Occurs when the user adds fonts to or removes fonts from the system 当用户在系统中添加或移除字体时发生。
2.
To add font attributes to a css style rule defined in an external style sheet 将字体属性添加到在外部样式表中定义的css样式规则中
3.
The only other mechanism provided to applications for changing the running configuration is to add fonts and directories to the list of application - provided font files 除此之外，更动字型设定的唯一方法就是把字型和目录加入应用程序提供的字型文件清单中。
