如何为C#应用添加iPhone屏幕适配支持？

问题背景 #

我开发的C#应用在Windows、Linux和Mac系统上运行正常，但在iOS设备上界面无法适配。已尝试修复部分驱动但未解决问题，核心渲染代码如下：

public unsafe void Run(int currentFrameIndex, int imageIndex, Semaphore waitSemaphore, Semaphore signalSemaphore, Fence signal)
{
    var bufferInfo = new DescriptorBufferInfo(_commandBuffers[currentFrameIndex], 0, (ulong)(sizeof(uint) * _commandBufferCapacities[currentFrameIndex]));

    _vk.UpdateDescriptorSets(_device, 1,
                             new WriteDescriptorSet(dstSet: _targetDescriptorSets[currentFrameIndex], dstBinding: 1, dstArrayElement: 0,
                                                    descriptorCount: 1, descriptorType: DescriptorType.StorageBuffer, pBufferInfo: &bufferInfo), 0,
                             null);

    var currentFrame = _frames[currentFrameIndex];

    _vk.ResetCommandPool(_device, currentFrame.CommandPool, 0).ThrowCode();
    _vk.AllocateCommandBuffers(_device,
                               new CommandBufferAllocateInfo(commandPool: currentFrame.CommandPool, level: CommandBufferLevel.Primary,
                                                             commandBufferCount: 1), out var commandBuffer).ThrowCode();

    Name(ObjectType.CommandBuffer, (ulong)commandBuffer.Handle, $"Command Buffer Frame {currentFrameIndex}");

    var renderContext = new RenderContext(_targetImageViews[imageIndex],
                                          _targetSize, currentFrameIndex);

    _vk.BeginCommandBuffer(commandBuffer,
                          new CommandBufferBeginInfo(flags: CommandBufferUsageFlags.CommandBufferUsageOneTimeSubmitBit))
    .ThrowCode();

    // var memoryBarrier = new ImageMemoryBarrier2KHR(srcStageMask: PipelineStageFlags2KHR.PipelineStage2TopOfPipeBitKhr,
    //     srcAccessMask: AccessFlags2KHR.Access2NoneKhr, dstStageMask: PipelineStageFlags2KHR.PipelineStage2TransferBitKhr,
    //     dstAccessMask: AccessFlags2KHR.Access2TransferWriteBitKhr,
    //     oldLayout: ImageLayout.Undefined, newLayout: ImageLayout.TransferDstOptimal,
    //     srcQueueFamilyIndex: Vk.QueueFamilyIgnored, dstQueueFamilyIndex: Vk.QueueFamilyIgnored,
    //     image: _targetImages.Span[imageIndex], subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1),
    //     sType: StructureType.ImageMemoryBarrier2Khr, pNext: null);
    // _khrSynchronization2.CmdPipelineBarrier2(commandBuffer, new DependencyInfoKHR(imageMemoryBarrierCount: 1,
    //     pImageMemoryBarriers: &memoryBarrier, dependencyFlags: 0, memoryBarrierCount: 0, pMemoryBarriers: null, bufferMemoryBarrierCount: 0, pBufferMemoryBarriers: null));

    _vk.CmdPipelineBarrier(commandBuffer, PipelineStageFlags.PipelineStageTopOfPipeBit,
                           PipelineStageFlags.PipelineStageTransferBit, 0, 0, null, 0, null, 1,
                           new ImageMemoryBarrier(srcAccessMask: AccessFlags.AccessNoneKhr,
                                                  dstAccessMask: AccessFlags.AccessTransferWriteBit, oldLayout: ImageLayout.Undefined,
                                                  newLayout: ImageLayout.TransferDstOptimal, srcQueueFamilyIndex: Vk.QueueFamilyIgnored,
                                                  dstQueueFamilyIndex: Vk.QueueFamilyIgnored, image: _targetImages.Span[imageIndex],
                                                  subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1)));

