gpu: convert Adapter from enum(usize) to *opaque

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

gpu/src/adapter.zig

@@ -1,41 +1,36 @@
 const testing = @import("std").testing;
 const ChainedStructOut = @import("types.zig").ChainedStructOut;
 
-pub const Adapter = enum(usize) {
-    _,
+pub const Adapter = *opaque {};
 
-    // TODO: verify there is a use case for nullable value of this type.
-    pub const none: Adapter = @intToEnum(Adapter, 0);
+pub const AdapterType = enum(u32) {
+    discrete_gpu,
+    integrated_gpu,
+    cpu,
+    unknown,
 
-    pub const Type = enum(u32) {
-        discrete_gpu,
-        integrated_gpu,
-        cpu,
-        unknown,
-
-        pub fn name(t: Type) []const u8 {
-            return switch (t) {
-                .discrete_gpu => "Discrete GPU",
-                .integrated_gpu => "Integrated GPU",
-                .cpu => "CPU",
-                .unknown => "Unknown",
-            };
-        }
-    };
-
-    pub const Properties = extern struct {
-        next_in_chain: *ChainedStructOut,
-        vendor_id: u32,
-        vendor_name: [*:0]const u8,
-        architecture: [*:0]const u8,
-        device_id: u32,
-        name: [*:0]const u8,
-        driver_description: [*:0]const u8,
-        adapter_type: Type,
-        backend_type: Type,
-    };
+    pub fn name(t: AdapterType) []const u8 {
+        return switch (t) {
+            .discrete_gpu => "Discrete GPU",
+            .integrated_gpu => "Integrated GPU",
+            .cpu => "CPU",
+            .unknown => "Unknown",
+        };
+    }
 };
 
-test "Adapter.Type name" {
-    try testing.expectEqualStrings("Discrete GPU", Adapter.Type.discrete_gpu.name());
+pub const AdapterProperties = extern struct {
+    next_in_chain: *ChainedStructOut,
+    vendor_id: u32,
+    vendor_name: [*:0]const u8,
+    architecture: [*:0]const u8,
+    device_id: u32,
+    name: [*:0]const u8,
+    driver_description: [*:0]const u8,
+    adapter_type: AdapterType,
+    backend_type: AdapterType,
+};
+
+test "AdapterType name" {
+    try testing.expectEqualStrings("Discrete GPU", AdapterType.discrete_gpu.name());
 }