SDL and pixels.

main.cpp

#include <iostream>
#include <SDL2/SDL.h>
#include "../include/fastnoise/FastNoise.h"

// Screen dimension constants
const int SCREEN_WIDTH = 1000;
const int SCREEN_HEIGHT = 1000;

// Starts up SDL and creates window
bool init();

// Frees media and shuts down SDL
void close();

// Current displayed image
SDL_Surface *gCurrentSurface = NULL;

// The window we'll be rendering to
SDL_Window *gWindow = NULL;

// The window renderer
SDL_Renderer *gRenderer = NULL;

SDL_Texture *texture = NULL;
Uint32 *pixels = NULL;

bool init()
{
  // Initialization flag
  SDL_Init(SDL_INIT_VIDEO);
  gWindow = SDL_CreateWindow("SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
  gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED);
  SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);

  texture = SDL_CreateTexture(gRenderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STATIC, 980, 980);
  pixels = new Uint32[980 * 980];

  return true;
}

int main(int argc, char *args[])
{
  // Start up SDL and create window
  if (!init())
  {
    printf("Failed to initialize!\n");
  }
  else
  {

    // Main loop flag
    bool quit = false;

    // Event handler
    SDL_Event e;

    // While application is running
    while (!quit)
    {
      // Handle events on queue
      while (SDL_PollEvent(&e) != 0)
      {
        // User requests quit
        if (e.type == SDL_QUIT)
        {
          quit = true;
        }
      }

      Uint32 format;
      int w, h;
      int pitch = 0;

      SDL_QueryTexture(texture, &format, nullptr, &w, &h);

      SDL_PixelFormat pixelFormat;
      pixelFormat.format = format;
      Uint32 color = SDL_MapRGB(&pixelFormat, 10, 200, 10);

      SDL_LockTexture(texture, NULL, (void **)&pixels, &pitch);

      // set pixels to solid white
      for (int i = 0; i < pitch * 980; i++)
      {
        pixels[i] = color;
      }

      SDL_UnlockTexture(texture);

      SDL_Rect dst;
      dst.x = 10;
      dst.y = 10;
      dst.w = 980;
      dst.h = 980;

      SDL_RenderClear(gRenderer);
      SDL_RenderCopy(gRenderer, texture, NULL, &dst);

      // Update screen
      SDL_RenderPresent(gRenderer);
    }
  }

  // Free resources and close SDL
  close();

  return 0;
}

void close()
{
  // Destroy window
  SDL_DestroyWindow(gWindow);
  SDL_DestroyRenderer(gRenderer);
  gWindow = NULL;
  gRenderer = NULL;

  // Quit SDL subsystems
  SDL_Quit();
}