Display widget interaction in embedded systems using child graphics contexts

摘要

A method and apparatus implementing a separate child context for each applet (or similar element) of a browser. A described embodiment of the present invention provides one or more child contexts that correspond to elements in the HTML for a web page displayed by a browser. For example, each applet executed by the browser has a corresponding and separate child context Each child context has an associated memory buffer. The browser also has a parent context, which each child context points to. When a graphic is displayed via a widget, the widget draws the graphic (such as a panel or a non-pressed button) in the child context of the applet and sets a "damage" flag in the child context. When the browser performs its main browser loop, it checks the status of the damaged flag for each element (including each applet). If the browser finds a damage flag that is set, this means that something was written into the child buffer and that the parent buffer needs updating. In this case, the browser "pulls" the information from the child buffer into the parent buffer, which is then used to update the display screen. Other components, called reactive components, present special problems and are treated specially. Reactive components are drawn directly into both the child and parent contexts and buffers without waiting for the main browser loop.