diff --git a/apps/theming/lib/Capabilities.php b/apps/theming/lib/Capabilities.php
index b0c6a71731b86..b6020051b4e1f 100644
--- a/apps/theming/lib/Capabilities.php
+++ b/apps/theming/lib/Capabilities.php
@@ -41,33 +41,13 @@
  * @package OCA\Theming
  */
 class Capabilities implements IPublicCapability {
-
-	/** @var ThemingDefaults */
-	protected $theming;
-
-	/** @var Util */
-	protected $util;
-
-	/** @var IURLGenerator */
-	protected $url;
-
-	/** @var IConfig */
-	protected $config;
-
-	protected IUserSession $userSession;
-
-	/**
-	 * @param ThemingDefaults $theming
-	 * @param Util $util
-	 * @param IURLGenerator $url
-	 * @param IConfig $config
-	 */
-	public function __construct(ThemingDefaults $theming, Util $util, IURLGenerator $url, IConfig $config, IUserSession $userSession) {
-		$this->theming = $theming;
-		$this->util = $util;
-		$this->url = $url;
-		$this->config = $config;
-		$this->userSession = $userSession;
+	public function __construct(
+		protected ThemingDefaults $theming,
+		protected Util $util,
+		protected IURLGenerator $url,
+		protected IConfig $config,
+		protected IUserSession $userSession,
+	) {
 	}
 
 	/**
@@ -92,7 +72,7 @@ public function __construct(ThemingDefaults $theming, Util $util, IURLGenerator
 	 *     },
 	 * }
 	 */
-	public function getCapabilities() {
+	public function getCapabilities(): array {
 		$color = $this->theming->getDefaultColorPrimary();
 		// Same as in DefaultTheme
 		if ($color === BackgroundService::DEFAULT_COLOR) {
diff --git a/apps/theming/lib/ITheme.php b/apps/theming/lib/ITheme.php
index 4ff455005a2c0..5b3ab6b726676 100644
--- a/apps/theming/lib/ITheme.php
+++ b/apps/theming/lib/ITheme.php
@@ -30,7 +30,6 @@
  * @since 25.0.0
  */
 interface ITheme {
-
 	public const TYPE_THEME = 1;
 	public const TYPE_FONT = 2;
 
diff --git a/apps/theming/lib/IconBuilder.php b/apps/theming/lib/IconBuilder.php
index 8d6546cdcce33..cb4d7442cc25f 100644
--- a/apps/theming/lib/IconBuilder.php
+++ b/apps/theming/lib/IconBuilder.php
@@ -31,35 +31,18 @@
 use OCP\Files\SimpleFS\ISimpleFile;
 
 class IconBuilder {
-	/** @var ThemingDefaults */
-	private $themingDefaults;
-	/** @var Util */
-	private $util;
-	/** @var ImageManager */
-	private $imageManager;
-
-	/**
-	 * IconBuilder constructor.
-	 *
-	 * @param ThemingDefaults $themingDefaults
-	 * @param Util $util
-	 * @param ImageManager $imageManager
-	 */
 	public function __construct(
-		ThemingDefaults $themingDefaults,
-		Util $util,
-		ImageManager $imageManager
+		private ThemingDefaults $themingDefaults,
+		private Util $util,
+		private ImageManager $imageManager,
 	) {
-		$this->themingDefaults = $themingDefaults;
-		$this->util = $util;
-		$this->imageManager = $imageManager;
 	}
 
