Useful framework. SpinButton can’t setWidth, no matter the width you set, buttons are placed below the textfield. And how to increase the color of the text or set to Bold?
Widgets rely on css instead. It make sense to split theme for code.
For width you can work on : div.v-spinbutton input
To add a custom css use setStyleName, so here html is : div.v-spinbutton.yourclass
Check the sampler and javadoc for full details.