Post editing sidebar does not always act sticky

[tomdxw]

Situation 1 (works fine)

1. Go to the new post page (/wp-admin/post-new.php).
2. Paste enough lorem ipsum into the visual editor that the page is able to scroll.
3. Scroll down.

Expected and actual behaviour:

#side-sortables gets position: fixed and sticks to the viewport as you scroll down the page

Situation 2 (does not work)

1. Add metaboxes to the post type (enough so that the page will scroll - ACF is an easy way to do this, or you could just install a bunch of plugins, or manually create the metaboxes).
2. Go to the new post page.
3. Scroll down.

(Make sure your viewport is taller than the editor).

Expected behaviour:

Just like the other situation, #side-sortables should get position: fixed and stick to the viewport as you scroll down the page.

Actual behaviour:

Nothing happens to #side-sortables and the sidebar does not follow the viewport as the user scrolls.

---

This happens because in wp-admin/js/editor-expand.js it compares the height of the editor against the height of the viewport.

// Sidebar pinning
if ( $postboxContainer.width() < 300 && heights.windowWidth > 600 && // sidebar position is changed with @media from CSS, make sure it is on the side
    $document.height() > ( $sideSortables.height() + postBodyTop + 120 ) && // the sidebar is not the tallest element
    heights.windowHeight < editorHeight ) { // the editor is taller than the viewport

It should compare the height of the whole page instead. i.e.:

heights.windowHeight < $('#poststuff').outerHeight() ) { // the page content is taller than the viewport

Attached a diff (make sure to do define('SCRIPT_DEBUG', true);when using this diff as I didn't recompile the JS).

[swissspidy]

Thanks for the patch!

Attached a diff (make sure to do define('SCRIPT_DEBUG', true);when using this diff as I didn't recompile the JS).

That's not needed for patches anyway, as the JavaScript gets minified during the build process.

[aprea]

FWIW this patch is a very welcome change and appears to fix the problem described in situation 2.

I ended up needed this for a production site and had to deregister editor-expand in favour of this patched version.

[desrosj]

I am going to close this out as a wontfix. The new block editor has redesigned the edit screen and the Classic Editor is being preserved as is, with the exception of major bugs.