I have 2 separate layers for the original eye background i called eyes-outline and another layer for my new eyes i called white-eyes. It's obvious that they are separate layers as in the left image I have white-eyes invisible and on the right image I have eyes-outline invisible.
But when I have white-eyes selected and try to erase the white area, it also erases the other layer eyes-outline layer. How is that possible that the eraser is manipulating 2 layers at the same time? I thought Gimp only can operate on 1 active selected layer? Even when I set the eyes-outline layer invisible and try to erase the white-eyes layer, and then make the eyes-outline visible again, it is erased as well... so it is impossible for me to erase only the white without affecting the other layer no matter if visible or invisible. Is that a bug?
Composite Mode
(right click the layer in the Layers menu) is set toAuto
?