Dynamically provide portal container element for modal components

[jonahschueller]

General

There have been many bug reports and discussions that shadcn/ui does not always handle nesting complex modal components correctly, e.g. opening a Popover inside of a Sheet might close the Sheet upon interaction with the Popover as it is hoisted to the document.body. I will not file yet another bug description, but propose a potential solution to this issue.

This behaviour occurs because shadcn/ui falls back to the default behaviour of radix-ui, which is to make use of document.body as the default portal container.

In the project I am currently working on the user can toggle the main page in to browser fullscreen.
When doing that, components like Dropdown are no longer visible to the user because they are appended to the document.body, but only the main page is visible.

I implemented a custom workaround, which I think could serve as some food for thought for an official solution:

Solution description

To fix this issue, I had to ensure that the portal container which is used by the mentioned components dynamically adjusts to the component it is wrapped in. For example, when a Popover is used at the root level it should use document.body, but if it is used inside of a Sheet it should refer to a <div> which is inside of the Sheet in order to prevent events outside of the sheet container.

This led me to: React Context API

I added a custom PortalContainerContext which holds the HTMLElement which should be used as the portal container by radix-ui.
Additionally, I adjusted the shadcn/ui components to fetch the portal container from the current context. When using e.g. a Sheet I wrap my sheet content into a PortalContainerProvider which will set the portal container of all components inside of the sheet, preventing the closing behaviour described previously.

This way I can dynamically adjust which element is used as the anchor point for various components.
Since I didn't wanted to make the PortalContainerContext a mandatory context in my app, it makes use of a default value of document.body. Therefore, it will behave as usual in all situations where no PortalContainerContext is given, but hook into a custom container, once provided.

Why should this be in shadcn/ui

Although, this solution can be implemented fairly easily, it still requires adjustment of every modal type shadcn component.
Additionally, one could argue that e.g. a Sheet should automatically provide this anchor by default to hide this functionality from the user.

Alternative solutions

I think the minimum viable solution could also include to expose the container property of the radix-ui Portals to the user of the component. This way, no adjustment of the components itself are needed.

Uncertainties / TBD

Although I have tested this solution in my specific use case (e.g. in Sheets or browser fullscreen) I am not sure if a) it fixes all of these types of issues I haven't encountered in my use case & b) is always the expected behaviour. For example for modal type like <Alert /> or <Dialog />.
A more advanced solutions (e.g. with multiple anchor points for different components) might be required to meet all requirements of all components.

Nevertheless, I think something like this would make a nice addition to shadcn/ui :)