glanceapp/glance · error

compiling theme preview: %v

Error message

compiling theme preview: %v

What it means

Returned by themeProperties.init() when executing themePresetPreviewTemplate fails — the small HTML preview rendered for each preset on the themes page. Same root causes as the style template: theme property values that decode but cannot be rendered, or (in forks) template expressions referencing missing fields.

Source

Thrown at internal/glance/theme.go:65

	ContrastMultiplier       float32        `yaml:"contrast-multiplier"`
	TextSaturationMultiplier float32        `yaml:"text-saturation-multiplier"`

	Key                  string        `yaml:"-"`
	CSS                  template.CSS  `yaml:"-"`
	PreviewHTML          template.HTML `yaml:"-"`
	BackgroundColorAsHex string        `yaml:"-"`
}

func (t *themeProperties) init() error {
	css, err := executeTemplateToString(themeStyleTemplate, t)
	if err != nil {
		return fmt.Errorf("compiling theme style: %v", err)
	}
	t.CSS = template.CSS(whitespaceAtBeginningOfLinePattern.ReplaceAllString(css, ""))

	previewHTML, err := executeTemplateToString(themePresetPreviewTemplate, t)
	if err != nil {
		return fmt.Errorf("compiling theme preview: %v", err)
	}
	t.PreviewHTML = template.HTML(previewHTML)

	if t.BackgroundColor != nil {
		t.BackgroundColorAsHex = t.BackgroundColor.ToHex()
	} else {
		t.BackgroundColorAsHex = "#151519"
	}

	return nil
}

func (t1 *themeProperties) SameAs(t2 *themeProperties) bool {
	if t1 == nil && t2 == nil {
		return true
	}
	if t1 == nil || t2 == nil {
		return false

View on GitHub (pinned to 91324e8de7)

Solutions

1. Read the chained error to find the failing preset/field
2. Make each preset fully specify documented fields with valid formats
3. Test presets one at a time to identify the offender

// Ensure every preset supplies required renderable fields (e.g. colors present or omitted consistently)
for _, p := range presets {
    if p.ColorScheme != "" && !validColorScheme(p.ColorScheme) { return fmt.Errorf("invalid color-scheme in preset") }
    if !validMultiplier(p.ContrastMultiplier) { return fmt.Errorf("invalid multiplier in preset") }
}

Catch at preset init (message includes the preset name), log name + chained cause, and remove/fix that preset before restart.

When it happens

Trigger: Executing the preview template with a themeProperties value containing fields in an invalid state (colors, multipliers); preset previews are generated for every preset, so any one bad preset in theme.presets triggers it (wrapped as 'initializing preset theme %s').

Common situations: Custom presets with exotic values; fork modifications to the preview template; theme fields partially specified leaving zero-value structs the template mishandles.

Related errors

• compiling theme style: %v
• initializing preset theme %s: %v
• initializing default theme: %v
• URL is required
• nested groups are not supported

AI-assisted analysis of glanceapp/glance@91324e8de7 (2026-08-15). Data as JSON: /api/errors/b74f90355cf8cb17. Report an issue: GitHub.