imgui/examples/example_sdl2_wgpu/main.cpp

// Dear ImGui: standalone example application for using SDL2 + WebGPU
// - Emscripten is supported for publishing on web. See https://emscripten.org.
// - Dawn is used as a WebGPU implementation on desktop.

// 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_sdl2.h"
#include "imgui_impl_wgpu.h"
#include <stdio.h>
#include <SDL.h>

// This example can also compile and run with Emscripten! See 'Makefile.emscripten' for details.
#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#include <emscripten/html5.h>
#if defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
#include <emscripten/html5_webgpu.h>
#endif
#include "../libs/emscripten/emscripten_mainloop_stub.h"
#endif

#include <webgpu/webgpu.h>
#if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN)
#include <webgpu/webgpu_cpp.h>
#endif

// Data
WGPUInstance             wgpu_instance = nullptr;
WGPUDevice               wgpu_device   = nullptr;
WGPUSurface              wgpu_surface  = nullptr;
WGPUQueue                wgpu_queue    = nullptr;
WGPUSurfaceConfiguration wgpu_surface_configuration {};
int                      wgpu_surface_width = 1280;
int                      wgpu_surface_height = 800;

// Forward declarations
static bool InitWGPU(void* window);

static void ResizeSurface(int width, int height)
{
    wgpu_surface_configuration.width  = wgpu_surface_width  = width;
    wgpu_surface_configuration.height = wgpu_surface_height = height;
    wgpuSurfaceConfigure(wgpu_surface, (WGPUSurfaceConfiguration*)&wgpu_surface_configuration);
}

static void ReleaseTextureAndConfigureSurface(WGPUTexture& texture, int fb_width, int fb_height)
{
    if (texture)
        wgpuTextureRelease(texture);
    if (fb_width > 0 && fb_height > 0)
        ResizeSurface(fb_width, fb_height);
}

// Main code
int main(int, char**)
{
    // Setup SDL

#if defined(__linux__)
    // It's necessary to specify "x11" or "wayland": default is "x11" it works also in wayland
    // Or comment the line and export SDL_VIDEODRIVER environment variable:
    //   export SDL_VIDEODRIVER=wayland             // To set wayland session type
    //   export SDL_VIDEODRIVER=$XDG_SESSION_TYPE   // To get current session type from WM: x11 | wayland
    SDL_SetHint(SDL_HINT_VIDEODRIVER, "x11");
#endif

    SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMECONTROLLER);
    // Create window
    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+WebGPU example", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, wgpu_surface_width, wgpu_surface_height, SDL_WINDOW_RESIZABLE);

    // Initialize WGPU
    InitWGPU(window);

    // 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)

    // Setup Platform/Renderer backends
    ImGui_ImplSDL2_InitForOther(window);
    ImGui_ImplWGPU_InitInfo init_info;
    init_info.Device = wgpu_device;
    init_info.NumFramesInFlight = 3;
    init_info.RenderTargetFormat = wgpu_surface_configuration.format;
    init_info.DepthStencilFormat = WGPUTextureFormat_Undefined;
    ImGui_ImplWGPU_Init(&init_info);

    // 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 \\ !
    // - Our Emscripten build process allows embedding fonts to be accessible at runtime from the "fonts/" folder. See Makefile.emscripten for details.
    //style.FontSizeBase = 20.0f;
    //io.Fonts->AddFontDefault();
#ifndef IMGUI_DISABLE_FILE_FUNCTIONS
    //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);
#endif

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // Main loop
    bool done = false;
#ifdef __EMSCRIPTEN__
    // For an Emscripten build we are disabling file-system access, so let's not attempt to do a fopen() of the imgui.ini file.
    // You may manually call LoadIniSettingsFromMemory() to load settings from your own storage.
    io.IniFilename = nullptr;
    EMSCRIPTEN_MAINLOOP_BEGIN
#else
    while (!done)
#endif
    {
        // 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.
        SDL_Event event;
        while (SDL_PollEvent(&event))
        {
            ImGui_ImplSDL2_ProcessEvent(&event);
            if (event.type == SDL_QUIT)
                done = true;
            if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
                done = true;
        }

        // React to changes in screen size
        int width, height;
        SDL_GetWindowSize(window, &width, &height);
        if (width != wgpu_surface_width || height != wgpu_surface_height)
        {
            ImGui_ImplWGPU_InvalidateDeviceObjects(); // FIXME-WGPU: Why doing this? this will recreate all font textures etc.
            ResizeSurface(width, height);
            ImGui_ImplWGPU_CreateDeviceObjects();
        }

