🐛 [Bug]: 画布中的组件或者元素的选中框，显示层级不正确

[gene9831]

Environment

Windows MsEdge 120

Version

v18.18

Version

latest

Link to minimal reproduction

https://github.com/opentiny/tiny-engine/

Step to reproduce

宽度或者高度超出画布的宽度或者高度时，选中一个组件或者元素，会显示出选中框。滚动页面，让被选中元素逐渐与画布边界相交，选中框的显示层级比画布背景高

What is expected

选中框的显示层级比画布背景低

What is actually happening

No response

Any additional comments (optional)

No response

[Issues-translate-bot]

Bot detected the issue body's language is not English, translate it automatically.

---

Title: 🐛 [Bug]: The display level of the checkbox of a component or element in the canvas is incorrect

[gene9831]

选中框使用的 fixed 定位，fixed 定位默认是相对于屏幕视口（viewport），所以选中框显示层级一直在画布之上，即使给画布容器加上 overflow: hidden 也无效
https://developer.mozilla.org/zh-CN/docs/Web/CSS/position#fixed

[Issues-translate-bot]

Bot detected the issue body's language is not English, translate it automatically.

---

The selected box uses fixed positioning. The fixed positioning is relative to the screen viewport by default, so the display level of the selected box is always above the canvas. Even adding overflow: hidden to the canvas container has no effect.
https://developer.mozilla.org/zh-CN/docs/Web/CSS/position#fixed