P: Magnetic Lasso can not be used on Layer Mask?

I don't. Like I said, someone would have to look at the code. (The magnetic lasso tool's been around for a long time, so who knows which engineer implemented it. Thomas Knoll? Mark Hamburg?)

Great! This would be a great addition to otherwise excellent selection tool.

As far as 'the tool looking for the color information', I was trying to find an information how exactly this tool works, but I could not find anything in depth.

I always thought it reads the pixel values from individual channels within the tool radius and then calculates the difference between the highest and lowest value at tool's mid point to establish the selection border?

Do you know how it works Jeffrey? Thanks.

My guess: The intention is that the tool needs color information to calculate the magnetic effect. Agree, from the user point of view and the cryptic message, that it's unintuitive. An engineer would need to look at the code to tell exactly what's going on under the hood. We'll look into it.

Thanks Jeffrey. What do you think would be the intention here if it in fact was intended. From the user point of view (is there any other ? ;), this seems unintuitive?

Hmm. Looks like it's expecting non-alpha data to compute what it needs to compute. Chris would know more. I would say it's intended, even though it's unexpected from the user view. It might be that the warning is just a poor choice of words.