Currently (AUI 9.7), the smallest spinner is “small”, but even this size is larger than a regular AUI Icon.
If you want to display a spinner and change that to an icon when the work is done, the latter will be smaller. We are talking about a few pixels here, but if you have to align the spinner/icon with some text, then either the text will jump or its distance will be disproportional next to the spinner.
Solution: if we had an “xsmall” spinner that is sized exactly like an AUI Icon, then we could use them interchangedly.
I’ll ask AUI team about an option of adding one more (even smaller) spinner. For now we cannot promise anything in that matter.
I checked the official Spinners - AUI Documentation, and I guess the designers deliberately made the spinner this size to fit the basic button height (as in the example provided).
In old AUI version, spinner was just an icon, not its own standalone component. It allowed us to use spinner everywhere in “perfect size” where an icon (16x16 I think) would fit.
I don’t want to change the current sizes, just add another option.
I totally understand your concern, but I cannot promise to deliver this feature. I’m passing the decision to the AUI team.
You might, though, consider an option of overriding the spinner’s size to your particular needs, yourself