Interface window child elements do not size & position properly

[amylizzle]

There's a bug somewhere in the pos/size handling for working out UI element positioning.

This is messed up:

window "wingetwindow"
	elem "wingetwindow"
		type = MAIN
		size = 200x180
		title = "winget test"
		is-visible = true
	elem "wingetinput"
		type = INPUT
		pos = 5,0
		size = 190,19
		text = "this is some test text"
	elem "wingetbuttonarg"
		type = BUTTON
		pos = 0,40
		size = 0,20
		text = "as arg"
		command = "wingettextverb \"arg: [[wingetwindow.background-color as arg]]\""
	elem "wingetbuttonesc"
		type = BUTTON
		pos = 0,60
		size = 0,20
		text = "as escaped"
		command = "wingettextverb \"escaped: [[wingetwindow.background-color as escaped]]\""
	elem "wingetbuttonstr"
		type = BUTTON
		pos = 0,80
		size = 0,20
		text = "as string"
		command = "wingettextverb \"string: [[wingetwindow.background-color as string]]\""		
	elem "wingetbuttonpar"
		type = BUTTON
		pos = 0,100
		size = 0,20
		text = "as params"
		command = "wingettextverb \"params: [[wingetwindow.background-color as params]]\""	
	elem "wingetbuttonjson"
		type = BUTTON
		pos = 0,120
		size = 0,20
		text = "as json"
		command = "wingettextverb \"json: [[wingetwindow.background-color as json]]\""
	elem "wingetbuttonjsondm"
		type = BUTTON
		pos = 0,140
		size = 0,20
		text = "as json-dm"
		command = "wingettextverb \"json-dm: [[wingetwindow.background-color as json-dm]]\""		
	elem "wingetbuttonraw"
		type = BUTTON
		pos = 0,160
		size = 0,20
		text = "as raw"
		command = "wingettextverb \"raw: [[wingetwindow.background-color as raw]]\""