Should clear errors after successful load with STB backend?

[a-hurst]

This is pretty minor, but I think it's worth reporting regardless: with the new STB PNG/JPG back end, reading in a JPEG image results in IMG_GetError() being populated with "Not a PNG" despite the image loading successfully (even with IMG_LoadJPEG_RW).

Not sure if it's a quirk with how stb_image identifies file formats or not, but a one-line fix would presumably be to just always call IMG_ClearError right before an image is successfully returned to avoid any confusion (e.g. encountering a different problem later that doesn't set an error, and getting a head-scratching "Not a PNG" when checking GetError for information). Would that approach work, or are there legitimate cases where you'd want an error set while still returning a valid image surface?

Thanks in advance!

[slouken]

I'm fine with adding that, but in general SDL functions may set errors even if they eventually return successfully. The application shouldn't check the error message to determine if a function succeeds or fails, only to find more detail if a function returns failure.

[a-hurst]

That makes sense (and is usually how I write things), the only time I check for error text before return value is in various PySDL2 unit tests just to make sure I get any error message before asserting a return value (how I caught this), and it's easy enough to ignore non-fatal errors in that context when I hit them.

I'm mostly reporting this because this specific error text is misleading and confusing; I spent a while trying to figure out whether I'd accidentally saved my JPEG with a .png extension before looking at the source and realizing it was an internal STB message.