feature request: signed strides

[claudeha]

Frame buffer slice strides are non-negative as per:
https://github.com/openexr/openexr/blob/d778a0b47b18fe1ede3824fe013cea9dd7404360/OpenEXR/IlmImf/ImfFrameBuffer.h#L98-L99

Negative strides could be useful for flipping images at I/O time.

Would it be possible to change size_t to ssize_t at the next ABI-break-point?

[cary-ilm]

The TSC discussed this. It's a useful feature, implemented in other places like OIIO.

If you would entertaining making the change, we'd happily review it and consider incorporating it.

The change will require careful testing, so besides just changing the type, the test suite should include tests that validate the behavior.

[fnordware]

The type should probably be ptrdiff_t, right?

[cary-ilm]

We're planning a 3.0 release for later in August. If anyone from the community would like to submit a PR that address this (with sufficient testing), now would be a good time to consider including it.