使用SDL2渲染精灵

Question

I am extremely new to game development. I am attempting to move sprites on a window with SDL. I was using http://gamedevgeek.com/tutorials/moving-sprites-with-sdl/ as a reference for this to help me get a feel for SDL. However, this method of blit doesn't work with SDL2. I researched and found that I must convert surfaces to textures and render those, but I am running into some frustrating difficulties. When ran, the background image seems to render fine, but the sprite only appears in the corner of the window, and when moved, it seems to be overwritten by the background. Here is the code:

#include <iostream>
#include "stdafx.h"
#include <SDL.h>
#include <SDL_image.h>
const int WIDTH = 900;
const int HEIGHT = 360;
const int SPRITE_SIZE = 256;

int main(int argc, char *argv[])
{
    SDL_Surface *imageSurface = NULL;
    SDL_Surface *windowSurface = NULL;
    SDL_Surface *temp = NULL;
    SDL_Surface *sprite = NULL;
    SDL_Surface *SDL_DisplayFormat(SDL_Surface *surface);
    SDL_Rect    rcSprite;
    SDL_Rect    gdSprite;
    SDL_Event windowEvent;
    SDL_Event   event;
    SDL_Renderer *renderer = NULL;
    SDL_Texture *texture;
    SDL_Texture *spriteTexture;

    const Uint8 *keystate;
    int colorkey;
    int count;
    int xPosition = 0;
    int yPosition = 0;
    int gameover = 0;


    SDL_Window *window = SDL_CreateWindow("ABDUCTO", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, WIDTH, HEIGHT, SDL_WINDOW_ALLOW_HIGHDPI);
    windowSurface = SDL_GetWindowSurface(window);

    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);

    imageSurface = IMG_Load("farm.png");
    sprite= IMG_Load("sprite6.png");

    texture = SDL_CreateTextureFromSurface(renderer, imageSurface);
    spriteTexture = SDL_CreateTextureFromSurface(renderer, sprite);

    SDL_FreeSurface(sprite);
    SDL_FreeSurface(imageSurface);

    //rcSprite used as source rectangle, gdSprite as destination rectangle. Initialize them to the same position
    rcSprite.x = xPosition;
    rcSprite.y = yPosition;
    rcSprite.w = SPRITE_SIZE;
    rcSprite.h = SPRITE_SIZE;

    gdSprite.x = xPosition;
    gdSprite.y = yPosition;
    gdSprite.w = SPRITE_SIZE;
    gdSprite.h = SPRITE_SIZE;

    while (!gameover)
    {
        if (SDL_PollEvent(&event))
        {
            switch (event.type)
            {
                case SDL_QUIT:
                    gameover = 1;
                    break;

            case SDL_KEYDOWN:
                switch (event.key.keysym.sym) 
                {
                    case SDLK_ESCAPE:
                    case SDLK_q:
                        gameover = 1;
                        break;

                }
                break;
            }
        }

        keystate = SDL_GetKeyboardState(NULL);

        // When key pressed, update the destination rectangle
        if (keystate[SDL_SCANCODE_LEFT]) {
            gdSprite.x -= 2;
        }
        if (keystate[SDL_SCANCODE_RIGHT]) {
            gdSprite.x += 2;
        }
        if (keystate[SDL_SCANCODE_UP]) {
            gdSprite.y -= 2;
        }
        if (keystate[SDL_SCANCODE_DOWN]) {
            gdSprite.y += 2;
        }
        if (gdSprite.x < 0) {
            gdSprite.x = 0;
        }
        else if (gdSprite.x > WIDTH - SPRITE_SIZE) {
            gdSprite.x = WIDTH - SPRITE_SIZE;
        }
        if(gdSprite.y < 0) {
            gdSprite.y = 0;
        }
        else if (gdSprite.y > HEIGHT - SPRITE_SIZE) {
            gdSprite.y = HEIGHT - SPRITE_SIZE;
        }

        //Render the window
        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderCopy(renderer, spriteTexture, &rcSprite, &gdSprite);
        SDL_RenderPresent(renderer);

        //SDL_BlitSurface(imageSurface, NULL, windowSurface, NULL);
        //SDL_BlitSurface(sprite, NULL, imageSurface, &rcSprite);
        //SDL_UpdateWindowSurface(window);


        //update the source rectangle to move with the sprite??
        rcSprite.x = gdSprite.x;
        rcSprite.y = gdSprite.y;

    }


    SDL_DestroyTexture(spriteTexture);
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);


    return 0;

    SDL_Quit();
}

Any input is appreciated. Thank you.

Answer 1

probably has to do something with the path of your images, or copying the files into the resources on compilation. are you on windows, osx or linux? What IDE are you using?

But i noticed two things:

1) Before the SDL_CreateWindow you should initialize SDL: SDL_Init(SDL_INIT_EVERYTHING);

2) SDL_Quit(); will never be called because one line above you quit the main function with return 0; => you should swap the lines!

noticed some more: 3) DON'T update the source rectangle to move with the sprite just render the whole sprite to the gdSprite loction: SDL_RenderCopy(renderer, sTexture, NULL, &gdSprite);