        WGPUSurfaceTexture surfaceTexture;
        wgpuSurfaceGetCurrentTexture(wgpu_surface, &surfaceTexture);

        // Check if surface texture is not optimal and try to re-configure Surface
        if (!ImGui_ImplWGPU_CheckSurfaceTextureOptimalStatus_Helper(surfaceTexture.status))
        {
            ReleaseTextureAndConfigureSurface(surfaceTexture.texture, width, height);
            continue;
        }

        // Start the Dear ImGui frame
        ImGui_ImplWGPU_NewFrame();
        ImGui_ImplSDL2_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();

        WGPUTextureViewDescriptor viewDescriptor {};
        viewDescriptor.format          = wgpu_surface_configuration.format;
        viewDescriptor.dimension       = WGPUTextureViewDimension_2D;
        viewDescriptor.mipLevelCount   = WGPU_MIP_LEVEL_COUNT_UNDEFINED;
        viewDescriptor.arrayLayerCount = WGPU_ARRAY_LAYER_COUNT_UNDEFINED;
        viewDescriptor.aspect          = WGPUTextureAspect_All;

        WGPUTextureView textureView    = wgpuTextureCreateView(surfaceTexture.texture, &viewDescriptor);

        WGPURenderPassColorAttachment color_attachments {};
        color_attachments.depthSlice = WGPU_DEPTH_SLICE_UNDEFINED;
        color_attachments.loadOp     = WGPULoadOp_Clear;
        color_attachments.storeOp    = WGPUStoreOp_Store;
        color_attachments.clearValue = { clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w };
        color_attachments.view       = textureView;

        WGPURenderPassDescriptor render_pass_desc {};
        render_pass_desc.colorAttachmentCount   = 1;
        render_pass_desc.colorAttachments       = &color_attachments;
        render_pass_desc.depthStencilAttachment = nullptr;

        WGPUCommandEncoderDescriptor enc_desc {};
        WGPUCommandEncoder encoder = wgpuDeviceCreateCommandEncoder(wgpu_device, &enc_desc);

        WGPURenderPassEncoder pass = wgpuCommandEncoderBeginRenderPass(encoder, &render_pass_desc);
        ImGui_ImplWGPU_RenderDrawData(ImGui::GetDrawData(), pass);
        wgpuRenderPassEncoderEnd(pass);

        WGPUCommandBufferDescriptor cmd_buffer_desc {};
        WGPUCommandBuffer cmd_buffer = wgpuCommandEncoderFinish(encoder, &cmd_buffer_desc);
        wgpuQueueSubmit(wgpu_queue, 1, &cmd_buffer);

#ifndef __EMSCRIPTEN__
        wgpuSurfacePresent(wgpu_surface);
        // Tick needs to be called in Dawn to display validation errors
#if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN)
        wgpuDeviceTick(wgpu_device);
#endif
#endif
        wgpuTextureViewRelease(textureView);
        wgpuRenderPassEncoderRelease(pass);
        wgpuCommandEncoderRelease(encoder);
        wgpuCommandBufferRelease(cmd_buffer);
    }
#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_END;
#endif

    // Cleanup
    ImGui_ImplWGPU_Shutdown();
    ImGui_ImplSDL2_Shutdown();
    ImGui::DestroyContext();

    wgpuSurfaceUnconfigure(wgpu_surface);
    wgpuSurfaceRelease(wgpu_surface);
    wgpuQueueRelease(wgpu_queue);
    wgpuDeviceRelease(wgpu_device);
    wgpuInstanceRelease(wgpu_instance);

    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

#if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN)
static WGPUAdapter GetAdapter(wgpu::Instance& instance)
{
    wgpu::Adapter acquiredAdapter;
    wgpu::RequestAdapterOptions adapterOptions;

    auto onRequestAdapter = [&](wgpu::RequestAdapterStatus status, wgpu::Adapter adapter, wgpu::StringView message)
    {
        if (status != wgpu::RequestAdapterStatus::Success)
        {
            printf("Failed to get an adapter: %s\n", message.data);
            return;
        }
        acquiredAdapter = std::move(adapter);
    };

