A main class wrapper for deck2pdf that runs the application headless using Monocle from jfxtras.org

HeadlessMain.java

package me.champeau.deck2pdf;

import java.lang.reflect.Field;
import java.util.Objects;
import javafx.application.Application;

/**
 * Adapted from https://gist.github.com/hastebrot/cbca1128dd791966e3a6
 */
public class HeadlessMain {

    //---------------------------------------------------------------------------------------------
    // CONSTANTS.
    //---------------------------------------------------------------------------------------------

    private static final String PROPERTY_JAVAFX_MACOSX_EMBEDDED = "javafx.macosx.embedded";
    private static final String PROPERTY_TESTFX_HEADLESS = "javafx.monocle.headless";

    private static final String PLATFORM_FACTORY_CLASS =
        "com.sun.glass.ui.PlatformFactory";
    private static final String PLATFORM_FACTORY_MONOCLE_IMPL =
        "com.sun.glass.ui.monocle.MonoclePlatformFactory";

    private static final String NATIVE_PLATFORM_FACTORY_CLASS =
        "com.sun.glass.ui.monocle.NativePlatformFactory";
    private static final String NATIVE_PLATFORM_HEADLESS_IMPL =
        "com.sun.glass.ui.monocle.headless.HeadlessPlatform";

    //---------------------------------------------------------------------------------------------
    // METHODS.
    //---------------------------------------------------------------------------------------------

    public static void main(String[] args) {
        new HeadlessMain().launch(Main.class, args);
    }

    public void launch(Class<? extends Application> appClass,
                       String... appArgs) {
        initMacosxEmbedded();
        initMonocleHeadless();
        Application.launch(appClass, appArgs);
    }

    //---------------------------------------------------------------------------------------------
    // PRIVATE METHODS.
    //---------------------------------------------------------------------------------------------

    private void initMacosxEmbedded() {
        if (checkSystemPropertyEquals(PROPERTY_JAVAFX_MACOSX_EMBEDDED, null)) {
            System.setProperty(PROPERTY_JAVAFX_MACOSX_EMBEDDED, "true");
        }
    }

    private void initMonocleHeadless() {
        if (checkSystemPropertyEquals(PROPERTY_TESTFX_HEADLESS, "true")) {
            try {
                assignMonoclePlatform();
                assignHeadlessPlatform();
            }
            catch (Exception exception) {
                throw new RuntimeException(exception);
            }
        }
    }

    private boolean checkSystemPropertyEquals(String propertyName,
                                              String valueOrNull) {
        return Objects.equals(System.getProperty(propertyName, null), valueOrNull);
    }

    private void assignMonoclePlatform()
                                throws Exception {
        Class<?> platformFactoryClass = Class.forName(PLATFORM_FACTORY_CLASS);
        Object platformFactoryImpl = Class.forName(PLATFORM_FACTORY_MONOCLE_IMPL).newInstance();
        assignPrivateStaticField(platformFactoryClass, "instance", platformFactoryImpl);
    }

    private void assignHeadlessPlatform()
                                 throws Exception {
        Class<?> nativePlatformFactoryClass = Class.forName(NATIVE_PLATFORM_FACTORY_CLASS);
        Object nativePlatformImpl = Class.forName(NATIVE_PLATFORM_HEADLESS_IMPL).newInstance();
        assignPrivateStaticField(nativePlatformFactoryClass, "platform", nativePlatformImpl);
    }

    private void assignPrivateStaticField(Class<?> cls,
                                          String name,
                                          Object value)
                                   throws Exception {
        Field field = cls.getDeclaredField(name);
        field.setAccessible(true);
        field.set(cls, value);
        field.setAccessible(false);
    }

}