Decrease warning levels

[tanaya-mankad]

Change WARN to INFO for issues that are handled internally and likely to be expected by the user.

[nealkruis]

This looks fine, but I would really like to clean up the warning level so that it is not a global variable. Can we fit that in here?

We should also confirm what happens for cubic interpolations when there are 2 or 3 grid axis values.

[tanaya-mankad]

This looks fine, but I would really like to clean up the warning level so that it is not a global variable. Can we fit that in here?

We should also confirm what happens for cubic interpolations when there are 2 or 3 grid axis values.

Do you mean the
extern int LOG_LEVEL? I was perplexed by that one but assumed it must exist for ease of use.

[nealkruis]

Yeah, that's the one. I think we can come up with a better design.

[tanaya-mankad]

As suspected, the cubic interpolation on axes that contain 2 or 3 values just fixes the underspecified point at the same value as the existing endpoint on the relevant side. In other words, if an interpolation happens between index 0 and index 1, the relative coordinates of all the points involved for cubic spline fitting are [-1, 0, 1, 2]. If either points (-1) or (2) are missing, they are fixed to be the same as points (0) or (1) respectively, here. It's currently already tested as well, though I haven't re-hand-calculated this to confirm it's right.

[tanaya-mankad]

As for LOG_LEVEL, its entire existence feels superfluous to me - it adds unnecessary complexity to what should be handled straight up by an error callback.
By the same token though, the error callback is also global, and can be overwritten by any piece of code in the same project that has access to the Btwxt namespace...
[edit] @nealkruis What do you think about having a callback object per btwxt instance? The global callback led to some design workarounds in E+ that I wasn't too fond of...

[nealkruis]

@tanaya-bigladder do we want to work on this, or just follow up with the callback change?

[tanaya-mankad]

@nealkruis yes, let's punt. I discovered yesterday that it's a can of worms that will be best with some serious refactoring. I know what we should do but we ought to discuss first.