add black theme

AndroidManifest.xml

@@ -3,8 +3,8 @@
 	xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
 	package="com.github.howeyc.crocgui"
-	android:versionCode="8"
+	android:versionCode="9"
-	android:versionName="1.4.1">
+	android:versionName="1.5.0">
 
     <application android:label="Croc">
 	<activity android:name="org.golang.app.GoNativeActivity"

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)
+}

settings.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crocgui/internal/croctheme"
+
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/container"
 	"fyne.io/fyne/v2/data/binding"
@@ -15,6 +17,8 @@ func setTheme(themeName string) {
 		a.Settings().SetTheme(theme.LightTheme())
 	case "dark":
 		a.Settings().SetTheme(theme.DarkTheme())
+	case "black":
+		a.Settings().SetTheme(croctheme.BlackTheme())
 	default:
 		// TODO: get system
 		a.Settings().SetTheme(theme.LightTheme())
@@ -23,7 +27,7 @@ func setTheme(themeName string) {
 
 func settingsTabItem(a fyne.App) *container.TabItem {
 	themeBinding := binding.BindPreferenceString("theme", a.Preferences())
-	themeSelect := widget.NewSelect([]string{"light", "dark"}, func(selection string) {
+	themeSelect := widget.NewSelect([]string{"light", "dark", "black"}, func(selection string) {
 		setTheme(selection)
 		themeBinding.Set(selection)
 	})