imgui-ash 0.1.0

//! Translation of the [vulkan backend](https://github.com/ocornut/imgui/blob/master/backends/imgui_impl_vulkan.cpp)
//! of [Dear ImGui](https://github.com/ocornut/imgui) to [imgui-rs](imgui).
//!
//! Notable changes include the use of VMA through [vk_mem]
//!
//! To get started fill out a [`RendererCreateInfo`] and render in each frame
//!
//!
//! ```rust
//! use imgui_ash::{RendererCreateInfo, SurfaceColorFormat};
//!
//! # let your_queue_familiy = 2;
//! # let your_queue = ash::vk::Queue::null();
//! # let your_render_pass = ash::vk::RenderPass::null();
//! # let your_subpass = 0;
//! # let frames_in_flight = 2;
//! # let your_msaa_samples = None;
//! # let your_pipeline_cache = ash::vk::PipelineCache::null();
//! # let your_n_textures = 2;
//!
//! let create_info = RendererCreateInfo::default()
//!     .queue_family(your_queue_familiy)
//!     .queue(your_queue)
//!     .render_pass(your_render_pass)
//!     .subpass(your_subpass);
//!     .image_count(frames_in_flight)
//!     .msaa_samples(your_msaa_samples)
//!     .pipeline_cache(your_pipeline_cache)
//!     .surface_color_fmt(Some(SurfaceColorFormat::Srgb))
//!     .descriptor_pool_size(your_n_textures);
//! ```
//!
//! You can then pass this create info along with device to [`Renderer::new`].
//!
//! Thereafter one can just call [`Renderer::new_frame`] and [`Renderer::render`]
//! upon each frame.
use ash::vk::{self, Handle};
use imgui::internal::RawWrapper;
use vk_mem::Alloc;

use self::util::RaiiWrapper;

mod fonts;
mod init;
mod util;

pub const MIN_DESCRIPTOR_POOL_SIZE: u32 = 1;

#[derive(Default, Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct RendererCreateInfo {
    /// The queue family of the device from which [`RendererCreateInfo::queue`]
    /// was allocated from
    pub queue_family: u32,
    /// A queue on the passed n device with `GRAPHICS` capabilities.
    pub queue: vk::Queue,
    /// A render pass the created pipeline must be compatible with, only used
    /// upon initialisation
    pub render_pass: vk::RenderPass,
    /// The subpass on the aforementioned [`RendererCreateInfo::render_pass`]
    pub subpass: u32,
    /// The number of frames in flight
    pub image_count: u32,
    /// Mutli sampling configuration for texture sampling
    pub msaa_samples: Option<vk::SampleCountFlags>,
    /// An optional pipeline cache
    pub pipeline_cache: vk::PipelineCache,
    /// Whether the outputting surface is linear or srgb logarithmic, generally
    /// linear is desired and as such is the default
    pub surface_color_fmt: SurfaceColorFormat,
    /// The size of the descriptor pool managed by this renderer. Must be greater 
    /// than [`MIN_DESCRIPTOR_POOL_SIZE`], any additional increment allows use 
    /// of another custom texture. If you wanted to render 3 custom textures 
    /// you would set this to `MIN_DESCRIPTOR_POOL_SIZE + 3` and add your 
    /// textures with [`Renderer::add_texture`]
    pub descriptor_pool_size: Option<u32>,
}

/// Whether the outputting surface has a linear output format or a logarithmic
/// srgb output format, generally linear is desired and is as such the default
#[derive(Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub enum SurfaceColorFormat {
    #[default]
    Linear,
    Srgb,
}

impl RendererCreateInfo {
    /// See [`RendererCreateInfo`]
    pub fn queue_family(mut self, queue_family: u32) -> Self {
        self.queue_family = queue_family;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn queue(mut self, queue: vk::Queue) -> Self {
        self.queue = queue;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn render_pass(mut self, render_pass: vk::RenderPass) -> Self {
        self.render_pass = render_pass;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn subpass(mut self, subpass: u32) -> Self {
        self.subpass = subpass;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn image_count(mut self, image_count: u32) -> Self {
        self.image_count = image_count;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn msaa_samples(mut self, msaa_samples: Option<vk::SampleCountFlags>) -> Self {
        self.msaa_samples = msaa_samples;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn pipeline_cache(mut self, pipeline_cache: vk::PipelineCache) -> Self {
        self.pipeline_cache = pipeline_cache;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn surface_color_fmt(mut self, surface_color_fmt: SurfaceColorFormat) -> Self {
        self.surface_color_fmt = surface_color_fmt;
        self
    }

