Expose host viewport info for iframe apps to support stickyToolbarOffset

[FelixWe]

Expose host viewport info for iframe apps to support stickyToolbarOffset

Problem

I am building a custom app in LOCATION_ENTRY_FIELD and using RichTextEditor from @contentful/field-editor-rich-text.

I want to keep the toolbar visible when the field iframe is partially scrolled out of view in the Entry Editor.
stickyToolbarOffset looks like the right API for this, but from inside the app iframe I cannot reliably know:

• how far the iframe is above the host viewport
• the host sticky header offset
• the current visible position of the iframe in the Entry Editor

Because of that, I cannot calculate the correct stickyToolbarOffset.

I also tried using IntersectionObserver to calculate the offset, but that did not work reliably because the app runs inside an iframe.

Expected

Some SDK API to expose host viewport geometry to iframe apps, for example:

sdk.window.getHostViewportInfo()
sdk.window.onHostViewportChanged(cb)

or even higher level:

sdk.window.getRecommendedStickyOffset()
sdk.window.onRecommendedStickyOffsetChanged(cb)

Current Workaround

The only reliable workaround I found is setting a fixed iframe height and letting the editor scroll inside the iframe, but the user experience is not as good as the native implementation.