Fix noticeable freeze after saving a scene

[Hilderin]

Fixes #93104 and maybe #92515

After testing with a project having a lot of Resources I was able to reproduce the problem.

MRP:
test-godot-resource-icon.zip

The problem came from the modifications in _get_entry_script_icon for the management of the resource icons, more specifically the calls to ResourceLoader::get_resource_type and EditorFileSystem::get_singleton()->find_file:

I reused the cache that was there but instead of resetting the cache at each _update_tree, I created a clear_icon_cache method and called it only when an icon script or a resource changes. I probably missed some places where the icons could change!?!

It's really not perfect but I guess the performance should be the same as before #77932.

My tests with 3000 resources:
Before: 4-4.5 seconds
After: 1.5-2 seconds

The time remaining on a save occurs in the Tree, I'm really not sure I should touch that:

[Calinou]

Tested locally, it works as expected.

However, I can't reproduce #93104 on an optimized editor build (optimize=speed lto=full). Saving is quite fast both before and after this PR, although it's slightly faster with this PR. This is also the case with a debug build (saving takes ~800 ms in master, ~700 ms with this PR).

In both cases, the FileSystem dock gets scrolled up when saving the scene. I'd prefer if the existing scroll bar position was kept instead, but that should be looked into in its own PR.

PC specifications

• CPU: Intel Core i9-13900K
• GPU: NVIDIA GeForce RTX 4090
• RAM: 64 GB (2×32 GB DDR5-5800 C30)
• SSD: Solidigm P44 Pro 2 TB
• OS: Linux (Fedora 39)

[Hilderin]

Thanks for testing this PR.
I tested on my system and effectively with an optimized build with optimize=speed lto=full the master version is pretty fast even if my PC is less performant then yours, it's around 1-2sec after the save and before the editor unfreeze. With the PR, it's less then a second.

For the scrollbar, I don't have the same issue about the scroll bar position.

My PC specifications:
CPU: Intel Core i5-11600KF 3.9Ghz
GPU: NVIDIA GeForce RTX 3060
OS: Windows 11

Master version:

Taskmgr_68ui63bvr9.mp4

This PR version:

Taskmgr_hsjTUfLPqD.mp4

[Hilderin]

One difference I found with my latest modifications are icons for the script that have a @icon. Before these scripts did not have an icon, now they do because of the line icon_path = file_info->script_class_icon_path; in EditorFileSystem::_update_file_icon_path.

Before:

After:

Should I removed this line?

[KoBeWi]

Technically it's consistent with the inspector showing icon in Script field, but personally I find it annoying. I think scripts should show script icon (for their language), not their @icon, which should be reserved for instances of these scripts.

[Hilderin]

I tend to agree with you. I'll revert it to what it was before.

[Hilderin]

Done!

[akien-mga]

Thanks!