[QGIS-Developer] Remaining "blocking" operations

[Nyall Dawson]

Hi all,

With a recent PR merge by Matthias, another one of the remaining
interface blocking operations is gone and moved to task manager. This
means that task manager is now being used for:
- saving vector/raster layers
- importing data to browser destinations via drag and drop
- saving maps as rasters/pdf from canvas (not composer)
- calculating feature counts for layer tree

There's also been some recent changes in composer which prevents the
interface blocking while refreshing map item, and a funded change by
the Swiss user group which dramatically decreases project load times
while compositions are present

With these changes QGIS master is feeling extremely responsive. So now
I'm wondering what other "blocking" operations remain in master.

A quick list off the top of my head:
- updating the snapping index
- exporting compositions/atlases
- running processing algs (work underway to fix this)
- calculating categorized/graduated renderer classes for large layers

What have I missed? What other tasks currently "lock up" the QGIS
interface while performing?

Nyall