Question

How to change window colors using ImGui with SDL2 in C++

Answer 1

// Read online: https://github.com/ocornut/imgui/tree/master/docs

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

int main(int argc, char* argv[]) 
{
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0) {
        std::cout << "SDL_Init Error: " << SDL_GetError();
        return -1;
    }

    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2", 
        SDL_WINDOWPOS_CENTERED, 
        SDL_WINDOWPOS_CENTERED, 
        1200, 800, 
        SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);

    SDL_Renderer* renderer = SDL_CreateRenderer(window, 
        -1, 
        SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_ACCELERATED);
    if (renderer == NULL) {
        SDL_Log("Error: SDL_CreateRenderer");
        return false;
    }

    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;

    ImGui::StyleColorsDark();

    ImGui_ImplSDL2_InitForSDLRenderer(window, renderer);
    ImGui_ImplSDLRenderer_Init(renderer);

    bool show_demo_window = true;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    bool close = false;
    while (!close) {
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            ImGui_ImplSDL2_ProcessEvent(&event);
            if (event.type == SDL_QUIT)
                close = true;
        }

        ImGui_ImplSDLRenderer_NewFrame();
        ImGui_ImplSDL2_NewFrame();
        ImGui::NewFrame();

        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        {
            ImGui::Begin("ImGui Window");  // Create a window called "ImGui"
            ImGui::Checkbox("Demo Window", &show_demo_window); 
            ImGui::ColorEdit3("clear color", (float*)&clear_color); 
            ImGui::End();
        }

        // Rendering
        ImGui::Render();
        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);
    }

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

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

 

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