ADDING VISUAL DESCRIPTION NODES TO A VISUAL DESCRIPTION TREE DURING LAYOUT

摘要

A layout engine generates a visual layout tree for a visual description tree of a document whose content is to be rendered in one or more display areas. A visual description tree describes the content of a document along with formatting and logical arrangement the content. Visual description nodes of a visual description tree represent the organization of the constituent elements a document hierarchically. A visual layout tree defines the layout of a document within one or more display areas. Visual layout nodes of a visual layout tree represent the layout of the content of a document hierarchically. The layout engine receives as input a visual description tree and generates the corresponding visual layout tree. A rendering engine then inputs the visual layout tree and generates a graphics buffer containing the pixels representing the layout of the document as defined by the visual layout tree.

主权项

1. A method performed by a computing device for generating visual layout nodes for a visual layout tree for use in rendering content of a document, the document being represented by a visual description tree having visual description nodes, the method comprising processing a visual description node of the visual description tree by:
determining a type of the visual description node; and under control of a layout object for processing visual description nodes of the determined type of visual description node,
generating a visual layout node of the visual layout tree for rendering content represented by the visual description node;adding an additional visual description node to the visual description tree, the additional visual description node having additional content to be rendered along with the content of the document; andprocessing the additional visual description node by generating a visual layout node of the visual layout tree for rendering content of the additional content.