add compute dimiensions for textbox
add compute dimiensions for textbox

marclaporte/WeasyPrint,Kozea/WeasyPrint,prepare/TestWeasyPrint,Kozea/WeasyPrint,prepare/TestWeasyPrint,andrewleech/WeasyPrint,andrewleech/WeasyPrint,jasco/WeasyPrint,marclaporte/WeasyPrint,jasco/WeasyPrint