经典的例子便是GUI，程序必须响应用户的某些行为，比如按键或是鼠标移动。
The classic example is a GUI where your program must respond when the user does something like press a key or move the mouse.
与当前获得焦点的窗口关联的xev程序将跟踪所有按键或鼠标移动。
A xev program attached to the currently focused window will track any key presses or mouse movements.
从上面执行的xev测试可以看到，单个按键或释放事件将导致xev程序打印四行或五行输出。
As you may recall from the xev testing performed above, an individual key press or key-release event causes four or five lines to be printed by the xev program.
应用推荐