    // Synchronously (wait until) acquire Adapter
    wgpu::Future  waitAdapterFunc { instance.RequestAdapter(&adapterOptions, wgpu::CallbackMode::WaitAnyOnly, onRequestAdapter) };
    wgpu::WaitStatus waitStatusAdapter = instance.WaitAny(waitAdapterFunc, UINT64_MAX);
    IM_ASSERT(acquiredAdapter != nullptr && waitStatusAdapter == wgpu::WaitStatus::Success && "Error on Adapter request");
#ifndef NDEBUG
    ImGui_ImplWGPU_PrintAdapterInfo_Helper(acquiredAdapter.Get());
#endif
    return acquiredAdapter.MoveToCHandle();
}

static WGPUDevice GetDevice(wgpu::Instance &instance, wgpu::Adapter &adapter)
{
    // Set device callback functions
    wgpu::DeviceDescriptor deviceDesc;
    deviceDesc.SetDeviceLostCallback(wgpu::CallbackMode::AllowSpontaneous, ImGui_ImplWGPU_DAWN_DeviceLostCallback_Helper);
    deviceDesc.SetUncapturedErrorCallback(ImGui_ImplWGPU_DAWN_ErrorCallback_Helper);

    wgpu::Device acquiredDevice;
    auto onRequestDevice = [&](wgpu::RequestDeviceStatus status, wgpu::Device localDevice, wgpu::StringView message)
    {
        if (status != wgpu::RequestDeviceStatus::Success)
        {
            printf("Failed to get an device: %s\n", message.data);
            return;
        }
        acquiredDevice = std::move(localDevice);
    };

    // Synchronously (wait until) get Device
    wgpu::Future waitDeviceFunc { adapter.RequestDevice(&deviceDesc, wgpu::CallbackMode::WaitAnyOnly, onRequestDevice) };
    wgpu::WaitStatus waitStatusDevice = instance.WaitAny(waitDeviceFunc, UINT64_MAX);
    IM_ASSERT(acquiredDevice != nullptr && waitStatusDevice == wgpu::WaitStatus::Success && "Error on Device request");
    return acquiredDevice.MoveToCHandle();
}
#elif defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
#ifdef __EMSCRIPTEN__
// Adapter and device initialization via JS
EM_ASYNC_JS( void, getAdapterAndDeviceViaJS, (),
{
    if (!navigator.gpu)
        throw Error("WebGPU not supported.");
    const adapter = await navigator.gpu.requestAdapter();
    const device = await adapter.requestDevice();
    Module.preinitializedWebGPUDevice = device;
} );
#else // __EMSCRIPTEN__
static void handle_request_adapter(WGPURequestAdapterStatus status, WGPUAdapter adapter, WGPUStringView message, void* userdata1, void* userdata2)
{
    if (status == WGPURequestAdapterStatus_Success)
    {
        WGPUAdapter* extAdapter = (WGPUAdapter*)userdata1;
        *extAdapter = adapter;
    }
    else
    {
        printf("Request_adapter status=%#.8x message=%.*s\n", status, (int)message.length, message.data);
    }
}

static void handle_request_device(WGPURequestDeviceStatus status, WGPUDevice device, WGPUStringView message, void* userdata1, void* userdata2)
{
    if (status == WGPURequestDeviceStatus_Success)
    {
        WGPUDevice* extDevice = (WGPUDevice*)userdata1;
        *extDevice = device;
    }
    else
    {
        printf("Request_device status=%#.8x message=%.*s\n", status, (int)message.length, message.data);
    }
}

static WGPUAdapter GetAdapter(WGPUInstance& instance)
{
    WGPURequestAdapterOptions adapterOptions = {};

    static WGPUAdapter localAdapter;
    WGPURequestAdapterCallbackInfo adapterCallbackInfo = {};
    adapterCallbackInfo.callback = handle_request_adapter;
    adapterCallbackInfo.userdata1 = &localAdapter;

    wgpuInstanceRequestAdapter(wgpu_instance, &adapterOptions, adapterCallbackInfo);
    IM_ASSERT(localAdapter && "Error on Adapter request");

#ifndef NDEBUG
    ImGui_ImplWGPU_PrintAdapterInfo_Helper(localAdapter);
#endif

    return localAdapter;
}

static WGPUDevice GetDevice(WGPUAdapter &adapter)
{
    static WGPUDevice localDevice;
    WGPURequestDeviceCallbackInfo deviceCallbackInfo = {};
    deviceCallbackInfo.callback = handle_request_device;
    deviceCallbackInfo.userdata1 = &localDevice;

    wgpuAdapterRequestDevice(adapter, NULL, deviceCallbackInfo);
    IM_ASSERT(localDevice && "Error on Device request");

    return localDevice;
}
#endif // __EMSCRIPTEN__
#endif // IMGUI_IMPL_WEBGPU_BACKEND_WGPU

static bool InitWGPU(void* window)
{
    WGPUTextureFormat preferred_fmt = WGPUTextureFormat_Undefined;  // acquired from SurfaceCapabilities

