返回屏幕的安全区域（以像素为单位）（只读）。
On some displays, certain areas of the screen might not be visible to the user.
This might be because the display's shape is non-rectangular or in the case of TV displays, it can be caused by overscan.
Avoid placing user interface elements in areas outside the safe area rectangle.
The maximum size of the safe area is the screen resolution in pixels and is defined as Rect(0, 0, Screen.width, Screen.height).