    _vk.CmdClearColorImage(commandBuffer, _targetImages.Span[imageIndex], ImageLayout.TransferDstOptimal,
                           new ClearColorValue(0f, 0f, 0f, 1f), 1,
                           new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1));

    // var memoryBarrier2 = new ImageMemoryBarrier2KHR(srcStageMask: PipelineStageFlags2KHR.PipelineStage2TransferBitKhr,
    //     srcAccessMask: AccessFlags2KHR.Access2TransferWriteBitKhr, dstStageMask: PipelineStageFlags2KHR.PipelineStage2ComputeShaderBitKhr,
    //     dstAccessMask: AccessFlags2KHR.Access2ShaderReadBitKhr | AccessFlags2KHR.Access2ShaderWriteBitKhr,
    //     oldLayout: ImageLayout.TransferDstOptimal, newLayout: ImageLayout.General,
    //     srcQueueFamilyIndex: Vk.QueueFamilyIgnored, dstQueueFamilyIndex: Vk.QueueFamilyIgnored,
    //     image: _targetImages.Span[imageIndex], subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1));
    // _khrSynchronization2.CmdPipelineBarrier2(commandBuffer, new DependencyInfoKHR(imageMemoryBarrierCount: 1,
    //     pImageMemoryBarriers: &memoryBarrier2));

    _vk.CmdPipelineBarrier(commandBuffer, PipelineStageFlags.PipelineStageTransferBit,
                           PipelineStageFlags.PipelineStageComputeShaderBit, 0, 0, null, 0, null, 1,
                           new ImageMemoryBarrier(srcAccessMask: AccessFlags.AccessTransferWriteBit,
                                                  dstAccessMask: AccessFlags.AccessShaderReadBit | AccessFlags.AccessShaderWriteBit, oldLayout: ImageLayout.TransferDstOptimal,
                                                  newLayout: ImageLayout.General, srcQueueFamilyIndex: Vk.QueueFamilyIgnored,
                                                  dstQueueFamilyIndex: Vk.QueueFamilyIgnored, image: _targetImages.Span[imageIndex],
                                                  subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1)));

    Span <uint> pValues = stackalloc uint[]
    {
        _targetSize.X, _targetSize.Y
    };

    _vk.CmdPushConstants(commandBuffer, _pipelineLayout, ShaderStageFlags.ShaderStageComputeBit, 0, (uint)pValues.Length * sizeof(uint), pValues);
    _vk.CmdBindDescriptorSets(commandBuffer, PipelineBindPoint.Compute, _pipelineLayout, 0, 1,
                              _targetDescriptorSets[imageIndex], 0, null);
    _computeShader.Record(renderContext, commandBuffer);

    // var memoryBarrier3 = new ImageMemoryBarrier2KHR(srcStageMask: PipelineStageFlags2KHR.PipelineStage2ComputeShaderBitKhr,
    //      srcAccessMask: AccessFlags2KHR.Access2ShaderReadBitKhr | AccessFlags2KHR.Access2ShaderWriteBitKhr, dstStageMask: PipelineStageFlags2KHR.PipelineStage2BottomOfPipeBitKhr,
    //      dstAccessMask: AccessFlags2KHR.Access2NoneKhr,
    //      oldLayout: ImageLayout.General, newLayout: ImageLayout.PresentSrcKhr,
    //      srcQueueFamilyIndex: Vk.QueueFamilyIgnored, dstQueueFamilyIndex: Vk.QueueFamilyIgnored,
    //      image: _targetImages.Span[imageIndex], subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1));
    //  _khrSynchronization2.CmdPipelineBarrier2(commandBuffer, new DependencyInfoKHR(imageMemoryBarrierCount: 1,
    //      pImageMemoryBarriers: &memoryBarrier3));

