Hello,
A small tool from me opens certain text files and displays the content in some sort of "preview", by chance a user selected a file that is "large" ~ 10 MB. (of course my test files are small enough :-) )
But this takes very long (~ 4 secs on that pc), first I thought it is reading the file but I stripped it down to the edit control update.
I extracted the issue to a sample au3 attached and a sample large file. The log lines are from the dummy1.au3.
(11:19:40.352) - -->Line0017): openfile
(11:19:40.461) - -->Line0021): closefile
(11:19:40.461)