[material-ui][Dialog] Keyboard scrolling doesn't work in fullscreen mode

[jmealy]

Steps to reproduce

Link to live example: https://stackblitz.com/edit/react-mn6y3k-zhswqk?file=Demo.tsx

This applies to Dialog components with scroll='body'

Steps:

1. Open the dialog with fullScreen=true
2. Try to scroll using the keyboard.

Current behavior

You cannot scroll using the keyboard until you manually focus on the Dialog contents using a click or a tab.

Expected behavior

I would expect to be able to scroll using the keyboard straight away, as it is when fullScreen=false

Context

Trying to create an accessible full screen Dialog component

Your environment

npx @mui/envinfo

  System:
    OS: macOS 14.1
  Binaries:
    Node: 22.4.1 - /opt/homebrew/bin/node
    npm: 10.8.1 - /opt/homebrew/bin/npm
    pnpm: Not Found
  Browsers:
    Chrome: 126.0.6478.182
    Edge: Not Found
    Safari: 17.1
  npmPackages:
    @emotion/react: ^11.11.0 => 11.11.1
    @emotion/styled: ^11.11.0 => 11.11.0
    @mui/base:  5.0.0-beta.28
    @mui/core-downloads-tracker:  5.15.1
    @mui/icons-material: ^5.14.20 => 5.15.1
    @mui/material: ^5.14.20 => 5.15.1
    @mui/private-theming:  5.15.1
    @mui/styled-engine:  5.15.1
    @mui/system:  5.15.1
    @mui/types:  7.2.11
    @mui/utils:  5.15.1
    @mui/x-date-pickers: ^5.0.20 => 5.0.20
    @types/react: ^18.2.75 => 18.2.75
    react: ^18.2.0 => 18.2.0
    react-dom: ^18.2.0 => 18.2.0
    typescript: ^5.4.5 => 5.4.5

Search keywords: fullscreen dialog keyboard scroll

[ZeeshanTamboli]

It's a bug. It should work since it is programmatically focused using focus() method.