sdl_backend.cpp

#if defined(CIMGUI_GO_USE_SDL2)
#define CIMGUI_USE_SDL2
#define CIMGUI_USE_OPENGL3

// Dear ImGui: standalone example application for SDL2 + OpenGL
// (SDL 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 "sdl_backend.h"
#include "cimgui/cimgui.h"
#include "cimgui/cimgui_impl.h"

#include <cstdlib>
#include <stdio.h>
#include "thirdparty/SDL/include/SDL.h"
#if defined(IMGUI_IMPL_OPENGL_ES2)
#include "thirdparty/SDL/include/SDL_opengles2.h"
#else
#include "thirdparty/SDL/include/SDL_opengl.h"
#endif

// This example can also compile and run with Emscripten! See 'Makefile.emscripten' for details.
#ifdef __EMSCRIPTEN__
#include "../libs/emscripten/emscripten_mainloop_stub.h"
#endif

ImVec4 sdl_clear_color = *ImVec4_ImVec4_Float(0.45, 0.55, 0.6, 1.0);

SDL_WindowFlags sdl_flags = (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);

// Setup SDL
int igInitSDL() {
    return SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER);
}

// Main code
SDL_Window* igCreateSDLWindow(const char* title, int width, int height,VoidCallback afterCreateContext)
{

    // Decide GL+GLSL versions
#if defined(IMGUI_IMPL_OPENGL_ES2)
    // GL ES 2.0 + GLSL 100
    const char* glsl_version = "#version 100";
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#elif defined(__APPLE__)
    // GL 3.2 Core + GLSL 150
    const char* glsl_version = "#version 150";
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG); // Always required on Mac
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
#else
    // GL 3.0 + GLSL 130
    const char* glsl_version = "#version 130";
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#endif

    // From 2.0.18: Enable native IME.
#ifdef SDL_HINT_IME_SHOW_UI
    SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
#endif

    // Create window with graphics context
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    SDL_Window* window = SDL_CreateWindow(title, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, sdl_flags);
    sdl_flags = (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI); // reset default flags
    SDL_GLContext gl_context = SDL_GL_CreateContext(window);
    SDL_GL_MakeCurrent(window, gl_context);
    SDL_GL_SetSwapInterval(1); // Enable vsync

    // Setup Dear ImGui context
    igCreateContext(0);

    if (afterCreateContext != NULL) {
        afterCreateContext();
    }

    ImGuiIO* io = igGetIO();
    io->ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io->ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
    io->ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
    io->ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
    //io.ConfigViewportsNoAutoMerge = true;
    //io.ConfigViewportsNoTaskBarIcon = true;

    // Setup Dear ImGui style
    igStyleColorsDark(0);
    //ImGui::StyleColorsLight();

    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
    ImGuiStyle* style = igGetStyle();
    if (io->ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        style->WindowRounding = 0.0f;
        style->Colors[ImGuiCol_WindowBg].w = 1.0f;
    }

    // Setup Platform/Renderer backends
    ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
    ImGui_ImplOpenGL3_Init(glsl_version);

    // 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).
    // - 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 \\ !
    // - Our Emscripten build process allows embedding fonts to be accessible at runtime from the "fonts/" folder. See Makefile.emscripten for details.
    //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, nullptr, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != nullptr);

    return window;
}

void igSDLRunLoop(SDL_Window *window, VoidCallback loop, VoidCallback beforeRender, VoidCallback afterRender,
               VoidCallback beforeDestroyContext) {
    ImGuiIO* io = igGetIO();
    // 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
    {
        if (beforeRender != NULL) {
            beforeRender();
        }

        // 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;
        }

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplSDL2_NewFrame();
        igNewFrame();

        // rendering
        if (loop != NULL) {
            loop();
        }

        // Rendering
        igRender();
        glViewport(0, 0, (int)io->DisplaySize.x, (int)io->DisplaySize.y);
        glClearColor(sdl_clear_color.x * sdl_clear_color.w, sdl_clear_color.y * sdl_clear_color.w, sdl_clear_color.z * sdl_clear_color.w, sdl_clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());

        // Update and Render additional Platform Windows
        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
        //  For this specific demo app we could also call SDL_GL_MakeCurrent(window, gl_context) directly)
        if (io->ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
        {
            SDL_Window* backup_current_window = SDL_GL_GetCurrentWindow();
            SDL_GLContext backup_current_context = SDL_GL_GetCurrentContext();
            igUpdatePlatformWindows();
            igRenderPlatformWindowsDefault(0, 0);
            SDL_GL_MakeCurrent(backup_current_window, backup_current_context);
        }

        SDL_GL_SwapWindow(window);
    }
#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_END;
#endif

    // Cleanup
    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplSDL2_Shutdown();

    if (beforeDestroyContext != NULL) {
        beforeDestroyContext();
    }

    igDestroyContext(0);

    SDL_GLContext gl_context = SDL_GL_GetCurrentContext();
    SDL_GL_DeleteContext(gl_context);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return;
}

void igSDLWindow_GetContentScale(SDL_Window *window, float *width, float *height) {
  SDL_RenderGetScale(SDL_GetRenderer(window), width, height);
}

void igSDLWindow_GetDisplaySize(SDL_Window *window, int *width, int *height) {
  SDL_GetWindowSize(window, width, height);
}

void igSDLWindow_GetWindowPos(SDL_Window *window, int *x, int *y) { SDL_GetWindowPosition(window, x, y); }

void igSDLWindow_SetWindowPos(SDL_Window *window, int x, int y) { SDL_SetWindowPosition(window, x, y); }

void igSDLWindow_SetSize(SDL_Window *window, int width, int height) { SDL_SetWindowSize(window, width, height); }

void igSDLWindow_SetTitle(SDL_Window *window, const char *title) { SDL_SetWindowTitle(window, title); }

void igSDLWindow_SetSizeLimits(SDL_Window *window, int minWidth, int minHeight, int maxWidth, int maxHeight) {
  SDL_SetWindowMinimumSize(window, minWidth, minHeight);
  SDL_SetWindowMaximumSize(window, maxWidth, maxHeight);
}

// set flag if value is 1, clear flag if value is 0
void igSDLWindowHint(SDL_WindowFlags hint, int value) {
    if (value == 1) {
            sdl_flags = (SDL_WindowFlags)(sdl_flags | hint);
    } else {
        sdl_flags = (SDL_WindowFlags)(sdl_flags & ~hint);
    }
    if (hint == 0) {
        sdl_flags = (SDL_WindowFlags)(0);
    }
}

#endif // CIMGUI_GO_USE_SDL2