    // Google DAWN backend: Adapter and Device acquisition, Surface creation
#if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN)
    wgpu::InstanceDescriptor instanceDescriptor  = {};
    instanceDescriptor.capabilities.timedWaitAnyEnable = true;
    wgpu::Instance instance = wgpu::CreateInstance(&instanceDescriptor);

    wgpu::Adapter adapter { GetAdapter(instance) };
    wgpu_device = GetDevice(instance, adapter);

    // Create the surface.
#ifdef __EMSCRIPTEN__
    wgpu::EmscriptenSurfaceSourceCanvasHTMLSelector canvasDesc{};
    canvasDesc.selector = "#canvas";

    wgpu::SurfaceDescriptor surfaceDesc = {};
    surfaceDesc.nextInChain = &canvasDesc;
    wgpu::Surface surface = instance.CreateSurface(&surfaceDesc);
#else
    wgpu::Surface surface = ImGui_ImplSDL2_CreateWGPUSurface(instance.Get(), (SDL_Window*)window);
#endif
    if (!surface)
        return false;

    // Moving Dawn objects into WGPU handles
    wgpu_instance = instance.MoveToCHandle();
    wgpu_surface  = surface.MoveToCHandle();

    WGPUSurfaceCapabilities surface_capabilities = {};
    wgpuSurfaceGetCapabilities(wgpu_surface, adapter.Get(), &surface_capabilities);

    preferred_fmt = surface_capabilities.formats[0];

    // WGPU backend: Adapter and Device acquisition, Surface creation
#elif defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
    wgpu_instance = wgpuCreateInstance(nullptr);

#ifdef __EMSCRIPTEN__
    getAdapterAndDeviceViaJS();

    wgpu_device   = emscripten_webgpu_get_device();
    assert(wgpu_device != nullptr && "Error creating the Device");

    WGPUSurfaceDescriptorFromCanvasHTMLSelector html_surface_desc = {};
    html_surface_desc.chain.sType = WGPUSType_SurfaceDescriptorFromCanvasHTMLSelector;
    html_surface_desc.selector    = "#canvas";

    WGPUSurfaceDescriptor surface_desc = {};
    surface_desc.nextInChain   = &html_surface_desc.chain;

    // Create the surface.
    wgpu_surface  = wgpuInstanceCreateSurface(wgpu_instance, &surface_desc);
    preferred_fmt = wgpuSurfaceGetPreferredFormat(wgpu_surface, {} /* adapter */);
#else // __EMSCRIPTEN__
    wgpuSetLogCallback(ImGui_ImplWGPU_WGPU_LogCallback_Helper, NULL);
    wgpuSetLogLevel(WGPULogLevel_Warn);

    static WGPUAdapter adapter = GetAdapter(wgpu_instance);
    wgpu_device = GetDevice(adapter);

    // Create the surface.
    wgpu_surface = ImGui_ImplSDL2_CreateWGPUSurface(wgpu_instance, (SDL_Window*)window);
    if (!wgpu_surface)
        return false;

    WGPUSurfaceCapabilities surface_capabilities = {};
    wgpuSurfaceGetCapabilities(wgpu_surface, adapter, &surface_capabilities);

    preferred_fmt = surface_capabilities.formats[0];
#endif // __EMSCRIPTEN__
#endif // IMGUI_IMPL_WEBGPU_BACKEND_WGPU

    wgpu_surface_configuration.presentMode = WGPUPresentMode_Fifo;
    wgpu_surface_configuration.alphaMode   = WGPUCompositeAlphaMode_Auto;
    wgpu_surface_configuration.usage       = WGPUTextureUsage_RenderAttachment;
    wgpu_surface_configuration.width       = wgpu_surface_width;
    wgpu_surface_configuration.height      = wgpu_surface_height;
    wgpu_surface_configuration.device      = wgpu_device;
    wgpu_surface_configuration.format      = preferred_fmt;

    wgpuSurfaceConfigure(wgpu_surface, &wgpu_surface_configuration);

    wgpu_queue    = wgpuDeviceGetQueue(wgpu_device);

    return true;
}