 	/**
 	 * @param $app string app name
 	 * @return string|false image blob
 	 */
-	public function getFavicon($app) {
+	public function getFavicon($app): bool|string {
 		if (!$this->imageManager->shouldReplaceIcons()) {
 			return false;
 		}
@@ -102,7 +85,7 @@ public function getFavicon($app) {
 	 * @param $app string app name
 	 * @return string|false image blob
 	 */
-	public function getTouchIcon($app) {
+	public function getTouchIcon($app): bool|string {
 		try {
 			$icon = $this->renderAppIcon($app, 512);
 			if ($icon === false) {
@@ -125,7 +108,7 @@ public function getTouchIcon($app) {
 	 * @param $size int size of the icon in px
 	 * @return Imagick|false
 	 */
-	public function renderAppIcon($app, $size) {
+	public function renderAppIcon($app, $size): Imagick|bool {
 		$appIcon = $this->util->getAppIcon($app);
 		if ($appIcon === false) {
 			return false;
@@ -150,8 +133,8 @@ public function renderAppIcon($app, $size) {
 			'<rect x="0" y="0" rx="100" ry="100" width="512" height="512" style="fill:' . $color . ';" />' .
 			'</svg>';
 		// resize svg magic as this seems broken in Imagemagick
-		if ($mime === "image/svg+xml" || substr($appIconContent, 0, 4) === "<svg") {
-			if (substr($appIconContent, 0, 5) !== "<?xml") {
+		if ($mime === "image/svg+xml" || str_starts_with($appIconContent, "<svg")) {
+			if (!str_starts_with($appIconContent, "<?xml")) {
 				$svg = "<?xml version=\"1.0\"?>".$appIconContent;
 			} else {
 				$svg = $appIconContent;
@@ -227,7 +210,7 @@ public function renderAppIcon($app, $size) {
 	 * @param $image string relative path to svg file in app directory
 	 * @return string|false content of a colorized svg file
 	 */
-	public function colorSvg($app, $image) {
+	public function colorSvg($app, $image): bool|string {
 		$imageFile = $this->util->getAppImage($app, $image);
 		if ($imageFile === false || $imageFile === "") {
 			return false;
diff --git a/apps/theming/lib/ImageManager.php b/apps/theming/lib/ImageManager.php
index 994e3f35118f9..c7a47b7fc037f 100644
--- a/apps/theming/lib/ImageManager.php
+++ b/apps/theming/lib/ImageManager.php
@@ -71,15 +71,11 @@ public function getImageUrl(string $key): string {
 			return $this->urlGenerator->linkToRoute('theming.Theming.getImage', [ 'key' => $key ]) . '?v=' . $cacheBusterCounter;
 		}
 
-		switch ($key) {
-			case 'logo':
-			case 'logoheader':
-			case 'favicon':
-				return $this->urlGenerator->imagePath('core', 'logo/logo.png') . '?v=' . $cacheBusterCounter;
-			case 'background':
-				return $this->urlGenerator->linkTo(Application::APP_ID, 'img/background/' . BackgroundService::DEFAULT_BACKGROUND_IMAGE);
-		}
-		return '';
+		return match ($key) {
+			'logo', 'logoheader', 'favicon' => $this->urlGenerator->imagePath('core', 'logo/logo.png') . '?v=' . $cacheBusterCounter,
+			'background' => $this->urlGenerator->linkTo(Application::APP_ID, 'img/background/' . BackgroundService::DEFAULT_BACKGROUND_IMAGE),
+			default => '',
+		};
 	}
 
 	/**
@@ -166,8 +162,8 @@ public function getCacheFolder(): ISimpleFolder {
 	 * Get a file from AppData
 	 *
 	 * @param string $filename
+	 * @return ISimpleFile
 	 * @throws NotFoundException
-	 * @return \OCP\Files\SimpleFS\ISimpleFile
 	 * @throws NotPermittedException
 	 */
 	public function getCachedImage(string $filename): ISimpleFile {
@@ -178,9 +174,6 @@ public function getCachedImage(string $filename): ISimpleFile {
 	/**
 	 * Store a file for theming in AppData
 	 *
-	 * @param string $filename
-	 * @param string $data
-	 * @return \OCP\Files\SimpleFS\ISimpleFile
 	 * @throws NotFoundException
 	 * @throws NotPermittedException
 	 */
@@ -342,10 +335,8 @@ public function cleanup() {
 	/**
 	 * Check if Imagemagick is enabled and if SVG is supported
 	 * otherwise we can't render custom icons
-	 *
-	 * @return bool
 	 */
-	public function shouldReplaceIcons() {
+	public function shouldReplaceIcons(): bool {
 		$cache = $this->cacheFactory->createDistributed('theming-' . $this->urlGenerator->getBaseUrl());
 		if ($value = $cache->get('shouldReplaceIcons')) {
 			return (bool)$value;
diff --git a/apps/theming/lib/Themes/DarkHighContrastTheme.php b/apps/theming/lib/Themes/DarkHighContrastTheme.php
index e6f1da94b4e8b..0c342fb8b1b5a 100644
--- a/apps/theming/lib/Themes/DarkHighContrastTheme.php
+++ b/apps/theming/lib/Themes/DarkHighContrastTheme.php
@@ -28,7 +28,6 @@
 use OCA\Theming\ITheme;
 
