Refactor mount point setting and controller :

* remove CustomMountPath, winDriveLetter and usesCustomMountPath
* new property mountPoint (can be null)
* differentiation between driveLetter and directory happens in controller

src/main/java/org/cryptomator/common/mount/WindowsDriveLetters.java

@@ -5,7 +5,6 @@
  *******************************************************************************/
 package org.cryptomator.common.mount;
 
-import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import org.apache.commons.lang3.SystemUtils;
 
@@ -13,8 +12,10 @@ import javax.inject.Inject;
 import javax.inject.Singleton;
 import java.nio.file.FileSystems;
 import java.nio.file.Path;
+import java.util.Collections;
 import java.util.Optional;
 import java.util.Set;
+import java.util.TreeSet;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.StreamSupport;
@@ -22,64 +23,48 @@ import java.util.stream.StreamSupport;
 @Singleton
 public final class WindowsDriveLetters {
 
-	private static final Set<String> A_TO_Z;
+	private static final Set<Path> A_TO_Z;
 
 	static {
-		try (IntStream stream = IntStream.rangeClosed('A', 'Z')) {
-			A_TO_Z = stream.mapToObj(i -> String.valueOf((char) i)).collect(ImmutableSet.toImmutableSet());
-		}
+		var sortedSet = new TreeSet<Path>();
+		IntStream.rangeClosed('A', 'Z').mapToObj(i -> Path.of((char) i + ":\\")).forEach(sortedSet::add);
+		A_TO_Z = Collections.unmodifiableSet(sortedSet);
 	}
 
 	@Inject
 	public WindowsDriveLetters() {
 	}
 
-	public Set<String> getAllDriveLetters() {
+	public Set<Path> getAll() {
 		return A_TO_Z;
 	}
 
-	public Set<String> getOccupiedDriveLetters() {
+	public Set<Path> getOccupied() {
 		if (!SystemUtils.IS_OS_WINDOWS) {
 			return Set.of();
 		} else {
 			Iterable<Path> rootDirs = FileSystems.getDefault().getRootDirectories();
-			return StreamSupport.stream(rootDirs.spliterator(), false).map(p -> p.toString().substring(0, 1)).collect(Collectors.toSet());
+			return StreamSupport.stream(rootDirs.spliterator(), false).collect(Collectors.toUnmodifiableSet());
 		}
 	}
 
-	public Set<String> getAvailableDriveLetters() {
-		return Sets.difference(getAllDriveLetters(), getOccupiedDriveLetters());
-	}
-
-	public Optional<String> getAvailableDriveLetter() {
-		return getAvailableDriveLetters().stream().findFirst();
-	}
-
-	public Optional<Path> getAvailableDriveLetterPath() {
-		return getAvailableDriveLetter().map(this::toPath);
+	public Set<Path> getAvailable() {
+		return Sets.difference(getAll(), getOccupied());
 	}
 
 	/**
-	 * Skips A and B and only returns them if all other are occupied.
+	 * Skips A and B and only returns them if all others are occupied.
 	 *
 	 * @return an Optional containing either the letter of a free drive letter or empty, if none is available
 	 */
-	public Optional<String> getDesiredAvailableDriveLetter() {
-		var availableDriveLetters = getAvailableDriveLetters();
-		var optString = availableDriveLetters.stream().filter(s -> !(s.equals("A") || s.equals("B"))).findFirst();
+	public Optional<Path> getFirstDesiredAvailable() {
+		var availableDriveLetters = getAvailable();
+		var optString = availableDriveLetters.stream().filter(this::notAOrB).findFirst();
 		return optString.or(() -> availableDriveLetters.stream().findFirst());
 	}
 
-	/**
-	 * Skips A and B and only returns them if all other are occupied.
-	 *
-	 * @return an Optional containing either the path to a free drive letter or empty, if none is available
-	 */
-	public Optional<Path> getDesiredAvailableDriveLetterPath() {
-		return getDesiredAvailableDriveLetter().map(this::toPath);
+	private boolean notAOrB(Path driveLetter) {
+		return !(Path.of("A:\\").equals(driveLetter) || Path.of("B:\\").equals(driveLetter));
 	}
 
