good but wrong teardown order; device wait idle

src/main.zig

@@ -29,7 +29,7 @@ pub fn main() !void {
     try nu.Render.init(alloc);
     defer nu.Render.deinit();
 
-    try nu.ImGui.init(alloc);
+    try nu.ImGui.init();
     defer nu.ImGui.deinit();
 
     try App.init(alloc);

src/nu.zig

@@ -26,7 +26,11 @@ pub fn run(
                 if (@typeInfo(@TypeOf(module.frame)).Fn.return_type) |R| {
                     switch (@typeInfo(R)) {
                         .ErrorUnion => try module.frame(),
-                        else => @compileError("frame must be void or !void."),
+                        .Void => module.frame(),
+                        else => {
+                            @compileLog(module.frame, @typeInfo(R));
+                            @compileError("frame must be void or !void.");
+                        },
                     }
                 } else {
                     module.frame();

src/nu/ImGui.zig

@@ -2,11 +2,105 @@
 
 const std = @import("std");
 
+const vk = @import("vk");
+const nu = @import("../nu.zig");
+const au = @import("Render/au.zig");
 const Render = @import("Render.zig");
+const Window = @import("Window.zig");
 
-pub fn init(alloc: std.mem.Allocator) !void {
-    _ = alloc;
+const im = @import("cimgui");
+
+pub fn loader_wrapper(procname: [*c]const u8, _: ?*anyopaque) callconv(.C) vk.PfnVoidFunction {
+    return au.glfwGetInstanceProcAddress(au.I.handle, procname);
+}
+
+var ctx: *im.c.ImGuiContext = undefined;
+var descriptor_pool: vk.DescriptorPool = undefined;
+
+pub fn init() !void {
+    ctx = im.c.igCreateContext(null) orelse {
+        return error.igCreateContextFailed;
+    };
+    errdefer im.c.igDestroyContext(ctx);
+
+    if (!im.c.ImGui_ImplVulkan_LoadFunctions(loader_wrapper, null)) {
+        return error.igVulkanLoadFunctionsFailed;
+    }
+
+    if (!im.c.ImGui_ImplGlfw_InitForVulkan(@ptrCast(Window.handle), true)) {
+        return error.igGlfwInitFailed;
+    }
+    errdefer im.c.ImGui_ImplGlfw_Shutdown();
+
+    descriptor_pool = try au.D.createDescriptorPool(&vk.DescriptorPoolCreateInfo{
+        .flags = .{ .free_descriptor_set_bit = true },
+        .pool_size_count = 1,
+        .p_pool_sizes = &.{vk.DescriptorPoolSize{
+            .descriptor_count = 32,
+            .type = .combined_image_sampler,
+        }},
+        .max_sets = 32,
+    }, null);
+    errdefer au.D.destroyDescriptorPool(descriptor_pool, null);
+
+    if (im.c.ImGui_ImplVulkan_Init(@constCast(&im.c.ImGui_ImplVulkan_InitInfo{
+        .Instance = @ptrFromInt(@intFromEnum(au.I.handle)),
+        .PhysicalDevice = @ptrFromInt(@intFromEnum(au.device_config.pdev)),
+        .Device = @ptrFromInt(@intFromEnum(au.D.handle)),
+        .QueueFamily = au.device_config.family,
+        .Queue = @ptrFromInt(@intFromEnum(au.Q.handle)),
+        .DescriptorPool = @ptrFromInt(@intFromEnum(descriptor_pool)),
+        .RenderPass = null,
+        .MinImageCount = 2,
+        .ImageCount = @intCast(nu.options.render.frames_in_flight),
+        .PipelineRenderingCreateInfo = @bitCast(vk.PipelineRenderingCreateInfo{
+            .view_mask = 0,
+            .depth_attachment_format = .undefined,
+            .stencil_attachment_format = .undefined,
+            .color_attachment_count = 1,
+            .p_color_attachment_formats = &.{au.device_config.format.format},
+        }),
+        .MSAASamples = 0,
+        .PipelineCache = null,
+        .Subpass = 0,
+        .UseDynamicRendering = true,
+        .Allocator = null,
+    })) != true) {
+        return error.igVulkanInitFailed;
+    }
+    errdefer im.c.ImGui_ImplVulkan_Shutdown();
+
+    if (!im.c.ImGui_ImplVulkan_CreateFontsTexture()) {
+        return error.igVulkanFontTextureFailed;
+    }
+
+    try Render.add_present_callback(present);
+    errdefer Render.remove_present_callback(present);
+}
+
+pub fn frame() void {
+    im.c.ImGui_ImplGlfw_NewFrame();
+    im.c.ImGui_ImplVulkan_NewFrame();
+    im.c.igNewFrame();
+
+    im.c.igShowDemoWindow(null);
+
+    im.c.igEndFrame();
+    im.c.igRender();
 }
 
