Extremely slow performance on merging down text layers in a large image
GIMP version: 2.10.6
Operating System: WINDOWS 10 64
Package: Installer from gimp.org
Description of the bug
To make it simpler I attached my script file ( scheme). Just copy it to scripts folder, refresh and run it. The file generates size a 25x6 fHD image, comprised of many layers. Before drawing it merges down the layers to background.
In GIMP 2.8.22 the script takes about 30 seconds to complete and draw image. In GIMP 2.10.x hangs on merging down the generated layers, mainly merging down text layers. NOTE: it's not really a "hang", it just takes extremely long time to merge each individual text layer down to background.
Reproduction
Is the bug reproducible? ALWAYS
Reproduction steps: Copy script file to \GIMP\2.10\scripts Just run my file and compare execution speeds in 2.8.22 and 2.10.x.
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Expected result: In GIMP 2.8.22 the script takes about 30 seconds to complete and draw image. 0 Disk usage, RAM fluctuates between 100 MB and 5 GB, settling finally on ca 3.5 GB when image is created. CPU usage typically at 24-30%.
Actual result: In GIMP 2.10.x the script never finishes ( takes extremely long times on merging layers, which I tested manually). Disk usage (SSD) is extremely high (500MB/s) no matter how much ram I allow gimp to use (32gb total on machine, settings limited to 24). CPU usage at this time is only at about 4%. I tried different settings with undo levels, from 0 to N, but this didn't seem to have effect on performance.
Additional information
If you need additional information or details, let me know.