 class DarkHighContrastTheme extends DarkTheme implements ITheme {
-
 	public function getId(): string {
 		return 'dark-highcontrast';
 	}
diff --git a/apps/theming/lib/Themes/DarkTheme.php b/apps/theming/lib/Themes/DarkTheme.php
index 8d88de75834ed..e89af7387626e 100644
--- a/apps/theming/lib/Themes/DarkTheme.php
+++ b/apps/theming/lib/Themes/DarkTheme.php
@@ -28,7 +28,6 @@
 use OCA\Theming\ITheme;
 
 class DarkTheme extends DefaultTheme implements ITheme {
-
 	public function getId(): string {
 		return 'dark';
 	}
diff --git a/apps/theming/lib/Themes/DefaultTheme.php b/apps/theming/lib/Themes/DefaultTheme.php
index 68038f053e397..b428c0858a819 100644
--- a/apps/theming/lib/Themes/DefaultTheme.php
+++ b/apps/theming/lib/Themes/DefaultTheme.php
@@ -39,35 +39,19 @@
 class DefaultTheme implements ITheme {
 	use CommonThemeTrait;
 
-	public Util $util;
-	public ThemingDefaults $themingDefaults;
-	public IUserSession $userSession;
-	public IURLGenerator $urlGenerator;
-	public ImageManager $imageManager;
-	public IConfig $config;
-	public IL10N $l;
-	public IAppManager $appManager;
-
 	public string $defaultPrimaryColor;
 	public string $primaryColor;
 
-	public function __construct(Util $util,
-		ThemingDefaults $themingDefaults,
-		IUserSession $userSession,
-		IURLGenerator $urlGenerator,
-		ImageManager $imageManager,
-		IConfig $config,
-		IL10N $l,
-		IAppManager $appManager) {
-		$this->util = $util;
-		$this->themingDefaults = $themingDefaults;
-		$this->userSession = $userSession;
-		$this->urlGenerator = $urlGenerator;
-		$this->imageManager = $imageManager;
-		$this->config = $config;
-		$this->l = $l;
-		$this->appManager = $appManager;
-
+	public function __construct(
+		public Util $util,
+		public ThemingDefaults $themingDefaults,
+		public IUserSession $userSession,
+		public IURLGenerator $urlGenerator,
+		public ImageManager $imageManager,
+		public IConfig $config,
+		public IL10N $l,
+		public IAppManager $appManager,
+	) {
 		$this->defaultPrimaryColor = $this->themingDefaults->getDefaultColorPrimary();
 		$this->primaryColor = $this->themingDefaults->getColorPrimary();
 
diff --git a/apps/theming/lib/Themes/DyslexiaFont.php b/apps/theming/lib/Themes/DyslexiaFont.php
index 3275a005c8d4a..f49654fcd05b8 100644
--- a/apps/theming/lib/Themes/DyslexiaFont.php
+++ b/apps/theming/lib/Themes/DyslexiaFont.php
@@ -28,7 +28,6 @@
 use OCA\Theming\ITheme;
 