-	public Path toPath(String driveLetter) {
-		return Path.of(driveLetter + ":\\");
-	}
 }

src/main/java/org/cryptomator/common/settings/VaultSettings.java

@@ -6,7 +6,6 @@
 package org.cryptomator.common.settings;
 
 import com.google.common.base.CharMatcher;
-import com.google.common.base.Strings;
 import com.google.common.io.BaseEncoding;
 
 import javafx.beans.Observable;
@@ -22,7 +21,6 @@ import javafx.beans.property.SimpleStringProperty;
 import javafx.beans.property.StringProperty;
 import java.nio.file.Path;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.Random;
 
 /**
@@ -32,7 +30,6 @@ public class VaultSettings {
 
 	public static final boolean DEFAULT_UNLOCK_AFTER_STARTUP = false;
 	public static final boolean DEFAULT_REVEAL_AFTER_MOUNT = true;
-	public static final boolean DEFAULT_USES_INDIVIDUAL_MOUNTPATH = false;
 	public static final boolean DEFAULT_USES_READONLY_MODE = false;
 	public static final String DEFAULT_MOUNT_FLAGS = "";
 	public static final int DEFAULT_MAX_CLEARTEXT_FILENAME_LENGTH = -1;
@@ -45,11 +42,8 @@ public class VaultSettings {
 	private final String id;
 	private final ObjectProperty<Path> path = new SimpleObjectProperty<>();
 	private final StringProperty displayName = new SimpleStringProperty();
-	private final StringProperty winDriveLetter = new SimpleStringProperty();
 	private final BooleanProperty unlockAfterStartup = new SimpleBooleanProperty(DEFAULT_UNLOCK_AFTER_STARTUP);
 	private final BooleanProperty revealAfterMount = new SimpleBooleanProperty(DEFAULT_REVEAL_AFTER_MOUNT);
-	private final BooleanProperty useCustomMountPath = new SimpleBooleanProperty(DEFAULT_USES_INDIVIDUAL_MOUNTPATH);
-	private final StringProperty customMountPath = new SimpleStringProperty();
 	private final BooleanProperty usesReadOnlyMode = new SimpleBooleanProperty(DEFAULT_USES_READONLY_MODE);
 	private final StringProperty mountFlags = new SimpleStringProperty(DEFAULT_MOUNT_FLAGS);
 	private final IntegerProperty maxCleartextFilenameLength = new SimpleIntegerProperty(DEFAULT_MAX_CLEARTEXT_FILENAME_LENGTH);
@@ -73,7 +67,7 @@ public class VaultSettings {
 	}
 
 	Observable[] observables() {
-		return new Observable[]{path, displayName, winDriveLetter, unlockAfterStartup, revealAfterMount, useCustomMountPath, customMountPath, usesReadOnlyMode, mountFlags, maxCleartextFilenameLength, actionAfterUnlock, autoLockWhenIdle, autoLockIdleSeconds};
+		return new Observable[]{actionAfterUnlock, autoLockIdleSeconds, autoLockWhenIdle, displayName, maxCleartextFilenameLength, mountFlags, mountPoint, path, revealAfterMount, unlockAfterStartup, usesReadOnlyMode};
 	}
 
 	public static VaultSettings withRandomId() {
@@ -117,18 +111,6 @@ public class VaultSettings {
 		return mountName;
 	}
 
-	public StringProperty winDriveLetter() {
-		return winDriveLetter;
-	}
-
-	public Optional<String> getWinDriveLetter() {
-		String current = this.winDriveLetter.get();
-		if (!Strings.isNullOrEmpty(current)) {
-			return Optional.of(current);
-		}
-		return Optional.empty();
-	}
-
 	public BooleanProperty unlockAfterStartup() {
 		return unlockAfterStartup;
 	}
@@ -137,20 +119,12 @@ public class VaultSettings {
 		return revealAfterMount;
 	}
 
-	public BooleanProperty useCustomMountPath() {
-		return useCustomMountPath;
-	}
-
-	public StringProperty customMountPath() {
-		return customMountPath;
+	public Path getMountPoint() {
+		return mountPoint.get();
 	}
 
