dirname() is a slow function compared with __DIR__ and using
'/../'. Moodle has a large number of legacy files that are included
each time a page loads and is not able to use an autoloader as it is
functional code. This allows those required includes to perform as
best as possible in this situation.
The central "content" region on My Home / user profile pages also needs to
be initialised in lib/ajax/blocks.php in order to allow blocks to be
dropped into that region successfully. Some tweaks were also necessary in
order to correct the "content" region's structure in order for drag-drop
to function on this region on these pages.
Non-standard block regions (including the central "content" region
used by My Home and user profile pages) were causing the temporary empty
block region used as a drop target to sometimes appear in the wrong place.
The call to init_requirements_data (which includes the block drag-drop JS)
happens at a late enough stage in page generation that we can simply
pass the context ID through to the JS, so that it can be sent as part of
the AJAX request. This prevents lib/ajax/blocks.php from having to try
to guess the context from the other bits of information it receives, so
block drag-drop should now work everywhere without issues.
Other than shifting the initialisation from course/lib.php to
lib/outputrequirementslib.php, some workarounds/tweaks were required
in order to make it work correctly on admin pages and My Home.