    _vk.CmdPipelineBarrier(commandBuffer, PipelineStageFlags.PipelineStageComputeShaderBit,
                           PipelineStageFlags.PipelineStageBottomOfPipeBit, 0, 0, null, 0, null, 1,
                           new ImageMemoryBarrier(srcAccessMask: AccessFlags.AccessShaderReadBit | AccessFlags.AccessShaderWriteBit,
                                                  dstAccessMask: AccessFlags.AccessNoneKhr, oldLayout: ImageLayout.General,
                                                  newLayout: ImageLayout.PresentSrcKhr, srcQueueFamilyIndex: Vk.QueueFamilyIgnored,
                                                  dstQueueFamilyIndex: Vk.QueueFamilyIgnored, image: _targetImages.Span[imageIndex],
                                                  subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1)));

    _vk.EndCommandBuffer(commandBuffer);

    var waitDstStageMask = PipelineStageFlags.PipelineStageTransferBit;

    _vk.QueueSubmit(Queue, 1,
                    new SubmitInfo(waitSemaphoreCount: 1, pWaitSemaphores: &waitSemaphore, commandBufferCount: 1,
                                   pCommandBuffers: &commandBuffer, signalSemaphoreCount: 1, pSignalSemaphores: &signalSemaphore,
                                   pWaitDstStageMask: &waitDstStageMask), signal).ThrowCode();
}

针对性修复方案 #

1. 修复描述符集绑定的帧索引不匹配问题 #

代码中UpdateDescriptorSets使用currentFrameIndex更新描述符集，但后续CmdBindDescriptorSets错误绑定了imageIndex对应的集合，iOS帧同步模型对资源匹配要求更严格，需改为：

_vk.CmdBindDescriptorSets(commandBuffer, PipelineBindPoint.Compute, _pipelineLayout, 0, 1,
                          _targetDescriptorSets[currentFrameIndex], 0, null);

2. 替换Present阶段的内存屏障目标阶段 #

iOS的MoltenVK对PipelineStageBottomOfPipeBit的同步支持存在兼容性问题，需将最后的内存屏障目标阶段改为PipelineStagePresentBitKHR，确保渲染结果正确提交到显示队列：

_vk.CmdPipelineBarrier(commandBuffer, PipelineStageFlags.PipelineStageComputeShaderBit,
                       PipelineStageFlags.PipelineStagePresentBitKHR, 0, 0, null, 0, null, 1,
                       new ImageMemoryBarrier(srcAccessMask: AccessFlags.AccessShaderReadBit | AccessFlags.AccessShaderWriteBit,
                                              dstAccessMask: AccessFlags.AccessNoneKhr, oldLayout: ImageLayout.General,
                                              newLayout: ImageLayout.PresentSrcKhr, srcQueueFamilyIndex: Vk.QueueFamilyIgnored,
                                              dstQueueFamilyIndex: Vk.QueueFamilyIgnored, image: _targetImages.Span[imageIndex],
                                              subresourceRange: new ImageSubresourceRange(ImageAspectFlags.ImageAspectColorBit, 0, 1, 0, 1)));

3. 启用KHR_synchronization2扩展同步机制 #

注释中的新版同步代码更符合Vulkan规范，MoltenVK对新版同步的兼容性更好，需：

• 确保项目已启用KHR_synchronization2扩展
• 移除所有旧版CmdPipelineBarrier代码，替换为注释中的CmdPipelineBarrier2实现

4. 修正目标尺寸的Retina适配 #

iOS设备使用Retina屏幕，逻辑像素与物理像素存在缩放比，需确保_targetSize使用物理像素尺寸：

// 通过平台API获取屏幕缩放因子，例如从UIKit的UIScreen.MainScreen.Scale获取
float scaleFactor = GetIOSScreenScale();
_targetSize = new Size((uint)(logicalSize.X * scaleFactor), (uint)(logicalSize.Y * scaleFactor));

5. 调整QueueSubmit的等待阶段 #

当前waitDstStageMask设置为PipelineStageTransferBit，但实际需要等待计算着色器执行完成，改为PipelineStageComputeShaderBit确保同步逻辑正确：

var waitDstStageMask = PipelineStageFlags.PipelineStageComputeShaderBit;

内容的提问来源于stack exchange，提问作者MaxiEri