// Welcome to the triangle example!
//
// This is the only example that is entirely detailed. All the other examples avoid code
// duplication by using helper functions.
//
// This example assumes that you are already more or less familiar with graphics programming and
// that you want to learn Vulkan. This means that for example it won't go into details about what a
// vertex or a shader is.
//
// This version of the triangle example is written using dynamic rendering instead of render pass
// and framebuffer objects. If your device does not support Vulkan 1.3 or the
// `khr_dynamic_rendering` extension, or if you want to see how to support older versions, see the
// original triangle example.

use std::{error::Error, sync::Arc};
use vulkano::{
    buffer::{Buffer, BufferContents, BufferCreateInfo, BufferUsage, Subbuffer},
    command_buffer::{
        allocator::StandardCommandBufferAllocator, CommandBufferBeginInfo, CommandBufferLevel,
        CommandBufferUsage, RecordingCommandBuffer, RenderingAttachmentInfo, RenderingInfo,
    },
    device::{
        physical::PhysicalDeviceType, Device, DeviceCreateInfo, DeviceExtensions, DeviceFeatures,
        Queue, QueueCreateInfo, QueueFlags,
    },
    image::{view::ImageView, Image, ImageUsage},
    instance::{Instance, InstanceCreateFlags, InstanceCreateInfo},
    memory::allocator::{AllocationCreateInfo, MemoryTypeFilter, StandardMemoryAllocator},
    pipeline::{
        graphics::{
            color_blend::{ColorBlendAttachmentState, ColorBlendState},
            input_assembly::InputAssemblyState,
            multisample::MultisampleState,
            rasterization::RasterizationState,
            subpass::PipelineRenderingCreateInfo,
            vertex_input::{Vertex, VertexDefinition},
            viewport::{Viewport, ViewportState},
            GraphicsPipelineCreateInfo,
        },
        layout::PipelineDescriptorSetLayoutCreateInfo,
        DynamicState, GraphicsPipeline, PipelineLayout, PipelineShaderStageCreateInfo,
    },
    render_pass::{AttachmentLoadOp, AttachmentStoreOp},
    swapchain::{
        acquire_next_image, Surface, Swapchain, SwapchainCreateInfo, SwapchainPresentInfo,
    },
    sync::{self, GpuFuture},
    Validated, Version, VulkanError, VulkanLibrary,
};
use winit::{
    application::ApplicationHandler,
    event::WindowEvent,
    event_loop::{ActiveEventLoop, EventLoop},
    window::{Window, WindowId},
};

fn main() -> Result<(), impl Error> {
    let event_loop = EventLoop::new().unwrap();
    let mut app = App::new(&event_loop);

    event_loop.run_app(&mut app)
}

struct App {
    instance: Arc<Instance>,
    device: Arc<Device>,
    queue: Arc<Queue>,
    command_buffer_allocator: Arc<StandardCommandBufferAllocator>,
    vertex_buffer: Subbuffer<[MyVertex]>,
    rcx: Option<RenderContext>,
}

struct RenderContext {
    window: Arc<Window>,
    swapchain: Arc<Swapchain>,
    attachment_image_views: Vec<Arc<ImageView>>,
    pipeline: Arc<GraphicsPipeline>,
    viewport: Viewport,
    recreate_swapchain: bool,
    previous_frame_end: Option<Box<dyn GpuFuture>>,
}

impl App {
    fn new(event_loop: &EventLoop<()>) -> Self {
        let library = VulkanLibrary::new().unwrap();

        // The first step of any Vulkan program is to create an instance.
        //
        // When we create an instance, we have to pass a list of extensions that we want to enable.
        //
        // All the window-drawing functionalities are part of non-core extensions that we need to
        // enable manually. To do so, we ask `Surface` for the list of extensions required to draw
        // to a window.
        let required_extensions = Surface::required_extensions(event_loop).unwrap();

        // Now creating the instance.
        let instance = Instance::new(
            library,
            InstanceCreateInfo {
                // Enable enumerating devices that use non-conformant Vulkan implementations.
                // (e.g. MoltenVK)
                flags: InstanceCreateFlags::ENUMERATE_PORTABILITY,
                enabled_extensions: required_extensions,
                ..Default::default()
            },
        )
        .unwrap();

