How can I render a texture to the screen in SDL2?

Question

I've recently started upgrading my SDL version from 1.2 to 2.0.3, and while on the SDL Wiki, I've come across SDL_Renderer, SDL_Window, and SDL_Texture. I did some research and found a link at StackExchange to be particularly informative. However, I'd like to know more about the process of getting a texture on the screen with this new software version.

My Question

By what process does SDL2 display a texture to the user's screen?

My Current Understanding

My current understanding is that a renderer is tied to a single window, which allows the coder to blit a texture (or multiple) to a renderer, which is then displayed to the window. Is this approximation correct?

Answer 1

I know how you feel, SDL2 is somewhat different from the earlier one, to make it easier, I'll explain how SDL_Renderer, SDL_Window, and SDL_Texture work. The code blocks are separated with explanations, but for a program they would be used together in the order given.

//CREATE WINDOW
SDL_Window *window = SDL_CreateWindow("Title", 100, 100, 400, 600,SDL_WINDOW_SHOWN);

You have created a variable named window which is in the type of SDL_Window, SDL_Create_Window creates a window and its attributes are inside the (), the first one is the title, next is the x coordinate, then the y coordinate, then the width of the window, the height of the window, then the command that the window could understand you can put SDL_WINDOW_RESIZABLE if you want the window to be resizable etc.

Mind you that the (0,0) coordinate is in the top left of the screen so the greater the x value, the it moves to the right and the greater the y value, the more it moves down.

//CREATE RENDERER
SDL_Renderer *renderer = SDL_CreateRenderer( window, -1, SDL_RENDERER_ACCELERATED);

You created a variable named renderer which is a type of SDL_Renderer, as you can see, SDL is very literal, SDL_CreateRenderer creates a renderer, the values inside the parentheses are (name of the window, the rendering drive, the command the renderer would understand), the renderer needs to know what or where your window is, thus, it asks for it then it needs to know what drive would work on it, you can put -1 to use the default one/the one you previously used, then the command.

//CREATE TEXTURE
SDL_Texture* texture = IMG_LoadTexture(renderer, "FILE");

You created a texture variable, IMG_LoadTexture has the ability to load a picture and immediately convert it into a texture, it asks for your renderer since the renderer is the one that would works on it and it also asks for the file name let's say your file's name is "texture.png" then you just input that in that area, the file should be placed inside the the folder that contains the other header files.

Now just loading a texture won't give you power over it, what you want now is to gain control over it, that is why we create an rect:

SDL_Rect texture_rect;
texture_rect.x = 0; //the x coordinate
texture_rect.y = 0; //the y coordinate
texture_rect.w = 50; //the width of the texture
texture_rect.h = 50; //the height of the texture

Now, our texture should display the the top left corner since the coordinate is at (0,0) and it should be 50x50, which would make the texture be shaped like a square

// GAME LOOP AREA 
SDL_RenderClear(renderer); //clears the renderer
SDL_RenderCopy(renderer, texture, NULL, &texture_rect); 
SDL_RenderPresent(renderer); //updates the renderer

SDL_RenderCopy is responsible for making the gameloop understand that there's something that wants to be rendered, inside the parentheses are (the renderer's name, the name of the texture, the area it wants to crop but you can leave this as NULL if you don't want the texture to be cropped, and the texture's rect)

Don't forget to destroy the texture in the end to avoid memory leaks (use something like SDL_DestroyTexture(texture) ) <- put this outside the gameloop so that when the gameloop exits, then this would be read.

Answer 2

The renderer cannot accept SDL_Surface*'s so you will have to convert them to textures by

SDL_Texture* texture = SDL_CreateTextureFromSurface(render, surface)

The renderer is basically an SDL_Window* that is hidden from the user where the graphics are rendered at first, then the rendered data gets switched with the window's data

To do this you must use SDL_RenderPresent(render)

To clear the window data, you must use SDL_RenderClear(render)

To copy the texture to the render, you must use

SDL_RenderCopy(render, texture, &src, &dst)

where src is the SDL_Rect area that you want to extract from an image, if you pass NULL, the whole image will be copied

and dst is where you want the image to be rendered at, if you pass NULL, it will be rendered at 0,0

there is a function called SDL_RenderCopyEx() which is the same as the other one but can rotate a sprite rendered