    /// See [`RendererCreateInfo`]
    pub fn descriptor_pool_size(mut self, descriptor_pool_size: Option<u32>) -> Self {
        self.descriptor_pool_size = descriptor_pool_size;
        self
    }
}

pub struct Renderer<A>
where
    A: vk_mem::Alloc,
{
    _instance: ash::Instance,
    device: ash::Device,
    create_info: RendererCreateInfo,
    device_objects: DeviceObjects,
    fonts_texture: Option<Texture>,
    render_index: usize,
    render_buffers: Vec<RenderBuffer>,

    allocator: A,
}

struct Texture {
    memory: vk_mem::Allocation,
    image: vk::Image,
    image_view: vk::ImageView,
    descriptor_set: vk::DescriptorSet,
}

struct GpuBuffer {
    buffer: vk::Buffer,
    alloc: vk_mem::Allocation,
    size: usize,
}

#[derive(Default)]
struct RenderBuffer {
    vertex: Option<GpuBuffer>,
    index: Option<GpuBuffer>,
}

struct DeviceObjects {
    tex_sampler: vk::Sampler,
    descriptor_layout: vk::DescriptorSetLayout,
    descriptor_pool: vk::DescriptorPool,
    pipeline_layout: vk::PipelineLayout,
    pipeline: vk::Pipeline,
    vert_shader: vk::ShaderModule,
    frag_shader: vk::ShaderModule,
    tex_command_pool: vk::CommandPool,
    tex_command_buffer: vk::CommandBuffer,
    wait_fence: vk::Fence,
}

impl<A> Renderer<A>
where
    A: vk_mem::Alloc,
{
    /// Creates a new [`Renderer`]. For details, look at [`RendererCreateInfo`]
    ///
    /// # Safety
    ///
    /// - the `device`, `instance`, [`RendererCreateInfo::queue`], [`RendererCreateInfo::render_pass`] handles must be valid
    /// - if [`RendererCreateInfo::pipeline_cache`] is not a null-handle the sampe applies
    /// - [`RendererCreateInfo::queue`] must belong the the `device`
    /// - the `device`, `instance`, [`RendererCreateInfo::queue`] and `allocator` must outlive the
    ///   [`Renderer`]
    /// - [`RendererCreateInfo::image_count`] must be greater than or equal to 2
    /// - [`RendererCreateInfo::descriptor_pool_size`] must be greater than or equal to [`MIN_DESCRIPTOR_POOL_SIZE`] if
    ///   supplied
    pub unsafe fn new(
        instance: &ash::Instance,
        device: &ash::Device,
        allocator: A,
        create_info: &RendererCreateInfo,
        context: &mut imgui::Context,
    ) -> Result<Self, RendererCreateError> {
        debug_assert!(
            !instance.handle().is_null(),
            "must pass in a valid instance (is null)"
        );
        debug_assert!(
            !device.handle().is_null(),
            "must pass in a valid device (is null)"
        );
        debug_assert!(
            !create_info.queue.is_null(),
            "must pass in a valid queue (is null)"
        );
        debug_assert!(
            !create_info.render_pass.is_null(),
            "must pass in a valid render pass (is null)"
        );
        debug_assert!(
            create_info.image_count >= 2,
            "must at least have two images, currently are {}",
            create_info.image_count
        );
        debug_assert!(
            create_info
                .descriptor_pool_size
                .is_none_or(|s| s >= MIN_DESCRIPTOR_POOL_SIZE),
            "if descriptor pool size is set explicitly it needs to be bigger than MIN_DESCRIPTOR_POOL_SIZE"
        );
        let device_objects = unsafe { Self::create_device_objects(instance, device, create_info)? };
        context
            .io_mut()
            .backend_flags
            .insert(imgui::BackendFlags::RENDERER_HAS_VTX_OFFSET);
        Ok(Self {
            _instance: instance.clone(),
            device: device.clone(),
            allocator,
            create_info: *create_info,
            device_objects: device_objects.finalise(),
            render_index: 0,
            fonts_texture: None,
            render_buffers: Vec::new(),
        })
    }

    pub fn new_frame(&mut self, context: &mut imgui::Context) -> Result<(), FontsCreateError> {
        if self.fonts_texture.is_some() {
            return Ok(());
        }
        unsafe { self.create_fonts_texture(context) }
    }

