iPhoneX 安全区域 safe-area-inset-*

• 屏幕上安全距离: safe-area-inset-top
• 屏幕右安全距离: safe-area-inset-right
• 屏幕下安全距离: safe-area-inset-bottom
• 屏幕左安全距离: safe-area-inset-left

iOS 11

padding-top: constant(safe-area-inset-top);
padding-right: constant(safe-area-inset-right);
padding-bottom: constant(safe-area-inset-bottom);
padding-left: constant(safe-area-inset-left);

iOS 11.2+

padding-top: env(safe-area-inset-top);
padding-right: env(safe-area-inset-right);
padding-bottom: env(safe-area-inset-bottom);
padding-left: env(safe-area-inset-left);

兼容性写法：

padding-top: constant(safe-area-inset-top);
padding-top: env(safe-area-inset-top);