默认的例子最大化后再最小化，控件都没了。 #282

Describe the bug A clear and concise description of what the bug is. 我想知道这是类库的bug还是例子程序的bug。屏幕是4K屏幕不知道是否有关。

To Reproduce Steps to reproduce the behavior:

1. [First Step]
2. [Second Step]
3. [Other Steps...]

Expected behavior A clear and concise description of what you expected to happen.

Screenshots If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• LCUI version: [Enter LCUI version here]
• Build tools: [Enter build tools name and version here, E.g: gcc/clang/VisualStudio 201X]
• OS and version: [Enter OS name and version here, E.g: WinXP/Win7/Win10/Ubuntu/Mac OS]

Additional context Add any other context about the problem here.