It's not the display of the menu which (you see as) is slow...but the operation you're doing there.
Filtering on "Favorite" or "Clone" or anything else actually rebuild the entire list.
The 19.000 roms of your mame set is scanned again.
It then verify (for each rom!!!) that
- you own this rom
- that this rom belongs to the favorite list or not
- that this is a clone or not
- that there's a filter on 'mature', 'pinball', 'bios', etc...to be applied or not
- that there's a filter on the genre to be applied or not
- that there's a filter on the numbers of players to be applied or not
...19.000 times, to finally display the result in a new list!
The same procedure is accomplished when mGalaxy launch...so you perhaps don't "see" it, but it take the same time at the mGalaxy opening!
Opening the filter menu isn't slower than filtering roms at launch time.
This procedure has been optimized since the early beginning of the mGalaxy development
On my i7 this is nearly instantaneous, on my Pentium IV arcade cabinet it takes about 2 secs.
I don't know why it it take so much time!? How much actually??
I've seen some performance breakdown with...slow hard drives, which doesn't deliver the rom list quickly enough to mGalaxy.