gpu: add foundation for interface

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/src/Adapter.zig

@@ -0,0 +1,79 @@
+//! A GPUAdapter which identifies an implementation of WebGPU on the system.
+//!
+//! An adapter is both an instance of compute/rendering functionality on the platform, and an
+//! instance of the WebGPU implementation on top of that functionality.
+//!
+//! Adapters do not uniquely represent underlying implementations: calling `requestAdapter()`
+//! multiple times returns a different adapter object each time.
+//!
+//! An adapter object may become invalid at any time. This happens inside "lose the device" and
+//! "mark adapters stale". An invalid adapter is unable to vend new devices.
+//!
+//! Note: This mechanism ensures that various adapter-creation scenarios look similar to
+//! applications, so they can easily be robust to more scenarios with less testing: first
+//! initialization, reinitialization due to an unplugged adapter, reinitialization due to a test
+//! GPUDevice.destroy() call, etc. It also ensures applications use the latest system state to make
+//! decisions about which adapter to use.
+//!
+//! https://gpuweb.github.io/gpuweb/#adapters
+//! https://gpuweb.github.io/gpuweb/#gpuadapter
+
+const FeatureName = @import("feature_name.zig").FeatureName;
+const SupportedLimits = @import("supported_limits.zig").SupportedLimits;
+
+const Adapter = @This();
+
+/// The features which can be used to create devices on this adapter.
+features: []FeatureName,
+
+/// The best limits which can be used to create devices on this adapter.
+///
+/// Each adapter limit will be the same or better than its default value in supported limits.
+limits: SupportedLimits,
+
+/// If set to true indicates that the adapter is a fallback adapter.
+///
+/// An adapter may be considered a fallback adapter if it has significant performance caveats in
+/// exchange for some combination of wider compatibility, more predictable behavior, or improved
+/// privacy. It is not guaranteed that a fallback adapter is available on every system.
+fallback: bool,
+
+// The type erased pointer to the Adapter implementation
+ptr: *anyopaque,
+vtable: *const VTable,
+
+pub const VTable = struct {
+    // TODO:
+    // WGPU_EXPORT void wgpuAdapterRequestDevice(WGPUAdapter adapter, WGPUDeviceDescriptor const * descriptor, WGPURequestDeviceCallback callback, void * userdata);
+    // WGPU_EXPORT WGPUDevice wgpuAdapterCreateDevice(WGPUAdapter adapter, WGPUDeviceDescriptor const * descriptor);
+    // WGPU_EXPORT void wgpuAdapterReference(WGPUAdapter adapter);
+    // WGPU_EXPORT void wgpuAdapterRelease(WGPUAdapter adapter);
+};
+
+/// Tests of the given feature can be used to create devices on this adapter.
+pub fn hasFeature(adapter: Adapter, feature: FeatureName) bool {
+    for (adapter.features) |f| {
+        if (f == feature) return true;
+    }
+    return false;
+}
+
+// TODO:
+// typedef struct WGPUAdapterProperties {
+//     WGPUChainedStructOut * nextInChain;
+//     uint32_t vendorID;
+//     uint32_t deviceID;
+//     char const * name;
+//     char const * driverDescription;
+//     WGPUAdapterType adapterType;
+//     WGPUBackendType backendType;
+// } WGPUAdapterProperties;
+
+// TODO:
+// typedef enum WGPUAdapterType {
+//     WGPUAdapterType_DiscreteGPU = 0x00000000,
+//     WGPUAdapterType_IntegratedGPU = 0x00000001,
+//     WGPUAdapterType_CPU = 0x00000002,
+//     WGPUAdapterType_Unknown = 0x00000003,
+//     WGPUAdapterType_Force32 = 0x7FFFFFFF
+// } WGPUAdapterType;