// 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/opengl/CommandBufferGL.h"

#include "dawn_native/BindGroup.h"
#include "dawn_native/BindGroupTracker.h"
#include "dawn_native/CommandEncoder.h"
#include "dawn_native/Commands.h"
#include "dawn_native/ExternalTexture.h"
#include "dawn_native/RenderBundle.h"
#include "dawn_native/VertexFormat.h"
#include "dawn_native/opengl/BufferGL.h"
#include "dawn_native/opengl/ComputePipelineGL.h"
#include "dawn_native/opengl/DeviceGL.h"
#include "dawn_native/opengl/Forward.h"
#include "dawn_native/opengl/PersistentPipelineStateGL.h"
#include "dawn_native/opengl/PipelineLayoutGL.h"
#include "dawn_native/opengl/RenderPipelineGL.h"
#include "dawn_native/opengl/SamplerGL.h"
#include "dawn_native/opengl/TextureGL.h"
#include "dawn_native/opengl/UtilsGL.h"

#include <cstring>

namespace dawn::native::opengl {

    namespace {

        GLenum IndexFormatType(wgpu::IndexFormat format) {
            switch (format) {
                case wgpu::IndexFormat::Uint16:
                    return GL_UNSIGNED_SHORT;
                case wgpu::IndexFormat::Uint32:
                    return GL_UNSIGNED_INT;
                case wgpu::IndexFormat::Undefined:
                    break;
            }
            UNREACHABLE();
        }

        GLenum VertexFormatType(wgpu::VertexFormat format) {
            switch (format) {
                case wgpu::VertexFormat::Uint8x2:
                case wgpu::VertexFormat::Uint8x4:
                case wgpu::VertexFormat::Unorm8x2:
                case wgpu::VertexFormat::Unorm8x4:
                    return GL_UNSIGNED_BYTE;
                case wgpu::VertexFormat::Sint8x2:
                case wgpu::VertexFormat::Sint8x4:
                case wgpu::VertexFormat::Snorm8x2:
                case wgpu::VertexFormat::Snorm8x4:
                    return GL_BYTE;
                case wgpu::VertexFormat::Uint16x2:
                case wgpu::VertexFormat::Uint16x4:
                case wgpu::VertexFormat::Unorm16x2:
                case wgpu::VertexFormat::Unorm16x4:
                    return GL_UNSIGNED_SHORT;
                case wgpu::VertexFormat::Sint16x2:
                case wgpu::VertexFormat::Sint16x4:
                case wgpu::VertexFormat::Snorm16x2:
                case wgpu::VertexFormat::Snorm16x4:
                    return GL_SHORT;
                case wgpu::VertexFormat::Float16x2:
                case wgpu::VertexFormat::Float16x4:
                    return GL_HALF_FLOAT;
                case wgpu::VertexFormat::Float32:
                case wgpu::VertexFormat::Float32x2:
                case wgpu::VertexFormat::Float32x3:
                case wgpu::VertexFormat::Float32x4:
                    return GL_FLOAT;
                case wgpu::VertexFormat::Uint32:
                case wgpu::VertexFormat::Uint32x2:
                case wgpu::VertexFormat::Uint32x3:
                case wgpu::VertexFormat::Uint32x4:
                    return GL_UNSIGNED_INT;
                case wgpu::VertexFormat::Sint32:
                case wgpu::VertexFormat::Sint32x2:
                case wgpu::VertexFormat::Sint32x3:
                case wgpu::VertexFormat::Sint32x4:
                    return GL_INT;
                default:
                    UNREACHABLE();
            }
        }

        GLboolean VertexFormatIsNormalized(wgpu::VertexFormat format) {
            switch (format) {
                case wgpu::VertexFormat::Unorm8x2:
                case wgpu::VertexFormat::Unorm8x4:
                case wgpu::VertexFormat::Snorm8x2:
                case wgpu::VertexFormat::Snorm8x4:
                case wgpu::VertexFormat::Unorm16x2:
                case wgpu::VertexFormat::Unorm16x4:
                case wgpu::VertexFormat::Snorm16x2:
                case wgpu::VertexFormat::Snorm16x4:
                    return GL_TRUE;
                default:
                    return GL_FALSE;
            }
        }

        bool VertexFormatIsInt(wgpu::VertexFormat format) {
            switch (format) {
                case wgpu::VertexFormat::Uint8x2:
                case wgpu::VertexFormat::Uint8x4:
                case wgpu::VertexFormat::Sint8x2:
                case wgpu::VertexFormat::Sint8x4:
                case wgpu::VertexFormat::Uint16x2:
                case wgpu::VertexFormat::Uint16x4:
                case wgpu::VertexFormat::Sint16x2:
                case wgpu::VertexFormat::Sint16x4:
                case wgpu::VertexFormat::Uint32:
                case wgpu::VertexFormat::Uint32x2:
                case wgpu::VertexFormat::Uint32x3:
                case wgpu::VertexFormat::Uint32x4:
                case wgpu::VertexFormat::Sint32:
                case wgpu::VertexFormat::Sint32x2:
                case wgpu::VertexFormat::Sint32x3:
                case wgpu::VertexFormat::Sint32x4:
                    return true;
                default:
                    return false;
            }
        }

        // Vertex buffers and index buffers are implemented as part of an OpenGL VAO that
        // corresponds to a VertexState. On the contrary in Dawn they are part of the global state.
        // This means that we have to re-apply these buffers on a VertexState change.
        class VertexStateBufferBindingTracker {
          public:
            void OnSetIndexBuffer(BufferBase* buffer) {
                mIndexBufferDirty = true;
                mIndexBuffer = ToBackend(buffer);
            }

            void OnSetVertexBuffer(VertexBufferSlot slot, BufferBase* buffer, uint64_t offset) {
                mVertexBuffers[slot] = ToBackend(buffer);
                mVertexBufferOffsets[slot] = offset;
                mDirtyVertexBuffers.set(slot);
            }

            void OnSetPipeline(RenderPipelineBase* pipeline) {
                if (mLastPipeline == pipeline) {
                    return;
                }

                mIndexBufferDirty = true;
                mDirtyVertexBuffers |= pipeline->GetVertexBufferSlotsUsed();

                mLastPipeline = pipeline;
            }

            void Apply(const OpenGLFunctions& gl) {
                if (mIndexBufferDirty && mIndexBuffer != nullptr) {
                    gl.BindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIndexBuffer->GetHandle());
                    mIndexBufferDirty = false;
                }

                for (VertexBufferSlot slot : IterateBitSet(
                         mDirtyVertexBuffers & mLastPipeline->GetVertexBufferSlotsUsed())) {
                    for (VertexAttributeLocation location : IterateBitSet(
                             ToBackend(mLastPipeline)->GetAttributesUsingVertexBuffer(slot))) {
                        const VertexAttributeInfo& attribute =
                            mLastPipeline->GetAttribute(location);

                        GLuint attribIndex = static_cast<GLuint>(static_cast<uint8_t>(location));
                        GLuint buffer = mVertexBuffers[slot]->GetHandle();
                        uint64_t offset = mVertexBufferOffsets[slot];

                        const VertexBufferInfo& vertexBuffer = mLastPipeline->GetVertexBuffer(slot);
                        uint32_t components = GetVertexFormatInfo(attribute.format).componentCount;
                        GLenum formatType = VertexFormatType(attribute.format);

                        GLboolean normalized = VertexFormatIsNormalized(attribute.format);
                        gl.BindBuffer(GL_ARRAY_BUFFER, buffer);
                        if (VertexFormatIsInt(attribute.format)) {
                            gl.VertexAttribIPointer(
                                attribIndex, components, formatType, vertexBuffer.arrayStride,
                                reinterpret_cast<void*>(
                                    static_cast<intptr_t>(offset + attribute.offset)));
                        } else {
                            gl.VertexAttribPointer(attribIndex, components, formatType, normalized,
                                                   vertexBuffer.arrayStride,
                                                   reinterpret_cast<void*>(static_cast<intptr_t>(
                                                       offset + attribute.offset)));
                        }
                    }
                }

                mDirtyVertexBuffers.reset();
            }

          private:
            bool mIndexBufferDirty = false;
            Buffer* mIndexBuffer = nullptr;

            ityp::bitset<VertexBufferSlot, kMaxVertexBuffers> mDirtyVertexBuffers;
            ityp::array<VertexBufferSlot, Buffer*, kMaxVertexBuffers> mVertexBuffers;
            ityp::array<VertexBufferSlot, uint64_t, kMaxVertexBuffers> mVertexBufferOffsets;

