iframe anchor position is not stable

[yheuhtozr]

Describe the bug

When you use the iframe-* layout and set an URL with an anchor (e.g. https://sli.dev/guide/syntax.html#notes), the page often won't show at the desired position when you load the slide (I often see it at the top or bottom of the webpage). Refreshing the viewport often solves the problem but sometimes not. I am not quite sure what causes this behavior. Possibly triggered by previous navigation inputs.

Incidentally, I also ran into #492 and find it an unintuitive behavior, thus a bug.

Minimal reproduction

(To be added when I'm back at a testing env.)

You can use https://sli.dev/new to create a new project to reproduce the issue.

Environment

• Slidev version: 0.50.0-beta.3
• Browser: Edge or Firefox
• OS: Windows 11 (Ubuntu 20.04 on WSL 2)