F_Cu = 0
B_Cu = 2
Remaining internal copper layers are even and incrementing
Non-copper layers are odd and incrementing.
This means that we can no longer do things like:
for( PCB_LAYER_ID layer = F_Cu; layer <= B_Cu; ++layer)
Instead, we have the class LAYER_RANGE:
for( PCB_LAYER_ID layer : LAYER_RANGE( F_Cu, B_Cu) )
Similarly, gt/lt tests should not refer to the integer value of the
layer. We have functions such as IsCopperLayer to test whether a layer
is copper or not.
When using the connectivity RTree, the third dimension is layer, so we
provide B_Cu with the special INT_MAX value, ensuring that elements
between F_Cu and B_Cu will be identified. There is a new, special
function GetBoardLayer() for interfacing with CN_ITEMS
Similarly, PNS layers remain unchanged and sequential. A set of
interface functions is provided to map PNS layers to Board layers and
back. This allows the PNS_LAYER_RANGE to function as expected
