imgui/examples/example_glfw_metal/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>

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

int main(int, char**)
{
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
        return 1;

    // Create window with graphics context
    float main_scale = ImGui_ImplGlfw_GetContentScaleForMonitor(glfwGetPrimaryMonitor()); // Valid on GLFW 3.3+ only
    glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
    GLFWwindow* window = glfwCreateWindow((int)(1280 * main_scale), (int)(800 * main_scale), "Dear ImGui GLFW+Metal example", nullptr, nullptr);
    if (window == nullptr)
        return 1;

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsLight();

    // Setup scaling
    ImGuiStyle& style = ImGui::GetStyle();
    style.ScaleAllSizes(main_scale);        // Bake a fixed style scale. (until we have a solution for dynamic style scaling, changing this requires resetting Style + calling this again)
    style.FontScaleDpi = main_scale;        // Set initial font scale. (using io.ConfigDpiScaleFonts=true makes this unnecessary. We leave both here for documentation purpose)

    id <MTLDevice> device = MTLCreateSystemDefaultDevice();
    id <MTLCommandQueue> commandQueue = [device newCommandQueue];

    // Setup Platform/Renderer backends
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplMetal_Init(device);

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return a nullptr. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
    // - Read 'docs/FONTS.md' for more instructions and details. If you like the default font but want it to scale better, consider using the 'ProggyVector' from the same author!
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //style.FontSizeBase = 20.0f;
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf");
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf");
    //IM_ASSERT(font != nullptr);

    NSWindow *nswin = glfwGetCocoaWindow(window);
    CAMetalLayer *layer = [CAMetalLayer layer];
    layer.device = device;
    layer.pixelFormat = MTLPixelFormatBGRA8Unorm;
    nswin.contentView.layer = layer;
    nswin.contentView.wantsLayer = YES;

    MTLRenderPassDescriptor *renderPassDescriptor = [MTLRenderPassDescriptor new];

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;
    float clear_color[4] = {0.45f, 0.55f, 0.60f, 1.00f};

    // Main loop
    while (!glfwWindowShouldClose(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();

            int width, height;
            glfwGetFramebufferSize(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();

            // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
            if (show_demo_window)
                ImGui::ShowDemoWindow(&show_demo_window);

            // 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
            {
                static float f = 0.0f;
                static int counter = 0;

                ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

                ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
                ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
                ImGui::Checkbox("Another Window", &show_another_window);

                ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
                ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

                if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                    counter++;
                ImGui::SameLine();
                ImGui::Text("counter = %d", counter);

                ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
                ImGui::End();
            }

            // 3. Show another simple window.
            if (show_another_window)
            {
                ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
                ImGui::Text("Hello from another window!");
                if (ImGui::Button("Close Me"))
                    show_another_window = false;
                ImGui::End();
            }

            // Rendering
            ImGui::Render();
            ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);

            [renderEncoder popDebugGroup];
            [renderEncoder endEncoding];

            [commandBuffer presentDrawable:drawable];
            [commandBuffer commit];
        }
    }

    // Cleanup
    ImGui_ImplMetal_Shutdown();
    ImGui_ImplGlfw_Shutdown();
    ImGui::DestroyContext();

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}