Menu Contributions/Dropdown Command

You can create dropdown commands using menu contributions, and then use multiple menu contributions to create the dropdown menu.

Command Definition

Any command can be used as a toolbar dropdown ... the command itself is not aware of its dropdown rendering. If it were to need that information, 2 common ways of sharing it are:

Create a parameterized command. The commands inserted in the dropdown menu would specify the parameter, and the dropdown tool item command would not.
Back your handler with a model and rely on that information

This command declaration defines a parameter:

  <extension point="org.eclipse.ui.commands">
     <category id="z.ex.dropdown.category1" name="DropDown Examples">
     </category>
     <command categoryId="z.ex.dropdown.category1" defaultHandler="z.ex.dropdown.internal.DropDownHandler" id="z.ex.dropdown.command1" name="Drop">
        <commandParameter id="z.ex.dropdown.msg" name="Message" optional="true">
        </commandParameter>
     </command>
  </extension>
  <extension point="org.eclipse.ui.commandImages">
     <image commandId="z.ex.dropdown.command1" icon="icons/change_obj.gif">
     </image>
  </extension>

I've thrown in a default image for fun.

Handler

The command example includes a default handler, which is common for simple global commands. The handler needs to check for the parameter and then do its stuff.

public class DropDownHandler extends AbstractHandler {
  private static final String PARM_MSG = "z.ex.dropdown.msg";

  public Object execute(ExecutionEvent event) throws ExecutionException {
    String msg = event.getParameter(PARM_MSG);
    if (msg == null) {
      System.out.println("No message");
    } else {
      System.out.println("msg: " + msg);
    }
    return null;
  }
}