Setting things up for using parallel STL C++17

[Jean-Marc Lasgouttes]

Le 31/08/2022 à 17:46, Pavel Sanda a écrit :
> Seems like too little music for a new tab. But I wouldn't be against
> preference checkbox for loading all images when document loads (by
> default false).

If the loading is done in background, I am not sure that it would hurt. 
I also think that we have too many repaints due to loading these images 
(but this is a different problem).

JMarc