Delay when returning to ES with large list of ROMs

[joolswills]

@tomaz82

I noticed a delay when returning to Emulation Station after launching a mame title (with a full set). I have bisected it to cd2f2ee

cd2f2ee42b911711db6bd6e0276bea494a389e88 is the first bad commit
commit cd2f2ee42b911711db6bd6e0276bea494a389e88
Author: Tomas Jakobsson <tompsson@hotmail.com>
Date:   Mon Oct 23 01:04:17 2017 +0200

    Use local game art ( image, marquee and video ) from romfolder/images if the gamelist didn't specify a path

:040000 040000 d26ee8a850036a49a79dd7dd56129fbcae47a6c3 7429a03f15f3de13139ed25546f517e2d5fbcb6b M	es-app

I assume this is because it is scanning for thumbnails/marquees for each entry as it's not noticeable with short lists. I was also using a remote filesystem, which may make the problem worse.

Ideally we would only scan once, and save this information in memory - if that's feasible (unless I have misunderstood the problem).

[joolswills]

I would like to revert this on the stable branch for now, until we have a solution on master. But happy to hear feedback on this.

[pjft]

No concerns with that.

[joolswills]

I have temporarily reverted this on the stable branch and bumped the version. I bumped master to 2.8.0rp-dev also so it's more clear when people are using the in development version.

[maksun]

Hello, I use 2.8.0rp-dev and I notice ES is taking around 30 seconds to start or restart. During this time (those ~30s) it stays at 100% CPU. If I replace my USB key (containing many ROMs) with an empty one, it starts normally. Could you please confirm we are talking about the same problem? Thanks.