gpu: mirror more WebGPU spec default values (#249)

Helps hexops/mach#182

gpu/src/Sampler.zig

@@ -42,16 +42,16 @@ pub const BindingLayout = extern struct {
 pub const Descriptor = extern struct {
     reserved: ?*anyopaque = null,
     label: ?[*:0]const u8 = null,
-    address_mode_u: AddressMode,
-    address_mode_v: AddressMode,
-    address_mode_w: AddressMode,
-    mag_filter: FilterMode,
-    min_filter: FilterMode,
-    mipmap_filter: FilterMode,
-    lod_min_clamp: f32,
-    lod_max_clamp: f32,
-    compare: CompareFunction,
-    max_anisotropy: u16,
+    address_mode_u: AddressMode = .clamp_to_edge,
+    address_mode_v: AddressMode = .clamp_to_edge,
+    address_mode_w: AddressMode = .clamp_to_edge,
+    mag_filter: FilterMode = .nearest,
+    min_filter: FilterMode = .nearest,
+    mipmap_filter: FilterMode = .nearest,
+    lod_min_clamp: f32 = 0,
+    lod_max_clamp: f32 = 32,
+    compare: CompareFunction = .none,
+    max_anisotropy: u16 = 1,
 };
 
 test {

gpu/src/Texture.zig

@@ -43,11 +43,11 @@ pub const Descriptor = struct {
     reserved: ?*anyopaque = null,
     label: ?[*:0]const u8 = null,
     usage: Usage,
-    dimension: Dimension,
+    dimension: Dimension = .dimension_2d,
     size: Extent3D,
     format: Format,
-    mip_level_count: u32,
-    sample_count: u32,
+    mip_level_count: u32 = 1,
+    sample_count: u32 = 1,
     view_formats: ?[]const Format = null,
 };
 

gpu/src/TextureView.zig

@@ -29,11 +29,11 @@ pub const Descriptor = struct {
     label: ?[*:0]const u8 = null,
     format: Texture.Format,
     dimension: TextureView.Dimension,
-    base_mip_level: u32,
+    base_mip_level: u32 = 0,
     mip_level_count: u32,
-    base_array_layer: u32,
+    base_array_layer: u32 = 0,
     array_layer_count: u32,
-    aspect: Texture.Aspect,
+    aspect: Texture.Aspect = .all,
 };
 
 pub const Dimension = enum(u32) {