[BUG] Loading thumbnails during startup causes a significant delay #80
Description
I've been testing v0.10.2 and the biggest thing that pops out at me is the initial loading time. After some testing, I've found it comes down to the amount of thumbnails displayed as it's loading in. My guess is that it's taking far too long to render each batch of thumbnails separately as it's loading. I see each page flash with different batches of filenames, then their thumbnails many times until all files are loaded. I think the fix could be as simple as delaying the display of any thumbnails at all until everything is fully loaded in.
This is on an Arch Linux variant using appimage v0.10.2. I bumped Parallel Workers up to 32, before that it was 16, before that it was 8. None seem to make much difference, really.
The testing I did was from when IH is first visible on screen -> green notification that everything has loaded with a stopwatch. So it's not perfectly scientific, but as you'll see, it's a huge difference in numbers so you don't need to know down to the millisecond.
Some results of testing:
I have my thumbnails set by default to display 50 at a time. Without doing anything other than waiting for it to finish loading (the green notification):
With thumbnails set to 50:
02m06s
With thumbnails set to 10:
00m58s
If, as soon as IH is visible on screen, I click on refresh on a single directory (I used my latest 2025 directory) immediately after it's first visible on screen:
With thumbnails set to 50:
01m14s
01m05s (second run)
With thumbnails set to 10:
00m52s
00m49s (second run)
If, as soon as IH is visible on screen, I deselect all directories as fast as I can:
00m28s
So it definitely loads much faster when it doesn't have to render all those multiple batches of thumbnails the whole time. I suggest delaying loading the display of thumbnails until after they've all loaded in from the cache first.
Maybe have Loading... centred in the thumbnail area or something, then only load them in once the full cache has been read? Something to alert the user it's working behind the scenes, even if nothing is showing up immediately.