This complete guide walks through creating windows, setting up accelerated renderers, drawing primitives, loading fonts, rendering text, handling window events, scaling, dynamic text on keypress, and best practices for SDL2 + SDL_ttf.

Compile with -lSDL2 -lSDL2_ttf.

SDL_Init(SDL_INIT_VIDEO);
TTF_Init();

Parameters

• SDL_INIT_VIDEO – enables the video subsystem; combine flags (e.g., | SDL_INIT_EVENTS).
• TTF_Init() – no params; returns 0 on success.

SDL_Window* win = SDL_CreateWindow(
    "Demo",                 /* window title                    */
    SDL_WINDOWPOS_CENTERED,  /* x position                      */
    SDL_WINDOWPOS_CENTERED,  /* y position                      */
    800,                     /* width  px                       */
    600,                     /* height px                       */
    SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE
);

Parameters

• title – UTF‑8 C‑string shown in title‑bar.
• x/y – screen coordinates or SDL_WINDOWPOS_UNDEFINED/SDL_WINDOWPOS_CENTERED.
• w/h – window size in logical pixels.
• flags
  • SDL_WINDOW_SHOWN – make visible immediately.
  • SDL_WINDOW_RESIZABLE – allow user‑driven size change.
  • SDL_WINDOW_FULLSCREEN, SDL_WINDOW_FULLSCREEN_DESKTOP, SDL_WINDOW_OPENGL…

SDL_Renderer* ren = SDL_CreateRenderer(
    win,           /* window                                       */
    -1,            /* driver index (‑1 = first supporting flags)   */
    SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC
);

SDL_SetRenderDrawBlendMode(ren, SDL_BLENDMODE_BLEND);

Parameters

• window – handle from SDL_CreateWindow.
• index – GPU driver (-1 auto select).
• flags
  • SDL_RENDERER_ACCELERATED – hardware acceleration.
  • SDL_RENDERER_SOFTWARE – fallback software.
  • SDL_RENDERER_PRESENTVSYNC – sync with display refresh.

Blend mode enables transparency for textures and primitives.

bool running = true;
SDL_StartTextInput();

/* text buffer & helpers */
std::string buffer = "Type: ";
SDL_Color white = {255,255,255,255};
SDL_Texture* textTex = NULL;
TTF_Font* font24 = TTF_OpenFont("NunitoSans-Regular.ttf", 24);

auto renderText = [&](const std::string& msg){
    if(textTex) SDL_DestroyTexture(textTex);
    SDL_Surface* s = TTF_RenderUTF8_Blended(font24, msg.c_str(), white);
    textTex = SDL_CreateTextureFromSurface(ren, s);
    SDL_FreeSurface(s);
};
renderText(buffer);

while (running) {
  SDL_Event e;
  while (SDL_PollEvent(&e)) {
    if (e.type == SDL_QUIT) running = false;

    if (e.type == SDL_TEXTINPUT) {
        buffer += e.text.text;      /* append typed character */
        renderText(buffer);
    }
    if (e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_BACKSPACE && buffer.size() > 6) {
        buffer.pop_back();          /* remove last char */
        renderText(buffer);
    }
    if (e.type == SDL_WINDOWEVENT && e.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
        int newW = e.window.data1;
        int newH = e.window.data2;
        /* handle resize */
    }
  }

  SDL_SetRenderDrawColor(ren, 30,30,30,255);
  SDL_RenderClear(ren);

  /* draw dynamic text */
  SDL_Rect dst; SDL_QueryTexture(textTex, NULL, NULL, &dst.w, &dst.h);
  dst.x = 50; dst.y = 40;
  SDL_RenderCopy(ren, textTex, NULL, &dst);

  SDL_RenderPresent(ren);
}

SDL_StopTextInput();

Key Points

• SDL_StartTextInput()/SDL_StopTextInput() – enable/disable Unicode text events.
• SDL_TEXTINPUT – event fired for every UTF‑8 character typed (handles IME & locale correctly).
• SDL_KEYDOWN – capture non‑text keys (e.g., backspace, function keys).
• Re‑render texture whenever the string changes to display updated text.

TTF_Font* font24 = TTF_OpenFont("NunitoSans-Regular.ttf", 24);
TTF_Font* font48 = TTF_OpenFont("NunitoSans-Regular.ttf", 48);

Parameters

• file – path to TrueType/OTF font.
• ptsize – requested height in points.

Reuse opened fonts to avoid reload overhead.

SDL_Surface* surf = TTF_RenderUTF8_Blended(font24, "Hello SDL2", white);
SDL_Texture* texStatic = SDL_CreateTextureFromSurface(ren, surf);
SDL_FreeSurface(surf);

SDL_Rect dst; SDL_QueryTexture(texStatic, NULL, NULL, &dst.w, &dst.h);
SDL_RenderCopy(ren, texStatic, NULL, &dst);

Use this method for labels that rarely change.

SDL_Surface* paragraph = TTF_RenderUTF8_Blended_Wrapped(
    font24,
    "Lorem ipsum dolor sit amet…",
    white,
    400  /* wrap max width px */
);

SDL_ttf handles newlines automatically.

SDL_RenderSetLogicalSize(ren, 800, 600);

Coordinates are mapped to virtual space and automatically scaled.

SDL_SetWindowFullscreen(win, SDL_WINDOW_FULLSCREEN_DESKTOP);

SDL_DisplayMode dm;
SDL_GetCurrentDisplayMode(0, &dm);
printf("%dx%d @ %dHz\n", dm.w, dm.h, dm.refresh_rate);

float ddpi, hdpi, vdpi;
SDL_GetDisplayDPI(0, &ddpi, &hdpi, &vdpi);

if(!win || !ren){ fprintf(stderr, "%s\n", SDL_GetError()); }
SDL_DestroyTexture(textTex);
SDL_DestroyTexture(texStatic);
TTF_CloseFont(font24);
SDL_DestroyRenderer(ren);
SDL_DestroyWindow(win);
TTF_Quit();
SDL_Quit();