[Dropdown Menu] Support for onOpenAutoFocus

[sekeidesign]

Feature request

Overview

We recently replaced our own Popover component to be built on top of react-dropdown-menu instead of react-popover since the two are almost identical, but the DropdownMenu also supports Submenus which is definitely something we want.

The migration was essentially free since both of these components share the vast majority of functionality and props, with the exception of onOpenAutoFocus.

We use onOpenAutoFocus to prevent the Popover from grabbing focus in our Combobox which then uses the Input trigger's onBlur event to close the Popover.

Example:

CleanShot.2024-09-18.at.14.33.53.mp4

import * as RadixPopover from '@radix-ui/react-popover'
...
<RadixPopover.Content 
    onOpenAutoFocus={event => {
        if (preventAutoFocus) {
            event.preventDefault()
        }
    }}
...
>

Compared with dropdown-menu

CleanShot.2024-09-18.at.14.36.57.mp4

import * as RadixPopover from '@radix-ui/react-dropdown-menu'
...
<RadixPopover.Content 
    // onOpenAutoFocus not supported!
...
>

Everything else is exactly the same and fully supported without any changes anywhere in our codebase.

Examples in other libraries

Radix already supports this in other "popover" style components:
https://www.radix-ui.com/primitives/docs/components/popover#content

Who does this impact? Who is this for?

It's a helpful event for managing focus that right now prevents us from using this component for our combobox.

[ilkiri23]

We were faced with a similar problem. It'd be very useful to have an onOpenAutoFocus prop

[sekeidesign]

We were faced with a similar problem. It'd be very useful to have an onOpenAutoFocus prop

I tried forking and taking a stab at it, but it started causing some intensely buggy behaviour. I suspect the reason the prop isn't there is because managing the focus is critical to how the dropdown menu functions :(

I'll close this and open a new PR for adding a Sub item to the Popover, which might be a better solution

[sekeidesign]

Changed to this, since I think it may be a better solution
#3140