-	public Optional<String> getCustomMountPath() {
-		if (useCustomMountPath.get()) {
-			return Optional.ofNullable(Strings.emptyToNull(customMountPath.get()));
-		} else {
-			return Optional.empty();
-		}
+	public ObjectProperty<Path> mountPoint() {
+		return mountPoint;
 	}
 
 	public BooleanProperty usesReadOnlyMode() {
@@ -196,12 +170,4 @@ public class VaultSettings {
 			return false;
 		}
 	}
-
-	public Path getMountPoint() {
-		return mountPoint.get();
-	}
-
-	public ObjectProperty<Path> mountPointProperty() {
-		return mountPoint;
-	}
 }

src/main/java/org/cryptomator/common/settings/VaultSettingsJsonAdapter.java

@@ -6,11 +6,14 @@
 package org.cryptomator.common.settings;
 
 import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.JsonWriter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 
 class VaultSettingsJsonAdapter {
@@ -22,11 +25,10 @@ class VaultSettingsJsonAdapter {
 		out.name("id").value(value.getId());
 		out.name("path").value(value.path().get().toString());
 		out.name("displayName").value(value.displayName().get());
-		out.name("winDriveLetter").value(value.winDriveLetter().get());
 		out.name("unlockAfterStartup").value(value.unlockAfterStartup().get());
 		out.name("revealAfterMount").value(value.revealAfterMount().get());
-		out.name("useCustomMountPath").value(value.useCustomMountPath().get());
-		out.name("customMountPath").value(value.customMountPath().get());
+		var mountPoint = value.mountPoint().get();
+		out.name("mountPoint").value(mountPoint != null ? mountPoint.toAbsolutePath().toString() : null);
 		out.name("usesReadOnlyMode").value(value.usesReadOnlyMode().get());
 		out.name("mountFlags").value(value.mountFlags().get());
 		out.name("maxCleartextFilenameLength").value(value.maxCleartextFilenameLength().get());
@@ -36,18 +38,18 @@ class VaultSettingsJsonAdapter {
 		out.endObject();
 	}
 
+	//TODO: usesCustomMountPath, customMountPath and winDriveLetter removed
+	//	-> migration required
 	public VaultSettings read(JsonReader in) throws IOException {
 		String id = null;
 		String path = null;
 		String mountName = null; //see https://github.com/cryptomator/cryptomator/pull/1318
 		String displayName = null;
-		String customMountPath = null;
-		String winDriveLetter = null;
 		boolean unlockAfterStartup = VaultSettings.DEFAULT_UNLOCK_AFTER_STARTUP;
 		boolean revealAfterMount = VaultSettings.DEFAULT_REVEAL_AFTER_MOUNT;
-		boolean useCustomMountPath = VaultSettings.DEFAULT_USES_INDIVIDUAL_MOUNTPATH;
 		boolean usesReadOnlyMode = VaultSettings.DEFAULT_USES_READONLY_MODE;
 		String mountFlags = VaultSettings.DEFAULT_MOUNT_FLAGS;
+		Path mountPoint = null;
 		int maxCleartextFilenameLength = VaultSettings.DEFAULT_MAX_CLEARTEXT_FILENAME_LENGTH;
 		WhenUnlocked actionAfterUnlock = VaultSettings.DEFAULT_ACTION_AFTER_UNLOCK;
 		boolean autoLockWhenIdle = VaultSettings.DEFAULT_AUTOLOCK_WHEN_IDLE;
@@ -61,13 +63,17 @@ class VaultSettingsJsonAdapter {
 				case "path" -> path = in.nextString();
 				case "mountName" -> mountName = in.nextString(); //see https://github.com/cryptomator/cryptomator/pull/1318
 				case "displayName" -> displayName = in.nextString();
-				case "winDriveLetter" -> winDriveLetter = in.nextString();
 				case "unlockAfterStartup" -> unlockAfterStartup = in.nextBoolean();
 				case "revealAfterMount" -> revealAfterMount = in.nextBoolean();
-				case "usesIndividualMountPath", "useCustomMountPath" -> useCustomMountPath = in.nextBoolean();
-				case "individualMountPath", "customMountPath" -> customMountPath = in.nextString();
 				case "usesReadOnlyMode" -> usesReadOnlyMode = in.nextBoolean();
 				case "mountFlags" -> mountFlags = in.nextString();
+				case "mountPoint" -> {
+					if (JsonToken.NULL == in.peek()) {
+						in.nextNull();
+					} else {
+						mountPoint = parseMountPoint(in.nextString());
+					}
+				}
 				case "maxCleartextFilenameLength" -> maxCleartextFilenameLength = in.nextInt();
 				case "actionAfterUnlock" -> actionAfterUnlock = parseActionAfterUnlock(in.nextString());
 				case "autoLockWhenIdle" -> autoLockWhenIdle = in.nextBoolean();
@@ -87,20 +93,27 @@ class VaultSettingsJsonAdapter {
 			vaultSettings.displayName().set(mountName);
 		}
 		vaultSettings.path().set(Paths.get(path));
-		vaultSettings.winDriveLetter().set(winDriveLetter);
 		vaultSettings.unlockAfterStartup().set(unlockAfterStartup);
 		vaultSettings.revealAfterMount().set(revealAfterMount);
-		vaultSettings.useCustomMountPath().set(useCustomMountPath);
-		vaultSettings.customMountPath().set(customMountPath);
 		vaultSettings.usesReadOnlyMode().set(usesReadOnlyMode);
 		vaultSettings.mountFlags().set(mountFlags);
 		vaultSettings.maxCleartextFilenameLength().set(maxCleartextFilenameLength);
 		vaultSettings.actionAfterUnlock().set(actionAfterUnlock);
 		vaultSettings.autoLockWhenIdle().set(autoLockWhenIdle);
 		vaultSettings.autoLockIdleSeconds().set(autoLockIdleSeconds);
+		vaultSettings.mountPoint().set(mountPoint);
 		return vaultSettings;
 	}
 