        // Choose device extensions that we're going to use. In order to present images to a
        // surface, we need a `Swapchain`, which is provided by the `khr_swapchain` extension.
        let mut device_extensions = DeviceExtensions {
            khr_swapchain: true,
            ..DeviceExtensions::empty()
        };

        // We then choose which physical device to use. First, we enumerate all the available
        // physical devices, then apply filters to narrow them down to those that can support our
        // needs.
        let (physical_device, queue_family_index) = instance
            .enumerate_physical_devices()
            .unwrap()
            .filter(|p| {
                // For this example, we require at least Vulkan 1.3, or a device that has the
                // `khr_dynamic_rendering` extension available.
                p.api_version() >= Version::V1_3 || p.supported_extensions().khr_dynamic_rendering
            })
            .filter(|p| {
                // Some devices may not support the extensions or features that your application,
                // or report properties and limits that are not sufficient for your application.
                // These should be filtered out here.
                p.supported_extensions().contains(&device_extensions)
            })
            .filter_map(|p| {
                // For each physical device, we try to find a suitable queue family that will
                // execute our draw commands.
                //
                // Devices can provide multiple queues to run commands in parallel (for example a
                // draw queue and a compute queue), similar to CPU threads. This is something you
                // have to have to manage manually in Vulkan. Queues of the same type belong to the
                // same queue family.
                //
                // Here, we look for a single queue family that is suitable for our purposes. In a
                // real-world application, you may want to use a separate dedicated transfer queue
                // to handle data transfers in parallel with graphics operations. You may also need
                // a separate queue for compute operations, if your application uses those.
                p.queue_family_properties()
                    .iter()
                    .enumerate()
                    .position(|(i, q)| {
                        // We select a queue family that supports graphics operations. When drawing
                        // to a window surface, as we do in this example, we also need to check
                        // that queues in this queue family are capable of presenting images to the
                        // surface.
                        q.queue_flags.intersects(QueueFlags::GRAPHICS)
                            && p.presentation_support(i as u32, event_loop).unwrap()
                    })
                    // The code here searches for the first queue family that is suitable. If none
                    // is found, `None` is returned to `filter_map`, which disqualifies this
                    // physical device.
                    .map(|i| (p, i as u32))
            })
            // All the physical devices that pass the filters above are suitable for the
            // application. However, not every device is equal, some are preferred over others.
            // Now, we assign each physical device a score, and pick the device with the lowest
            // ("best") score.
            //
            // In this example, we simply select the best-scoring device to use in the application.
            // In a real-world setting, you may want to use the best-scoring device only as a
            // "default" or "recommended" device, and let the user choose the device themself.
            .min_by_key(|(p, _)| {
                // We assign a lower score to device types that are likely to be faster/better.
                match p.properties().device_type {
                    PhysicalDeviceType::DiscreteGpu => 0,
                    PhysicalDeviceType::IntegratedGpu => 1,
                    PhysicalDeviceType::VirtualGpu => 2,
                    PhysicalDeviceType::Cpu => 3,
                    PhysicalDeviceType::Other => 4,
                    _ => 5,
                }
            })
            .expect("no suitable physical device found");

        // Some little debug infos.
        println!(
            "Using device: {} (type: {:?})",
            physical_device.properties().device_name,
            physical_device.properties().device_type,
        );

        // If the selected device doesn't have Vulkan 1.3 available, then we need to enable the
        // `khr_dynamic_rendering` extension manually. This extension became a core part of Vulkan
        // in version 1.3 and later, so it's always available then and it does not need to be
        // enabled. We can be sure that this extension will be available on the selected physical
        // device, because we filtered out unsuitable devices in the device selection code above.
        if physical_device.api_version() < Version::V1_3 {
            device_extensions.khr_dynamic_rendering = true;
        }

