I have discovered a problem with JFXPanel which I think relays on resizePixelBuffer method: on my Mac Pro with retina display JFXPanel takes a long time to start up (every time it's shown). I made little change in my component that inherits from JFXPanel and replaced the code in resizePixelBuffer that creates BufferedImage with the following:

GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice device = env.getDefaultScreenDevice();
GraphicsConfiguration config = device.getDefaultConfiguration();
pixelsIm = config.createCompatibleImage(pWidth * newScaleFactor,
                    pHeight * newScaleFactor, Transparency.TRANSLUCENT);

Actually, I have used reflection and written over addNotify because resizePixelBuffer is private, so my code is as follows:

private Object getDeclFieldValue(String fldName) {
        try {

            Field fld = JFXPanel.class.getDeclaredField(fldName);
            fld.setAccessible(true);
            return fld.get(this);
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }

    private void setDeclFieldValue(String fldName, Object val) {
        try {

            Field fld = JFXPanel.class.getDeclaredField(fldName);
            fld.setAccessible(true);
            fld.set(this, val);
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    private void callDeclMethod(String metName) {
        try {
            Method m = JFXPanel.class.getDeclaredMethod(metName);
            m.invoke(this);
        } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
        }
    }
    
    private BufferedImage createBuffImage(int pW, int pH) {
        GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice device = env.getDefaultScreenDevice();
        GraphicsConfiguration config = device.getDefaultConfiguration();
        return config.createCompatibleImage(pW,
                pH, Transparency.TRANSLUCENT);
    }

    private void resizePixelBufferX(int newScaleFactor) {
        int pWidth = (Integer) getDeclFieldValue("pWidth");
        int pHeight = (Integer) getDeclFieldValue("pHeight");
        if ((pWidth <= 0) || (pHeight <= 0)) {
            setDeclFieldValue("pixelsIm", null);
// pixelsIm = null;
        } else {
            BufferedImage oldIm = (BufferedImage) getDeclFieldValue("pixelsIm");
            BufferedImage newIm = createBuffImage(pWidth * newScaleFactor,
                    pHeight * newScaleFactor);
            setDeclFieldValue("pixelsIm", newIm);
            if (oldIm != null) {
                double ratio = newScaleFactor / (Integer) getDeclFieldValue("scaleFactor");
                // Transform old size to the new coordinate space.
                int oldW = (int) Math.round(oldIm.getWidth() * ratio);
                int oldH = (int) Math.round(oldIm.getHeight() * ratio);

                Graphics g = newIm.getGraphics();
                try {
                    g.drawImage(oldIm, 0, 0, oldW, oldH, null);
                } finally {
                    g.dispose();
                }
            }
        }
    }

    @Override
    public void addNotify() {
        Integer sf = (Integer) getDeclFieldValue("scaleFactor");
        BufferedImage oldIm = (BufferedImage) getDeclFieldValue("pixelsIm");
        setDeclFieldValue("pixelsIm", null);
        final EmbeddedWindow stage = (EmbeddedWindow) getDeclFieldValue("stage");
        setDeclFieldValue("stage", null);
        super.addNotify();
        setDeclFieldValue("stage", stage);
        setDeclFieldValue("pixelsIm", oldIm);
        resizePixelBufferX(sf);
        Runnable r = new Runnable() {
            @Override
            public void run() {
                if ((stage != null) && !stage.isShowing()) {
                    stage.show();
                    callDeclMethod("sendMoveEventToFX");
                }
            }
        };
        if (Platform.isFxApplicationThread()) {
            r.run();
        } else {
            Platform.runLater(r);
        }
    }

After this I have no problem with this issue. I have tested even on my Windows machine and it does not seem to be a problem there either.