Tonemapping example image loader not working

[DGriffin91]

Bevy version 32a5c7d

Previously, in the tonemapping example an exr or hdr image file could be dragged and dropped onto the window to view the image with the selected tonemapping settings. This no longer works.

The issue was introduced at 35073cf with #9885

thread 'Compute Task Pool (21)' panicked at 'called `Result::unwrap()` on an `Err` value: InvalidSourceSyntax', crates\bevy_asset\src\path.rs:115:70

[cart]

General answer is "its complicated".
The AssetSource / AssetReader / AssetWriter abstraction is intentionally scoped to specific folders to allow us to make assumptions about them (ex: this folder is processed, this source might not come from a filesystem, etc). AssetPaths are also intended to be platform (and source-type) agnostic. But absolute paths like C:\some\path are a windows-specific convention.

Of course, we should support loading assets in these cases, but I think how we do that needs to change. I think it should probably be a combination of two things:

1. Enable mounting new asset sources at runtime (instead of needing to anticipate at startup)
2. Create an abstraction that can convert from absolute (sometimes OS-specific) file paths to equivalent platform-agnostic AssetPaths. In the case of a windows-specific path like the one above, this would involve mounting a new C asset source and converting windows-specific paths to platform-agnostic AssetPaths. (ex: C:\some\asset.png would become C://some/asset.png.

Some discussion here on discord:
https://discord.com/channels/691052431525675048/1164297864441249823

[cart]

Note that we are planning on being more principled (and platform-agnostic) about AssetPaths in the future. Ex: you should use / instead of \, windows-style "drives" would not be allowed (ex: C:\), etc.

[DGriffin91]

I think this makes sense as long as there's a reasonable way for an end user to specify a file path in a typical OS native fashion. There should be a reasonably straightforward way to make a bevy app that allows the end user to use C:\, or \ instead of /

It sounds like the abstraction in 2. is designed for this purpose. Just clarifying where the more principled paths are required.

(Some example applications would be: digital content creation, scientific visualization, anything with a OS file dialog)

[cart]

Yup fully agreed that this is necessary. One "quick fix" for these apps that doesn't require Bevy changes: change the root asset folder to the root of the current drive (ex: / on linux/macos C:\ on windows). Then you can just pass in the full absolute paths (unchanged on macos/linux and with the C: stripped out on windows).

[DGriffin91]

What about for files on other drive letters? I personally only have windows, users, etc... on C:\ and keep everything else on other drives.