        // Now initializing the device. This is probably the most important object of Vulkan.
        //
        // An iterator of created queues is returned by the function alongside the device.
        let (device, mut queues) = Device::new(
            // Which physical device to connect to.
            physical_device,
            DeviceCreateInfo {
                // The list of queues that we are going to use. Here we only use one queue, from
                // the previously chosen queue family.
                queue_create_infos: vec![QueueCreateInfo {
                    queue_family_index,
                    ..Default::default()
                }],

                // A list of optional features and extensions that our program needs to work
                // correctly. Some parts of the Vulkan specs are optional and must be enabled
                // manually at device creation. In this example the only things we are going to
                // need are the `khr_swapchain` extension that allows us to draw to a window, and
                // `khr_dynamic_rendering` if we don't have Vulkan 1.3 available.
                enabled_extensions: device_extensions,

                // In order to render with Vulkan 1.3's dynamic rendering, we need to enable it
                // here. Otherwise, we are only allowed to render with a render pass object, as in
                // the standard triangle example. The feature is required to be supported by the
                // device if it supports Vulkan 1.3 and higher, or if the `khr_dynamic_rendering`
                // extension is available, so we don't need to check for support.
                enabled_features: DeviceFeatures {
                    dynamic_rendering: true,
                    ..DeviceFeatures::empty()
                },

                ..Default::default()
            },
        )
        .unwrap();

        // Since we can request multiple queues, the `queues` variable is in fact an iterator. We
        // only use one queue in this example, so we just retrieve the first and only element of
        // the iterator.
        let queue = queues.next().unwrap();

        let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));

        // Before we can start creating and recording command buffers, we need a way of allocating
        // them. Vulkano provides a command buffer allocator, which manages raw Vulkan command
        // pools underneath and provides a safe interface for them.
        let command_buffer_allocator = Arc::new(StandardCommandBufferAllocator::new(
            device.clone(),
            Default::default(),
        ));

        // We now create a buffer that will store the shape of our triangle.
        let vertices = [
            MyVertex {
                position: [-0.5, -0.25],
            },
            MyVertex {
                position: [0.0, 0.5],
            },
            MyVertex {
                position: [0.25, -0.1],
            },
        ];
        let vertex_buffer = Buffer::from_iter(
            memory_allocator,
            BufferCreateInfo {
                usage: BufferUsage::VERTEX_BUFFER,
                ..Default::default()
            },
            AllocationCreateInfo {
                memory_type_filter: MemoryTypeFilter::PREFER_DEVICE
                    | MemoryTypeFilter::HOST_SEQUENTIAL_WRITE,
                ..Default::default()
            },
            vertices,
        )
        .unwrap();

        App {
            instance,
            device,
            queue,
            command_buffer_allocator,
            vertex_buffer,
            rcx: None,
        }
    }
}

impl ApplicationHandler for App {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        // The objective of this example is to draw a triangle on a window. To do so, we first need
        // to create the window. We use the `WindowBuilder` from the `winit` crate to do that here.
        //
        // Before we can render to a window, we must first create a `vulkano::swapchain::Surface`
        // object from it, which represents the drawable surface of a window. For that we must wrap
        // the `winit::window::Window` in an `Arc`.
        let window = Arc::new(
            event_loop
                .create_window(Window::default_attributes())
                .unwrap(),
        );
        let surface = Surface::from_window(self.instance.clone(), window.clone()).unwrap();
        let window_size = window.inner_size();

        // Before we can draw on the surface, we have to create what is called a swapchain.
        // Creating a swapchain allocates the color buffers that will contain the image that will
        // ultimately be visible on the screen. These images are returned alongside the swapchain.
        let (swapchain, images) = {
            // Querying the capabilities of the surface. When we create the swapchain we can only
            // pass values that are allowed by the capabilities.
            let surface_capabilities = self
                .device
                .physical_device()
                .surface_capabilities(&surface, Default::default())
                .unwrap();

            // Choosing the internal format that the images will have.
            let (image_format, _) = self
                .device
                .physical_device()
                .surface_formats(&surface, Default::default())
                .unwrap()[0];

