Hello,

While discussing in #1104 we concluded that the iframe is facing issues with scrolling.
I spend a bit of time with copilot debugging this and found that it was resolved by changing:

// In docview.js - onIFrameLoad function
$docHtml.css('overflow-y', 'hidden');
$docBody.css('overflow-y', 'hidden');

to

// In docview.js - onIFrameLoad function
$docHtml.css('overflow-y', 'visible');
$docBody.css('overflow-y', 'visible');

resolved the issue. (with a bit of extra to make the test work)
If @fschulze can approve me adding this fix, i'll make a PR for it.

A bit of extra feedback from Copilot:

Proposed Fix

Solution 1: Change overflow-y: hidden to overflow-y: visible (Minimal Change)

File: devpi_web/static/docview.js

function onIFrameLoad(event) {
// ...existing code...

// BEFORE (blocks scrolling):
$docHtml.css('height', 'auto');
$docHtml.css('overflow-y', 'hidden');  // ❌
$docBody.css('height', 'auto');
$docBody.css('overflow-y', 'hidden');  // ❌

// AFTER (enables scrolling):
$docHtml.css('height', 'auto');
$docHtml.css('overflow-y', 'visible');  // ✅ or 'auto'
$docBody.css('height', 'auto');
$docBody.css('overflow-y', 'visible');  // ✅ or 'auto'

// ...existing code...

}
Rationale:

overflow-y: visible allows content to overflow naturally, enabling the ResizeObserver to measure the true content height
The parent page's scrollbar can still handle scrolling (the intended behavior)
If auto-resize works correctly, the iframe will be sized properly; if it fails, users can still scroll
Alternative: Use overflow-y: auto instead of visible if you want the iframe to have its own scrollbar as a fallback.

Solution 2: Remove Auto-Resize, Use Flexbox Layout (Better UX)

For a more robust solution, consider simplifying the approach:

File: devpi_web/templates/+doc.pt (or equivalent)

File: devpi_web/static/docview.js

// Simplify or remove the complex auto-resize logic
// Let CSS handle the layout
Benefits:

More reliable (no complex JavaScript height calculations)
Works with CORS restrictions (no need to access iframe.contentWindow.document)
Better browser compatibility
Iframe has its own scrollbar (standard web behavior)