 class DyslexiaFont extends DefaultTheme implements ITheme {
-
 	public function getId(): string {
 		return 'opendyslexic';
 	}
@@ -77,7 +76,7 @@ public function getCustomCss(): string {
 					 url('$fontPathOtf') format('opentype'),
 					 url('$fontPathTtf') format('truetype');
 			}
-			
+
 			@font-face {
 				font-family: 'OpenDyslexic';
 				font-style: normal;
diff --git a/apps/theming/lib/Themes/HighContrastTheme.php b/apps/theming/lib/Themes/HighContrastTheme.php
index e21e802fbe325..749428192a432 100644
--- a/apps/theming/lib/Themes/HighContrastTheme.php
+++ b/apps/theming/lib/Themes/HighContrastTheme.php
@@ -28,7 +28,6 @@
 use OCA\Theming\ITheme;
 
 class HighContrastTheme extends DefaultTheme implements ITheme {
-
 	public function getId(): string {
 		return 'light-highcontrast';
 	}
diff --git a/apps/theming/lib/Themes/LightTheme.php b/apps/theming/lib/Themes/LightTheme.php
index 7e6773992a10c..b806f108e7060 100644
--- a/apps/theming/lib/Themes/LightTheme.php
+++ b/apps/theming/lib/Themes/LightTheme.php
@@ -28,7 +28,6 @@
 use OCA\Theming\ITheme;
 
 class LightTheme extends DefaultTheme implements ITheme {
-
 	public function getId(): string {
 		return 'light';
 	}
diff --git a/apps/theming/lib/ThemingDefaults.php b/apps/theming/lib/ThemingDefaults.php
index 210029ae63694..48436a9c80871 100644
--- a/apps/theming/lib/ThemingDefaults.php
+++ b/apps/theming/lib/ThemingDefaults.php
@@ -54,17 +54,6 @@
 use OCP\IUserSession;
 
 class ThemingDefaults extends \OC_Defaults {
-
-	private IConfig $config;
-	private IL10N $l;
-	private ImageManager $imageManager;
-	private IUserSession $userSession;
-	private IURLGenerator $urlGenerator;
-	private ICacheFactory $cacheFactory;
-	private Util $util;
-	private IAppManager $appManager;
-	private INavigationManager $navigationManager;
-
 	private string $name;
 	private string $title;
 	private string $entity;
@@ -78,38 +67,18 @@ class ThemingDefaults extends \OC_Defaults {
 	private string $AndroidClientUrl;
 	private string $FDroidClientUrl;
 
-	/**
-	 * ThemingDefaults constructor.
-	 *
-	 * @param IConfig $config
-	 * @param IL10N $l
-	 * @param ImageManager $imageManager
-	 * @param IUserSession $userSession
-	 * @param IURLGenerator $urlGenerator
-	 * @param ICacheFactory $cacheFactory
-	 * @param Util $util
-	 * @param IAppManager $appManager
-	 */
-	public function __construct(IConfig $config,
-		IL10N $l,
-		IUserSession $userSession,
-		IURLGenerator $urlGenerator,
-		ICacheFactory $cacheFactory,
-		Util $util,
-		ImageManager $imageManager,
-		IAppManager $appManager,
-		INavigationManager $navigationManager
+	public function __construct(
+		private IConfig $config,
+		private IL10N $l,
+		private IUserSession $userSession,
+		private IURLGenerator $urlGenerator,
+		private ICacheFactory $cacheFactory,
+		private Util $util,
+		private ImageManager $imageManager,
+		private IAppManager $appManager,
+		private INavigationManager $navigationManager,
 	) {
 		parent::__construct();
-		$this->config = $config;
-		$this->l = $l;
-		$this->imageManager = $imageManager;
-		$this->userSession = $userSession;
-		$this->urlGenerator = $urlGenerator;
-		$this->cacheFactory = $cacheFactory;
-		$this->util = $util;
-		$this->appManager = $appManager;
-		$this->navigationManager = $navigationManager;
 