+	private Path parseMountPoint(String mountPoint) {
+		try {
+			return Path.of(mountPoint);
+		} catch (InvalidPathException e) {
+			LOG.warn("Invalid string as mount point. Defaulting to null.");
+			return null;
+		}
+	}
+
 	private WhenUnlocked parseActionAfterUnlock(String actionAfterUnlockName) {
 		try {
 			return WhenUnlocked.valueOf(actionAfterUnlockName.toUpperCase());

src/main/java/org/cryptomator/common/vaults/Vault.java

@@ -12,6 +12,7 @@ import com.google.common.base.Strings;
 import org.apache.commons.lang3.SystemUtils;
 import org.cryptomator.common.Constants;
 import org.cryptomator.common.Environment;
+import org.cryptomator.common.mount.WindowsDriveLetters;
 import org.cryptomator.common.settings.Settings;
 import org.cryptomator.common.settings.VaultSettings;
 import org.cryptomator.cryptofs.CryptoFileSystem;
@@ -83,12 +84,13 @@ public class Vault {
 	private final BooleanBinding needsMigration;
 	private final BooleanBinding unknownError;
 	private final ObjectBinding<Mountpoint> mountPoint;
+	private final WindowsDriveLetters windowsDriveLetters;
 	private final BooleanProperty showingStats;
 
 	private AtomicReference<MountHandle> mountHandle = new AtomicReference<>(null);
 
 	@Inject
-	Vault(Environment env, Settings settings, VaultSettings vaultSettings, VaultConfigCache configCache, AtomicReference<CryptoFileSystem> cryptoFileSystem, VaultState state, @Named("lastKnownException") ObjectProperty<Exception> lastKnownException, ObservableValue<MountService> mountService, VaultStats stats) {
+	Vault(Environment env, Settings settings, VaultSettings vaultSettings, VaultConfigCache configCache, AtomicReference<CryptoFileSystem> cryptoFileSystem, VaultState state, @Named("lastKnownException") ObjectProperty<Exception> lastKnownException, ObservableValue<MountService> mountService, VaultStats stats, WindowsDriveLetters windowsDriveLetters) {
 		this.env = env;
 		this.settings = settings;
 		this.vaultSettings = vaultSettings;
@@ -107,6 +109,7 @@ public class Vault {
 		this.needsMigration = Bindings.createBooleanBinding(this::isNeedsMigration, state);
 		this.unknownError = Bindings.createBooleanBinding(this::isUnknownError, state);
 		this.mountPoint = Bindings.createObjectBinding(this::getMountPoint, state);
+		this.windowsDriveLetters = windowsDriveLetters;
 		this.showingStats = new SimpleBooleanProperty(false);
 	}
 
