Document the requirement to refresh if adding items

container/theme.go

@@ -24,6 +24,9 @@ type ThemeOverride struct {
 // Containers will be traversed and all child widgets will reflect the theme in this container.
 // This should be used sparingly to avoid a jarring user experience.
 //
+// If the content `obj` of this theme override is a container and items are later added to the container
+// ensure that you call `Refresh()` on this `ThemeOverride` to ensure the new items match the theme.
+//
 // Since: 2.5
 func NewThemeOverride(obj fyne.CanvasObject, th fyne.Theme) *ThemeOverride {
 	t := &ThemeOverride{Content: obj, Theme: th, holder: NewStack(obj)}

container/theme_test.go

@@ -4,11 +4,27 @@ import (
 	"image"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
+	"fyne.io/fyne/v2/internal/cache"
 	"fyne.io/fyne/v2/test"
 	"fyne.io/fyne/v2/theme"
 	"fyne.io/fyne/v2/widget"
 )
 
+func TestThemeOverride_AddChild(t *testing.T) {
+	b := widget.NewButton("Test", func() {})
+	group := NewHBox(b)
+	override := NewThemeOverride(group, test.Theme())
+
+	child := widget.NewLabel("Added")
+	assert.NotEqual(t, cache.WidgetTheme(b), cache.WidgetTheme(child))
+
+	group.Add(child)
+	override.Refresh()
+	assert.Equal(t, cache.WidgetTheme(b), cache.WidgetTheme(child))
+}
+
 func TestThemeOverride_Icons(t *testing.T) {
 	b := widget.NewButtonWithIcon("", theme.HomeIcon(), func() {})
 	o := NewThemeOverride(b, test.Theme())