Why is LibreOffice Calc so slow at sorting ?

Hi all,
I’ve been using LibreOffice (now for several years on Linux (now Debian 10), and I often sort some small tables (typically 50 lines, 15columns), an operation that has always been immediate (a fraction of second).

Since some months, it takes some ten seconds if I use “Tri Croissant”(sort ascending) in the “Données” (Data) menu, or the “Trier…” (sort) dialog box from the same menu. Furthermore, If I use the sort option from the column-header menu in autofilter mode, it takes 20 or 30 seconds during which my computer is totally blocked, I cannot even select another window (but the cursor still follows the mouse).

How can it be explained (last update of LibreOffice?) and corrected?

Details on my config (from LibreOffice Help/Apropos):
Build ID: 1:6.1.5-3+deb10u6
Threads CPU : 4; OS : Linux 4.19; UI Render : par défaut; VCL: gtk3;
Locale : fr-CH (fr_FR.UTF-8); Calc: group threaded

Have you ever tried to use a more recent version of LibreOffice (Buster backports repository, or native from libreoffice.org)?

Anyway - try to run **Safe Mode** of LibreOffice (`Help -> Restart in Safe Mode`) and check the effect on performance.

Even in Safe mode, I get the same slow sort. Before that, the only extension I had was a grammatical corrector (Grammalecte), that seem not invloved…

Concerning the version of LibreOffice, I have no root access to my system (it’s a professional one), I’m just looking for configuration options that could be responsible of this strange slow down (with-maybe-defaults that could have been change by the last upgrade).

What about performance on new sheets (of a similar size and layout) using .ods file format. Same issue?

Another test (!!!). Start Libreoffice from a terminal using the following command:

SAL_USE_VCLPLUGIN=gen libreoffice
(Don’t complain about the look&feel, it’s just a test) - Same poor performance?

I have a similar setup and the same problem. In my case, changing the VCL plugin as suggested by @anon73440385 caused a huge improvement in performance. Thanks! Three points may be relevant.

1: My slowdown issue was not in the actual sorting process, but rather in opening the pop-up dialog window for sorting, and changing the options that window offers. After waiting tens of seconds to specify my choices, the activity after selecting OK was fast enough.

2: I am viewing my desktop remotely over VNC (specifically, tigervnc). Could this be relevant to VCL performance? (VCL stands for Visual Class Library, so my conjecture is, “Yes!”)

3: After starting Calc using the suggested command (SAL_USE_VCLPLUGIN=gen libreoffice) my acceptably-performing but somewhat ugly LibreOffice setup is summarized as follows:
Build ID: 1:6.1.5-3+deb10u7;
CPU threads: 8; OS: Linux 4.19; UI render: default; VCL: x11;
Locale: en-US (en_US.UTF-8); Calc: group threaded