            // Please take a look at the docs for the meaning of the parameters we didn't mention.
            Swapchain::new(
                self.device.clone(),
                surface,
                SwapchainCreateInfo {
                    // Some drivers report an `min_image_count` of 1, but fullscreen mode requires
                    // at least 2. Therefore we must ensure the count is at least 2, otherwise the
                    // program would crash when entering fullscreen mode on those drivers.
                    min_image_count: surface_capabilities.min_image_count.max(2),

                    image_format,

                    // The size of the window, only used to initially setup the swapchain.
                    //
                    // NOTE:
                    // On some drivers the swapchain extent is specified by
                    // `surface_capabilities.current_extent` and the swapchain size must use this
                    // extent. This extent is always the same as the window size.
                    //
                    // However, other drivers don't specify a value, i.e.
                    // `surface_capabilities.current_extent` is `None`. These drivers will allow
                    // anything, but the only sensible value is the window size.
                    //
                    // Both of these cases need the swapchain to use the window size, so we just
                    // use that.
                    image_extent: window_size.into(),

                    image_usage: ImageUsage::COLOR_ATTACHMENT,

                    // The alpha mode indicates how the alpha value of the final image will behave.
                    // For example, you can choose whether the window will be opaque or
                    // transparent.
                    composite_alpha: surface_capabilities
                        .supported_composite_alpha
                        .into_iter()
                        .next()
                        .unwrap(),

                    ..Default::default()
                },
            )
            .unwrap()
        };

        // When creating the swapchain, we only created plain images. To use them as an attachment
        // for rendering, we must wrap then in an image view.
        //
        // Since we need to draw to multiple images, we are going to create a different image view
        // for each image.
        let attachment_image_views = window_size_dependent_setup(&images);

        // The next step is to create the shaders.
        //
        // The raw shader creation API provided by the vulkano library is unsafe for various
        // reasons, so The `shader!` macro provides a way to generate a Rust module from GLSL
        // source - in the example below, the source is provided as a string input directly to the
        // shader, but a path to a source file can be provided as well. Note that the user must
        // specify the type of shader (e.g. "vertex", "fragment", etc.) using the `ty` option of
        // the macro.
        //
        // The items generated by the `shader!` macro include a `load` function which loads the
        // shader using an input logical device. The module also includes type definitions for
        // layout structures defined in the shader source, for example uniforms and push constants.
        //
        // A more detailed overview of what the `shader!` macro generates can be found in the
        // vulkano-shaders crate docs. You can view them at https://docs.rs/vulkano-shaders/
        mod vs {
            vulkano_shaders::shader! {
                ty: "vertex",
                src: r"
                    #version 450

                    layout(location = 0) in vec2 position;

                    void main() {
                        gl_Position = vec4(position, 0.0, 1.0);
                    }
                ",
            }
        }

        mod fs {
            vulkano_shaders::shader! {
                ty: "fragment",
                src: r"
                    #version 450

                    layout(location = 0) out vec4 f_color;

                    void main() {
                        f_color = vec4(1.0, 0.0, 0.0, 1.0);
                    }
                ",
            }
        }

        // Before we draw, we have to create what is called a **pipeline**. A pipeline describes
        // how a GPU operation is to be performed. It is similar to an OpenGL program, but it also
        // contains many settings for customization, all baked into a single object. For drawing,
        // we create a **graphics** pipeline, but there are also other types of pipeline.
        let pipeline = {
            // First, we load the shaders that the pipeline will use: the vertex shader and the
            // fragment shader.
            //
            // A Vulkan shader can in theory contain multiple entry points, so we have to specify
            // which one.
            let vs = vs::load(self.device.clone())
                .unwrap()
                .entry_point("main")
                .unwrap();
            let fs = fs::load(self.device.clone())
                .unwrap()
                .entry_point("main")
                .unwrap();

            // Automatically generate a vertex input state from the vertex shader's input
            // interface, that takes a single vertex buffer containing `Vertex` structs.
            let vertex_input_state = MyVertex::per_vertex().definition(&vs).unwrap();

            // Make a list of the shader stages that the pipeline will have.
            let stages = [
                PipelineShaderStageCreateInfo::new(vs),
                PipelineShaderStageCreateInfo::new(fs),
            ];

