Shadowing is now control by layer property ':can-shadow' only.
can-shadow is a commutative relation, if layer1 can shadow layer2 then layer2
can shadow layer1.
the shadow operator is a binary operator accepting two layer names, it is not
commutative and the order of the operands is determined by the order of the
layers in the dotfile (like the ownership stealing mechanism).
If ':can-shadow' is set explicity to nil in the dotfile then the layer won't
shadow any layer.
For instance to install both ivy and helm layer:
(setq dotspacemacs-configuration-layers
'(
ivy
(helm :can-shadow nil)
)
note that due to the commutative relation the above example can also be
written (in this case, ':can-shadow' should be read ':can-be-shawdowed'):
(setq dotspacemacs-configuration-layers
'(
(ivy :can-shadow nil)
helm
)
Layers can now declare in their layers.el file that they shadow one or more
layers using the following functions:
- configuration-layer/shadow-layers
- configuration-layer/shadow-layer
Those function are commutative so:
(configuration-layer/shadow-layer 'layer1 'layer2)
is the same as
(configuration-layer/shadow-layer 'layer2 'layer1)
and means that
layer1 shadows layer2
and
layer2 shadows layer1
The typical use-case is helm and ivy layers. Helm shadows the ivy layer and
Ivy shadows the helm layer.
Shadowing is sensitive to the order of declaration of layers in the dotfile,
for instance:
(setq dotspacemacs-configuration-layers '(
helm
ivy
))
means that ivy shadows helm so helm layer is effectively ignored,
whereas
(setq dotspacemacs-configuration-layers '(
ivy
helm
))
means that helm shadows ivy so ivy layer is effectively ignored.
This mechanism can be turned off using the :can-shadow keyword:
(setq dotspacemacs-configuration-layers '(
ivy
(helm :can-shadow nil)
))
means that both ivy and helm layers will be installed (not recommended in this
case)
Note that the `:can-shadow` mechanism will be fully implemented in a next
commit.