@@ -178,7 +181,7 @@ public class Vault {
 			if (mountProvider.hasCapability(MOUNT_TO_SYSTEM_CHOSEN_PATH)) {
 				// no need to set a mount point
 			} else if (mountProvider.hasCapability(MOUNT_AS_DRIVE_LETTER)) {
-				// TODO find any free drive letter?
+				builder.setMountpoint(windowsDriveLetters.getFirstDesiredAvailable().orElseThrow());
 			} else if (mountProvider.hasCapability(MOUNT_WITHIN_EXISTING_PARENT)) {
 				Files.createDirectories(defaultMountPointBase);
 				builder.setMountpoint(defaultMountPointBase);

src/main/java/org/cryptomator/ui/vaultoptions/MountOptionsController.java

@@ -1,15 +1,13 @@
 package org.cryptomator.ui.vaultoptions;
 
-import com.google.common.base.Strings;
 import org.cryptomator.common.Environment;
-import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.common.mount.WindowsDriveLetters;
+import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.integrations.mount.MountCapability;
 import org.cryptomator.integrations.mount.MountService;
 import org.cryptomator.ui.common.FxController;
 
 import javax.inject.Inject;
-import javafx.beans.binding.Bindings;
 import javafx.beans.value.ObservableValue;
 import javafx.fxml.FXML;
 import javafx.scene.control.CheckBox;
@@ -38,10 +36,13 @@ public class MountOptionsController implements FxController {
 
 	private final ObservableValue<Boolean> mountpointDirSupported;
 	private final ObservableValue<Boolean> mountpointDriveLetterSupported;
-	private final ObservableValue<Boolean> mountpointParentSupported; //TODO: use it in GUI
 	private final ObservableValue<Boolean> readOnlySupported;
 	private final ObservableValue<Boolean> mountFlagsSupported;
+	private final ObservableValue<Path> driveLetter;
+	private final ObservableValue<String> directoryPath;
+
 
+	//-- FXML objects --
 	public CheckBox readOnlyCheckbox;
 	public CheckBox customMountFlagsCheckbox;
 	public TextField mountFlagsField;
@@ -49,7 +50,8 @@ public class MountOptionsController implements FxController {
 	public RadioButton mountPointAutoBtn;
 	public RadioButton mountPointDriveLetterBtn;
 	public RadioButton mountPointDirBtn;
-	public ChoiceBox<String> driveLetterSelection;
+	public TextField directoryPathField;
+	public ChoiceBox<Path> driveLetterSelection;
 
 	@Inject
 	MountOptionsController(@VaultOptionsWindow Stage window, @VaultOptionsWindow Vault vault, ObservableValue<MountService> mountService, WindowsDriveLetters windowsDriveLetters, ResourceBundle resourceBundle, Environment environment) {
@@ -57,11 +59,12 @@ public class MountOptionsController implements FxController {
 		this.vault = vault;
 		this.windowsDriveLetters = windowsDriveLetters;
 		this.resourceBundle = resourceBundle;
-		this.mountpointDirSupported = mountService.map(s -> s.hasCapability(MountCapability.MOUNT_TO_EXISTING_DIR));
+		this.mountpointDirSupported = mountService.map(s -> s.hasCapability(MountCapability.MOUNT_TO_EXISTING_DIR) || s.hasCapability(MountCapability.MOUNT_WITHIN_EXISTING_PARENT));
 		this.mountpointDriveLetterSupported = mountService.map(s -> s.hasCapability(MountCapability.MOUNT_AS_DRIVE_LETTER));
-		this.mountpointParentSupported = mountService.map(s -> s.hasCapability(MountCapability.MOUNT_WITHIN_EXISTING_PARENT));
 		this.mountFlagsSupported = mountService.map(s -> s.hasCapability(MountCapability.MOUNT_FLAGS));
 		this.readOnlySupported = mountService.map(s -> s.hasCapability(MountCapability.READ_ONLY));
+		this.driveLetter = vault.getVaultSettings().mountPoint().map(p -> isDriveLetter(p) ? p : null);
+		this.directoryPath = vault.getVaultSettings().mountPoint().map(p -> isDriveLetter(p) ? null : p.toString());
 	}
 
 	@FXML
@@ -73,26 +76,24 @@ public class MountOptionsController implements FxController {
 		mountFlagsField.disableProperty().bind(customMountFlagsCheckbox.selectedProperty().not());
 		customMountFlagsCheckbox.setSelected(vault.isHavingCustomMountFlags());
 
