task object have

• handle id : required, number
• task type : optional, default(background), foreground
  • foreground task have window properties
  • background task
• code to run : required, function

window construction & destruction

To construct a window, user need to set the items as below

• title : optional, default(not specified),
• size : optional, default(auto-sized by contents)
• position : optional, default(center of webpage)
• contents : must, not yet specified,
• status bar : optional, default(not display)
• base button : optional, default(close), minimize, maximize

To destruct a window, user click the close button at title-bar

• current opened window's title item must be shown at taskbar
• at taskbar, user can close, minimize, maximize a specific window.