src/dawn_native/metal/SamplerMTL.mm

// Copyright 2017 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "dawn_native/metal/SamplerMTL.h"

#include "dawn_native/metal/DeviceMTL.h"
#include "dawn_native/metal/UtilsMetal.h"

namespace dawn_native { namespace metal {

    namespace {
        MTLSamplerMinMagFilter FilterModeToMinMagFilter(wgpu::FilterMode mode) {
            switch (mode) {
                case wgpu::FilterMode::Nearest:
                    return MTLSamplerMinMagFilterNearest;
                case wgpu::FilterMode::Linear:
                    return MTLSamplerMinMagFilterLinear;
            }
        }

        MTLSamplerMipFilter FilterModeToMipFilter(wgpu::FilterMode mode) {
            switch (mode) {
                case wgpu::FilterMode::Nearest:
                    return MTLSamplerMipFilterNearest;
                case wgpu::FilterMode::Linear:
                    return MTLSamplerMipFilterLinear;
            }
        }

        MTLSamplerAddressMode AddressMode(wgpu::AddressMode mode) {
            switch (mode) {
                case wgpu::AddressMode::Repeat:
                    return MTLSamplerAddressModeRepeat;
                case wgpu::AddressMode::MirrorRepeat:
                    return MTLSamplerAddressModeMirrorRepeat;
                case wgpu::AddressMode::ClampToEdge:
                    return MTLSamplerAddressModeClampToEdge;
            }
        }
    }

    // static
    ResultOrError<Ref<Sampler>> Sampler::Create(Device* device,
                                                const SamplerDescriptor* descriptor) {
        DAWN_INVALID_IF(
            descriptor->compare != wgpu::CompareFunction::Undefined &&
                device->IsToggleEnabled(Toggle::MetalDisableSamplerCompare),
            "Sampler compare function (%s) not supported. Compare functions are disabled with the "
            "Metal backend.",
            descriptor->compare);

        Ref<Sampler> sampler = AcquireRef(new Sampler(device, descriptor));
        DAWN_TRY(sampler->Initialize(descriptor));
        return sampler;
    }

    MaybeError Sampler::Initialize(const SamplerDescriptor* descriptor) {
        NSRef<MTLSamplerDescriptor> mtlDescRef = AcquireNSRef([MTLSamplerDescriptor new]);
        MTLSamplerDescriptor* mtlDesc = mtlDescRef.Get();

        mtlDesc.minFilter = FilterModeToMinMagFilter(descriptor->minFilter);
        mtlDesc.magFilter = FilterModeToMinMagFilter(descriptor->magFilter);
        mtlDesc.mipFilter = FilterModeToMipFilter(descriptor->mipmapFilter);

        mtlDesc.sAddressMode = AddressMode(descriptor->addressModeU);
        mtlDesc.tAddressMode = AddressMode(descriptor->addressModeV);
        mtlDesc.rAddressMode = AddressMode(descriptor->addressModeW);

        mtlDesc.lodMinClamp = descriptor->lodMinClamp;
        mtlDesc.lodMaxClamp = descriptor->lodMaxClamp;
        // https://developer.apple.com/documentation/metal/mtlsamplerdescriptor/1516164-maxanisotropy
        mtlDesc.maxAnisotropy = std::min<uint16_t>(GetMaxAnisotropy(), 16u);

        if (descriptor->compare != wgpu::CompareFunction::Undefined) {
            // Sampler compare is unsupported before A9, which we validate in
            // Sampler::Create.
            mtlDesc.compareFunction = ToMetalCompareFunction(descriptor->compare);
            // The value is default-initialized in the else-case, and we don't set it or the
            // Metal debug device errors.
        }

        mMtlSamplerState = AcquireNSPRef(
            [ToBackend(GetDevice())->GetMTLDevice() newSamplerStateWithDescriptor:mtlDesc]);

        if (mMtlSamplerState == nil) {
            return DAWN_OUT_OF_MEMORY_ERROR("Failed to allocate sampler.");
        }
        return {};
    }

    id<MTLSamplerState> Sampler::GetMTLSamplerState() {
        return mMtlSamplerState.Get();
    }

}}  // namespace dawn_native::metal