GENERATING VISUAL LAYOUT NODES TO FILL A DISPLAY AREA BASED ON AN ANCHOR POINT

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 a visual layout tree that is virtualized for use in rendering content of a document, the document being represented by a visual description tree having visual description nodes, the virtualized visual layout tree having visual layout nodes, the method comprising:
receiving an anchor point within the document, the anchor point identifying an anchor visual description node within the visual description tree; receiving a target location within a display area in which content associated with the anchor point is to be positioned; generating visual layout nodes for visual description nodes along a path from the root of the visual description tree to the anchor visual description node; generating a visual layout node for the anchor visual description node, the visual layout node specifying layout of content of the anchor visual description node for the anchor point to be positioned at the target location within the display area; and after generating the visual layout node for the anchor visual description node, when a visual description node that is a descendant of a visual description node along the path from the root of the visual description tree to the anchor visual description node has no content that would appear within the display area, not generating a visual layout node for that descendant visual description node.