imgui/examples/example_sdl_sdlrenderer/main.cpp

// Dear ImGui: standalone example application for SDL2 + SDL_Renderer
// (SDL is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan/Metal graphics context creation, etc.)
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

// Important to understand: SDL_Renderer is an _optional_ component of SDL. We do not recommend you use SDL_Renderer
// because it provides a rather limited API to the end-user. We provide this backend for the sake of completeness.
// For a multi-platform app consider using e.g. SDL+DirectX on Windows and SDL+OpenGL on Linux/OSX.

#include "imgui.h"
#include "imgui_impl_sdl.h"
#include "imgui_impl_sdlrenderer.h"
#include <stdio.h>
#include <SDL.h>

#if !SDL_VERSION_ATLEAST(2,0,17)
#error This backend requires SDL 2.0.17+ because of SDL_RenderGeometry() function
#endif

// Data
static SDL_Window*      g_AppWindow = NULL;
static SDL_Renderer*    g_AppWindowRenderer = NULL;

// Forward declarations of helper functions
bool MainLoopStep();

// Main code
int main(int, char**)
{
    // Setup SDL
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
    {
        printf("Error: %s\n", SDL_GetError());
        return -1;
    }

    // Create window with SDL_Renderer graphics context
    SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+SDL_Renderer example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_ACCELERATED);
    if (renderer == NULL)
    {
        SDL_Log("Error creating SDL_Renderer!");
        return 0;
    }
    g_AppWindow = window;
    g_AppWindowRenderer = renderer;
    //SDL_RendererInfo info;
    //SDL_GetRendererInfo(renderer, &info);
    //SDL_Log("Current SDL_Renderer: %s", info.name);

    // 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 Platform/Renderer backends
    ImGui_ImplSDL2_InitForSDLRenderer(window, renderer);
    ImGui_ImplSDLRenderer_Init(renderer);

    // 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 NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
    // - 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.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf", 18.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != NULL);

    // Main loop
    while (true)
    {
        if (!MainLoopStep())
            break;
    }

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

    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

bool MainLoopStep()
{
    // 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_Window* window = g_AppWindow;
    SDL_Renderer* renderer = g_AppWindowRenderer;
    SDL_Event event;
    while (SDL_PollEvent(&event))
    {
        ImGui_ImplSDL2_ProcessEvent(&event);
        if (event.type == SDL_QUIT)
            return false;
        if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
            return false;
    }

    // Start the Dear ImGui frame
    ImGuiIO& io = ImGui::GetIO();
    ImGui_ImplSDLRenderer_NewFrame();
    ImGui_ImplSDL2_NewFrame();
    ImGui::NewFrame();

    // Our state
    // (we use static, which essentially makes the variable globals, as a convenience to keep the example code easy to follow)
    static bool show_demo_window = true;
    static bool show_another_window = false;
    static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // 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 / ImGui::GetIO().Framerate, ImGui::GetIO().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();
    SDL_RenderSetScale(renderer, io.DisplayFramebufferScale.x, io.DisplayFramebufferScale.y);
    SDL_SetRenderDrawColor(renderer, (Uint8)(clear_color.x * 255), (Uint8)(clear_color.y * 255), (Uint8)(clear_color.z * 255), (Uint8)(clear_color.w * 255));
    SDL_RenderClear(renderer);
    ImGui_ImplSDLRenderer_RenderDrawData(ImGui::GetDrawData());
    SDL_RenderPresent(renderer);

    return true;
}