    pub fn add_texture(
        &self,
        sampler: vk::Sampler,
        view: vk::ImageView,
        layout: vk::ImageLayout,
    ) -> Result<vk::DescriptorSet, TextureError> {
        let layouts = [self.device_objects.descriptor_layout];
        let descriptor_set_info = vk::DescriptorSetAllocateInfo::default()
            .descriptor_pool(self.device_objects.descriptor_pool)
            .set_layouts(&layouts);

        let descriptor_set = RaiiWrapper::new(
            unsafe { self.device.allocate_descriptor_sets(&descriptor_set_info) }
                .map_err(TextureError::DescriptorSetCreateError)?[0],
            |ds| unsafe {
                self.device
                    .free_descriptor_sets(self.device_objects.descriptor_pool, &[ds])
                    .expect("cannot fail, see spec");
            },
        );

        let descriptor_image_info = [vk::DescriptorImageInfo::default()
            .sampler(sampler)
            .image_view(view)
            .image_layout(layout)];

        let write_desc = vk::WriteDescriptorSet::default()
            .dst_set(*descriptor_set)
            .descriptor_count(1)
            .descriptor_type(vk::DescriptorType::COMBINED_IMAGE_SAMPLER)
            .image_info(&descriptor_image_info);

        unsafe {
            self.device.update_descriptor_sets(&[write_desc], &[]);
        }
        Ok(descriptor_set.finalise())
    }

    /// # Safety
    ///
    /// - the descriptor_set must have been added with [`Renderer::add_texture`]
    pub unsafe fn remove_texture(&self, descriptor_set: vk::DescriptorSet) {
        unsafe {
            self.device
                .free_descriptor_sets(self.device_objects.descriptor_pool, &[descriptor_set])
                .expect("cannot fail according to spec")
        }
    }

    pub fn render(
        &mut self,
        draw_data: &imgui::DrawData,
        command_buffer: vk::CommandBuffer,
    ) -> Result<(), RendererError> {
        let fb_width = draw_data.display_size[0] * draw_data.framebuffer_scale[0];
        let fb_height = draw_data.display_size[1] * draw_data.framebuffer_scale[1];
        if fb_width <= 0.0 || fb_height <= 0.0 {
            return Ok(());
        }

        if self.render_buffers.is_empty() {
            self.render_buffers
                .resize_with(self.create_info.image_count as _, Default::default);
        }

        assert_eq!(
            self.create_info.image_count,
            self.render_buffers.len() as _,
            "if image count has changed, call set_image_count"
        );

        let index = (self.render_index + 1) % self.render_buffers.len();
        self.render_index = index;

        if draw_data.total_vtx_count > 0 {
            let vertex_size =
                draw_data.total_vtx_count as usize * core::mem::size_of::<imgui::DrawVert>();
            let idx_size =
                draw_data.total_idx_count as usize * core::mem::size_of::<imgui::DrawIdx>();
            create_or_update_buffer(
                self.allocator.allocator(),
                &mut self.render_buffers[index].vertex,
                vertex_size,
                vk::BufferUsageFlags::VERTEX_BUFFER,
            )
            .unwrap();
            create_or_update_buffer(
                self.allocator.allocator(),
                &mut self.render_buffers[index].index,
                idx_size,
                vk::BufferUsageFlags::INDEX_BUFFER,
            )
            .unwrap();
            {
                let mut vtx_dst = unsafe {
                    self.allocator
                        .allocator()
                        .map_memory(&mut self.render_buffers[index].vertex.as_mut().unwrap().alloc)
                }
                .map_err(RendererError::MmapError)? as *mut _;
                let mut idx_dst = unsafe {
                    self.allocator
                        .allocator()
                        .map_memory(&mut self.render_buffers[index].index.as_mut().unwrap().alloc)
                }
                .map_err(RendererError::MmapError)? as *mut _;

                for list in draw_data.draw_lists() {
                    unsafe {
                        core::ptr::copy_nonoverlapping(
                            list.vtx_buffer().as_ptr(),
                            vtx_dst,
                            list.vtx_buffer().len(),
                        );
                        core::ptr::copy_nonoverlapping(
                            list.idx_buffer().as_ptr(),
                            idx_dst,
                            list.idx_buffer().len(),
                        );
                        vtx_dst = vtx_dst.add(list.vtx_buffer().len());
                        idx_dst = idx_dst.add(list.idx_buffer().len());
                    }
                }

