QtWebEngineProcess 100% CPU

QtWebEngineProcess is jumping to ~100% of CPU when I run RStudio Preview of a dataframe (960 rows, 20 columns)..

I am running:
MacOS 10.15
RStudio 1.2.5001
R 3.6.0 GUI 1.7 El Capitan Build

Googling says that DropBox uses QtWebEngineProcess, so I paused DropBox sync (my .Rproj is in a DropBox local directory).

This all started suddenly, after I did an RStudio re-install yesterday.
I ran in terminal:
rm -rf ~/library/Caches/RStudio
rm -rf ~/Library/Application Support/RStudio

A closed topic discussed a similar problem, but the fixes therein are not resolving my problem.


Can you provide a reproducible example?

I just ran into a similar problem with a .Rmd file.
It was working fine till I added a lot of symbols to a plot.
I can get the resulting R file to work if I knittr::purl the file first.
But as soon as I open the .Rmd file in the RStudio editor, QtWebEngineProcess kicks in
and bogs everything down.
Maybe it's working on rendering (in background) the graphics from the last run,
I can't get at the gear icon next to the Preview menu on the toolbar to turn off some of the inline preview options.
(At least I couldn't do so in the time I allowed QtWebEngineProcess to thrash).
Is there any other way to set the preview options on an Rmd file other than via the gear icon?

This seems like a pretty important bug if that's really what's happening,

Ok .. So I waited... and was able to turn off in-line previews. Now things seem to work fine.

Again, a reproducible example would help us isolate and fix the underlying issue.

I am blocked from generating a reprex, because every time I try, my RStudio grinds to a halt.
But, in my case (MacOS 10.15.1, RStudio 1.2.5001, R 3.6.0 GUI 1.7)
-preview works for dataframes (20 columns, 1000 rows)
-preview works for nested dataframes, but
if I generate an unnested dataframe, preview grinds RStudio to a halt.

Activity monitor flips between:

I can examine the unnested dataframe summary in 'List' view in the 'Global Environment'.

I may be doing something foolish with nest/unnest, still learning the updates on those functions in Tidyverse.

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