1. A method comprising: receiving data that defines a first layout specifying a fixed graphical placement for rendering of graphical content portions contained within the data; identifying graphical placement relationships between the graphical content portions in the first layout, and defining a sort order for the graphical content portions in the first layout based on the graphical placement relationships; generating an ordered tree structure for the graphical content portions based on the sort order, the ordered tree structure comprising a plurality of nodes, each node identifying one of the graphical content portions, the plurality of nodes arranged in the ordered tree structure such that an in-order traversal of each node of the ordered tree structure maintains a presentation order of the graphical content portions in the first layout, the ordered tree structure allowing graphical placement of the graphical content portions in a second layout in accordance with the presentation order based on the in-order traversal of each node of the ordered tree structure, the second layout different than the first layout; and providing the ordered tree structure to allow rendering of the graphical content portions in accordance with the second layout.