Adjustment Layer Brush and Mask Question

[Steve22]

Hi

If I have an adjustment layer and I select a brush and start painting on the main image a mask will appear next to the adjustment layer showing (masking) the areas I am painting.

This seems to happen no matter what colour brush I use unless it is white, then nothing seems to happen.  This caught me out for sometime thinking the program was not working.

If I start painting on the adjustment layer with a pure white brush, why does the mask not appear as a black mask being painted over with white?

Regards
Steve

[firstdefence]

An empty mask is black, but a mask that is white is full so painting white onto it will do nothing, painting black will effectively erase the mask and reveal what is underneath the adjustment layer.

 

[Steve22]

Thanks for the explanation, however that is not really what I was asking.

If I add an adjustment layer to an image and then start painting on the image with a coloured brush Affinity Photo will create a white (full) mask on the adjustment layer and start filling it in.

If I add an adjustment layer to an image and then start painting on the image with pure white coloured brush nothing happens, that is no mask is created. 

I'm asking why no mask is created when using pure white, Is this a bug?  Affinity Photo should still create a mask of some sort?  You would have thought that since you start painting with pure white that Affinity Photo would create an black (empty) mask.

Regards

Steve