adjusted UI Appearance API

Author: overheadhunter

src/main/java/org/cryptomator/integrations/uiappearance/UiAppearanceListener.java

@@ -0,0 +1,8 @@
+package org.cryptomator.integrations.uiappearance;
+
+@FunctionalInterface
+public interface UiAppearanceListener {
+
+	void systemAppearanceChanged(Theme newTheme);
+
+}

src/main/java/org/cryptomator/integrations/uiappearance/UiAppearanceProvider.java

@@ -5,9 +5,37 @@
  */
 public interface UiAppearanceProvider {
 
-	Theme getCurrentTheme() throws UiAppearanceException;
+	/**
+	 * Gets the best-matching theme for the OS's current L&F. This might be an approximation, as the OS might support more variations than we do.
+	 *
+	 * @implSpec Should default to {@link Theme#LIGHT} if the OS theme can't be determined, should not throw exceptions.
+	 * @return The current OS theme
+	 */
+	Theme getSystemTheme();
 
-	void addListener() throws UiAppearanceException;
-	void removeListener() throws UiAppearanceProvider;
+	/**
+	 * Adjusts parts of the UI to the desired theme, that can not be directly controlled from within Java.
+	 * This might be required for window decorations or tray icons. Can be no-op.
+	 *
+	 * @implSpec A best-effort attempt should be made. If adjustments fail, do not throw an exception.
+	 * @param theme What theme to adjust to
+	 */
+	void adjustToTheme(Theme theme);
+
+	/**
+	 * Registers a listener that gets notified when the system theme changes.
+	 *
+	 * @param listener The listener
+	 * @throws UiAppearanceException If registering the listener failed.
+	 */
+	void addListener(UiAppearanceListener listener) throws UiAppearanceException;
+
+	/**
+	 * Removes a previously registered listener.
+	 *
+	 * @param listener The listener
+	 * @throws UiAppearanceException If removing the listener failed.
+	 */
+	void removeListener(UiAppearanceListener listener) throws UiAppearanceException;
 
 }