I am in the process of styling my app, and as an experiment, I took some styling from the javafx caspian.css stylesheet and added some of it to my stylesheet to get a starting point. Unfortunately I get this NPE:

Glass detected outstanding Java exception at Java_com_sun_glass_ui_mac_MacWindow__1setVisible:src/com/sun/mat/ui/GlassWindow.m:1225
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.ChoiceBoxSkin$3.changed(ChoiceBoxSkin.java:147)
at com.sun.javafx.scene.control.skin.ChoiceBoxSkin$3.changed(ChoiceBoxSkin.java:144)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:367)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:100)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:91)
at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:6225)
at javafx.scene.Node.setFocused(Node.java:6276)
at javafx.scene.Scene$KeyHandler.setWindowFocused(Scene.java:3478)
at javafx.scene.Scene$KeyHandler$1.invalidated(Scene.java:3497)
at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:155)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:100)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:197)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:167)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:163)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:128)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:161)
at javafx.stage.Window.setFocused(Window.java:360)
at com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:65)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:50)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1009)
at com.sun.glass.ui.Window.notifyFocus(Window.java:988)
at com.sun.glass.ui.mac.MacWindow._setVisible(Native Method)
at com.sun.glass.ui.Window.setVisible(Window.java:422)
at com.sun.javafx.tk.quantum.WindowStage.setVisible(WindowStage.java:411)
at javafx.stage.Window$10.invalidated(Window.java:745)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:127)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:161)
at javafx.stage.Window.setShowing(Window.java:782)
at javafx.stage.Window.hide(Window.java:807)
at com.sun.javafx.stage.WindowCloseRequestHandler.dispatchBubblingEvent(WindowCloseRequestHandler.java:45)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
at javafx.event.Event.fireEvent(Event.java:171)
at com.sun.javafx.stage.WindowPeerListener.closing(WindowPeerListener.java:82)
at com.sun.javafx.tk.quantum.GlassStage.requestClosingAllWindows(GlassStage.java:203)
at com.sun.javafx.tk.quantum.QuantumToolkit$11.handleQuitAction(QuantumToolkit.java:347)
at com.sun.glass.ui.mac.MacApplication$3.action(MacApplication.java:98)
Aug 16, 2012 11:59:13 AM com.wefend.pc.WefendPc stop



The styling I added:

/*******************************************************************************
 * *
 * ChoiceBox *
 * *
 ******************************************************************************/

.choice-box {
    -fx-skin: "com.sun.javafx.scene.control.skin.ChoiceBoxSkin";
    -fx-background-color: -fx-shadow-highlight-color, -fx-outer-border, -fx-inner-border, -fx-body-color;
    -fx-background-insets: 0 0 -1 0, 0, 1, 2;
    -fx-background-radius: 5, 5, 4, 3;
    -fx-padding: 0.0em 0.5em 0.0em 0.0em; /* 0 6 0 0 */
    -fx-alignment: CENTER;
    -fx-content-display: LEFT;
}

.choice-box:focused {
    -fx-color: -fx-focused-base;
    -fx-background-color: -fx-focus-color, -fx-outer-border, -fx-inner-border, -fx-body-color;
    -fx-background-insets: -1.4, 0, 1, 2;
    -fx-background-radius: 6.4, 5, 4, 3;
}

.choice-box:hover {
    -fx-color: -fx-hover-base;
}

.choice-box:showing {
    -fx-color: -fx-pressed-base;
}

.choice-box .label {
    -fx-padding: 0.166667em 0.333333em 0.25em 0.5em; /* 2 4 3 6 */
    -fx-text-fill: -fx-text-base-color;
}

.choice-box .open-button {
    -fx-background-color: null;
    -fx-padding: 0.083333em 0.0em 0.0em 0.666667em; /* 1 0 0 8 */
}

.choice-box .arrow {
    -fx-background-color: -fx-mark-highlight-color, -fx-mark-color;
    -fx-background-insets: 1 0 -1 0, 0;
    /* padding determines the size of the arrow;
       this should match the design size in the SVG */
    -fx-padding: 0.166667em 0.333333em 0.166667em 0.333333em; /* 2 3.5 2 3.5 */
    -fx-shape: "M 0 0 h 7 l -3.5 4 z";
}

.choice-box .context-menu {
    -fx-background-radius: 6, 5, 4;
}

.choice-box .menu-item {
    -fx-accelerator-gutter: 0;
}

/* TODO: need to use the ID here. For some reason, the other form does not
 * work. This might be related to popup issues.
 */
/*.choice-box > * > .menu-item-radio {*/
#choice-box-menu-item > * > .menu-item-radio {
    /* When we show RadioMenuItems in ChoiceBox, we replace the radio shape with
       a check mark, which looks much better */
    -fx-shape: "M0,5H2L4,8L8,0H10L5,10H3Z";
    -fx-scale-shape: false;
}

.choice-box:disabled {
    -fx-opacity: -fx-disabled-opacity;
}