Macro wgpu_core::gfx_select
source · macro_rules! gfx_select { ($id:expr => $c0:ident.$c1:tt.$method:ident $params:tt) => { ... }; ($id:expr => $c0:ident.$method:ident $params:tt) => { ... }; ($id:expr => {$($c:tt)*}, $method:ident $params:tt) => { ... }; }
Expand description
Dispatch on an Id
’s backend to a backend-generic method.
Uses of this macro have the form:
gfx_select!(id => value.method(args...))
This expands to an expression that calls value.method::<A>(args...)
for
the backend A
selected by id
. The expansion matches on id.backend()
,
with an arm for each backend type in wgpu_types::Backend
which calls the
specialization of method
for the given backend. This allows resource
identifiers to select backends dynamically, even though many wgpu_core
methods are compiled and optimized for a specific back end.
This macro is typically used to call methods on wgpu_core::global::Global
,
many of which take a single hal::Api
type parameter. For example, to
create a new buffer on the device indicated by device_id
, one would say:
gfx_select!(device_id => global.device_create_buffer(device_id, ...))
where the device_create_buffer
method is defined like this:
impl Global {
pub fn device_create_buffer<A: HalApi>(&self, ...) -> ...
{ ... }
}
That gfx_select!
call uses device_id
’s backend to select the right
backend type A
for a call to Global::device_create_buffer<A>
.
However, there’s nothing about this macro that is specific to hub::Global
.
For example, Firefox’s embedding of wgpu_core
defines its own types with
methods that take hal::Api
type parameters. Firefox uses gfx_select!
to
dynamically dispatch to the right specialization based on the resource’s id.