Enumerations and Flags

Enumeration implementation

Enumerations in WebGPU are implemented as Kotlin enum classes. The values are derived from the WebGPU C header specifications available at wgpu.yml.

The naming conventions follow the C specifications rather than the IDL values, as they provide a more natural and intuitive representation for developers.

Flag types

Flag types (bit flags) are implemented as Kotlin value class masks wrapping a ULong, so a mask is a single integer in both directions: descriptors accept it and GPUBuffer.usage / GPUTexture.usage return it.

// From bitflags.kt
@JvmInline
value class GPUBufferUsage private constructor(val value: ULong) {
    public infix fun or(other: GPUBufferUsage): GPUBufferUsage
    public infix fun of(values: Array<GPUBufferUsage>): GPUBufferUsage

    public companion object {
        public val None: GPUBufferUsage
        public val MapRead: GPUBufferUsage
        public val MapWrite: GPUBufferUsage
        public val CopySrc: GPUBufferUsage
        // ...

        /** `true` when every bit of [other] is present in this mask. */
        public operator fun GPUBufferUsage.contains(other: GPUBufferUsage): Boolean

        /** Rebuilds a mask from raw bits, preserving unknown bits. */
        public fun fromBits(value: ULong): GPUBufferUsage
    }
}

a in mask means "every bit of a is present in mask"; because None has no bits, None in mask is true for every mask, including None itself.

fromBits preserves unknown bits: it performs no GPU validation, so a mask carrying bits the current contract does not name is still a valid value to pass around, and the backend decides whether a command accepts it.

Constants

Constants in WebGPU are transformed into mask values with explicit ULong values. This approach ensures type safety while maintaining compatibility with the native WebGPU headers.

The use of ULong as the underlying type aligns with the data type used for constants in the native WebGPU implementation, ensuring consistent behavior across platforms.