* Provides a convenient wrapper for TextFields that adds a clickable trigger button (looks like a combobox by default).
* The trigger has no default action, so you must assign a function to implement the trigger click handler by
* overriding {@link #onTriggerClick}. You can create a TriggerField directly, as it renders exactly like a combobox
* for which you can provide a custom implementation. For example:
* <pre><code>
* Provides a convenient wrapper for TextFields that adds a clickable trigger button (looks like a combobox by default).
* The trigger has no default action, so you must assign a function to implement the trigger click handler by
* overriding {@link #onTriggerClick}. You can create a TriggerField directly, as it renders exactly like a combobox
* for which you can provide a custom implementation. For example:
* <pre><code>