imgui/imgui_macos_main.mm

// Dear ImGui: standalone example application for GLFW + Metal, using programmable pipeline
// (GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan/Metal graphics context creation, etc.)

// Learn about Dear ImGui:
// - FAQ                  https://dearimgui.com/faq
// - Getting Started      https://dearimgui.com/getting-started
// - Documentation        https://dearimgui.com/docs (same as your local docs/ folder).
// - Introduction, links and more at the top of imgui.cpp

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_metal.h"
#include <stdio.h>
#include <thread>
#include "imgui_main.h"

#define GLFW_INCLUDE_NONE
#define GLFW_EXPOSE_NATIVE_COCOA
#include <GLFW/glfw3.h>
#include <GLFW/glfw3native.h>

#import <Metal/Metal.h>
#import <QuartzCore/QuartzCore.h>

static GLFWwindow* g_main_window = nullptr;

static void glfw_error_callback(int error, const char* description)
{
    fprintf(stderr, "Glfw Error %d: %s\n", error, description);
}

int init_imgui() {
    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    configure_imgui(io);
    // Setup window
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
        return 1;

    // Create window with graphics context
    glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
    g_main_window = glfwCreateWindow(1280, 720, get_window_title().c_str(), nullptr, nullptr);
    if (g_main_window == nullptr)
        return 1;

    return 0;
}

bool imgui_new_frame() {
    return true;
}

void render_imgui() {

}

void shutdown_imgui() {
    // Cleanup
    ImGui_ImplMetal_Shutdown();
    ImGui_ImplGlfw_Shutdown();
    ImGui::DestroyContext();

    glfwDestroyWindow(g_main_window);
    glfwTerminate();
}

float get_dpi_scale() {
    return 1.0f;
}

void run_imgui() {
    init_imgui();
    
    id <MTLDevice> device = MTLCreateSystemDefaultDevice();
    id <MTLCommandQueue> commandQueue = [device newCommandQueue];

    // Setup Platform/Renderer backends
    ImGui_ImplGlfw_InitForOther(g_main_window, true);
    ImGui_ImplMetal_Init(device);

    NSWindow* nswin = glfwGetCocoaWindow(g_main_window);
    CAMetalLayer* layer = [CAMetalLayer layer];
    layer.device = device;
    layer.pixelFormat = MTLPixelFormatBGRA8Unorm;
    nswin.contentView.layer = layer;
    nswin.contentView.wantsLayer = YES;
    
    float clear_color[4] = {0.45f, 0.55f, 0.60f, 1.00f};
    
    MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor new];
    while (!glfwWindowShouldClose(g_main_window)) {
        @autoreleasepool {
            // Poll and handle events (inputs, window resize, etc.)
            // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
            // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application, or clear/overwrite your copy of the mouse data.
            // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
            // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
            glfwPollEvents();
            std::this_thread::sleep_for(std::chrono::milliseconds(5));

            int width, height;
            glfwGetFramebufferSize(g_main_window, &width, &height);
            layer.drawableSize = CGSizeMake(width, height);
            id<CAMetalDrawable> drawable = [layer nextDrawable];

            id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
            renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(clear_color[0] * clear_color[3], clear_color[1] * clear_color[3], clear_color[2] * clear_color[3], clear_color[3]);
            renderPassDescriptor.colorAttachments[0].texture = drawable.texture;
            renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
            renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
            id <MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
            [renderEncoder pushDebugGroup:@"ImGui demo"];

            // Start the Dear ImGui frame
            ImGui_ImplMetal_NewFrame(renderPassDescriptor);
            ImGui_ImplGlfw_NewFrame();
            ImGui::NewFrame();
            
            ImGuiIO& io = ImGui::GetIO();
            tick_imgui(io.DeltaTime);
            draw_imgui(io.DeltaTime);
            
            // Rendering
            ImGui::Render();
            ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);

            // Update and Render additional Platform Windows
            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
            {
                ImGui::UpdatePlatformWindows();
                ImGui::RenderPlatformWindowsDefault();
            }

            [renderEncoder popDebugGroup];
            [renderEncoder endEncoding];

            [commandBuffer presentDrawable:drawable];
            [commandBuffer commit];
            std::this_thread::yield();
        }
    }
    shutdown_imgui();
}