-		// mount point options:
-		mountPointToggleGroup.selectedToggleProperty().addListener(this::toggleMountPoint);
-		driveLetterSelection.getItems().addAll(windowsDriveLetters.getAllDriveLetters());
+		//driveLetter choice box
+		driveLetterSelection.getItems().addAll(windowsDriveLetters.getAll());
 		driveLetterSelection.setConverter(new WinDriveLetterLabelConverter(windowsDriveLetters, resourceBundle));
-		driveLetterSelection.setValue(vault.getVaultSettings().winDriveLetter().get());
+		driveLetterSelection.setOnShowing(event -> driveLetterSelection.setConverter(new WinDriveLetterLabelConverter(windowsDriveLetters, resourceBundle))); //TODO: does this work?
 
-		if (vault.getVaultSettings().useCustomMountPath().get() && vault.getVaultSettings().getCustomMountPath().isPresent()) {
-			mountPointToggleGroup.selectToggle(mountPointDirBtn);
-		} else if (!Strings.isNullOrEmpty(vault.getVaultSettings().winDriveLetter().get())) {
-			mountPointToggleGroup.selectToggle(mountPointDriveLetterBtn);
-		} else {
+		//mountPoint toggle group
+		var mountPoint = vault.getVaultSettings().getMountPoint();
+		if (mountPoint == null) {
+			//prepare and select auto
 			mountPointToggleGroup.selectToggle(mountPointAutoBtn);
+		} else if (mountPoint.getParent() == null && isDriveLetter(mountPoint)) {
+			//prepare and select drive letter
+			mountPointToggleGroup.selectToggle(mountPointDriveLetterBtn);
+		} else if (driveLetterSelection.getValue() == null) {
+			//prepare and select dir
+			mountPointToggleGroup.selectToggle(mountPointDirBtn);
 		}
-
-		vault.getVaultSettings().useCustomMountPath().bind(mountPointToggleGroup.selectedToggleProperty().isEqualTo(mountPointDirBtn));
-		vault.getVaultSettings().winDriveLetter().bind( //
-				Bindings.when(mountPointToggleGroup.selectedToggleProperty().isEqualTo(mountPointDriveLetterBtn)) //
-						.then(driveLetterSelection.getSelectionModel().selectedItemProperty()) //
-						.otherwise((String) null) //
-		);
+		mountPointToggleGroup.selectedToggleProperty().addListener(this::selectedToggleChanged);
 	}
 
 	@FXML
@@ -111,16 +112,29 @@ public class MountOptionsController implements FxController {
 
 	@FXML
 	public void chooseCustomMountPoint() {
-		chooseCustomMountPointOrReset(mountPointDirBtn);
+		try {
+			Path chosenPath = chooseCustomMountPointInternal();
+			vault.getVaultSettings().mountPoint().set(chosenPath);
+		} catch (NoDirSelectedException e) {
+			//no-op
+		}
 	}
 
-	private void chooseCustomMountPointOrReset(Toggle previousMountToggle) {
+	/**
+	 * Prepares and opens a directory chooser dialog.
+	 * This method blocks until the dialog is closed.
+	 *
+	 * @return the absolute path to the chosen directory
+	 * @throws NoDirSelectedException if dialog is closed without choosing a directory
+	 */
+	private Path chooseCustomMountPointInternal() throws NoDirSelectedException {
 		DirectoryChooser directoryChooser = new DirectoryChooser();
 		directoryChooser.setTitle(resourceBundle.getString("vaultOptions.mount.mountPoint.directoryPickerTitle"));
 		try {
-			var initialDir = Path.of(vault.getVaultSettings().getCustomMountPath().orElse(System.getProperty("user.home")));
+			var mp = vault.getVaultSettings().mountPoint().get();
+			var initialDir = mp != null && !isDriveLetter(mp) ? mp : Path.of(System.getProperty("user.home"));
 