                unsafe {
                    self.allocator.allocator().unmap_memory(
                        &mut self.render_buffers[index].vertex.as_mut().unwrap().alloc,
                    );
                    self.allocator.allocator().unmap_memory(
                        &mut self.render_buffers[index].index.as_mut().unwrap().alloc,
                    );

                    self.allocator
                        .allocator()
                        .flush_allocations(
                            [
                                &self.render_buffers[index].vertex.as_ref().unwrap().alloc,
                                &self.render_buffers[index].index.as_ref().unwrap().alloc,
                            ],
                            None,
                            None,
                        )
                        .map_err(RendererError::FlushError)?;
                }
            }
        }

        unsafe {
            self.setup_render_state(
                draw_data,
                self.device_objects.pipeline,
                command_buffer,
                &self.render_buffers[index],
                fb_width,
                fb_height,
            )
        };

        let clip_off = draw_data.display_pos;
        let clip_scale = draw_data.framebuffer_scale;

        let mut global_vtx_offset = 0;
        let mut global_idx_offset = 0;
        if draw_data.draw_lists_count() > 0 {
            for draw_list in draw_data.draw_lists() {
                for draw_cmd in draw_list.commands() {
                    match draw_cmd {
                        imgui::DrawCmd::Elements { count, cmd_params } => {
                            let mut clip_min = [
                                (cmd_params.clip_rect[0] - clip_off[0]) * clip_scale[0],
                                (cmd_params.clip_rect[1] - clip_off[1]) * clip_scale[1],
                            ];
                            let mut clip_max = [
                                (cmd_params.clip_rect[2] - clip_off[0]) * clip_scale[0],
                                (cmd_params.clip_rect[3] - clip_off[1]) * clip_scale[1],
                            ];

                            if clip_min[0] < 0.0 {
                                clip_min[0] = 0.0;
                            }
                            if clip_min[1] < 0.0 {
                                clip_min[1] = 0.0;
                            }
                            if clip_max[0] > fb_width {
                                clip_max[0] = fb_width;
                            }
                            if clip_max[1] > fb_height {
                                clip_max[1] = fb_height;
                            }
                            if clip_max[0] <= clip_min[0] || clip_max[1] <= clip_min[1] {
                                continue;
                            }

                            let scissor = vk::Rect2D::default()
                                .offset(
                                    vk::Offset2D::default()
                                        .x(clip_min[0] as _)
                                        .y(clip_min[1] as _),
                                )
                                .extent(
                                    vk::Extent2D::default()
                                        .width((clip_max[0] - clip_min[0]) as _)
                                        .height((clip_max[1] - clip_min[1]) as _),
                                );

                            let desc_set =
                                vk::DescriptorSet::from_raw(cmd_params.texture_id.id() as _);
                            unsafe {
                                self.device.cmd_set_scissor(command_buffer, 0, &[scissor]);
                                self.device.cmd_bind_descriptor_sets(
                                    command_buffer,
                                    vk::PipelineBindPoint::GRAPHICS,
                                    self.device_objects.pipeline_layout,
                                    0,
                                    &[desc_set],
                                    &[],
                                );
                                self.device.cmd_draw_indexed(
                                    command_buffer,
                                    count as _,
                                    1,
                                    (cmd_params.idx_offset + global_idx_offset) as _,
                                    (cmd_params.vtx_offset + global_vtx_offset) as _,
                                    0,
                                );
                            }
                        }
                        imgui::DrawCmd::ResetRenderState => unsafe {
                            self.setup_render_state(
                                draw_data,
                                self.device_objects.pipeline,
                                command_buffer,
                                &self.render_buffers[index],
                                fb_width,
                                fb_height,
                            );
                        },
                        imgui::DrawCmd::RawCallback { callback, raw_cmd } => unsafe {
                            callback(draw_list.raw(), raw_cmd);
                        },
                    }
                }
                global_vtx_offset += draw_list.vtx_buffer().len();
                global_idx_offset += draw_list.idx_buffer().len();
            }
        }
        // Note: at this point both vkCmdSetViewport() and vkCmdSetScissor() have been called.
        // Our last values will leak into user/application rendering IF:
        // - Your app uses a pipeline with VK_DYNAMIC_STATE_VIEWPORT or VK_DYNAMIC_STATE_SCISSOR dynamic state
        // - And you forgot to call vkCmdSetViewport() and vkCmdSetScissor() yourself to explicitly set that state.
        // If you use VK_DYNAMIC_STATE_VIEWPORT or VK_DYNAMIC_STATE_SCISSOR you are responsible for setting the values before rendering.
        // In theory we should aim to backup/restore those values but I am not sure this is possible.
        // We perform a call to vkCmdSetScissor() to set back a full viewport which is likely to fix things for 99% users but technically this is not perfect. (See github imgui#4644)
        let scissor = vk::Rect2D::default()
            .offset(vk::Offset2D::default().x(0).y(0))
            .extent(
                vk::Extent2D::default()
                    .width(fb_width as u32)
                    .height(fb_height as u32),
            );
        unsafe {
            self.device.cmd_set_scissor(command_buffer, 0, &[scissor]);
        }
        Ok(())
    }