            // We must now create a **pipeline layout** object, which describes the locations and
            // types of descriptor sets and push constants used by the shaders in the pipeline.
            //
            // Multiple pipelines can share a common layout object, which is more efficient. The
            // shaders in a pipeline must use a subset of the resources described in its pipeline
            // layout, but the pipeline layout is allowed to contain resources that are not present
            // in the shaders; they can be used by shaders in other pipelines that share the same
            // layout. Thus, it is a good idea to design shaders so that many pipelines have common
            // resource locations, which allows them to share pipeline layouts.
            let layout = PipelineLayout::new(
                self.device.clone(),
                // Since we only have one pipeline in this example, and thus one pipeline layout,
                // we automatically generate the creation info for it from the resources used in
                // the shaders. In a real application, you would specify this information manually
                // so that you can re-use one layout in multiple pipelines.
                PipelineDescriptorSetLayoutCreateInfo::from_stages(&stages)
                    .into_pipeline_layout_create_info(self.device.clone())
                    .unwrap(),
            )
            .unwrap();

            // We describe the formats of attachment images where the colors, depth and/or stencil
            // information will be written. The pipeline will only be usable with this particular
            // configuration of the attachment images.
            let subpass = PipelineRenderingCreateInfo {
                // We specify a single color attachment that will be rendered to. When we begin
                // rendering, we will specify a swapchain image to be used as this attachment, so
                // here we set its format to be the same format as the swapchain.
                color_attachment_formats: vec![Some(swapchain.image_format())],
                ..Default::default()
            };

            // Finally, create the pipeline.
            GraphicsPipeline::new(
                self.device.clone(),
                None,
                GraphicsPipelineCreateInfo {
                    stages: stages.into_iter().collect(),
                    // How vertex data is read from the vertex buffers into the vertex shader.
                    vertex_input_state: Some(vertex_input_state),
                    // How vertices are arranged into primitive shapes. The default primitive shape
                    // is a triangle.
                    input_assembly_state: Some(InputAssemblyState::default()),
                    // How primitives are transformed and clipped to fit the framebuffer. We use a
                    // resizable viewport, set to draw over the entire window.
                    viewport_state: Some(ViewportState::default()),
                    // How polygons are culled and converted into a raster of pixels. The default
                    // value does not perform any culling.
                    rasterization_state: Some(RasterizationState::default()),
                    // How multiple fragment shader samples are converted to a single pixel value.
                    // The default value does not perform any multisampling.
                    multisample_state: Some(MultisampleState::default()),
                    // How pixel values are combined with the values already present in the
                    // framebuffer. The default value overwrites the old value with the new one,
                    // without any blending.
                    color_blend_state: Some(ColorBlendState::with_attachment_states(
                        subpass.color_attachment_formats.len() as u32,
                        ColorBlendAttachmentState::default(),
                    )),
                    // Dynamic states allows us to specify parts of the pipeline settings when
                    // recording the command buffer, before we perform drawing. Here, we specify
                    // that the viewport should be dynamic.
                    dynamic_state: [DynamicState::Viewport].into_iter().collect(),
                    subpass: Some(subpass.into()),
                    ..GraphicsPipelineCreateInfo::layout(layout)
                },
            )
            .unwrap()
        };

        // Dynamic viewports allow us to recreate just the viewport when the window is resized.
        // Otherwise we would have to recreate the whole pipeline.
        let viewport = Viewport {
            offset: [0.0, 0.0],
            extent: window_size.into(),
            depth_range: 0.0..=1.0,
        };

        // In some situations, the swapchain will become invalid by itself. This includes for
        // example when the window is resized (as the images of the swapchain will no longer match
        // the window's) or, on Android, when the application went to the background and goes back
        // to the foreground.
        //
        // In this situation, acquiring a swapchain image or presenting it will return an error.
        // Rendering to an image of that swapchain will not produce any error, but may or may not
        // work. To continue rendering, we need to recreate the swapchain by creating a new
        // swapchain. Here, we remember that we need to do this for the next loop iteration.
        let recreate_swapchain = false;

