Themes

Switch between dark, light and system themes in a Fyne application.

Usage

Show Code

package main

import (
  "image/color"

  "fyne.io/fyne/v2"
  "fyne.io/fyne/v2/app"
  "fyne.io/fyne/v2/container"
  "fyne.io/fyne/v2/theme"
  "fyne.io/fyne/v2/widget"
)

// customTheme wraps a base theme but forces a specific variant.
type customTheme struct {
  base    fyne.Theme
  variant fyne.ThemeVariant
}

func (t *customTheme) Color(n fyne.ThemeColorName, _ fyne.ThemeVariant) color.Color {
  return t.base.Color(n, t.variant)
}
func (t *customTheme) Icon(n fyne.ThemeIconName) fyne.Resource { return t.base.Icon(n) }
func (t *customTheme) Font(s fyne.TextStyle) fyne.Resource     { return t.base.Font(s) }
func (t *customTheme) Size(n fyne.ThemeSizeName) float32       { return t.base.Size(n) }

func main() {
  a := app.New()
  w := a.NewWindow("Theme Toggle")

  mode := 0 // 0=System, 1=Dark, 2=Light

  apply := func() {
    switch mode {
    case 0:
      // system
      fyne.CurrentApp().Settings().SetTheme(theme.DefaultTheme())
    case 1:
      // dark
      fyne.CurrentApp().Settings().SetTheme(
        &customTheme{base: theme.DefaultTheme(), variant: theme.VariantDark},
      )
    case 2:
      // light.
      fyne.CurrentApp().Settings().SetTheme(
        &customTheme{base: theme.DefaultTheme(), variant: theme.VariantLight},
      )
    }
  }

  btn := widget.NewButton("Toggle Theme", func() {
    mode = (mode + 1) % 3
    apply()
  })

  w.SetContent(container.NewCenter(btn))
  w.Resize(fyne.NewSize(520, 300))
  apply() // start in System/adaptive
  w.ShowAndRun()
}