            RenderPipelineBase* mLastPipeline = nullptr;
        };

        class BindGroupTracker : public BindGroupTrackerBase<false, uint64_t> {
          public:
            void OnSetPipeline(RenderPipeline* pipeline) {
                BindGroupTrackerBase::OnSetPipeline(pipeline);
                mPipeline = pipeline;
            }

            void OnSetPipeline(ComputePipeline* pipeline) {
                BindGroupTrackerBase::OnSetPipeline(pipeline);
                mPipeline = pipeline;
            }

            void Apply(const OpenGLFunctions& gl) {
                BeforeApply();
                for (BindGroupIndex index :
                     IterateBitSet(mDirtyBindGroupsObjectChangedOrIsDynamic)) {
                    ApplyBindGroup(gl, index, mBindGroups[index], mDynamicOffsetCounts[index],
                                   mDynamicOffsets[index].data());
                }
                AfterApply();
            }

          private:
            void ApplyBindGroup(const OpenGLFunctions& gl,
                                BindGroupIndex index,
                                BindGroupBase* group,
                                uint32_t dynamicOffsetCount,
                                uint64_t* dynamicOffsets) {
                const auto& indices = ToBackend(mPipelineLayout)->GetBindingIndexInfo()[index];
                uint32_t currentDynamicOffsetIndex = 0;

                for (BindingIndex bindingIndex{0};
                     bindingIndex < group->GetLayout()->GetBindingCount(); ++bindingIndex) {
                    const BindingInfo& bindingInfo =
                        group->GetLayout()->GetBindingInfo(bindingIndex);

                    switch (bindingInfo.bindingType) {
                        case BindingInfoType::Buffer: {
                            BufferBinding binding = group->GetBindingAsBufferBinding(bindingIndex);
                            GLuint buffer = ToBackend(binding.buffer)->GetHandle();
                            GLuint index = indices[bindingIndex];
                            GLuint offset = binding.offset;

                            if (bindingInfo.buffer.hasDynamicOffset) {
                                offset += dynamicOffsets[currentDynamicOffsetIndex];
                                ++currentDynamicOffsetIndex;
                            }

                            GLenum target;
                            switch (bindingInfo.buffer.type) {
                                case wgpu::BufferBindingType::Uniform:
                                    target = GL_UNIFORM_BUFFER;
                                    break;
                                case wgpu::BufferBindingType::Storage:
                                case kInternalStorageBufferBinding:
                                case wgpu::BufferBindingType::ReadOnlyStorage:
                                    target = GL_SHADER_STORAGE_BUFFER;
                                    break;
                                case wgpu::BufferBindingType::Undefined:
                                    UNREACHABLE();
                            }

                            gl.BindBufferRange(target, index, buffer, offset, binding.size);
                            break;
                        }

                        case BindingInfoType::Sampler: {
                            Sampler* sampler = ToBackend(group->GetBindingAsSampler(bindingIndex));
                            GLuint samplerIndex = indices[bindingIndex];

                            for (PipelineGL::SamplerUnit unit :
                                 mPipeline->GetTextureUnitsForSampler(samplerIndex)) {
                                // Only use filtering for certain texture units, because int
                                // and uint texture are only complete without filtering
                                if (unit.shouldUseFiltering) {
                                    gl.BindSampler(unit.unit, sampler->GetFilteringHandle());
                                } else {
                                    gl.BindSampler(unit.unit, sampler->GetNonFilteringHandle());
                                }
                            }
                            break;
                        }

                        case BindingInfoType::Texture: {
                            TextureView* view =
                                ToBackend(group->GetBindingAsTextureView(bindingIndex));
                            GLuint handle = view->GetHandle();
                            GLenum target = view->GetGLTarget();
                            GLuint viewIndex = indices[bindingIndex];

                            for (auto unit : mPipeline->GetTextureUnitsForTextureView(viewIndex)) {
                                gl.ActiveTexture(GL_TEXTURE0 + unit);
                                gl.BindTexture(target, handle);
                                if (ToBackend(view->GetTexture())->GetGLFormat().format ==
                                    GL_DEPTH_STENCIL) {
                                    Aspect aspect = view->GetAspects();
                                    ASSERT(HasOneBit(aspect));
                                    switch (aspect) {
                                        case Aspect::None:
                                        case Aspect::Color:
                                        case Aspect::CombinedDepthStencil:
                                        case Aspect::Plane0:
                                        case Aspect::Plane1:
                                            UNREACHABLE();
                                        case Aspect::Depth:
                                            gl.TexParameteri(target, GL_DEPTH_STENCIL_TEXTURE_MODE,
                                                             GL_DEPTH_COMPONENT);
                                            break;
                                        case Aspect::Stencil:
                                            gl.TexParameteri(target, GL_DEPTH_STENCIL_TEXTURE_MODE,
                                                             GL_STENCIL_INDEX);
                                            break;
                                    }
                                }
                            }
                            break;
                        }

                        case BindingInfoType::StorageTexture: {
                            TextureView* view =
                                ToBackend(group->GetBindingAsTextureView(bindingIndex));
                            Texture* texture = ToBackend(view->GetTexture());
                            GLuint handle = texture->GetHandle();
                            GLuint imageIndex = indices[bindingIndex];

                            GLenum access;
                            switch (bindingInfo.storageTexture.access) {
                                case wgpu::StorageTextureAccess::WriteOnly:
                                    access = GL_WRITE_ONLY;
                                    break;
                                case wgpu::StorageTextureAccess::Undefined:
                                    UNREACHABLE();
                            }

                            // OpenGL ES only supports either binding a layer or the entire
                            // texture in glBindImageTexture().
                            GLboolean isLayered;
                            if (view->GetLayerCount() == 1) {
                                isLayered = GL_FALSE;
                            } else if (texture->GetArrayLayers() == view->GetLayerCount()) {
                                isLayered = GL_TRUE;
                            } else {
                                UNREACHABLE();
                            }

                            gl.BindImageTexture(imageIndex, handle, view->GetBaseMipLevel(),
                                                isLayered, view->GetBaseArrayLayer(), access,
                                                texture->GetGLFormat().internalFormat);
                            break;
                        }

                        case BindingInfoType::ExternalTexture: {
                            const std::array<Ref<TextureViewBase>, kMaxPlanesPerFormat>&
                                textureViews = mBindGroups[index]
                                                   ->GetBindingAsExternalTexture(bindingIndex)
                                                   ->GetTextureViews();

                            // Only single-plane formats are supported right now, so assert only one
                            // view exists.
                            ASSERT(textureViews[1].Get() == nullptr);
                            ASSERT(textureViews[2].Get() == nullptr);

                            TextureView* view = ToBackend(textureViews[0].Get());
                            GLuint handle = view->GetHandle();
                            GLenum target = view->GetGLTarget();
                            GLuint viewIndex = indices[bindingIndex];

                            for (auto unit : mPipeline->GetTextureUnitsForTextureView(viewIndex)) {
                                gl.ActiveTexture(GL_TEXTURE0 + unit);
                                gl.BindTexture(target, handle);
                            }
                            break;
                        }
                    }
                }
            }

            PipelineGL* mPipeline = nullptr;
        };

        void ResolveMultisampledRenderTargets(const OpenGLFunctions& gl,
                                              const BeginRenderPassCmd* renderPass) {
            ASSERT(renderPass != nullptr);

