Oh, it have to be set to `TRUE`!! I did it and the issue was solved. Now if I'm zooming in/out using scroll all the characters is perfectly sharp at any scale as it was before Scintilla update. Thank you @nyamatongwe for providing the solution, explanation and for your time! geany community is the best! 😁
For those facing a problem in the future: in file scintilla/gtk/PlatGTK.cxx SetFractionalPositions I removed macros guard and change boolean calling argument. Just run the following commands below before building geany (e.g. for geany-git in arch I did it in prepare function in PKGBUILD).
``` awk '/void SetFractionalPositions/,/}/ {if ($0 !~ /#/) gsub("FALSE", "TRUE"); print; next; } 1' scintilla/gtk/PlatGTK.cxx > temp_file mv temp_file scintilla/gtk/PlatGTK.cxx ```