LuaMotif and Callbacks

[Marc Balmer <marc@...>]

It is very easy to define a callback when creating a widget hierarchy in
LuaMotif:

myform = Form {
	RowColum {
		Label {
			labelString = 'Hello, World!'
		},
		PushButton {
			labelString = 'pushme',
			activateCallback = function ()
				print('A button has been pushed')
			end
		}
	}
}

But what when you want to pass parameters to that function?  I resorted
to some kind of convention (to avoid the word 'hack'):

data = {42, 'Mr. Wong', 'foo', function () print('hello') end }

myform = Form {
	RowColum {
		Label {
			labelString = 'Hello, World!'
		},
		PushButton {
			labelString = 'pushme',
			activateCallback = Callback {
				function (data)
					print('hi there ' .. data[2])
				end,
				data
			}
		}
	}
}

"Callback" is a pseudo widget that by convention takes a function in [1]
and data to be passed to the function in [2].