add black theme

internal/croctheme/blackTheme.go

@@ -0,0 +1,39 @@
+package croctheme
+
+import (
+	"image/color"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/theme"
+)
+
+func BlackTheme() fyne.Theme {
+	return &blackTheme{}
+}
+
+type blackTheme struct{}
+
+var _ fyne.Theme = (*blackTheme)(nil)
+
+func (b blackTheme) Color(name fyne.ThemeColorName, variant fyne.ThemeVariant) color.Color {
+	if name == theme.ColorNameBackground {
+		return color.Black
+	}
+	if name == theme.ColorNameShadow {
+		return color.White
+	}
+
+	return theme.DarkTheme().Color(name, theme.VariantDark)
+}
+
+func (b blackTheme) Icon(name fyne.ThemeIconName) fyne.Resource {
+	return theme.DarkTheme().Icon(name)
+}
+
+func (b blackTheme) Font(style fyne.TextStyle) fyne.Resource {
+	return theme.DarkTheme().Font(style)
+}
+
+func (bm blackTheme) Size(name fyne.ThemeSizeName) float32 {
+	return theme.DarkTheme().Size(name)
+}