    unsafe fn setup_render_state(
        &self,
        draw_data: &imgui::DrawData,
        pipeline: vk::Pipeline,
        command_buffer: vk::CommandBuffer,
        _render_buffer: &RenderBuffer,
        width: f32,
        height: f32,
    ) {
        let device = &self.device;
        unsafe {
            device.cmd_bind_pipeline(command_buffer, vk::PipelineBindPoint::GRAPHICS, pipeline);
        }

        if draw_data.total_vtx_count > 0 {
            unsafe {
                device.cmd_bind_vertex_buffers(
                    command_buffer,
                    0,
                    &[self.render_buffers[self.render_index]
                        .vertex
                        .as_ref()
                        .unwrap()
                        .buffer],
                    &[0],
                );
                device.cmd_bind_index_buffer(
                    command_buffer,
                    self.render_buffers[self.render_index]
                        .index
                        .as_ref()
                        .unwrap()
                        .buffer,
                    0,
                    if core::mem::size_of::<imgui::DrawIdx>() == 2 {
                        vk::IndexType::UINT16
                    } else {
                        vk::IndexType::UINT32
                    },
                );
            }
        }
        {
            let viewport = vk::Viewport::default()
                .x(0.0)
                .y(0.0)
                .width(width)
                .height(height)
                .min_depth(0.0)
                .max_depth(1.0);
            unsafe {
                device.cmd_set_viewport(command_buffer, 0, &[viewport]);
            }
        }

        // setup scale and translation
        // Our visible imgui space lies from draw_data->DisplayPps (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
        {
            let scale = [
                2.0 / draw_data.display_size[0],
                2.0 / draw_data.display_size[1],
            ];
            let scale_bytes = bytemuck::cast_slice(&scale);
            let translate = [
                -1.0 - draw_data.display_pos[0] * scale[0],
                -1.0 - draw_data.display_pos[1] * scale[1],
            ];
            let translate_bytes = bytemuck::cast_slice(&translate);

            let is_srgb = [match self.create_info.surface_color_fmt {
                SurfaceColorFormat::Srgb => vk::TRUE,
                _ => vk::FALSE,
            }];
            unsafe {
                #[allow(clippy::erasing_op)]
                device.cmd_push_constants(
                    command_buffer,
                    self.device_objects.pipeline_layout,
                    vk::ShaderStageFlags::VERTEX,
                    core::mem::size_of::<f32>() as u32 * 0,
                    scale_bytes,
                );
                device.cmd_push_constants(
                    command_buffer,
                    self.device_objects.pipeline_layout,
                    vk::ShaderStageFlags::VERTEX,
                    core::mem::size_of::<f32>() as u32 * 2,
                    translate_bytes,
                );
                device.cmd_push_constants(
                    command_buffer,
                    self.device_objects.pipeline_layout,
                    vk::ShaderStageFlags::VERTEX,
                    core::mem::size_of::<f32>() as u32 * 4,
                    bytemuck::cast_slice(&is_srgb),
                );
            }
        }
    }

    unsafe fn destroy_device_objects(device: &ash::Device, device_objects: &DeviceObjects) {
        unsafe {
            device.destroy_command_pool(device_objects.tex_command_pool, None);
            device.destroy_descriptor_pool(device_objects.descriptor_pool, None);
            device.destroy_pipeline(device_objects.pipeline, None);
            device.destroy_shader_module(device_objects.vert_shader, None);
            device.destroy_shader_module(device_objects.frag_shader, None);
            device.destroy_pipeline_layout(device_objects.pipeline_layout, None);
            device.destroy_descriptor_set_layout(device_objects.descriptor_layout, None);
            device.destroy_sampler(device_objects.tex_sampler, None);
            device.destroy_fence(device_objects.wait_fence, None);
        }
    }
}

#[derive(Debug, thiserror::Error)]
pub enum RendererCreateError {
    #[error("failed to create texture sampler")]
    SamplerCreateError(#[source] vk::Result),

