Find ways to optimize XMB horizontal list scrolling [$10]

[inactive123]

See this issue for more details -

#4517

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[RobLoach]

@Tatsuya79 did some work on this over at #4517 . I created a PR with the option to enable/disable it: #5172

[nayslayer]

I've spent the previous evening examining the playlist loader and rewrote it into a faster version that you can see in this gist. It is mostly the same, but instead of allocating a buffer per string it leaves all strings inside the file buffer and carries it around with the playlist. This allows to forego about 6 mallocs for entry and to load the playlist 3x faster. Basically the file is read into memory, scanned once and mapped into playlist entries. I don't have time to integrate it properly, though, so I'll have let the issue rest for a week or two.

[CenTdemeern1]

What about only processing the parts of the playlist file that are currently on screen?
As in, the playlist config file is stored in memory, and is scanned quickly for element count and position.
Then, when the position in the playlist is scrolled on screen, actually process the required part of the config file and load related data.
That would also greatly decrease memory usage, not having all UI elements loaded at once.

I'd like everyone to keep in mind that I don't really know if something like this already exists, or how everything is implemented. I'm just saying what's on my mind.
Please don't judge me for this if this is the new worst idea known to mankind.