Kid 0 - XuiDropButton
"Selection" callback when XuiPullDown item selected
v0 : item - 0 is topmost item
XuiDropButton grids display a text string on the XuiDropButton grid, and a list of items in an XuiPullDown that toggles up and down when the XuiDropButton is selected. XuiDropButton grids generate Selection callback messages when the user selects any item from the XuiPullDown grid.
The XuiDropButton grid manages the XuiPullDown window, so the text on the XuiDropButton is its TextString property and the XuiPullDown list is the its TextArray property.
