sdl_box_example.cpp

#include <SDL.h>
#include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <format>

int main(int argc, char* argv[])
{
    std::string app_title = "SDL Box Example";
    int screen_width = 1024, screen_height = 768;
    SDL_Window* main_window = NULL;
    SDL_Renderer* renderer = NULL;
    SDL_Event event = { 0 };
    bool should_quit = false;
    SDL_FRect box_destination = { };            // Use SDL_FRect instead of SDL_Rect for subpixel rendering.
    std::stringstream error;                    // Aid in creating error strings for output later.

    try {
        // INITIALIZATION:
        // ------------------------------------------------------------------------------------------------------------
        // Initialize SDL and create a window and renderer

        if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) < 0) {
            error << "Failed to initialize SDL: " << SDL_GetError();
            throw(error.str());
        }

        if ((main_window = SDL_CreateWindow(
            app_title.c_str(),
            SDL_WINDOWPOS_CENTERED,         // Use Centered Top Coordinate
            SDL_WINDOWPOS_CENTERED,         // Use Centered Left Coordinate
            screen_width, screen_height,    // Width & Height
            0                               // Flags (Window is implicitly shown if SDL_WINDOW_HIDDEN is not set)
        )) == 0) {
            error << "Failed to create a window: " << SDL_GetError();
            throw(error.str());
        }

        // -1 to use the first available render driver.
        //  0 to default to SDL_RENDERER_ACCELERATED (hardware), and fallback or fallback to software if necessary.
        if ((renderer = SDL_CreateRenderer(
            main_window,    // The window to associate with this renderer, multiple windows & renderers are possible

            -1,             // Index of render driver, -1 for default

            0               // Flags, 0 to default to SDL_RENDERER_ACCELERATED (hardware), and fallback or fallback to 
                            // software if necessary.
        )) == 0) {
            error << "Failed to create the renderer: " << SDL_GetError();
            throw(error.str());
        }

        // Comment this line out if you do not want VSync. VSync is when the rendering waits for the monitor to finish
        // drawing the last frame so that you do not start drawing the current frame before it's done. Without VSync
        // you could see just how fast your computer can render, but also it prevents seeing screen tearing (only 
        // partial frames being drawn).
        SDL_RenderSetVSync(renderer, 1); // 1 for on, 0 for off.
        // With this on you might expect a framerate of around 59 or 60 depending on your monitor. I have a gaming
        // monitor with a refresh rate of 165, so I will see my fps as close to 165.

        // CONFIGURE THE BOX / PLAYER, IT'S INITIAL LOCATION AND SIZE:
        // ------------------------------------------------------------------------------------------------------------
        box_destination.w = 100.0f;
        box_destination.h = 100.0f;
        box_destination.x = screen_width / 2.F - box_destination.w / 2.F;   // Center is half the screen width minus half the box width
        box_destination.y = screen_height / 2.F - box_destination.h / 2.F;  // Center is half the screen height minus half the box height

        // PRIMARY & EVENT LOOP:
        while (!should_quit) {
            while (SDL_PollEvent(&event)) {
                switch (event.type) {
                case SDL_QUIT:
                    should_quit = 1;
                    break;
                case SDL_KEYDOWN:
                    switch (event.key.keysym.sym) {
                    case SDLK_ESCAPE:
                        should_quit = 1;
                        break;
                    }
                    break;
                }
            }

            // RENDERING:
            // --------------------------------------------------------------------------------------------------------

            // Clear the background:
            // Always start fresh and clear, you're never guaranteed to have a blank canvas or the previous rendered 
            // canvas here.
            SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
            SDL_RenderClear(renderer);

            // Render the box:
            SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); // Black with an opacity of 255 (totally visible)
            SDL_RenderFillRectF(renderer, &box_destination);

            // Show on screen:
            SDL_RenderPresent(renderer);
        }

    }
    catch (std::string error_str) {
        // This is a simple way to show a message box, if main_window failed to create this will still work
        // since main_window will be NULL (the message box will just not have a parent):
        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, app_title.c_str(), error_str.c_str(), main_window);

        // Output the error to the console, if you have one
        std::cout << error_str << std::endl;
    }

    // CLEAN-UP & SHUTDOWN:
    // ----------------------------------------------------------------------------------------------------------------
    if (renderer) SDL_DestroyRenderer(renderer);
    if (main_window) SDL_DestroyWindow(main_window);
    SDL_Quit();

    return 0;
}