幫助係統

這些類為應用程序提供在綫幫助，采用 3 細節級彆：

1. Tool Tips and Status Bar message - flyweight help, extremely brief, entirely integrated in the user interface, requiring little or no user interaction to invoke.
2. What's This? - 輕量，但可以是三段式解釋。
3. Online Help - can encompass any amount of information, but is typically slower to call up, somewhat separated from the user's work, and often users feel that using online help is a digression from their real task.