 		$this->name = parent::getName();
 		$this->title = parent::getTitle();
@@ -124,27 +93,27 @@ public function __construct(IConfig $config,
 		$this->docBaseUrl = parent::getDocBaseUrl();
 	}
 
-	public function getName() {
+	public function getName(): string {
 		return strip_tags($this->config->getAppValue('theming', 'name', $this->name));
 	}
 
-	public function getHTMLName() {
+	public function getHTMLName(): string {
 		return $this->config->getAppValue('theming', 'name', $this->name);
 	}
 
-	public function getTitle() {
+	public function getTitle(): string {
 		return strip_tags($this->config->getAppValue('theming', 'name', $this->title));
 	}
 
-	public function getEntity() {
+	public function getEntity(): string {
 		return strip_tags($this->config->getAppValue('theming', 'name', $this->entity));
 	}
 
-	public function getProductName() {
+	public function getProductName(): string {
 		return strip_tags($this->config->getAppValue('theming', 'productName', $this->productName));
 	}
 
-	public function getBaseUrl() {
+	public function getBaseUrl(): string {
 		return $this->config->getAppValue('theming', 'url', $this->url);
 	}
 
@@ -157,19 +126,19 @@ public function getSlogan(?string $lang = null) {
 		return \OCP\Util::sanitizeHTML($this->config->getAppValue('theming', 'slogan', parent::getSlogan($lang)));
 	}
 
-	public function getImprintUrl() {
-		return (string)$this->config->getAppValue('theming', 'imprintUrl', '');
+	public function getImprintUrl(): string {
+		return $this->config->getAppValue('theming', 'imprintUrl', '');
 	}
 
-	public function getPrivacyUrl() {
-		return (string)$this->config->getAppValue('theming', 'privacyUrl', '');
+	public function getPrivacyUrl(): string {
+		return $this->config->getAppValue('theming', 'privacyUrl', '');
 	}
 
-	public function getDocBaseUrl() {
-		return (string)$this->config->getAppValue('theming', 'docBaseUrl', $this->docBaseUrl);
+	public function getDocBaseUrl(): string {
+		return $this->config->getAppValue('theming', 'docBaseUrl', $this->docBaseUrl);
 	}
 
-	public function getShortFooter() {
+	public function getShortFooter(): string {
 		$slogan = $this->getSlogan();
 		$baseUrl = $this->getBaseUrl();
 		$entity = $this->getEntity();
@@ -188,11 +157,11 @@ public function getShortFooter() {
 		$links = [
 			[
 				'text' => $this->l->t('Legal notice'),
-				'url' => (string)$this->getImprintUrl()
+				'url' => $this->getImprintUrl()
 			],
 			[
 				'text' => $this->l->t('Privacy policy'),
-				'url' => (string)$this->getPrivacyUrl()
+				'url' => $this->getPrivacyUrl()
 			],
 		];
 
@@ -307,45 +276,31 @@ public function getLogo($useSvg = true): string {
 
 	/**
 	 * Themed background image url
-	 *
-	 * @return string
 	 */
 	public function getBackground(): string {
 		return $this->imageManager->getImageUrl('background');
 	}
 
-	/**
-	 * @return string
-	 */
-	public function getiTunesAppId() {
+	public function getiTunesAppId(): string {
 		return $this->config->getAppValue('theming', 'iTunesAppId', $this->iTunesAppId);
 	}
 
-	/**
-	 * @return string
-	 */
-	public function getiOSClientUrl() {
+	public function getiOSClientUrl(): string {
 		return $this->config->getAppValue('theming', 'iOSClientUrl', $this->iOSClientUrl);
 	}
 
-	/**
-	 * @return string
-	 */
-	public function getAndroidClientUrl() {
+	public function getAndroidClientUrl(): string {
 		return $this->config->getAppValue('theming', 'AndroidClientUrl', $this->AndroidClientUrl);
 	}
 
