1.cpp

#include <SDL.h>
#include <SDL_image.h>
#include <SDL_ttf.h>
#include <stdexcept>
#include <string>
#include <iostream>

2.cpp

if (TTF_Init() == -1){
    std::cout << TTF_GetError() << std::endl;
    return 2;
}

3.cpp

SDL_Texture* RenderText(std::string message, std::string fontFile, 
                        SDL_Color color, int fontSize)
{
    //Open the font
    TTF_Font *font = nullptr;
    font = TTF_OpenFont(fontFile.c_str(), fontSize);
    if (font == nullptr)
        throw std::runtime_error("Failed to load font: " + fontFile + TTF_GetError());
	
    //Render the message to an SDL_Surface, as that's what TTF_RenderText_X returns
    SDL_Surface *surf = TTF_RenderText_Blended(font, message.c_str(), color);
    SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, surf);
    //Clean up unneeded stuff
    SDL_FreeSurface(surf);
    TTF_CloseFont(font);

    return texture;
}

4.cpp

SDL_Texture *image = nullptr;
try {
    SDL_Color color = { 255, 255, 255 };
    image = RenderText("TTF fonts are cool!", "../res/Lesson6/SourceSansPro-Regular.ttf", 
        color, 64);
}
catch (const std::runtime_error &e){
    std::cout << e.what() << std::endl;
    return 4;
}