SDL (Simple DirectMedia Layer) - Creating a window

In this section, we will demonstrate how to create and destroy basic SDL windows. The following code will create a window called "SDL Example", 800 by 600 pixels in width and height respectively, and print it on the screen for 3000 miliseconds.

#include <stdio.h> /* printf and fprintf */

#ifdef _WIN32
#include <SDL/SDL.h> /* Windows-specific SDL2 library */
#else
#include <SDL2/SDL.h> /* macOS- and GNU/Linux-specific */
#endif

/* Sets constants */
#define WIDTH 800
#define HEIGHT 600
#define DELAY 3000

int main (int argc, char **argv)
{
  /* Initialises data */
  SDL_Window *window = NULL;
  
  /*
  * Initialises the SDL video subsystem (as well as the events subsystem).
  * Returns 0 on success or a negative error code on failure using SDL_GetError().
  */
  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
    fprintf(stderr, "SDL failed to initialise: %s\n", SDL_GetError());
    return 1;
  }

  /* Creates a SDL window */
  window = SDL_CreateWindow("SDL Example", /* Title of the SDL window */
			    SDL_WINDOWPOS_UNDEFINED, /* Position x of the window */
			    SDL_WINDOWPOS_UNDEFINED, /* Position y of the window */
			    WIDTH, /* Width of the window in pixels */
			    HEIGHT, /* Height of the window in pixels */
			    0); /* Additional flag(s) */

  /* Checks if window has been created; if not, exits program */
  if (window == NULL) {
    fprintf(stderr, "SDL window failed to initialise: %s\n", SDL_GetError());
    return 1;
  }

  /* Pauses all SDL subsystems for a variable amount of milliseconds */
  SDL_Delay(DELAY);

  /* Frees memory */
  SDL_DestroyWindow(window);
  
  /* Shuts down all SDL subsystems */
  SDL_Quit(); 
  
  return 0;
}

^{You can download the source code of this section in this GitLab repository. All source code is stored in this group.}

Setting up data

In order to create the window, we need to specify its height and width. In this case we define the global constants using a macro. We'll make the width 800 pixels long and the height 600 pixels high.

#define WIDTH 800
#define HEIGHT 600

In this program, we will have to pause the SDL subsystems to let the window stay open. We'll define the delay to be 3000 milliseconds.

#define DELAY 3000

In C, it's a good idea to initialise your variables first in order to understand when and how they are being used. In this case, we initialise a SDL_Window pointer called window. In SDL, almost all objects are initialised as pointers.

SDL_Window *window = NULL;

Creating the window

In order to create the window, we need to use the SDL_CreateWindow function and set some parameters too.

window = SDL_CreateWindow("SDL Example", /* Title of the SDL window */
			  SDL_WINDOWPOS_UNDEFINED, /* Position x of the window */
			  SDL_WINDOWPOS_UNDEFINED, /* Position y of the window */
			  WIDTH, /* Width of the window in pixels */
			  HEIGHT, /* Height of the window in pixels */
			  0); /* Additional flag(s) */

You can learn more about SDL_CreateWindow in the SDL Wiki.

Using SDL_Delay

In the example code, we used the function SDL_Delay in order to pause the SDL subsystems for a variable amount of time in milliseconds and allow the window to be shown on the screen whilst it is open. In this case, the pause is defined with the DELAY macro as being 3000 milliseconds.

SDL_Delay(DELAY);

You can learn more about SDL_Delay in the SDL Wiki.

Destroying the window

In order to close the window and free memory, we must destroy the window. Destroying window is much simpler than creating it.

SDL_DestroyWindow(window);

You can learn more about SDL_DestroyWindow in the SDL Wiki.