            GLuint readFbo = 0;
            GLuint writeFbo = 0;

            for (ColorAttachmentIndex i :
                 IterateBitSet(renderPass->attachmentState->GetColorAttachmentsMask())) {
                if (renderPass->colorAttachments[i].resolveTarget != nullptr) {
                    if (readFbo == 0) {
                        ASSERT(writeFbo == 0);
                        gl.GenFramebuffers(1, &readFbo);
                        gl.GenFramebuffers(1, &writeFbo);
                    }

                    const TextureBase* colorTexture =
                        renderPass->colorAttachments[i].view->GetTexture();
                    ASSERT(colorTexture->IsMultisampledTexture());
                    ASSERT(colorTexture->GetArrayLayers() == 1);
                    ASSERT(renderPass->colorAttachments[i].view->GetBaseMipLevel() == 0);

                    GLuint colorHandle = ToBackend(colorTexture)->GetHandle();
                    gl.BindFramebuffer(GL_READ_FRAMEBUFFER, readFbo);
                    gl.FramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                            ToBackend(colorTexture)->GetGLTarget(), colorHandle, 0);

                    const TextureBase* resolveTexture =
                        renderPass->colorAttachments[i].resolveTarget->GetTexture();
                    GLuint resolveTextureHandle = ToBackend(resolveTexture)->GetHandle();
                    GLuint resolveTargetMipmapLevel =
                        renderPass->colorAttachments[i].resolveTarget->GetBaseMipLevel();
                    gl.BindFramebuffer(GL_DRAW_FRAMEBUFFER, writeFbo);
                    if (resolveTexture->GetArrayLayers() == 1) {
                        gl.FramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                                GL_TEXTURE_2D, resolveTextureHandle,
                                                resolveTargetMipmapLevel);
                    } else {
                        GLuint resolveTargetArrayLayer =
                            renderPass->colorAttachments[i].resolveTarget->GetBaseArrayLayer();
                        gl.FramebufferTextureLayer(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                                   resolveTextureHandle, resolveTargetMipmapLevel,
                                                   resolveTargetArrayLayer);
                    }

                    gl.BlitFramebuffer(0, 0, renderPass->width, renderPass->height, 0, 0,
                                       renderPass->width, renderPass->height, GL_COLOR_BUFFER_BIT,
                                       GL_NEAREST);
                }
            }

            gl.DeleteFramebuffers(1, &readFbo);
            gl.DeleteFramebuffers(1, &writeFbo);
        }

        // OpenGL SPEC requires the source/destination region must be a region that is contained
        // within srcImage/dstImage. Here the size of the image refers to the virtual size, while
        // Dawn validates texture copy extent with the physical size, so we need to re-calculate the
        // texture copy extent to ensure it should fit in the virtual size of the subresource.
        Extent3D ComputeTextureCopyExtent(const TextureCopy& textureCopy,
                                          const Extent3D& copySize) {
            Extent3D validTextureCopyExtent = copySize;
            const TextureBase* texture = textureCopy.texture.Get();
            Extent3D virtualSizeAtLevel = texture->GetMipLevelVirtualSize(textureCopy.mipLevel);
            ASSERT(textureCopy.origin.x <= virtualSizeAtLevel.width);
            ASSERT(textureCopy.origin.y <= virtualSizeAtLevel.height);
            if (copySize.width > virtualSizeAtLevel.width - textureCopy.origin.x) {
                ASSERT(texture->GetFormat().isCompressed);
                validTextureCopyExtent.width = virtualSizeAtLevel.width - textureCopy.origin.x;
            }
            if (copySize.height > virtualSizeAtLevel.height - textureCopy.origin.y) {
                ASSERT(texture->GetFormat().isCompressed);
                validTextureCopyExtent.height = virtualSizeAtLevel.height - textureCopy.origin.y;
            }

            return validTextureCopyExtent;
        }

        void CopyTextureToTextureWithBlit(const OpenGLFunctions& gl,
                                          const TextureCopy& src,
                                          const TextureCopy& dst,
                                          const Extent3D& copySize) {
            Texture* srcTexture = ToBackend(src.texture.Get());
            Texture* dstTexture = ToBackend(dst.texture.Get());

            // Generate temporary framebuffers for the blits.
            GLuint readFBO = 0, drawFBO = 0;
            gl.GenFramebuffers(1, &readFBO);
            gl.GenFramebuffers(1, &drawFBO);
            gl.BindFramebuffer(GL_READ_FRAMEBUFFER, readFBO);
            gl.BindFramebuffer(GL_DRAW_FRAMEBUFFER, drawFBO);

            // Reset state that may affect glBlitFramebuffer().
            gl.Disable(GL_SCISSOR_TEST);
            GLenum blitMask = 0;
            if (src.aspect & Aspect::Color) {
                blitMask |= GL_COLOR_BUFFER_BIT;
            }
            if (src.aspect & Aspect::Depth) {
                blitMask |= GL_DEPTH_BUFFER_BIT;
            }
            if (src.aspect & Aspect::Stencil) {
                blitMask |= GL_STENCIL_BUFFER_BIT;
            }
            // Iterate over all layers, doing a single blit for each.
            for (uint32_t layer = 0; layer < copySize.depthOrArrayLayers; ++layer) {
                // Bind all required aspects for this layer.
                for (Aspect aspect : IterateEnumMask(src.aspect)) {
                    GLenum glAttachment;
                    switch (aspect) {
                        case Aspect::Color:
                            glAttachment = GL_COLOR_ATTACHMENT0;
                            break;
                        case Aspect::Depth:
                            glAttachment = GL_DEPTH_ATTACHMENT;
                            break;
                        case Aspect::Stencil:
                            glAttachment = GL_STENCIL_ATTACHMENT;
                            break;
                        case Aspect::CombinedDepthStencil:
                        case Aspect::None:
                        case Aspect::Plane0:
                        case Aspect::Plane1:
                            UNREACHABLE();
                    }
                    if (srcTexture->GetArrayLayers() == 1 &&
                        srcTexture->GetDimension() == wgpu::TextureDimension::e2D) {
                        gl.FramebufferTexture2D(GL_READ_FRAMEBUFFER, glAttachment,
                                                srcTexture->GetGLTarget(), srcTexture->GetHandle(),
                                                src.mipLevel);
                    } else {
                        gl.FramebufferTextureLayer(GL_READ_FRAMEBUFFER, glAttachment,
                                                   srcTexture->GetHandle(),
                                                   static_cast<GLint>(src.mipLevel),
                                                   static_cast<GLint>(src.origin.z + layer));
                    }
                    if (dstTexture->GetArrayLayers() == 1 &&
                        dstTexture->GetDimension() == wgpu::TextureDimension::e2D) {
                        gl.FramebufferTexture2D(GL_DRAW_FRAMEBUFFER, glAttachment,
                                                dstTexture->GetGLTarget(), dstTexture->GetHandle(),
                                                dst.mipLevel);
                    } else {
                        gl.FramebufferTextureLayer(GL_DRAW_FRAMEBUFFER, glAttachment,
                                                   dstTexture->GetHandle(),
                                                   static_cast<GLint>(dst.mipLevel),
                                                   static_cast<GLint>(dst.origin.z + layer));
                    }
                }
                gl.BlitFramebuffer(src.origin.x, src.origin.y, src.origin.x + copySize.width,
                                   src.origin.y + copySize.height, dst.origin.x, dst.origin.y,
                                   dst.origin.x + copySize.width, dst.origin.y + copySize.height,
                                   blitMask, GL_NEAREST);
            }
            gl.Enable(GL_SCISSOR_TEST);
            gl.DeleteFramebuffers(1, &readFBO);
            gl.DeleteFramebuffers(1, &drawFBO);
        }
        bool TextureFormatIsSnorm(wgpu::TextureFormat format) {
            return format == wgpu::TextureFormat::RGBA8Snorm ||
                   format == wgpu::TextureFormat::RG8Snorm ||
                   format == wgpu::TextureFormat::R8Snorm;
        }
    }  // namespace

    CommandBuffer::CommandBuffer(CommandEncoder* encoder, const CommandBufferDescriptor* descriptor)
        : CommandBufferBase(encoder, descriptor) {
    }

    MaybeError CommandBuffer::Execute() {
        const OpenGLFunctions& gl = ToBackend(GetDevice())->gl;

        auto LazyClearSyncScope = [](const SyncScopeResourceUsage& scope) {
            for (size_t i = 0; i < scope.textures.size(); i++) {
                Texture* texture = ToBackend(scope.textures[i]);

