Create a function hello that will be registered as an action.

When the action is called, build a dad dialog called "heldi", with a vertical box that contains two labels "Hello" and "world!" and standard dialog box close buttons. When the cancel button is clicked, the dialog box will return -1; clicking the ok button will return 0. The vbox is closed by a "end" call to dad(). When the dialog is ran in modal mode, it will be open and block other pcb-rnd windows until the user closes it.

Tip #1: change "begin_vbox" to "begin_hbox" to get a horizontal layout.

Tip #2: boxes can be nested (but each box must have a corresponding "end").

In the "main" section of the script, register the action using fgw_func_reg().

More details on DAD: DAD developer's doc