        // In the loop below we are going to submit commands to the GPU. Submitting a command
        // produces an object that implements the `GpuFuture` trait, which holds the resources for
        // as long as they are in use by the GPU.
        //
        // Destroying the `GpuFuture` blocks until the GPU is finished executing it. In order to
        // avoid that, we store the submission of the previous frame here.
        let previous_frame_end = Some(sync::now(self.device.clone()).boxed());

        self.rcx = Some(RenderContext {
            window,
            swapchain,
            attachment_image_views,
            pipeline,
            viewport,
            recreate_swapchain,
            previous_frame_end,
        });
    }

    fn window_event(
        &mut self,
        event_loop: &ActiveEventLoop,
        _window_id: WindowId,
        event: WindowEvent,
    ) {
        let rcx = self.rcx.as_mut().unwrap();

        match event {
            WindowEvent::CloseRequested => {
                event_loop.exit();
            }
            WindowEvent::Resized(_) => {
                rcx.recreate_swapchain = true;
            }
            WindowEvent::RedrawRequested => {
                let window_size = rcx.window.inner_size();

                // Do not draw the frame when the screen size is zero. On Windows, this can occur
                // when minimizing the application.
                if window_size.width == 0 || window_size.height == 0 {
                    return;
                }

                // It is important to call this function from time to time, otherwise resources
                // will keep accumulating and you will eventually reach an out of memory error.
                // Calling this function polls various fences in order to determine what the GPU
                // has already processed, and frees the resources that are no longer needed.
                rcx.previous_frame_end.as_mut().unwrap().cleanup_finished();

                // Whenever the window resizes we need to recreate everything dependent on the
                // window size. In this example that includes the swapchain, the framebuffers and
                // the dynamic state viewport.
                if rcx.recreate_swapchain {
                    let (new_swapchain, new_images) = rcx
                        .swapchain
                        .recreate(SwapchainCreateInfo {
                            image_extent: window_size.into(),
                            ..rcx.swapchain.create_info()
                        })
                        .expect("failed to recreate swapchain");

                    rcx.swapchain = new_swapchain;

                    // Now that we have new swapchain images, we must create new image views from
                    // them as well.
                    rcx.attachment_image_views = window_size_dependent_setup(&new_images);

                    rcx.viewport.extent = window_size.into();

                    rcx.recreate_swapchain = false;
                }

                // Before we can draw on the output, we have to *acquire* an image from the
                // swapchain. If no image is available (which happens if you submit draw commands
                // too quickly), then the function will block. This operation returns the index of
                // the image that we are allowed to draw upon.
                //
                // This function can block if no image is available. The parameter is an optional
                // timeout after which the function call will return an error.
                let (image_index, suboptimal, acquire_future) = match acquire_next_image(
                    rcx.swapchain.clone(),
                    None,
                )
                .map_err(Validated::unwrap)
                {
                    Ok(r) => r,
                    Err(VulkanError::OutOfDate) => {
                        rcx.recreate_swapchain = true;
                        return;
                    }
                    Err(e) => panic!("failed to acquire next image: {e}"),
                };

                // `acquire_next_image` can be successful, but suboptimal. This means that the
                // swapchain image will still work, but it may not display correctly. With some
                // drivers this can be when the window resizes, but it may not cause the swapchain
                // to become out of date.
                if suboptimal {
                    rcx.recreate_swapchain = true;
                }

                // In order to draw, we have to record a *command buffer*. The command buffer
                // object holds the list of commands that are going to be executed.
                //
                // Recording a command buffer is an expensive operation (usually a few hundred
                // microseconds), but it is known to be a hot path in the driver and is expected to
                // be optimized.
                //
                // Note that we have to pass a queue family when we create the command buffer. The
                // command buffer will only be executable on that given queue family.
                let mut builder = RecordingCommandBuffer::new(
                    self.command_buffer_allocator.clone(),
                    self.queue.queue_family_index(),
                    CommandBufferLevel::Primary,
                    CommandBufferBeginInfo {
                        usage: CommandBufferUsage::OneTimeSubmit,
                        ..Default::default()
                    },
                )
                .unwrap();