                // Clear subresources that are not render attachments. Render attachments will be
                // cleared in RecordBeginRenderPass by setting the loadop to clear when the texture
                // subresource has not been initialized before the render pass.
                scope.textureUsages[i].Iterate(
                    [&](const SubresourceRange& range, wgpu::TextureUsage usage) {
                        if (usage & ~wgpu::TextureUsage::RenderAttachment) {
                            texture->EnsureSubresourceContentInitialized(range);
                        }
                    });
            }

            for (BufferBase* bufferBase : scope.buffers) {
                ToBackend(bufferBase)->EnsureDataInitialized();
            }
        };

        size_t nextComputePassNumber = 0;
        size_t nextRenderPassNumber = 0;

        Command type;
        while (mCommands.NextCommandId(&type)) {
            switch (type) {
                case Command::BeginComputePass: {
                    mCommands.NextCommand<BeginComputePassCmd>();
                    for (const SyncScopeResourceUsage& scope :
                         GetResourceUsages().computePasses[nextComputePassNumber].dispatchUsages) {
                        LazyClearSyncScope(scope);
                    }
                    DAWN_TRY(ExecuteComputePass());

                    nextComputePassNumber++;
                    break;
                }

                case Command::BeginRenderPass: {
                    auto* cmd = mCommands.NextCommand<BeginRenderPassCmd>();
                    LazyClearSyncScope(GetResourceUsages().renderPasses[nextRenderPassNumber]);
                    LazyClearRenderPassAttachments(cmd);
                    DAWN_TRY(ExecuteRenderPass(cmd));

                    nextRenderPassNumber++;
                    break;
                }

                case Command::CopyBufferToBuffer: {
                    CopyBufferToBufferCmd* copy = mCommands.NextCommand<CopyBufferToBufferCmd>();
                    if (copy->size == 0) {
                        // Skip no-op copies.
                        break;
                    }

                    ToBackend(copy->source)->EnsureDataInitialized();
                    ToBackend(copy->destination)
                        ->EnsureDataInitializedAsDestination(copy->destinationOffset, copy->size);

                    gl.BindBuffer(GL_PIXEL_PACK_BUFFER, ToBackend(copy->source)->GetHandle());
                    gl.BindBuffer(GL_PIXEL_UNPACK_BUFFER,
                                  ToBackend(copy->destination)->GetHandle());
                    gl.CopyBufferSubData(GL_PIXEL_PACK_BUFFER, GL_PIXEL_UNPACK_BUFFER,
                                         copy->sourceOffset, copy->destinationOffset, copy->size);

                    gl.BindBuffer(GL_PIXEL_PACK_BUFFER, 0);
                    gl.BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
                    break;
                }

                case Command::CopyBufferToTexture: {
                    CopyBufferToTextureCmd* copy = mCommands.NextCommand<CopyBufferToTextureCmd>();
                    if (copy->copySize.width == 0 || copy->copySize.height == 0 ||
                        copy->copySize.depthOrArrayLayers == 0) {
                        // Skip no-op copies.
                        continue;
                    }
                    auto& src = copy->source;
                    auto& dst = copy->destination;
                    Buffer* buffer = ToBackend(src.buffer.Get());

                    DAWN_INVALID_IF(
                        dst.aspect == Aspect::Stencil,
                        "Copies to stencil textures are unsupported on the OpenGL backend.");

                    ASSERT(dst.aspect == Aspect::Color);

                    buffer->EnsureDataInitialized();
                    SubresourceRange range = GetSubresourcesAffectedByCopy(dst, copy->copySize);
                    if (IsCompleteSubresourceCopiedTo(dst.texture.Get(), copy->copySize,
                                                      dst.mipLevel)) {
                        dst.texture->SetIsSubresourceContentInitialized(true, range);
                    } else {
                        ToBackend(dst.texture)->EnsureSubresourceContentInitialized(range);
                    }

                    gl.BindBuffer(GL_PIXEL_UNPACK_BUFFER, buffer->GetHandle());

                    TextureDataLayout dataLayout;
                    dataLayout.offset = 0;
                    dataLayout.bytesPerRow = src.bytesPerRow;
                    dataLayout.rowsPerImage = src.rowsPerImage;

                    DoTexSubImage(gl, dst, reinterpret_cast<void*>(src.offset), dataLayout,
                                  copy->copySize);
                    gl.BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
                    break;
                }

                case Command::CopyTextureToBuffer: {
                    CopyTextureToBufferCmd* copy = mCommands.NextCommand<CopyTextureToBufferCmd>();
                    if (copy->copySize.width == 0 || copy->copySize.height == 0 ||
                        copy->copySize.depthOrArrayLayers == 0) {
                        // Skip no-op copies.
                        continue;
                    }
                    auto& src = copy->source;
                    auto& dst = copy->destination;
                    auto& copySize = copy->copySize;
                    Texture* texture = ToBackend(src.texture.Get());
                    Buffer* buffer = ToBackend(dst.buffer.Get());
                    const Format& formatInfo = texture->GetFormat();
                    const GLFormat& format = texture->GetGLFormat();
                    GLenum target = texture->GetGLTarget();

                    // TODO(crbug.com/dawn/667): Implement validation in WebGPU/Compat to
                    // avoid this codepath. OpenGL does not support readback from non-renderable
                    // texture formats.
                    if (formatInfo.isCompressed ||
                        (TextureFormatIsSnorm(formatInfo.format) &&
                         GetDevice()->IsToggleEnabled(Toggle::DisableSnormRead))) {
                        UNREACHABLE();
                    }

                    buffer->EnsureDataInitializedAsDestination(copy);

                    ASSERT(texture->GetDimension() != wgpu::TextureDimension::e1D);
                    SubresourceRange subresources =
                        GetSubresourcesAffectedByCopy(src, copy->copySize);
                    texture->EnsureSubresourceContentInitialized(subresources);
                    // The only way to move data from a texture to a buffer in GL is via
                    // glReadPixels with a pack buffer. Create a temporary FBO for the copy.
                    gl.BindTexture(target, texture->GetHandle());

                    GLuint readFBO = 0;
                    gl.GenFramebuffers(1, &readFBO);
                    gl.BindFramebuffer(GL_READ_FRAMEBUFFER, readFBO);

                    const TexelBlockInfo& blockInfo = formatInfo.GetAspectInfo(src.aspect).block;

                    gl.BindBuffer(GL_PIXEL_PACK_BUFFER, buffer->GetHandle());
                    gl.PixelStorei(GL_PACK_ROW_LENGTH, dst.bytesPerRow / blockInfo.byteSize);

                    GLenum glAttachment;
                    GLenum glFormat;
                    GLenum glType;
                    switch (src.aspect) {
                        case Aspect::Color:
                            glAttachment = GL_COLOR_ATTACHMENT0;
                            glFormat = format.format;
                            glType = format.type;
                            break;
                        case Aspect::Depth:
                            glAttachment = GL_DEPTH_ATTACHMENT;
                            glFormat = GL_DEPTH_COMPONENT;
                            glType = GL_FLOAT;
                            break;
                        case Aspect::Stencil:
                            glAttachment = GL_STENCIL_ATTACHMENT;
                            glFormat = GL_STENCIL_INDEX;
                            glType = GL_UNSIGNED_BYTE;
                            break;

                        case Aspect::CombinedDepthStencil:
                        case Aspect::None:
                        case Aspect::Plane0:
                        case Aspect::Plane1:
                            UNREACHABLE();
                    }

                    uint8_t* offset =
                        reinterpret_cast<uint8_t*>(static_cast<uintptr_t>(dst.offset));
                    switch (texture->GetDimension()) {
                        case wgpu::TextureDimension::e2D: {
                            if (texture->GetArrayLayers() == 1) {
                                gl.FramebufferTexture2D(GL_READ_FRAMEBUFFER, glAttachment, target,
                                                        texture->GetHandle(), src.mipLevel);
                                gl.ReadPixels(src.origin.x, src.origin.y, copySize.width,
                                              copySize.height, glFormat, glType, offset);
                                break;
                            }
                            // Implementation for 2D array is the same as 3D.
                            [[fallthrough]];
                        }