-	/**
-	 * @return string
-	 */
-	public function getFDroidClientUrl() {
+	public function getFDroidClientUrl(): string {
 		return $this->config->getAppValue('theming', 'FDroidClientUrl', $this->FDroidClientUrl);
 	}
 
 	/**
 	 * @return array scss variables to overwrite
 	 */
-	public function getScssVariables() {
+	public function getScssVariables(): array {
 		$cacheBuster = $this->config->getAppValue('theming', 'cachebuster', '0');
 		$cache = $this->cacheFactory->createDistributed('theming-' . $cacheBuster . '-' . $this->urlGenerator->getBaseUrl());
 		if ($value = $cache->get('getScssVariables')) {
@@ -391,9 +346,9 @@ public function getScssVariables() {
 	 *
 	 * @param string $app name of the app
 	 * @param string $image filename of the image
-	 * @return bool|string false if image should not replaced, otherwise the location of the image
+	 * @return bool|string false if image should not be replaced, otherwise the location of the image
 	 */
-	public function replaceImagePath($app, $image) {
+	public function replaceImagePath($app, $image): bool|string {
 		if ($app === '' || $app === 'files_sharing') {
 			$app = 'core';
 		}
@@ -502,19 +457,15 @@ public function undo($setting): string {
 
 	/**
 	 * Color of text in the header and primary buttons
-	 *
-	 * @return string
 	 */
-	public function getTextColorPrimary() {
+	public function getTextColorPrimary(): string {
 		return $this->util->invertTextColor($this->getColorPrimary()) ? '#000000' : '#ffffff';
 	}
 
 	/**
 	 * Color of text in the header and primary buttons
-	 *
-	 * @return string
 	 */
-	public function getDefaultTextColorPrimary() {
+	public function getDefaultTextColorPrimary(): string {
 		return $this->util->invertTextColor($this->getDefaultColorPrimary()) ? '#000000' : '#ffffff';
 	}
 
diff --git a/apps/theming/lib/Util.php b/apps/theming/lib/Util.php
index a2f8ee0abad23..85f3bc63e9c3f 100644
--- a/apps/theming/lib/Util.php
+++ b/apps/theming/lib/Util.php
@@ -38,23 +38,17 @@
 use OCP\IUserSession;
 
 class Util {
-
-	private IConfig $config;
-	private IAppManager $appManager;
-	private IAppData $appData;
-	private ImageManager $imageManager;
-
-	public function __construct(IConfig $config, IAppManager $appManager, IAppData $appData, ImageManager $imageManager) {
-		$this->config = $config;
-		$this->appManager = $appManager;
-		$this->appData = $appData;
-		$this->imageManager = $imageManager;
+	public function __construct(
+		private IConfig $config,
+		private IAppManager $appManager,
+		private IAppData $appData,
+		private ImageManager $imageManager,
+	) {
 	}
 
 	/**
 	 * Should we invert the text on this background color?
 	 * @param string $color rgb color value
-	 * @return bool
 	 */
 	public function invertTextColor(string $color): bool {
 		return $this->colorContrast($color, '#ffffff') < 4.5;
@@ -63,25 +57,17 @@ public function invertTextColor(string $color): bool {
 	/**
 	 * Is this color too bright ?
 	 * @param string $color rgb color value
-	 * @return bool
 	 */
 	public function isBrightColor(string $color): bool {
-		$l = $this->calculateLuma($color);
-		if ($l > 0.6) {
-			return true;
-		} else {
-			return false;
-		}
+		return $this->calculateLuma($color) > 0.6;
 	}
 
