Code from https://github.com/Twinklebear/TwinklebearDev-Lessons/blob/master/Lesson4/src/main.cpp

main.cpp

#include <string>
#include <iostream>
#include <SDL.h>
#include <SDL_image.h>
#include "res_path.h"
#include "cleanup.h"

/*
 * Lesson 4: Handling Events
 */
//Screen attributes
const int SCREEN_WIDTH  = 640;
const int SCREEN_HEIGHT = 480;

/*
 * Log an SDL error with some error message to the output stream of our choice
 * @param os The output stream to write the message too
 * @param msg The error message to write, format will be msg error: SDL_GetError()
 */
void logSDLError(std::ostream &os, const std::string &msg){
	os << msg << " error: " << SDL_GetError() << std::endl;
}
/*
 * Loads an image into a texture on the rendering device
 * @param file The image file to load
 * @param ren The renderer to load the texture onto
 * @return the loaded texture, or nullptr if something went wrong.
 */
SDL_Texture* loadTexture(const std::string &file, SDL_Renderer *ren){
	SDL_Texture *texture = IMG_LoadTexture(ren, file.c_str());
	if (texture == nullptr){
		logSDLError(std::cout, "LoadTexture");
	}
	return texture;
}
/*
 * Draw an SDL_Texture to an SDL_Renderer at position x, y, with some desired
 * width and height
 * @param tex The source texture we want to draw
 * @param rend The renderer we want to draw too
 * @param x The x coordinate to draw too
 * @param y The y coordinate to draw too
 * @param w The width of the texture to draw
 * @param h The height of the texture to draw
 */
void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, int x, int y, int w, int h){
	//Setup the destination rectangle to be at the position we want
	SDL_Rect dst;
	dst.x = x;
	dst.y = y;
	dst.w = w;
	dst.h = h;
	SDL_RenderCopy(ren, tex, NULL, &dst);
}
/*
 * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving
 * the texture's width and height
 * @param tex The source texture we want to draw
 * @param rend The renderer we want to draw too
 * @param x The x coordinate to draw too
 * @param y The y coordinate to draw too
 */
void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, int x, int y){
	int w, h;
	SDL_QueryTexture(tex, NULL, NULL, &w, &h);
	renderTexture(tex, ren, x, y, w, h);
}

int main(int, char**){
	//Start up SDL and make sure it went ok
	if (SDL_Init(SDL_INIT_VIDEO) != 0){
		logSDLError(std::cout, "SDL_Init");
		return 1;
	}

	//Setup our window and renderer, this time let's put our window in the center
	//of the screen
	SDL_Window *window = SDL_CreateWindow("Lesson 4", SDL_WINDOWPOS_CENTERED,
			SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
	if (window == nullptr){
		logSDLError(std::cout, "CreateWindow");
		SDL_Quit();
		return 1;
	}
	SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
	if (renderer == nullptr){
		logSDLError(std::cout, "CreateRenderer");
		cleanup(window);
		SDL_Quit();
		return 1;
	}

	//The texture we'll be using
	const std::string resPath = getResourcePath("Lesson4");
	SDL_Texture *image = loadTexture(resPath + "image.png", renderer);
	if (image == nullptr){
		cleanup(image, renderer, window);
		IMG_Quit();
		SDL_Quit();
		return 1;
	}

	//Our texture size won't change, so we can get it here
	//instead of constantly allocating/deleting ints in the loop
	int iW, iH;
	SDL_QueryTexture(image, NULL, NULL, &iW, &iH);
	int x = SCREEN_WIDTH / 2 - iW / 2;
	int y = SCREEN_HEIGHT / 2 - iH / 2;

	//Our event structure
	SDL_Event e;
	//For tracking if we want to quit
	bool quit = false;
	while (!quit){
		//Read any events that occured, for now we'll just quit if any event occurs
		while (SDL_PollEvent(&e)){
			//If user closes the window
			if (e.type == SDL_QUIT){
				quit = true;
			}
			//If user presses any key
			if (e.type == SDL_KEYDOWN){
				quit = true;
			}
			//If user clicks the mouse
			if (e.type == SDL_MOUSEBUTTONDOWN){
				quit = true;
			}
		}
		//Rendering
		SDL_RenderClear(renderer);
		//Draw the image
		renderTexture(image, renderer, x, y);
		//Update the screen
		SDL_RenderPresent(renderer);
	}
	//Destroy the various items
	cleanup(image, renderer, window);
	IMG_Quit();
	SDL_Quit();

	return 0;
}