-			if (Files.exists(initialDir)) {
+			if (Files.isDirectory(initialDir)) {
 				directoryChooser.setInitialDirectory(initialDir.toFile());
 			}
 		} catch (InvalidPathException e) {
@@ -128,49 +142,74 @@ public class MountOptionsController implements FxController {
 		}
 		File file = directoryChooser.showDialog(window);
 		if (file != null) {
-			vault.getVaultSettings().customMountPath().set(file.getAbsolutePath());
+			return file.toPath();
 		} else {
-			mountPointToggleGroup.selectToggle(previousMountToggle);
+			throw new NoDirSelectedException();
+		}
+	}
+
+	private void selectedToggleChanged(ObservableValue<? extends Toggle> observable, Toggle oldToggle, Toggle newToggle) {
+		Path mountPointToBe = null;
+		try {
+			//Remark: the mountpoint corresponding to the newToggle must be null, otherwise it would not be new!
+			if (mountPointDriveLetterBtn.equals(newToggle)) {
+				mountPointToBe = driveLetterSelection.getItems().get(0);
+			} else if (mountPointDirBtn.equals(newToggle)) {
+				mountPointToBe = chooseCustomMountPointInternal();
+			}
+			vault.getVaultSettings().mountPoint().set(mountPointToBe);
+		} catch (NoDirSelectedException e) {
+			if (!mountPointDirBtn.equals(oldToggle)) {
+				mountPointToggleGroup.selectToggle(oldToggle);
+
+			}
 		}
 	}
 
-	private void toggleMountPoint(@SuppressWarnings("unused") ObservableValue<? extends Toggle> observable, Toggle oldValue, Toggle newValue) {
-		if (mountPointDirBtn.equals(newValue) && Strings.isNullOrEmpty(vault.getVaultSettings().customMountPath().get())) {
-			chooseCustomMountPointOrReset(oldValue);
+	private boolean isDriveLetter(Path mountPoint) {
+		if (mountPoint != null) {
+			var s = mountPoint.toString();
+			return s.length() == 3 && mountPoint.toString().endsWith(":\\");
 		}
+		return false;
 	}
 
-	/**
-	 * Converts 'C' to "C:" to translate between model and GUI.
-	 */
-	private static class WinDriveLetterLabelConverter extends StringConverter<String> {
+	private static class WinDriveLetterLabelConverter extends StringConverter<Path> {
 
-		private final Set<String> occupiedDriveLetters;
+		private final Set<Path> occupiedDriveLetters;
 		private final ResourceBundle resourceBundle;
 
 		WinDriveLetterLabelConverter(WindowsDriveLetters windowsDriveLetters, ResourceBundle resourceBundle) {
-			this.occupiedDriveLetters = windowsDriveLetters.getOccupiedDriveLetters();
+			this.occupiedDriveLetters = windowsDriveLetters.getOccupied();
 			this.resourceBundle = resourceBundle;
 		}
 
 		@Override
-		public String toString(String driveLetter) {
-			if (Strings.isNullOrEmpty(driveLetter)) {
+		public String toString(Path driveLetter) {
+			if (driveLetter == null) {
 				return "";
 			} else if (occupiedDriveLetters.contains(driveLetter)) {
-				return driveLetter + ": (" + resourceBundle.getString("vaultOptions.mount.winDriveLetterOccupied") + ")";
+				return driveLetter.toString().substring(0, 2) + " (" + resourceBundle.getString("vaultOptions.mount.winDriveLetterOccupied") + ")";
 			} else {
-				return driveLetter + ":";
+				return driveLetter.toString().substring(0, 2);
 			}
 		}
 
 		@Override
-		public String fromString(String string) {
-			throw new UnsupportedOperationException();
+		public Path fromString(String string) {
+			if (string.isEmpty()) {
+				return null;
+			} else {
+				return Path.of(string + "\\");
+			}
 		}
 
 	}
 
+	//@formatter:off
+	private static class NoDirSelectedException extends Exception {}
+	//@formatter:on
+
 	// Getter & Setter
 
 	public ObservableValue<Boolean> mountFlagsSupportedProperty() {
@@ -189,14 +228,6 @@ public class MountOptionsController implements FxController {
 		return mountpointDirSupported.getValue();
 	}
 
-	public ObservableValue<Boolean> mountpointParentSupportedProperty() {
-		return mountpointParentSupported;
-	}
-
-	public boolean isMountpointParentSupported() {
-		return mountpointParentSupported.getValue();
-	}
-
 	public ObservableValue<Boolean> mountpointDriveLetterSupportedProperty() {
 		return mountpointDriveLetterSupported;
 	}
@@ -213,9 +244,20 @@ public class MountOptionsController implements FxController {
 		return readOnlySupported.getValue();
 	}
 
