Fix Image pixel access error propagation for compressed formats

[mirsella]

follow up to #22414

in my comment #22414 (comment) i realized the warn added in #22414 would never actually trigger because pixel_bytes and pixel_bytes_mut were returning Option instead of Result, which caused the UnsupportedTextureFormat error to be lost and converted to OutOfBounds.

this changes:

• pixel_data_offset now returns Result instead of Option
• pixel_bytes and pixel_bytes_mut now return Result instead of Option
• errors are properly propagated so the warn in sprite picking actually triggers for compressed textures
• added a regression test compressed_texture_format_is_reported_correctly
• updated examples/2d/cpu_draw.rs for the new signature

should i remove the regression test if it's useless ?

thanks

[mirsella]

i can also add TextureAccessError::UnInitializated/NotLoaded (#22414 (comment)) if its a good pattern

[github-actions]

It looks like your PR is a breaking change, but you didn't provide a migration guide.

Please review the instructions for writing migration guides, then expand or revise the content in the migration guides directory to reflect your changes.

[alice-i-cecile]

Generally like this, and I think the regression test is fine. A few comments:

1. Needs a simple migration guide.
2. Can we flatten out the Result<Option return types? Is returning Ok(None) actually useful here, or should that just be a new kind of error? If we'd like to keep them, we should be very clear in the docs what Ok(None) means.

[mirsella]

i think ive documented all functions with:

Returns Ok(None) if the image data is not initialized.

adding a new kind of error is what im proposing here

i can also add TextureAccessError::UnInitializated/NotLoaded (#22414 (comment)) if its a good pattern

so it can replace the Ok(None) if that's appropriate, i find this better too. what error variant name do you prefer ?

[alice-i-cecile]

I prefer Unitialized: I think that NotLoaded implies that loading was started but not finished, which may or may not be true.

[mirsella]

should be good now :)