gpu: convert Texture.Usage to packed struct

gpu/src/NativeInstance.zig

@@ -504,7 +504,7 @@ const device_vtable = Device.VTable{
             const desc = c.WGPUSwapChainDescriptor{
                 .nextInChain = null,
                 .label = if (descriptor.label) |l| l else null,
-                .usage = @enumToInt(descriptor.usage),
+                .usage = @bitCast(u32, descriptor.usage),
                 .format = @enumToInt(descriptor.format),
                 .width = descriptor.width,
                 .height = descriptor.height,
@@ -1017,7 +1017,7 @@ const swap_chain_vtable = SwapChain.VTable{
             c.wgpuSwapChainConfigure(
                 @ptrCast(c.WGPUSwapChain, ptr),
                 @enumToInt(format),
-                @enumToInt(allowed_usage),
+                @bitCast(u32, allowed_usage),
                 width,
                 height,
             );

gpu/src/SwapChain.zig

@@ -57,7 +57,7 @@ pub const Descriptor = struct {
     pub fn equal(a: *const Descriptor, b: *const Descriptor) bool {
         if ((a.label == null) != (b.label == null)) return false;
         if (a.label != null and !std.mem.eql(u8, a.label.?, b.label.?)) return false;
-        if (a.usage != b.usage) return false;
+        if (!a.usage.equal(b.usage)) return false;
         if (a.format != b.format) return false;
         if (a.width != b.width) return false;
         if (a.height != b.height) return false;

gpu/src/Texture.zig

@@ -1,3 +1,5 @@
+const std = @import("std");
+
 const Extent3D = @import("data.zig").Extent3D;
 
 const TextureView = @import("TextureView.zig");
@@ -48,14 +50,33 @@ pub const Descriptor = struct {
     sample_count: u32,
 };
 
-pub const Usage = enum(u32) {
+pub const Usage = packed struct {
-    none = 0x00000000,
+    copy_src: bool = false,
-    copy_src = 0x00000001,
+    copy_dst: bool = false,
-    copy_dst = 0x00000002,
+    texture_binding: bool = false,
-    texture_binding = 0x00000004,
+    storage_binding: bool = false,
-    storage_binding = 0x00000008,
+    render_attachment: bool = false,
-    render_attachment = 0x00000010,
+    present: bool = false,
-    present = 0x00000020,
+
+    _pad0: u2 = 0,
+    _pad1: u8 = 0,
+    _pad2: u16 = 0,
+
+    comptime {
+        std.debug.assert(
+            @sizeOf(@This()) == @sizeOf(u32) and
+                @bitSizeOf(@This()) == @bitSizeOf(u32),
+        );
+    }
+
+    pub fn equal(a: Usage, b: Usage) bool {
+        return a.copy_src == b.copy_src and
+            a.copy_dst == b.copy_dst and
+            a.texture_binding == b.texture_binding and
+            a.storage_binding == b.storage_binding and
+            a.render_attachment == b.render_attachment and
+            a.present == b.present;
+    }
 };
 
 pub const Format = enum(u32) {

src/main.zig

@@ -150,7 +150,7 @@ pub fn App(comptime Context: type, comptime config: AppConfig) type {
                 swap_chain_format = .bgra8_unorm;
                 descriptor = .{
                     .label = "basic swap chain",
-                    .usage = .render_attachment,
+                    .usage = .{ .render_attachment = true },
                     .format = swap_chain_format,
                     .width = framebuffer_size.width,
                     .height = framebuffer_size.height,
@@ -174,7 +174,7 @@ pub fn App(comptime Context: type, comptime config: AppConfig) type {
                 swap_chain_format = @intToEnum(gpu.Texture.Format, @intCast(u32, c.machUtilsBackendBinding_getPreferredSwapChainTextureFormat(binding)));
                 swap_chain.?.configure(
                     swap_chain_format,
-                    .render_attachment,
+                    .{ .render_attachment = true },
                     framebuffer_size.width,
                     framebuffer_size.height,
                 );
@@ -221,7 +221,7 @@ pub fn App(comptime Context: type, comptime config: AppConfig) type {
                         app.swap_chain = app.device.nativeCreateSwapChain(app.surface, &app.target_desc);
                     } else app.swap_chain.?.configure(
                         app.swap_chain_format,
-                        .render_attachment,
+                        .{ .render_attachment = true },
                         app.target_desc.width,
                         app.target_desc.height,
                     );