                builder
                    // Before we can draw, we have to *enter a render pass*. We specify which
                    // attachments we are going to use for rendering here, which needs to match
                    // what was previously specified when creating the pipeline.
                    .begin_rendering(RenderingInfo {
                        // As before, we specify one color attachment, but now we specify the image
                        // view to use as well as how it should be used.
                        color_attachments: vec![Some(RenderingAttachmentInfo {
                            // `Clear` means that we ask the GPU to clear the content of this
                            // attachment at the start of rendering.
                            load_op: AttachmentLoadOp::Clear,
                            // `Store` means that we ask the GPU to store the rendered output in
                            // the attachment image. We could also ask it to discard the result.
                            store_op: AttachmentStoreOp::Store,
                            // The value to clear the attachment with. Here we clear it with a blue
                            // color.
                            //
                            // Only attachments that have `AttachmentLoadOp::Clear` are provided
                            // with clear values, any others should use `None` as the clear value.
                            clear_value: Some([0.0, 0.0, 1.0, 1.0].into()),
                            ..RenderingAttachmentInfo::image_view(
                                // We specify image view corresponding to the currently acquired
                                // swapchain image, to use for this attachment.
                                rcx.attachment_image_views[image_index as usize].clone(),
                            )
                        })],
                        ..Default::default()
                    })
                    .unwrap()
                    // We are now inside the first subpass of the render pass.
                    //
                    // TODO: Document state setting and how it affects subsequent draw commands.
                    .set_viewport(0, [rcx.viewport.clone()].into_iter().collect())
                    .unwrap()
                    .bind_pipeline_graphics(rcx.pipeline.clone())
                    .unwrap()
                    .bind_vertex_buffers(0, self.vertex_buffer.clone())
                    .unwrap();

                unsafe {
                    builder
                        // We add a draw command.
                        .draw(self.vertex_buffer.len() as u32, 1, 0, 0)
                        .unwrap();
                }

                builder
                    // We leave the render pass.
                    .end_rendering()
                    .unwrap();

                // Finish recording the command buffer by calling `end`.
                let command_buffer = builder.end().unwrap();

                let future = rcx
                    .previous_frame_end
                    .take()
                    .unwrap()
                    .join(acquire_future)
                    .then_execute(self.queue.clone(), command_buffer)
                    .unwrap()
                    // The color output is now expected to contain our triangle. But in order to
                    // show it on the screen, we have to *present* the image by calling
                    // `then_swapchain_present`.
                    //
                    // This function does not actually present the image immediately. Instead it
                    // submits a present command at the end of the queue. This means that it will
                    // only be presented once the GPU has finished executing the command buffer
                    // that draws the triangle.
                    .then_swapchain_present(
                        self.queue.clone(),
                        SwapchainPresentInfo::swapchain_image_index(
                            rcx.swapchain.clone(),
                            image_index,
                        ),
                    )
                    .then_signal_fence_and_flush();

                match future.map_err(Validated::unwrap) {
                    Ok(future) => {
                        rcx.previous_frame_end = Some(future.boxed());
                    }
                    Err(VulkanError::OutOfDate) => {
                        rcx.recreate_swapchain = true;
                        rcx.previous_frame_end = Some(sync::now(self.device.clone()).boxed());
                    }
                    Err(e) => {
                        println!("failed to flush future: {e}");
                        rcx.previous_frame_end = Some(sync::now(self.device.clone()).boxed());
                    }
                }
            }
            _ => {}
        }
    }

    fn about_to_wait(&mut self, _event_loop: &ActiveEventLoop) {
        let rcx = self.rcx.as_mut().unwrap();
        rcx.window.request_redraw();
    }
}

// We use `#[repr(C)]` here to force rustc to use a defined layout for our data, as the default
// representation has *no guarantees*.
#[derive(BufferContents, Vertex)]
#[repr(C)]
struct MyVertex {
    #[format(R32G32_SFLOAT)]
    position: [f32; 2],
}

/// This function is called once during initialization, then again whenever the window is resized.
fn window_size_dependent_setup(images: &[Arc<Image>]) -> Vec<Arc<ImageView>> {
    images
        .iter()
        .map(|image| ImageView::new_default(image.clone()).unwrap())
        .collect::<Vec<_>>()
}