detached context menu from button to fix misbehavior

src/main/java/org/cryptomator/ui/mainwindow/VaultListController.java

@@ -22,7 +22,9 @@ import javafx.collections.ListChangeListener;
 import javafx.collections.ObservableList;
 import javafx.event.Event;
 import javafx.fxml.FXML;
+import javafx.geometry.Side;
 import javafx.scene.control.Button;
+import javafx.scene.control.ContextMenu;
 import javafx.scene.control.ListView;
 import javafx.scene.input.ContextMenuEvent;
 import javafx.scene.input.DragEvent;
@@ -67,6 +69,8 @@ public class VaultListController implements FxController {
 	public ListView<Vault> vaultList;
 	public StackPane root;
 	public Button addVaultBtn;
+	@FXML
+	private ContextMenu addVaultContextMenu;
 
 	@Inject
 	VaultListController(@MainWindow Stage mainWindow, //
@@ -146,9 +150,11 @@ public class VaultListController implements FxController {
 
 	@FXML
 	private void showMenu() {
-		double screenX = addVaultBtn.localToScreen(addVaultBtn.getBoundsInLocal()).getMinX();
-		double screenY = addVaultBtn.localToScreen(addVaultBtn.getBoundsInLocal()).getMaxY();
-		addVaultBtn.getContextMenu().show(addVaultBtn, screenX, screenY);
+		if (addVaultContextMenu.isShowing()) {
+			addVaultContextMenu.hide();
+		} else {
+			addVaultContextMenu.show(addVaultBtn, Side.BOTTOM, 0.0, 0.0);
+		}
 	}
 
 	private void deselect(MouseEvent released) {

src/main/resources/fxml/vault_list.fxml

@@ -32,23 +32,23 @@
 			<graphic>
 				<FontAwesome5IconView glyph="CARET_DOWN"/>
 			</graphic>
-			<contextMenu>
-				<ContextMenu>
-					<items>
-						<MenuItem styleClass="add-vault-menu-item" text="%main.vaultlist.addVaultBtn.menuItemNew" onAction="#didClickAddNewVault" >
-							<graphic>
-								<FontAwesome5IconView glyph="PLUS" textAlignment="CENTER" wrappingWidth="14" />
-							</graphic>
-						</MenuItem>
-						<MenuItem styleClass="add-vault-menu-item" text="%main.vaultlist.addVaultBtn.menuItemExisting" onAction="#didClickAddExistingVault" >
-							<graphic>
-								<FontAwesome5IconView glyph="FOLDER_OPEN" textAlignment="CENTER" wrappingWidth="14" />
-							</graphic>
-						</MenuItem>
-					</items>
-				</ContextMenu>
-			</contextMenu>
 		</Button>
+		<fx:define>
+			<ContextMenu fx:id="addVaultContextMenu">
+				<items>
+					<MenuItem styleClass="add-vault-menu-item" text="%main.vaultlist.addVaultBtn.menuItemNew" onAction="#didClickAddNewVault" >
+						<graphic>
+							<FontAwesome5IconView glyph="PLUS" textAlignment="CENTER" wrappingWidth="14" />
+						</graphic>
+					</MenuItem>
+					<MenuItem styleClass="add-vault-menu-item" text="%main.vaultlist.addVaultBtn.menuItemExisting" onAction="#didClickAddExistingVault" >
+						<graphic>
+							<FontAwesome5IconView glyph="FOLDER_OPEN" textAlignment="CENTER" wrappingWidth="14" />
+						</graphic>
+					</MenuItem>
+				</items>
+			</ContextMenu>
+		</fx:define>
 	</VBox>
 	<Region styleClass="drag-n-drop-border" visible="${controller.draggingVaultOver}"/>
 </StackPane>