Let the first sector of a pie chart unfold counterclockwise

When I create a pie chart, and I set attribute direction = "counterclockwise", I would like that the first sector can be configured to unfold counterclockwise as well.

Although I could “manually” compute the angular width of the sector and subtract it from the desired value in the rotation argument, that would still fix the first edge (in clockwise order) when I turn on/off categories in the legend, and thus the last edge would not be aligned with the desired rotation. The desired behavior would be that the last edge is fixed so that the rotation argument fixes the rotation of the first sector shown, no matter which one it is.

In this example, the first sector “a” unfolds clockwise, while the categories are plot counterclockwise from the reference direction (12 o’clock):

As a workaround, I can subtract the width of first category from the desired value for rotation; this is ok as long as all traces are active, but not when they are clicked on/off on legend:

[nicolaskruchten]

This makes sense and we’d certainly accept a pull request that added a new attribute to pie traces to control the placement of the first slice to make it work more similarly to something like Excel 😃

This attribute could be called e.g. firstslicedirection with accepted values forward and reverse (defaulting to reverse to preserve the current behaviour for existing users).

[nicolaskruchten]

I think that it’s more flexible/orthogonal to support forward/reverse with respect to the existing direction attribute, so if direction is clockwise then the reverse firstslicedirection means “counterclockwise” and vice-versa.