+	public ObservableValue<Path> driveLetterProperty() {
+		return driveLetter;
+	}
+
+	public Path getDriveLetter() {
+		return driveLetter.getValue();
+	}
+
+	public ObservableValue<String> directoryPathProperty() {
+		return directoryPath;
+	}
 
-	public String getCustomMountPath() {
-		return vault.getVaultSettings().customMountPath().get();
+	public String getDirectoryPath() {
+		return directoryPath.getValue();
 	}
 
 }

src/main/resources/fxml/vault_options_mount.fxml

@@ -44,18 +44,18 @@
 
 		<HBox spacing="6" visible="${controller.mountpointDriveLetterSupported}" managed="${controller.mountpointDriveLetterSupported}">
 			<RadioButton toggleGroup="${mountPointToggleGroup}" fx:id="mountPointDriveLetterBtn" text="%vaultOptions.mount.mountPoint.driveLetter"/>
-			<ChoiceBox fx:id="driveLetterSelection" disable="${!mountPointWinDriveLetter.selected}"/>
+			<ChoiceBox fx:id="driveLetterSelection" disable="${!mountPointDriveLetterBtn.selected}" value="${controller.driveLetter}"/>
 		</HBox>
 
-		<HBox fx:id="customMountPointRadioBtn" spacing="6" alignment="CENTER_LEFT" visible="${controller.mountpointDirSupported}" managed="${controller.mountpointDirSupported}">
+		<HBox spacing="6" alignment="CENTER_LEFT" visible="${controller.mountpointDirSupported}" managed="${controller.mountpointDirSupported}">
 			<RadioButton toggleGroup="${mountPointToggleGroup}" fx:id="mountPointDirBtn" text="%vaultOptions.mount.mountPoint.custom"/>
-			<Button text="%vaultOptions.mount.mountPoint.directoryPickerButton" onAction="#chooseCustomMountPoint" contentDisplay="LEFT" disable="${!mountPointCustomDir.selected}">
+			<Button text="%vaultOptions.mount.mountPoint.directoryPickerButton" onAction="#chooseCustomMountPoint" contentDisplay="LEFT" disable="${!mountPointDirBtn.selected}">
 				<graphic>
 					<FontAwesome5IconView glyph="FOLDER_OPEN" glyphSize="15"/>
 				</graphic>
 			</Button>
 		</HBox>
-		<TextField text="${controller.customMountPath}" visible="${mountPointDirBtn.selected}" maxWidth="Infinity" disable="true" managed="${customMountPointRadioBtn.managed}">
+		<TextField fx:id="directoryPathField" text="${controller.directoryPath}" visible="${mountPointDirBtn.selected}" managed="${mountPointDirBtn.managed}" maxWidth="Infinity" editable="false" >
 			<VBox.margin>
 				<Insets left="24"/>
 			</VBox.margin>

src/main/resources/i18n/strings.properties

@@ -382,9 +382,9 @@ vaultOptions.mount.winDriveLetterOccupied=occupied
 vaultOptions.mount.mountPoint=Mount Point
 vaultOptions.mount.mountPoint.auto=Automatically pick a suitable location
 vaultOptions.mount.mountPoint.driveLetter=Use assigned drive letter
-vaultOptions.mount.mountPoint.custom=Custom path
+vaultOptions.mount.mountPoint.custom=Use chosen directory
 vaultOptions.mount.mountPoint.directoryPickerButton=Choose…
-vaultOptions.mount.mountPoint.directoryPickerTitle=Pick an empty directory
+vaultOptions.mount.mountPoint.directoryPickerTitle=Pick a directory
 ## Master Key
 vaultOptions.masterkey=Password
 vaultOptions.masterkey.changePasswordBtn=Change Password

src/test/java/org/cryptomator/common/settings/VaultSettingsJsonAdapterTest.java

@@ -34,8 +34,6 @@ public class VaultSettingsJsonAdapterTest {
 				() -> assertEquals("foo", vaultSettings.getId()),
 				() -> assertEquals(Paths.get("/foo/bar"), vaultSettings.path().get()),
 				() -> assertEquals("test", vaultSettings.displayName().get()),
-				() -> assertEquals("X", vaultSettings.winDriveLetter().get()),
-				() -> assertEquals("/home/test/crypto", vaultSettings.customMountPath().get()),
 				() -> assertEquals("--foo --bar", vaultSettings.mountFlags().get())
 		);
 	}