                        case wgpu::TextureDimension::e3D: {
                            const uint64_t bytesPerImage = dst.bytesPerRow * dst.rowsPerImage;
                            for (uint32_t z = 0; z < copySize.depthOrArrayLayers; ++z) {
                                gl.FramebufferTextureLayer(GL_READ_FRAMEBUFFER, glAttachment,
                                                           texture->GetHandle(), src.mipLevel,
                                                           src.origin.z + z);
                                gl.ReadPixels(src.origin.x, src.origin.y, copySize.width,
                                              copySize.height, glFormat, glType, offset);

                                offset += bytesPerImage;
                            }
                            break;
                        }

                        case wgpu::TextureDimension::e1D:
                            UNREACHABLE();
                    }

                    gl.PixelStorei(GL_PACK_ROW_LENGTH, 0);

                    gl.BindBuffer(GL_PIXEL_PACK_BUFFER, 0);
                    gl.DeleteFramebuffers(1, &readFBO);
                    break;
                }

                case Command::CopyTextureToTexture: {
                    CopyTextureToTextureCmd* copy =
                        mCommands.NextCommand<CopyTextureToTextureCmd>();
                    if (copy->copySize.width == 0 || copy->copySize.height == 0 ||
                        copy->copySize.depthOrArrayLayers == 0) {
                        // Skip no-op copies.
                        continue;
                    }
                    auto& src = copy->source;
                    auto& dst = copy->destination;

                    // TODO(crbug.com/dawn/817): add workaround for the case that imageExtentSrc
                    // is not equal to imageExtentDst. For example when copySize fits in the virtual
                    // size of the source image but does not fit in the one of the destination
                    // image.
                    Extent3D copySize = ComputeTextureCopyExtent(dst, copy->copySize);
                    Texture* srcTexture = ToBackend(src.texture.Get());
                    Texture* dstTexture = ToBackend(dst.texture.Get());

                    SubresourceRange srcRange = GetSubresourcesAffectedByCopy(src, copy->copySize);
                    SubresourceRange dstRange = GetSubresourcesAffectedByCopy(dst, copy->copySize);

                    srcTexture->EnsureSubresourceContentInitialized(srcRange);
                    if (IsCompleteSubresourceCopiedTo(dstTexture, copySize, dst.mipLevel)) {
                        dstTexture->SetIsSubresourceContentInitialized(true, dstRange);
                    } else {
                        dstTexture->EnsureSubresourceContentInitialized(dstRange);
                    }
                    if (gl.IsAtLeastGL(4, 3) || gl.IsAtLeastGLES(3, 2)) {
                        gl.CopyImageSubData(srcTexture->GetHandle(), srcTexture->GetGLTarget(),
                                            src.mipLevel, src.origin.x, src.origin.y, src.origin.z,
                                            dstTexture->GetHandle(), dstTexture->GetGLTarget(),
                                            dst.mipLevel, dst.origin.x, dst.origin.y, dst.origin.z,
                                            copySize.width, copySize.height,
                                            copy->copySize.depthOrArrayLayers);
                    } else {
                        CopyTextureToTextureWithBlit(gl, src, dst, copySize);
                    }
                    break;
                }

                case Command::ClearBuffer: {
                    ClearBufferCmd* cmd = mCommands.NextCommand<ClearBufferCmd>();
                    if (cmd->size == 0) {
                        // Skip no-op fills.
                        break;
                    }
                    Buffer* dstBuffer = ToBackend(cmd->buffer.Get());

                    bool clearedToZero =
                        dstBuffer->EnsureDataInitializedAsDestination(cmd->offset, cmd->size);

                    if (!clearedToZero) {
                        const std::vector<uint8_t> clearValues(cmd->size, 0u);
                        gl.BindBuffer(GL_ARRAY_BUFFER, dstBuffer->GetHandle());
                        gl.BufferSubData(GL_ARRAY_BUFFER, cmd->offset, cmd->size,
                                         clearValues.data());
                    }

                    break;
                }

                case Command::ResolveQuerySet: {
                    // TODO(crbug.com/dawn/434): Resolve non-precise occlusion query.
                    SkipCommand(&mCommands, type);
                    break;
                }

                case Command::WriteTimestamp: {
                    return DAWN_UNIMPLEMENTED_ERROR("WriteTimestamp unimplemented");
                }

                case Command::InsertDebugMarker:
                case Command::PopDebugGroup:
                case Command::PushDebugGroup: {
                    // Due to lack of linux driver support for GL_EXT_debug_marker
                    // extension these functions are skipped.
                    SkipCommand(&mCommands, type);
                    break;
                }

                case Command::WriteBuffer: {
                    WriteBufferCmd* write = mCommands.NextCommand<WriteBufferCmd>();
                    uint64_t offset = write->offset;
                    uint64_t size = write->size;
                    if (size == 0) {
                        continue;
                    }

                    Buffer* dstBuffer = ToBackend(write->buffer.Get());
                    uint8_t* data = mCommands.NextData<uint8_t>(size);
                    dstBuffer->EnsureDataInitializedAsDestination(offset, size);

                    gl.BindBuffer(GL_ARRAY_BUFFER, dstBuffer->GetHandle());
                    gl.BufferSubData(GL_ARRAY_BUFFER, offset, size, data);
                    break;
                }

                default:
                    UNREACHABLE();
            }
        }

        return {};
    }

    MaybeError CommandBuffer::ExecuteComputePass() {
        const OpenGLFunctions& gl = ToBackend(GetDevice())->gl;
        ComputePipeline* lastPipeline = nullptr;
        BindGroupTracker bindGroupTracker = {};

        Command type;
        while (mCommands.NextCommandId(&type)) {
            switch (type) {
                case Command::EndComputePass: {
                    mCommands.NextCommand<EndComputePassCmd>();
                    return {};
                }

                case Command::Dispatch: {
                    DispatchCmd* dispatch = mCommands.NextCommand<DispatchCmd>();
                    bindGroupTracker.Apply(gl);

                    gl.DispatchCompute(dispatch->x, dispatch->y, dispatch->z);
                    gl.MemoryBarrier(GL_ALL_BARRIER_BITS);
                    break;
                }

                case Command::DispatchIndirect: {
                    DispatchIndirectCmd* dispatch = mCommands.NextCommand<DispatchIndirectCmd>();
                    bindGroupTracker.Apply(gl);

                    uint64_t indirectBufferOffset = dispatch->indirectOffset;
                    Buffer* indirectBuffer = ToBackend(dispatch->indirectBuffer.Get());

                    gl.BindBuffer(GL_DISPATCH_INDIRECT_BUFFER, indirectBuffer->GetHandle());
                    gl.DispatchComputeIndirect(static_cast<GLintptr>(indirectBufferOffset));
                    gl.MemoryBarrier(GL_ALL_BARRIER_BITS);
                    break;
                }

                case Command::SetComputePipeline: {
                    SetComputePipelineCmd* cmd = mCommands.NextCommand<SetComputePipelineCmd>();
                    lastPipeline = ToBackend(cmd->pipeline).Get();
                    lastPipeline->ApplyNow();

                    bindGroupTracker.OnSetPipeline(lastPipeline);
                    break;
                }

                case Command::SetBindGroup: {
                    SetBindGroupCmd* cmd = mCommands.NextCommand<SetBindGroupCmd>();
                    uint32_t* dynamicOffsets = nullptr;
                    if (cmd->dynamicOffsetCount > 0) {
                        dynamicOffsets = mCommands.NextData<uint32_t>(cmd->dynamicOffsetCount);
                    }
                    bindGroupTracker.OnSetBindGroup(cmd->index, cmd->group.Get(),
                                                    cmd->dynamicOffsetCount, dynamicOffsets);
                    break;
                }

                case Command::InsertDebugMarker:
                case Command::PopDebugGroup:
                case Command::PushDebugGroup: {
                    // Due to lack of linux driver support for GL_EXT_debug_marker
                    // extension these functions are skipped.
                    SkipCommand(&mCommands, type);
                    break;
                }

                case Command::WriteTimestamp: {
                    return DAWN_UNIMPLEMENTED_ERROR("WriteTimestamp unimplemented");
                }

                default:
                    UNREACHABLE();
            }
        }

        // EndComputePass should have been called
        UNREACHABLE();
    }

    MaybeError CommandBuffer::ExecuteRenderPass(BeginRenderPassCmd* renderPass) {
        const OpenGLFunctions& gl = ToBackend(GetDevice())->gl;
        GLuint fbo = 0;

