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

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

gpu/src/bind_group.zig

@@ -9,7 +9,7 @@ pub const BindGroup = *opaque {};
 pub const BindGroupEntry = extern struct {
     next_in_chain: *const ChainedStruct,
     binding: u32,
-    buffer: Buffer = Buffer.none, // nullable
+    buffer: ?Buffer,
     offset: u64,
     size: u64,
     sampler: Sampler = Sampler.none, // nullable

gpu/src/bind_group_layout.zig

@@ -1,6 +1,7 @@
 const ChainedStruct = @import("types.zig").ChainedStruct;
 const ShaderStageFlags = @import("types.zig").ShaderStageFlags;
 const Buffer = @import("buffer.zig").Buffer;
+const BufferBindingLayout = @import("buffer.zig").BufferBindingLayout;
 const Sampler = @import("sampler.zig").Sampler;
 const Texture = @import("texture.zig").Texture;
 const StorageTextureBindingLayout = @import("types.zig").StorageTextureBindingLayout;
@@ -11,7 +12,7 @@ pub const BindGroupLayoutEntry = extern struct {
     next_in_chain: *const ChainedStruct,
     binding: u32,
     visibility: ShaderStageFlags,
-    buffer: Buffer.BindingLayout,
+    buffer: BufferBindingLayout,
     sampler: Sampler.BindingLayout,
     texture: Texture.BindingLayout,
     storage_texture: StorageTextureBindingLayout,

gpu/src/buffer.zig

@@ -1,28 +1,25 @@
 const std = @import("std");
 const ChainedStruct = @import("types.zig").ChainedStruct;
 
-pub const Buffer = enum(usize) {
+pub const Buffer = *opaque {};
-    _,
 
-    pub const none: Buffer = @intToEnum(Buffer, 0);
+pub const BufferBindingType = enum(u32) {
-
-    pub const BindingType = enum(u32) {
     undef = 0x00000000,
     uniform = 0x00000001,
     storage = 0x00000002,
     read_only_storage = 0x00000003,
-    };
+};
 
-    pub const MapAsyncStatus = enum(u32) {
+pub const BufferMapAsyncStatus = enum(u32) {
     success = 0x00000000,
     err = 0x00000001,
     unknown = 0x00000002,
     device_lost = 0x00000003,
     destroyed_before_callback = 0x00000004,
     unmapped_before_callback = 0x00000005,
-    };
+};
 
-    pub const Usage = packed struct {
+pub const BufferUsage = packed struct {
     map_read: bool = false,
     map_write: bool = false,
     copy_src: bool = false,
@@ -43,25 +40,24 @@ pub const Buffer = enum(usize) {
         );
     }
 
-        pub const none = Usage{};
+    pub const none = BufferUsage{};
 
-        pub fn equal(a: Usage, b: Usage) bool {
+    pub fn equal(a: BufferUsage, b: BufferUsage) bool {
         return @truncate(u10, @bitCast(u32, a)) == @truncate(u10, @bitCast(u32, b));
     }
-    };
+};
 
-    pub const BindingLayout = extern struct {
+pub const BufferBindingLayout = extern struct {
     next_in_chain: *const ChainedStruct,
-        type: BindingType,
+    type: BufferBindingType,
     has_dynamic_offset: bool = false,
     min_binding_size: u64 = 0,
-    };
+};
 
-    pub const Descriptor = extern struct {
+pub const BufferDescriptor = extern struct {
     next_in_chain: *const ChainedStruct,
     label: ?[*:0]const u8 = null,
-        usage: Usage,
+    usage: BufferUsage,
     size: u64,
     mapped_at_creation: bool,
-    };
 };