SDL2 Hello World | SDL2 Getting Started | SDL | OpenGL

sdl2hello.cc

// SDL2 Hello, World!
// This should display a white screen for 2 seconds
// with the text 'Hello World!'
// Prerequisites (Fedora):
//   sudo dnf install SDL2-static
//   sudo dnf install SDL2-devel (Actually, this gets installed as a dependency of SDL2-static)
//   sudo dnf install SDL2_ttf-devel
// Compile:
//   gcc -g sdl2hello.cc -o sdl2hello -lSDL2 -lSDL2main -lSDL2_ttf
// Run:
//   ./hello_sdl2
// Bugs:
//   Has hard-coded path to the .ttf file.
//   - There must be a way to say "Get the system sans serif font".
//   - I guess I could use an environment variable to point to the location of .ttf files and other resources needed by the app.
//     Or have well-known installation directory to look for a bundled .ttf file,like ~/.config/name-of-app or /usr/share/name-of-app
//     Better: the $XDG_CONFIG_DIRS preference-ordered set of directories.
//     (Does Windows have something similar?)
//   - Update: Good blog post about general problem of how an executable can find resource files
//     https://web.archive.org/web/20150910164707/http://voices.canonical.com/jussi.pakkanen/2011/11/15/accessing-files-how-hard-can-it-be/
//     Via: https://github.com/mesonbuild/meson/issues/860#issuecomment-502482754

#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>

#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480

void drawText ( SDL_Surface* screen, char* string, int size, int x, int y, SDL_Color fgC, SDL_Color bgC) {
  // Remember to call TTF_Init(), TTF_Quit(), before/after using this function.
  TTF_Font* font = TTF_OpenFont("/usr/share/fonts/dejavu-sans-mono-fonts/DejaVuSansMono-Bold.ttf", size);
  if(!font) {
    printf("[ERROR] TTF_OpenFont() Failed with: %s\n", TTF_GetError());
    exit(2);
  }
  TTF_SetFontStyle(font, TTF_STYLE_BOLD);
  //SDL_Surface* textSurface = TTF_RenderText_Solid(font, string, fgC);     // aliased glyphs
  SDL_Surface* textSurface = TTF_RenderText_Shaded(font, string, fgC, bgC);   // anti-aliased glyphs
  SDL_Rect textLocation = { x, y, 0, 0 };
  SDL_BlitSurface(textSurface, NULL, screen, &textLocation);
  SDL_FreeSurface(textSurface);
  TTF_CloseFont(font);
}


int main(int argc, char* args[]) {
  SDL_Window* window = NULL;
  SDL_Surface* screenSurface = NULL;
  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    fprintf(stderr, "could not initialize sdl2: %s\n", SDL_GetError());
    return 1;
  }
  window = SDL_CreateWindow(
			    "hello_sdl2",
			    SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
			    SCREEN_WIDTH, SCREEN_HEIGHT,
			    SDL_WINDOW_SHOWN
			    );
  if (window == NULL) {
    fprintf(stderr, "could not create window: %s\n", SDL_GetError());
    return 1;
  }
  screenSurface = SDL_GetWindowSurface(window);
  SDL_FillRect(screenSurface, NULL, SDL_MapRGB(screenSurface->format, 0xFF, 0xFF, 0xFF));
  SDL_UpdateWindowSurface(window);
  
  //-----------------------------------------------------
  // Draw some Text
  //-----------------------------------------------------
  if(TTF_Init() == -1) {
    printf("[ERROR] TTF_Init() Failed with: %s\n", TTF_GetError());
    exit(2);
  }
  SDL_Color fg = { 0x00,0x00,0xff }, bg = {0xff,0xff,0xff};      // Blue text on white background
  drawText( screenSurface, (char*) "Hello World! @ (x=50, y=100)", 18, 50, 100, fg, bg);
  SDL_UpdateWindowSurface(window);
  TTF_Quit();

  SDL_Delay(2000);
  SDL_DestroyWindow(window);
  SDL_Quit();
  return 0;
}