 pub fn deinit() void {
+    Render.remove_present_callback(present);
+    im.c.ImGui_ImplVulkan_Shutdown();
+    au.D.destroyDescriptorPool(descriptor_pool, null);
+    im.c.ImGui_ImplGlfw_Shutdown();
+    im.c.igDestroyContext(ctx);
+}
+
+pub fn present(cmd: au.CommandBufferProxy) void {
+    im.c.ImGui_ImplVulkan_RenderDrawData(
+        im.c.igGetDrawData(),
+        @ptrFromInt(@intFromEnum(cmd.handle)),
+        null,
+    );
 }

src/nu/Render.zig

@@ -30,11 +30,33 @@ pub const Options = struct {
 var sc: au.SwapChain = undefined;
 var flights: au.Flights = undefined;
 
+const PresentCallback = *const fn (au.CommandBufferProxy) void;
+var present_callbacks: std.ArrayList(PresentCallback) = undefined;
+
+pub fn add_present_callback(cb: PresentCallback) !void {
+    if (std.mem.indexOfScalar(PresentCallback, present_callbacks.items, cb)) |_| {
+        return;
+    } else {
+        try present_callbacks.append(cb);
+    }
+}
+
+pub fn remove_present_callback(cb: PresentCallback) void {
+    if (std.mem.indexOfScalar(PresentCallback, present_callbacks.items, cb)) |idx| {
+        _ = present_callbacks.orderedRemove(idx);
+    } else {
+        return;
+    }
+}
+
 pub fn init(alloc: std.mem.Allocator) !void {
     // todo pick apart au into helpers; not a sub-module filled with its own globals.
     try au.init(alloc);
     errdefer au.deinit();
 
+    present_callbacks = std.ArrayList(PresentCallback).init(alloc);
+    errdefer present_callbacks.deinit();
+
     sc = try au.SwapChain.init(alloc);
     errdefer sc.deinit();
 
@@ -67,6 +89,9 @@ pub fn frame() !void {
 
         try cmd.beginCommandBuffer(&.{ .flags = .{ .one_time_submit_bit = true } });
         target.begin_rendering(cmd, render_area);
+        for (present_callbacks.items) |cb| {
+            cb(cmd);
+        }
         target.end_rendering(cmd);
         try cmd.endCommandBuffer();
 
@@ -98,6 +123,7 @@ pub fn frame() !void {
 }
 
 pub fn deinit() void {
+    present_callbacks.deinit();
     au.D.deviceWaitIdle() catch {};
     flights.deinit();
     sc.deinit();

src/nu/Render/au.zig

@@ -373,26 +373,26 @@ pub fn debug_callback(
     return vk.FALSE;
 }
 
-extern fn glfwVulkanSupported() c_int;
+pub extern fn glfwVulkanSupported() c_int;
 
-extern fn glfwGetInstanceProcAddress(
+pub extern fn glfwGetInstanceProcAddress(
     instance: vk.Instance,
     procname: [*:0]const u8,
 ) vk.PfnVoidFunction;
 
-extern fn glfwGetPhysicalDevicePresentationSupport(
+pub extern fn glfwGetPhysicalDevicePresentationSupport(
     instance: vk.Instance,
     pdev: vk.PhysicalDevice,
     queuefamily: u32,
 ) c_int;
 
-extern fn glfwCreateWindowSurface(
+pub extern fn glfwCreateWindowSurface(
     instance: vk.Instance,
     window: *nu.Window.c.GLFWwindow,
     allocation_callbacks: ?*const vk.AllocationCallbacks,
     surface: *vk.SurfaceKHR,
 ) vk.Result;
 
-extern fn glfwGetRequiredInstanceExtensions(
+pub extern fn glfwGetRequiredInstanceExtensions(
     count: *u32,
 ) [*][*:0]const u8;