SDL 렌더러 란 무엇입니까?

SDL 렌더러 란 무엇입니까?

---

나는 SDL2로 시작하고 SDL_Renderer가 무엇인지 이해하는 데 어려움을 겪고 있습니다.

뭔데? 그것은 무엇을합니까? SDL_Renderer, SDL_Window, SDL_Surface 및 SDL_Texture의 차이점은 무엇이며 어떻게 관련됩니까?

이 소개 코드를 이해하려고 할 때 문제가 발생했습니다.

#include <iostream>
#include <SDL2/SDL.h>

int main()
{
    /* Starting SDL */
    if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
        std::cout << "SDL_Init Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    /* Create a Window */
    SDL_Window *window = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN);
    if (window == nullptr) {
        std::cout << "SDL_CreateWindow Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    /* Create a Render */
    SDL_Renderer *render = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    if (render == nullptr) {
        std::cout << "SDL_CreateRenderer Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    /* Load bitmap image */
    SDL_Surface *bmp = SDL_LoadBMP("./Tutorial/res/Lesson1/hello.bmp");
    if (bmp == nullptr) {
        std::cout << "SDL_LoadBMP Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    /* Upload surface to render, and then, free the surface */
    SDL_Texture *texture = SDL_CreateTextureFromSurface(render, bmp);
    SDL_FreeSurface(bmp);
    if (texture == nullptr){
        std::cout << "SDL_CreateTextureFromSurface Error: " << SDL_GetError() << std::endl;
        return 1;
    }

    /* Draw the render on window */
    SDL_RenderClear(render); // Fill render with color
    SDL_RenderCopy(render, texture, NULL, NULL); // Copy the texture into render
    SDL_RenderPresent(render); // Show render on window

    /* Wait 2 seconds */
    SDL_Delay(5000);

    /* Free all objects*/
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(render);
    SDL_DestroyWindow(window);

    /* Quit program */
    SDL_Quit();
    return 0;
}

저는 Twinklebear 튜토리얼 (SDL Wiki에서 제안)을 사용하고 있었고 SDL Wiki Documentation과 일부 책도 살펴 보았습니다. 그러나 그들 모두는 내가 이러한 정의를 알고 있다고 가정합니다.

---

SDL_Window

SDL_Window 크기, 위치, 전체 화면, 테두리 등 창 자체에 대한 모든 정보를 보유하는 구조체입니다.

---

SDL_Renderer

SDL_Renderer is a struct that handles all rendering. It is tied to a SDL_Window so it can only render within that SDL_Window. It also keeps track the settings related to the rendering. There are several important functions tied to the SDL_Renderer

• SDL_SetRenderDrawColor(renderer, r, g, b, a);
  This sets the color you clear the screen to ( see below )

• SDL_RenderClear(renderer);
  This clears the rendering target with the draw color set above

• SDL_RenderCopy(
  This is probably the function you'll be using the most, it's used for rendering a SDL_Texture and has the following parameters :

  • SDL_Renderer* renderer,
    The renderer you want to use for rendering.
  • SDL_Texture* texture,
    The texture you want to render.
  • const SDL_Rect* srcrect, The part of the texture you want to render, NULL if you want to render the entire texture
  • const SDL_Rect* dstrect)
    Where you want to render the texture in the window. If the width and height of this SDL_Rect is smaller or larger than the dimensions of the texture itself, the texture will be stretched according to this SDL_Rect
• SDL_RenderPresent(renderer);
  The other SDL_Render* functions draws to a hidden target. This function will take all of that and draw it in the window tied to the renderer.

---

SDL_Textures and SDL_Surface

The SDL_Renderer renders SDL_Texture, which stores the pixel information of one element. It's the new version of SDL_Surface which is much the same. The difference is mostly that SDL_Surface is just a struct containing pixel information, while SDL_Texture is an efficient, driver-specific representation of pixel data.

You can convert an SDL_Surface* to SDL_Texture using

SDL_Texture* SDL_CreateTextureFromSurface(SDL_Renderer* renderer,
                                          SDL_Surface*  surface)

After this, the SDL_Surface should be freed using

SDL_FreeSurface( SDL_Surface* surface )

Another important difference is that SDL_Surface uses software rendering (via CPU) while SDL_Texture uses hardware rendering (via GPU).

---

SDL_Rect

The simplest struct in SDL. It contains only four shorts. x, y which holds the position and w, h which holds width and height.

It's important to note that 0, 0 is the upper-left corner in SDL. So a higher y-value means lower, and the bottom-right corner will have the coordinate x + w, y + h

---

You can read more about SDL2 on my blog.

---

Think of SDL_Window as physical pixels, and SDL_Renderer and a place to store settings/context.

So you create a bunch of resources, and hang them off of the renderer; and then when its ready, you tell renderer to put it all together and send the results to the window.

참고URL : https://stackoverflow.com/questions/21007329/what-is-an-sdl-renderer