Add KDE Plasma dark mode support

src/main/kotlin/io/github/gaming32/additiveinstaller/darkModeDetector.kt

@@ -13,43 +13,76 @@ private const val REGDWORD_TOKEN = "REG_DWORD"
 private const val DARK_THEME_CMD = "$REGQUERY_UTIL\"HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize\" /v AppsUseLightTheme"
 private val DARK_THEME_PATTERN = Regex(".*dark.*", RegexOption.IGNORE_CASE)
 
-fun isDarkMode() = when (operatingSystem) {
-    OperatingSystem.WINDOWS -> isWindowsDarkMode()
-    OperatingSystem.MACOS -> isMacOsDarkMode()
-    OperatingSystem.LINUX -> isGnome() && isGnomeDarkMode()
-    else -> false
-}
-
-private fun isMacOsDarkMode() = query("defaults read -g AppleInterfaceStyle") == "Dark"
-
-private fun isWindowsDarkMode() = try {
-    query(DARK_THEME_CMD)
-        .substringAfter(REGDWORD_TOKEN)
-        .ifEmpty { null }
-        ?.trim()
-        ?.substring(2)
-        ?.toInt(16) == 0
-} catch (e: Exception) {
-    false
-}
-
-private fun isGnomeDarkMode() = query("gsettings get org.gnome.desktop.interface gtk-theme") matches DARK_THEME_PATTERN
-
-private fun isGnome() = operatingSystem == OperatingSystem.LINUX && (
-    queryResultContains("echo \$XDG_CURRENT_DESKTOP", "gnome") ||
-    queryResultContains("echo \$XDG_DATA_DIRS | grep -Eo 'gnome'", "gnome") ||
-    queryResultContains("ps -e | grep -E -i \"gnome\"", "gnome")
-)
-
-private fun queryResultContains(cmd: String, subResult: String) = query(cmd).contains(subResult, ignoreCase = true)
-
-private fun query(cmd: String) = try {
-    Runtime.getRuntime()
-        .exec(cmd)
-        .inputStream
-        .bufferedReader()
-        .use(BufferedReader::readText)
-} catch (e: IOException) {
-    logger.error(e) { "Exception caught while querying the OS" }
-    ""
+fun isDarkMode(): Boolean {
+    return when (operatingSystem) {
+        OperatingSystem.WINDOWS -> isWindowsDarkMode()
+        OperatingSystem.MACOS -> isMacOsDarkMode()
+        OperatingSystem.LINUX -> (isGnome() && isGnomeDarkMode()) || (isKde() && isKdeDarkMode())
+        else -> false
+    }
+}
+
+private fun isMacOsDarkMode(): Boolean {
+    val result = query("defaults read -g AppleInterfaceStyle")
+    return result == "Dark"
+}
+
+private fun isWindowsDarkMode(): Boolean {
+    return try {
+        val result = query(DARK_THEME_CMD)
+        result.substringAfter(REGDWORD_TOKEN)
+            .ifEmpty { null }
+            ?.trim()
+            ?.substring(2)
+            ?.toInt(16) == 0
+    } catch (e: Exception) {
+        false
+    }
+}
+
+private fun isGnomeDarkMode(): Boolean {
+    val result = query("gsettings get org.gnome.desktop.interface gtk-theme")
+    return result matches DARK_THEME_PATTERN
+}
+
+private fun isGnome(): Boolean {
+    return operatingSystem == OperatingSystem.LINUX && (
+            queryResultContains("echo \$XDG_CURRENT_DESKTOP", "gnome") ||
+                    queryResultContains("echo \$XDG_DATA_DIRS | grep -Eo 'gnome'", "gnome") ||
+                    queryResultContains("ps -e | grep -E -i \"gnome\"", "gnome")
+            )
+}
+
+private fun isKdeDarkMode(): Boolean {
+    val currentLookAndFeel = query("lookandfeeltool --current")
+    if (currentLookAndFeel.isEmpty()) {
+        val alternativeLookAndFeel = query("kreadconfig5 --group KDE --key LookAndFeelPackage")
+        return alternativeLookAndFeel.contains("dark", ignoreCase = true)
+    }
+    return currentLookAndFeel.contains("dark", ignoreCase = true)
+}
+
+private fun isKde(): Boolean {
+    return operatingSystem == OperatingSystem.LINUX && (
+            queryResultContains("echo \$XDG_CURRENT_DESKTOP", "KDE") ||
+                    queryResultContains("echo \$XDG_DATA_DIRS | grep -Eo 'kde'", "kde") ||
+                    queryResultContains("ps -e | grep -E -i \"kde\"", "kde")
+            )
+}
+
+private fun queryResultContains(cmd: String, subResult: String): Boolean {
+    return query(cmd).contains(subResult, ignoreCase = true)
+}
+
+private fun query(cmd: String): String {
+    return try {
+        Runtime.getRuntime()
+            .exec(cmd)
+            .inputStream
+            .bufferedReader()
+            .use(BufferedReader::readText)
+    } catch (e: IOException) {
+        logger.error { "Exception caught while querying the OS" }
+        ""
+    }
 }