    #[error("failed to create descriptor set layout for sampling texture")]
    DescriptorSetCreateError(#[source] vk::Result),

    #[error("failed to create descriptor pool for sampling textures")]
    DescriptorPoolCreateError(#[source] vk::Result),

    #[error("failed to create pipeline layout")]
    PipelineLayoutCreateError(#[source] vk::Result),

    #[error("failed to create shader modules")]
    ShaderModuleCreateError(#[source] vk::Result),

    #[error("failed to create graphics pipeline")]
    PipelineCreateError(#[source] vk::Result),

    #[error("failed to create command pool for texture transfer")]
    TexCommandPoolCreateError(#[source] vk::Result),

    #[error("failed to create command buffer for texture transfer")]
    TexCommandBufferAllocError(#[source] vk::Result),

    #[error("failed to allocate synchronisation objects")]
    SyncobjCreateError(#[source] vk::Result),
}

#[derive(thiserror::Error, Debug)]
pub enum FontsCreateError {
    #[error("failed to reset command pool for texture transfer")]
    CommandPoolResetError(#[source] vk::Result),

    #[error("failed to begin command buffer for texture transfer")]
    CommandBeginError(#[source] vk::Result),

    #[error("failed to allocate image for font atlas texture")]
    ImageAllocError(#[source] vk::Result),

    #[error("failed to create image view for font atlas texture")]
    ImageViewCreateError(#[source] vk::Result),

    #[error("failed to create texture for font atlas")]
    TextureCreateError(
        #[source]
        #[from]
        TextureError,
    ),

    #[error("failed to create image transfer buffer for copying atlas into image")]
    TransferbufferCreateError(#[source] vk::Result),

    #[error("failed to map memory for copy operation")]
    MmapError(#[source] vk::Result),

    #[error("failed to flush allocated region after copy")]
    FlushError(#[source] vk::Result),

    #[error("failed to end command buffer recording for transfer operation")]
    CommandEndError(#[source] vk::Result),

    #[error("failed to submit copy operation to queue")]
    SubmitError(#[source] vk::Result),
}

#[derive(thiserror::Error, Debug)]
pub enum TextureError {
    #[error("failed to create descriptor set for texture")]
    DescriptorSetCreateError(#[source] vk::Result),
}

#[derive(thiserror::Error, Debug)]
pub enum RendererError {
    #[error("failed to map memory for vertex or index copy")]
    MmapError(#[source] vk::Result),

    #[error("flushing allocations for copied vertex data failed")]
    FlushError(#[source] vk::Result),
}

fn create_or_update_buffer(
    allocator: &vk_mem::Allocator,
    buffer: &mut Option<GpuBuffer>,
    new_size: usize,
    usage: vk::BufferUsageFlags,
) -> ash::prelude::VkResult<()> {
    if let Some(buf) = buffer {
        if buf.size >= new_size {
            return Ok(());
        }
        unsafe { allocator.destroy_buffer(buf.buffer, &mut buf.alloc) };
    }
    *buffer = None;

    let buffer_info = vk::BufferCreateInfo::default()
        .size(new_size as _)
        .usage(usage)
        .sharing_mode(vk::SharingMode::EXCLUSIVE);

    let alloc_info = vk_mem::AllocationCreateInfo {
        usage: vk_mem::MemoryUsage::AutoPreferDevice,
        flags: vk_mem::AllocationCreateFlags::HOST_ACCESS_SEQUENTIAL_WRITE,
        ..Default::default()
    };

    let (buf, alloc) = unsafe { allocator.create_buffer(&buffer_info, &alloc_info) }?;
    *buffer = Some(GpuBuffer {
        buffer: buf,
        alloc,
        size: new_size,
    });
    Ok(())
}

impl<A> Drop for Renderer<A>
where
    A: vk_mem::Alloc,
{
    fn drop(&mut self) {
        unsafe {
            for buffer in self.render_buffers.drain(..) {
                if let Some(GpuBuffer {
                    buffer, mut alloc, ..
                }) = buffer.vertex
                {
                    self.allocator
                        .allocator()
                        .destroy_buffer(buffer, &mut alloc);
                }
                if let Some(GpuBuffer {
                    buffer, mut alloc, ..
                }) = buffer.index
                {
                    self.allocator
                        .allocator()
                        .destroy_buffer(buffer, &mut alloc);
                }
            }
            self.destroy_fonts_texture(None);
            Self::destroy_device_objects(&self.device, &self.device_objects);
        }
    }
}