        // Create the framebuffer used for this render pass and calls the correct glDrawBuffers
        {
            // TODO(kainino@chromium.org): This is added to possibly work around an issue seen on
            // Windows/Intel. It should break any feedback loop before the clears, even if there
            // shouldn't be any negative effects from this. Investigate whether it's actually
            // needed.
            gl.BindFramebuffer(GL_READ_FRAMEBUFFER, 0);
            // TODO(kainino@chromium.org): possible future optimization: create these framebuffers
            // at Framebuffer build time (or maybe CommandBuffer build time) so they don't have to
            // be created and destroyed at draw time.
            gl.GenFramebuffers(1, &fbo);
            gl.BindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);

            // Mapping from attachmentSlot to GL framebuffer attachment points. Defaults to zero
            // (GL_NONE).
            ityp::array<ColorAttachmentIndex, GLenum, kMaxColorAttachments> drawBuffers = {};

            // Construct GL framebuffer

            ColorAttachmentIndex attachmentCount(uint8_t(0));
            for (ColorAttachmentIndex i :
                 IterateBitSet(renderPass->attachmentState->GetColorAttachmentsMask())) {
                TextureViewBase* textureView = renderPass->colorAttachments[i].view.Get();
                GLuint texture = ToBackend(textureView->GetTexture())->GetHandle();

                GLenum glAttachment = GL_COLOR_ATTACHMENT0 + static_cast<uint8_t>(i);

                // Attach color buffers.
                if (textureView->GetTexture()->GetArrayLayers() == 1) {
                    GLenum target = ToBackend(textureView->GetTexture())->GetGLTarget();
                    gl.FramebufferTexture2D(GL_DRAW_FRAMEBUFFER, glAttachment, target, texture,
                                            textureView->GetBaseMipLevel());
                } else {
                    gl.FramebufferTextureLayer(GL_DRAW_FRAMEBUFFER, glAttachment, texture,
                                               textureView->GetBaseMipLevel(),
                                               textureView->GetBaseArrayLayer());
                }
                drawBuffers[i] = glAttachment;
                attachmentCount = i;
                attachmentCount++;
            }
            gl.DrawBuffers(static_cast<uint8_t>(attachmentCount), drawBuffers.data());

            if (renderPass->attachmentState->HasDepthStencilAttachment()) {
                TextureViewBase* textureView = renderPass->depthStencilAttachment.view.Get();
                GLuint texture = ToBackend(textureView->GetTexture())->GetHandle();
                const Format& format = textureView->GetTexture()->GetFormat();

                // Attach depth/stencil buffer.
                GLenum glAttachment = 0;
                if (format.aspects == (Aspect::Depth | Aspect::Stencil)) {
                    glAttachment = GL_DEPTH_STENCIL_ATTACHMENT;
                } else if (format.aspects == Aspect::Depth) {
                    glAttachment = GL_DEPTH_ATTACHMENT;
                } else if (format.aspects == Aspect::Stencil) {
                    glAttachment = GL_STENCIL_ATTACHMENT;
                } else {
                    UNREACHABLE();
                }

                if (textureView->GetTexture()->GetArrayLayers() == 1) {
                    GLenum target = ToBackend(textureView->GetTexture())->GetGLTarget();
                    gl.FramebufferTexture2D(GL_DRAW_FRAMEBUFFER, glAttachment, target, texture,
                                            textureView->GetBaseMipLevel());
                } else {
                    gl.FramebufferTextureLayer(GL_DRAW_FRAMEBUFFER, glAttachment, texture,
                                               textureView->GetBaseMipLevel(),
                                               textureView->GetBaseArrayLayer());
                }
            }
        }

        ASSERT(gl.CheckFramebufferStatus(GL_DRAW_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);

        // Set defaults for dynamic state before executing clears and commands.
        PersistentPipelineState persistentPipelineState;
        persistentPipelineState.SetDefaultState(gl);
        gl.BlendColor(0, 0, 0, 0);
        gl.Viewport(0, 0, renderPass->width, renderPass->height);
        gl.DepthRangef(0.0, 1.0);
        gl.Scissor(0, 0, renderPass->width, renderPass->height);

        // Clear framebuffer attachments as needed
        {
            for (ColorAttachmentIndex index :
                 IterateBitSet(renderPass->attachmentState->GetColorAttachmentsMask())) {
                uint8_t i = static_cast<uint8_t>(index);
                auto* attachmentInfo = &renderPass->colorAttachments[index];

                // Load op - color
                if (attachmentInfo->loadOp == wgpu::LoadOp::Clear) {
                    gl.ColorMask(true, true, true, true);

                    wgpu::TextureComponentType baseType =
                        attachmentInfo->view->GetFormat().GetAspectInfo(Aspect::Color).baseType;
                    switch (baseType) {
                        case wgpu::TextureComponentType::Float: {
                            const std::array<float, 4> appliedClearColor =
                                ConvertToFloatColor(attachmentInfo->clearColor);
                            gl.ClearBufferfv(GL_COLOR, i, appliedClearColor.data());
                            break;
                        }
                        case wgpu::TextureComponentType::Uint: {
                            const std::array<uint32_t, 4> appliedClearColor =
                                ConvertToUnsignedIntegerColor(attachmentInfo->clearColor);
                            gl.ClearBufferuiv(GL_COLOR, i, appliedClearColor.data());
                            break;
                        }
                        case wgpu::TextureComponentType::Sint: {
                            const std::array<int32_t, 4> appliedClearColor =
                                ConvertToSignedIntegerColor(attachmentInfo->clearColor);
                            gl.ClearBufferiv(GL_COLOR, i, appliedClearColor.data());
                            break;
                        }

                        case wgpu::TextureComponentType::DepthComparison:
                            UNREACHABLE();
                    }
                }

                if (attachmentInfo->storeOp == wgpu::StoreOp::Discard) {
                    // TODO(natlee@microsoft.com): call glDiscard to do optimization
                }
            }

            if (renderPass->attachmentState->HasDepthStencilAttachment()) {
                auto* attachmentInfo = &renderPass->depthStencilAttachment;
                const Format& attachmentFormat = attachmentInfo->view->GetTexture()->GetFormat();

                // Load op - depth/stencil
                bool doDepthClear = attachmentFormat.HasDepth() &&
                                    (attachmentInfo->depthLoadOp == wgpu::LoadOp::Clear);
                bool doStencilClear = attachmentFormat.HasStencil() &&
                                      (attachmentInfo->stencilLoadOp == wgpu::LoadOp::Clear);

                if (doDepthClear) {
                    gl.DepthMask(GL_TRUE);
                }
                if (doStencilClear) {
                    gl.StencilMask(GetStencilMaskFromStencilFormat(attachmentFormat.format));
                }

                if (doDepthClear && doStencilClear) {
                    gl.ClearBufferfi(GL_DEPTH_STENCIL, 0, attachmentInfo->clearDepth,
                                     attachmentInfo->clearStencil);
                } else if (doDepthClear) {
                    gl.ClearBufferfv(GL_DEPTH, 0, &attachmentInfo->clearDepth);
                } else if (doStencilClear) {
                    const GLint clearStencil = attachmentInfo->clearStencil;
                    gl.ClearBufferiv(GL_STENCIL, 0, &clearStencil);
                }
            }
        }

        RenderPipeline* lastPipeline = nullptr;
        uint64_t indexBufferBaseOffset = 0;
        GLenum indexBufferFormat;
        uint32_t indexFormatSize;

