Headless compilation on Windows is now possible again.

Using workaround:
javafxports/openjdk-jfx#66 (comment)

pom.xml

@@ -583,9 +583,6 @@
             </activation>
             <properties>
                 <current.os>win</current.os>
-                <!-- Deactivating headless build by removing the headless 
-                    JVM options. This is a workaround for bug https://github.com/javafxports/openjdk-jfx/issues/66 -->
-                <jvm.options></jvm.options>
             </properties>
         </profile>
         <profile>

src/test/java/de/itemis/jmo/dodo/ui/AddDownloadSourceDialogUiTest.java

@@ -21,6 +21,10 @@ public class AddDownloadSourceDialogUiTest {
 
     private AddDownloadSourceDialogUiTestDriver dialog;
 
+    static {
+        OpenJfxMonocleWindowsBugWorkaround.runIfOnWindows();
+    }
+
     @BeforeEach
     public void setUp() {
         dialog = new JavaFxAddDownloadSourceDialogUiTestDriver();

src/test/java/de/itemis/jmo/dodo/ui/DodoUiTest.java

@@ -22,7 +22,12 @@ public class DodoUiTest {
      * Managed in a static way, because it is not possible to "restart" a JavaFX app during one test
      * run.
      */
-    private static final DodoUiTestDriver DODO = new JavaFxDodoTestDriver();
+    private static final DodoUiTestDriver DODO;
+
+    static {
+        OpenJfxMonocleWindowsBugWorkaround.runIfOnWindows();
+        DODO = new JavaFxDodoTestDriver();
+    }
 
     @BeforeAll
     public static void setUpStatic() {

src/test/java/de/itemis/jmo/dodo/ui/OpenJfxMonocleWindowsBugWorkaround.java

@@ -0,0 +1,61 @@
+package de.itemis.jmo.dodo.ui;
+
+import static com.google.common.base.Strings.nullToEmpty;
+
+import com.google.common.base.StandardSystemProperty;
+
+import de.itemis.jmo.dodo.util.InstantiationNotAllowedException;
+
+/**
+ * <p>
+ * The currently used version of OpenJFX (11.0.2) has a bug when run in headless mode with Monocle
+ * on Windows machines. A fix will not be available before release 13.x. However, there exists a
+ * workaround.
+ * </p>
+ * <p>
+ * Run {@link #runIfOnWindows()} before any JavaFX code is run or initialized, e. g.:
+ *
+ * <pre>
+ * package a.b.c
+ *
+ * public class SomeMain {
+ *     static {
+ *         OpenJfxMonocleWindowsBugWorkaround.runIfOnWindows();
+ *     }
+ *
+ *     public static void main(String[] args) {
+ *         // Run FX App
+ *     }
+ * }
+ * </pre>
+ *
+ * @see <a href="https://github.com/javafxports/openjdk-jfx">OpenJFX</a>
+ * @see <a href="https://wiki.openjdk.java.net/display/OpenJFX/Monocle">Monocle</a>
+ * @see <a href=
+ *      "https://github.com/javafxports/openjdk-jfx/issues/66#issuecomment-468370664">Workaround</a>
+ */
+final class OpenJfxMonocleWindowsBugWorkaround {
+
+    private static boolean alreadyLoaded = false;
+
+    private OpenJfxMonocleWindowsBugWorkaround() {
+        throw new InstantiationNotAllowedException();
+    }
+
+    /**
+     * Check if we are running on a Windows OS and perform workaround if so.
+     *
+     * @see <a href=
+     *      "https://github.com/javafxports/openjdk-jfx/issues/66#issuecomment-468370664">Workaround</a>
+     */
+    public static void runIfOnWindows() {
+        if (!alreadyLoaded && osIsWindows()) {
+            alreadyLoaded = true;
+            System.load("C:\\Windows\\System32\\WindowsCodecs.dll");
+        }
+    }
+
+    private static boolean osIsWindows() {
+        return nullToEmpty(System.getProperty(StandardSystemProperty.OS_NAME.key())).toLowerCase().contains("windows");
+    }
+}