ruler, _ := textmeasure.NewRuler()
ruler.InitFonts(d2fonts.D2Fonts) // registers SourceCodePro
ruler.SetFontFamily(myMono.Name, myMono.FilePaths) // or use SourceCodePro
err := graph.SetDimensions(mtexts, ruler, fontFamily, &myMono)

Defensive patterns

Strategy: validation

Validate before calling

ruler, _ := textmeasure.NewRuler()
ruler.InitFonts(d2fonts.D2Fonts) // includes SourceCodePro
mono := d2fonts.SourceCodePro
if graph.Theme != nil && graph.Theme.SpecialRules.Mono {
    // theme forces mono; ensure that family is loaded too
}
if !ruler.HasFontFamilyLoaded(&mono) {
    return fmt.Errorf("mono family %s not fully loaded", mono.Name)
}
err := graph.SetDimensions(mtexts, ruler, fontFamily, &mono)

Type guard

func monoFontReady(ruler *textmeasure.Ruler, mono *d2fonts.FontFamily) bool {
    return ruler != nil && mono != nil && ruler.HasFontFamilyLoaded(mono)
}

Try / catch

if err := graph.SetDimensions(mtexts, ruler, fontFamily, monoFontFamily); err != nil {
    if strings.Contains(err.Error(), "mono font family") {
        ruler.InitFonts(d2fonts.D2Fonts)
        monoFontFamily = &d2fonts.SourceCodePro // safe default
        err = graph.SetDimensions(mtexts, ruler, fontFamily, monoFontFamily)
    }
    return err
}

Prevention

Never strip SourceCodePro from your ruler's font set; it is the default mono family
If a diagram uses `mono: true` or a custom mono name, verify that family is registered first
Use InitFonts(d2fonts.D2Fonts) on every ruler you create
Check theme.SpecialRules.Mono to anticipate which family SetDimensions will require

When it happens

Trigger: Calling SetDimensions with a non-nil ruler and non-nil monoFontFamily where ruler.HasFontFamilyLoaded(monoFontFamily) is false; or theme.SpecialRules.Mono / a `mono: true` style selects a family the ruler hasn't fully loaded.

Common situations: Custom rulers built without SourceCodePro; self-hosted font setups registering only some weights; using a custom mono font name in diagram code that was never added to the ruler.

Related errors

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/e7dcdcb14c62b187. Report an issue: GitHub.