        VertexStateBufferBindingTracker vertexStateBufferBindingTracker;
        BindGroupTracker bindGroupTracker = {};

        auto DoRenderBundleCommand = [&](CommandIterator* iter, Command type) {
            switch (type) {
                case Command::Draw: {
                    DrawCmd* draw = iter->NextCommand<DrawCmd>();
                    vertexStateBufferBindingTracker.Apply(gl);
                    bindGroupTracker.Apply(gl);

                    if (draw->firstInstance > 0) {
                        gl.DrawArraysInstancedBaseInstance(
                            lastPipeline->GetGLPrimitiveTopology(), draw->firstVertex,
                            draw->vertexCount, draw->instanceCount, draw->firstInstance);
                    } else {
                        // This branch is only needed on OpenGL < 4.2
                        gl.DrawArraysInstanced(lastPipeline->GetGLPrimitiveTopology(),
                                               draw->firstVertex, draw->vertexCount,
                                               draw->instanceCount);
                    }
                    break;
                }

                case Command::DrawIndexed: {
                    DrawIndexedCmd* draw = iter->NextCommand<DrawIndexedCmd>();
                    vertexStateBufferBindingTracker.Apply(gl);
                    bindGroupTracker.Apply(gl);

                    if (draw->firstInstance > 0) {
                        gl.DrawElementsInstancedBaseVertexBaseInstance(
                            lastPipeline->GetGLPrimitiveTopology(), draw->indexCount,
                            indexBufferFormat,
                            reinterpret_cast<void*>(draw->firstIndex * indexFormatSize +
                                                    indexBufferBaseOffset),
                            draw->instanceCount, draw->baseVertex, draw->firstInstance);
                    } else {
                        // This branch is only needed on OpenGL < 4.2; ES < 3.2
                        if (draw->baseVertex != 0) {
                            gl.DrawElementsInstancedBaseVertex(
                                lastPipeline->GetGLPrimitiveTopology(), draw->indexCount,
                                indexBufferFormat,
                                reinterpret_cast<void*>(draw->firstIndex * indexFormatSize +
                                                        indexBufferBaseOffset),
                                draw->instanceCount, draw->baseVertex);
                        } else {
                            // This branch is only needed on OpenGL < 3.2; ES < 3.2
                            gl.DrawElementsInstanced(
                                lastPipeline->GetGLPrimitiveTopology(), draw->indexCount,
                                indexBufferFormat,
                                reinterpret_cast<void*>(draw->firstIndex * indexFormatSize +
                                                        indexBufferBaseOffset),
                                draw->instanceCount);
                        }
                    }
                    break;
                }

                case Command::DrawIndirect: {
                    DrawIndirectCmd* draw = iter->NextCommand<DrawIndirectCmd>();
                    vertexStateBufferBindingTracker.Apply(gl);
                    bindGroupTracker.Apply(gl);

                    uint64_t indirectBufferOffset = draw->indirectOffset;
                    Buffer* indirectBuffer = ToBackend(draw->indirectBuffer.Get());

                    gl.BindBuffer(GL_DRAW_INDIRECT_BUFFER, indirectBuffer->GetHandle());
                    gl.DrawArraysIndirect(
                        lastPipeline->GetGLPrimitiveTopology(),
                        reinterpret_cast<void*>(static_cast<intptr_t>(indirectBufferOffset)));
                    break;
                }

                case Command::DrawIndexedIndirect: {
                    DrawIndexedIndirectCmd* draw = iter->NextCommand<DrawIndexedIndirectCmd>();

                    vertexStateBufferBindingTracker.Apply(gl);
                    bindGroupTracker.Apply(gl);

                    Buffer* indirectBuffer = ToBackend(draw->indirectBuffer.Get());
                    ASSERT(indirectBuffer != nullptr);

                    gl.BindBuffer(GL_DRAW_INDIRECT_BUFFER, indirectBuffer->GetHandle());
                    gl.DrawElementsIndirect(
                        lastPipeline->GetGLPrimitiveTopology(), indexBufferFormat,
                        reinterpret_cast<void*>(static_cast<intptr_t>(draw->indirectOffset)));
                    break;
                }

                case Command::InsertDebugMarker:
                case Command::PopDebugGroup:
                case Command::PushDebugGroup: {
                    // Due to lack of linux driver support for GL_EXT_debug_marker
                    // extension these functions are skipped.
                    SkipCommand(iter, type);
                    break;
                }

                case Command::SetRenderPipeline: {
                    SetRenderPipelineCmd* cmd = iter->NextCommand<SetRenderPipelineCmd>();
                    lastPipeline = ToBackend(cmd->pipeline).Get();
                    lastPipeline->ApplyNow(persistentPipelineState);

                    vertexStateBufferBindingTracker.OnSetPipeline(lastPipeline);
                    bindGroupTracker.OnSetPipeline(lastPipeline);
                    break;
                }

                case Command::SetBindGroup: {
                    SetBindGroupCmd* cmd = iter->NextCommand<SetBindGroupCmd>();
                    uint32_t* dynamicOffsets = nullptr;
                    if (cmd->dynamicOffsetCount > 0) {
                        dynamicOffsets = iter->NextData<uint32_t>(cmd->dynamicOffsetCount);
                    }
                    bindGroupTracker.OnSetBindGroup(cmd->index, cmd->group.Get(),
                                                    cmd->dynamicOffsetCount, dynamicOffsets);
                    break;
                }

                case Command::SetIndexBuffer: {
                    SetIndexBufferCmd* cmd = iter->NextCommand<SetIndexBufferCmd>();

                    indexBufferBaseOffset = cmd->offset;
                    indexBufferFormat = IndexFormatType(cmd->format);
                    indexFormatSize = IndexFormatSize(cmd->format);
                    vertexStateBufferBindingTracker.OnSetIndexBuffer(cmd->buffer.Get());
                    break;
                }

                case Command::SetVertexBuffer: {
                    SetVertexBufferCmd* cmd = iter->NextCommand<SetVertexBufferCmd>();
                    vertexStateBufferBindingTracker.OnSetVertexBuffer(cmd->slot, cmd->buffer.Get(),
                                                                      cmd->offset);
                    break;
                }

                default:
                    UNREACHABLE();
                    break;
            }
        };

        Command type;
        while (mCommands.NextCommandId(&type)) {
            switch (type) {
                case Command::EndRenderPass: {
                    mCommands.NextCommand<EndRenderPassCmd>();

                    if (renderPass->attachmentState->GetSampleCount() > 1) {
                        ResolveMultisampledRenderTargets(gl, renderPass);
                    }
                    gl.DeleteFramebuffers(1, &fbo);
                    return {};
                }

                case Command::SetStencilReference: {
                    SetStencilReferenceCmd* cmd = mCommands.NextCommand<SetStencilReferenceCmd>();
                    persistentPipelineState.SetStencilReference(gl, cmd->reference);
                    break;
                }

                case Command::SetViewport: {
                    SetViewportCmd* cmd = mCommands.NextCommand<SetViewportCmd>();
                    if (gl.IsAtLeastGL(4, 1)) {
                        gl.ViewportIndexedf(0, cmd->x, cmd->y, cmd->width, cmd->height);
                    } else {
                        // Floating-point viewport coords are unsupported on OpenGL ES, but
                        // truncation is ok because other APIs do not guarantee subpixel precision
                        // either.
                        gl.Viewport(static_cast<int>(cmd->x), static_cast<int>(cmd->y),
                                    static_cast<int>(cmd->width), static_cast<int>(cmd->height));
                    }
                    gl.DepthRangef(cmd->minDepth, cmd->maxDepth);
                    break;
                }

                case Command::SetScissorRect: {
                    SetScissorRectCmd* cmd = mCommands.NextCommand<SetScissorRectCmd>();
                    gl.Scissor(cmd->x, cmd->y, cmd->width, cmd->height);
                    break;
                }

                case Command::SetBlendConstant: {
                    SetBlendConstantCmd* cmd = mCommands.NextCommand<SetBlendConstantCmd>();
                    const std::array<float, 4> blendColor = ConvertToFloatColor(cmd->color);
                    gl.BlendColor(blendColor[0], blendColor[1], blendColor[2], blendColor[3]);
                    break;
                }

                case Command::ExecuteBundles: {
                    ExecuteBundlesCmd* cmd = mCommands.NextCommand<ExecuteBundlesCmd>();
                    auto bundles = mCommands.NextData<Ref<RenderBundleBase>>(cmd->count);

                    for (uint32_t i = 0; i < cmd->count; ++i) {
                        CommandIterator* iter = bundles[i]->GetCommands();
                        iter->Reset();
                        while (iter->NextCommandId(&type)) {
                            DoRenderBundleCommand(iter, type);
                        }
                    }
                    break;
                }

                case Command::BeginOcclusionQuery: {
                    return DAWN_UNIMPLEMENTED_ERROR("BeginOcclusionQuery unimplemented.");
                }

                case Command::EndOcclusionQuery: {
                    return DAWN_UNIMPLEMENTED_ERROR("EndOcclusionQuery unimplemented.");
                }

                case Command::WriteTimestamp:
                    return DAWN_UNIMPLEMENTED_ERROR("WriteTimestamp unimplemented");

                default: {
                    DoRenderBundleCommand(&mCommands, type);
                    break;
                }
            }
        }