 	/**
 	 * get color for on-page elements:
 	 * theme color by default, grey if theme color is to bright
 	 * @param string $color
-	 * @param ?bool $brightBackground
-	 * @return string
 	 */
-	public function elementColor($color, ?bool $brightBackground = null, ?string $backgroundColor = null, bool $highContrast = false) {
+	public function elementColor($color, ?bool $brightBackground = null, ?string $backgroundColor = null, bool $highContrast = false): string {
 		if ($backgroundColor !== null) {
 			$brightBackground = $brightBackground ?? $this->isBrightColor($backgroundColor);
 			// Minimal amount that is possible to change the luminance
@@ -140,10 +126,6 @@ public function darken(string $color, int $factor): string {
 	 *
 	 * Copied from cssphp, copyright Leaf Corcoran, licensed under MIT
 	 *
-	 * @param int $red
-	 * @param int $green
-	 * @param int $blue
-	 *
 	 * @return float[]
 	 */
 	public function toHSL(int $red, int $green, int $blue): array {
@@ -210,7 +192,7 @@ public function hexToRGB(string $color): array {
 	 * @param $color
 	 * @return string base64 encoded radio button svg
 	 */
-	public function generateRadioButton($color) {
+	public function generateRadioButton($color): string {
 		$radioButtonIcon = '<svg xmlns="http://www.w3.org/2000/svg" height="16" width="16">' .
 			'<path d="M8 1a7 7 0 0 0-7 7 7 7 0 0 0 7 7 7 7 0 0 0 7-7 7 7 0 0 0-7-7zm0 1a6 6 0 0 1 6 6 6 6 0 0 1-6 6 6 6 0 0 1-6-6 6 6 0 0 1 6-6zm0 2a4 4 0 1 0 0 8 4 4 0 0 0 0-8z" fill="'.$color.'"/></svg>';
 		return base64_encode($radioButtonIcon);
@@ -221,7 +203,7 @@ public function generateRadioButton($color) {
 	 * @param string $app app name
 	 * @return string|ISimpleFile path to app icon / file of logo
 	 */
-	public function getAppIcon($app) {
+	public function getAppIcon($app): ISimpleFile|string {
 		$app = str_replace(['\0', '/', '\\', '..'], '', $app);
 		try {
 			$appPath = $this->appManager->getAppPath($app);
@@ -237,7 +219,6 @@ public function getAppIcon($app) {
 		}
 
 		if ($this->config->getAppValue('theming', 'logoMime', '') !== '') {
-			$logoFile = null;
 			try {
 				$folder = $this->appData->getFolder('global/images');
 				return $folder->getFile('logo');
@@ -252,7 +233,7 @@ public function getAppIcon($app) {
 	 * @param string $image relative path to image in app folder
 	 * @return string|false absolute path to image
 	 */
-	public function getAppImage($app, $image) {
+	public function getAppImage($app, $image): bool|string {
 		$app = str_replace(['\0', '/', '\\', '..'], '', $app);
 		$image = str_replace(['\0', '\\', '..'], '', $image);
 		if ($app === "core") {
@@ -297,32 +278,24 @@ public function getAppImage($app, $image) {
 	 *
 	 * @param string $svg content of a svg file
 	 * @param string $color color to match
-	 * @return string
 	 */
-	public function colorizeSvg($svg, $color) {
-		$svg = preg_replace('/#0082c9/i', $color, $svg);
-		return $svg;
+	public function colorizeSvg($svg, $color): string {
+		return preg_replace('/#0082c9/i', $color, $svg);
 	}
 
 	/**
 	 * Check if a custom theme is set in the server configuration
-	 *
-	 * @return bool
 	 */
-	public function isAlreadyThemed() {
-		$theme = $this->config->getSystemValue('theme', '');
-		if ($theme !== '') {
-			return true;
-		}
-		return false;
+	public function isAlreadyThemed(): bool {
+		return $this->config->getSystemValue('theme', '') !== '';
 	}
 
-	public function isBackgroundThemed() {
+	public function isBackgroundThemed(): bool {
 		$backgroundLogo = $this->config->getAppValue('theming', 'backgroundMime', '');
 		return $backgroundLogo !== '' && $backgroundLogo !== 'backgroundColor';
 	}
 
-	public function isLogoThemed() {
+	public function isLogoThemed(): bool {
 		return $this->imageManager->hasImage('logo')
 			|| $this->imageManager->hasImage('logoheader');
 	}