Spinners contain a small edit field with two half-height buttons attached, as shown in Figure 21-16. Spinners blur the difference between bounded and unbounded controls.

• 微调控制项是常见的键盘或鼠标数字输入控件，如图21-16所示。 它包含一个小的编辑字段，附有两个半高的按钮，使得有界控件和无界控件之间的差别非常模糊。