        // EndRenderPass should have been called
        UNREACHABLE();
    }

    void DoTexSubImage(const OpenGLFunctions& gl,
                       const TextureCopy& destination,
                       const void* data,
                       const TextureDataLayout& dataLayout,
                       const Extent3D& copySize) {
        Texture* texture = ToBackend(destination.texture.Get());
        ASSERT(texture->GetDimension() != wgpu::TextureDimension::e1D);

        const GLFormat& format = texture->GetGLFormat();
        GLenum target = texture->GetGLTarget();
        data = static_cast<const uint8_t*>(data) + dataLayout.offset;
        gl.ActiveTexture(GL_TEXTURE0);
        gl.BindTexture(target, texture->GetHandle());
        const TexelBlockInfo& blockInfo =
            texture->GetFormat().GetAspectInfo(destination.aspect).block;

        uint32_t x = destination.origin.x;
        uint32_t y = destination.origin.y;
        uint32_t z = destination.origin.z;
        if (texture->GetFormat().isCompressed) {
            size_t rowSize = copySize.width / blockInfo.width * blockInfo.byteSize;
            Extent3D virtSize = texture->GetMipLevelVirtualSize(destination.mipLevel);
            uint32_t width = std::min(copySize.width, virtSize.width - x);

            // In GLES glPixelStorei() doesn't affect CompressedTexSubImage*D() and
            // GL_UNPACK_COMPRESSED_BLOCK_* isn't defined, so we have to workaround
            // this limitation by copying the compressed texture data once per row.
            // See OpenGL ES 3.2 SPEC Chapter 8.4.1, "Pixel Storage Modes and Pixel
            // Buffer Objects" for more details. For Desktop GL, we use row-by-row
            // copies only for uploads where bytesPerRow is not a multiple of byteSize.
            if (dataLayout.bytesPerRow % blockInfo.byteSize == 0 && gl.GetVersion().IsDesktop()) {
                size_t imageSize =
                    rowSize * (copySize.height / blockInfo.height) * copySize.depthOrArrayLayers;

                uint32_t height = std::min(copySize.height, virtSize.height - y);

                gl.PixelStorei(GL_UNPACK_ROW_LENGTH,
                               dataLayout.bytesPerRow / blockInfo.byteSize * blockInfo.width);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_SIZE, blockInfo.byteSize);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_WIDTH, blockInfo.width);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_HEIGHT, blockInfo.height);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_DEPTH, 1);

                if (texture->GetArrayLayers() == 1 &&
                    texture->GetDimension() == wgpu::TextureDimension::e2D) {
                    gl.CompressedTexSubImage2D(target, destination.mipLevel, x, y, width, height,
                                               format.internalFormat, imageSize, data);
                } else {
                    gl.PixelStorei(GL_UNPACK_IMAGE_HEIGHT,
                                   dataLayout.rowsPerImage * blockInfo.height);
                    gl.CompressedTexSubImage3D(target, destination.mipLevel, x, y, z, width, height,
                                               copySize.depthOrArrayLayers, format.internalFormat,
                                               imageSize, data);
                    gl.PixelStorei(GL_UNPACK_IMAGE_HEIGHT, 0);
                }

                gl.PixelStorei(GL_UNPACK_ROW_LENGTH, 0);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_SIZE, 0);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_WIDTH, 0);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_HEIGHT, 0);
                gl.PixelStorei(GL_UNPACK_COMPRESSED_BLOCK_DEPTH, 0);
            } else {
                if (texture->GetArrayLayers() == 1 &&
                    texture->GetDimension() == wgpu::TextureDimension::e2D) {
                    const uint8_t* d = static_cast<const uint8_t*>(data);

                    for (; y < destination.origin.y + copySize.height; y += blockInfo.height) {
                        uint32_t height = std::min(blockInfo.height, virtSize.height - y);
                        gl.CompressedTexSubImage2D(target, destination.mipLevel, x, y, width,
                                                   height, format.internalFormat, rowSize, d);
                        d += dataLayout.bytesPerRow;
                    }
                } else {
                    const uint8_t* slice = static_cast<const uint8_t*>(data);

                    for (; z < destination.origin.z + copySize.depthOrArrayLayers; ++z) {
                        const uint8_t* d = slice;

                        for (y = destination.origin.y; y < destination.origin.y + copySize.height;
                             y += blockInfo.height) {
                            uint32_t height = std::min(blockInfo.height, virtSize.height - y);
                            gl.CompressedTexSubImage3D(target, destination.mipLevel, x, y, z, width,
                                                       height, 1, format.internalFormat, rowSize,
                                                       d);
                            d += dataLayout.bytesPerRow;
                        }

                        slice += dataLayout.rowsPerImage * dataLayout.bytesPerRow;
                    }
                }
            }
        } else {
            uint32_t width = copySize.width;
            uint32_t height = copySize.height;
            if (dataLayout.bytesPerRow % blockInfo.byteSize == 0) {
                gl.PixelStorei(GL_UNPACK_ROW_LENGTH,
                               dataLayout.bytesPerRow / blockInfo.byteSize * blockInfo.width);
                if (texture->GetArrayLayers() == 1 &&
                    texture->GetDimension() == wgpu::TextureDimension::e2D) {
                    gl.TexSubImage2D(target, destination.mipLevel, x, y, width, height,
                                     format.format, format.type, data);
                } else {
                    gl.PixelStorei(GL_UNPACK_IMAGE_HEIGHT,
                                   dataLayout.rowsPerImage * blockInfo.height);
                    gl.TexSubImage3D(target, destination.mipLevel, x, y, z, width, height,
                                     copySize.depthOrArrayLayers, format.format, format.type, data);
                    gl.PixelStorei(GL_UNPACK_IMAGE_HEIGHT, 0);
                }
                gl.PixelStorei(GL_UNPACK_ROW_LENGTH, 0);
            } else {
                if (texture->GetArrayLayers() == 1 &&
                    texture->GetDimension() == wgpu::TextureDimension::e2D) {
                    const uint8_t* d = static_cast<const uint8_t*>(data);
                    for (; y < destination.origin.y + height; ++y) {
                        gl.TexSubImage2D(target, destination.mipLevel, x, y, width, 1,
                                         format.format, format.type, d);
                        d += dataLayout.bytesPerRow;
                    }
                } else {
                    const uint8_t* slice = static_cast<const uint8_t*>(data);
                    for (; z < destination.origin.z + copySize.depthOrArrayLayers; ++z) {
                        const uint8_t* d = slice;
                        for (y = destination.origin.y; y < destination.origin.y + height; ++y) {
                            gl.TexSubImage3D(target, destination.mipLevel, x, y, z, width, 1, 1,
                                             format.format, format.type, d);
                            d += dataLayout.bytesPerRow;
                        }
                        slice += dataLayout.rowsPerImage * dataLayout.bytesPerRow;
                    }
                }
            }
        }
    }

}  // namespace dawn::native::opengl