Bug 75988 [Preferences] IPreferencePage#performOk() returning false should prevent the dialog from closing
I think that if this method returns false, it should prevent the dialog from closing. Today, in order to perform validation I have to register key listeners to all fields an use #setValid(false) to disable the "OK" button.
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
}
		setSelectedNodePreference(storeValue);
	}
	/**
	 * Sets the name of the selected item preference. Public equivalent to
	 * <code>setSelectedNodePreference</code>.
	 * 
	 * @param pageId
	 *            The identifier for the page
	 * @since 3.0
	 */
	public void setSelectedNode(String pageId) {
		setSelectedNodePreference(pageId);
	}
	/**
	 * Sets the name of the selected item preference.
	 * 
	 * @param pageId
	 *            The identifier for the page
	 */
	protected void setSelectedNodePreference(String pageId) {
		lastPreferenceId = pageId;
	}
	/**
	 * Changes the shell size to the given size, ensuring that it is no larger
	 * than the display bounds.
	 * 
	 * @param width
	 *            the shell width
	 * @param height