尽管使用时间增量，SDL2程序运行得太快

Question

我正在尝试在C + SDL2中制作一个简单的乒乓球游戏时，在Games From Scratch页面上。我试图让球移动，但发现它总是移动太快，即使在跟随此之后。

以下是有问题的代码：

// Update ball position
prevTime = curTime;
curTime = SDL_GetTicks() - prevTime;
delta = curTime / 1000;
ball.y = (int) (ball.y - (BALL_SPD * delta));

想知道是否有人可以帮我解决这个问题？我只是试图让球慢慢移动到屏幕顶部，但它几乎立刻就过快了。

这里是完整的代码：

#include <SDL.h>
#include <stdio.h>
#include <stdbool.h>

#define SCR_W 1280
#define SCR_H 720
#define BALL_SPD 5

int setUpWindowAndRenderer(SDL_Window **w, SDL_Renderer **r);
void setUpPaddles(SDL_Rect *player1, SDL_Rect *player2);
void setUpBoard(SDL_Rect *dash);

int main(int argc, char *args[]){
    // SDL Initialisation and creation of window and renderer
    SDL_Window *window = NULL;
    SDL_Renderer *renderer = NULL;

    if(setUpWindowAndRenderer(&window, &renderer) < 0){
        printf("setUpWindowAndRenderer() failed! Exiting...\n");
        exit(EXIT_FAILURE);
    }

    // SDL_SetRelativeMouseMode(SDL_TRUE);

    // Stores user input
    SDL_Event e;

    // Tests to see if game has been quit in main loop
    bool quit = false;

    // Set up both player paddles
    SDL_Rect player1;
    SDL_Rect player2;
    setUpPaddles(&player1, &player2);

    // Set up ball
    SDL_Rect ball;
    ball.x = SCR_W / 4;
    ball.y = SCR_H / 2;
    ball.w = 25;
    ball.h = 25;

    // Set up delta/timing
    float delta = 0, curTime = 0, prevTime = 0;

    // Mouse y-position
    int mY;

    // Central line initial rect
    SDL_Rect lineRect = {(SCR_W / 2) - 5, SCR_H, 10, 25};

    // Main game loop
    while(!quit){
        // Check user input
        while(SDL_PollEvent(&e)){
            if(e.type == SDL_QUIT){
                quit = true;
            } else if(e.type == SDL_KEYDOWN){
                switch(e.key.keysym.sym){
                    case SDLK_w:
                        // GO THE FUCK UP
                        break;
                    case SDLK_s:
                        // GO DOWN TO THE GROUND BOI
                        break;
                    default:
                        printf("Invalid key.\n");
                        break;
                }
            }
        }

        // Update Player 1 Paddle
        // Update P1 paddle to mouse y position
        SDL_GetMouseState(NULL, &mY);
        player1.y = mY - (player1.h / 2);

        // Limit position if paddle y pos goes below zero or above window height
        if(player1.y < 0){
            player1.y = 0;
        }
        if(player1.y + player1.h > SCR_H){
            player1.y = SCR_H - player1.h;
        }

        // Update ball position
        prevTime = curTime;
        curTime = SDL_GetTicks() - prevTime;
        delta = curTime / 1000;
        ball.y = (int) (ball.y - (BALL_SPD * delta));

        // Limit position if ball y pos goes below zero or above window height
        if(ball.y < 0){
            ball.y = 0;
        }
        if(ball.y + ball.h > SCR_H){
            ball.y = SCR_H;
        }

        // Clear screen
        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
        SDL_RenderClear(renderer);

        // Draw central line
        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
        while(lineRect.y <= SCR_H && lineRect.y >= 0){
            SDL_RenderFillRect(renderer, &lineRect);
            lineRect.y -= 50;
        }
        lineRect.y = SCR_H;

        // Draw paddles and ball
        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
        SDL_RenderFillRect(renderer, &player1);
        SDL_RenderFillRect(renderer, &player2);
        SDL_RenderFillRect(renderer, &ball);

        SDL_RenderPresent(renderer);
    }

    SDL_Quit();
    return 0;
}

int setUpWindowAndRenderer(SDL_Window **w, SDL_Renderer **r){
    if(SDL_Init(SDL_INIT_VIDEO) < 0){
        printf("SDL_Init() failed! %s\n", SDL_GetError());
        return -1;
    }


    if((*w = SDL_CreateWindow("Pong Clone", SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED, SCR_W, SCR_H, 0)) == NULL){
        printf("SDL_CreateWindow() failed! %s\n", SDL_GetError());
        return -1;
    }


    if((*r = SDL_CreateRenderer(*w, -1, 0)) == NULL){
        printf("SDL_CreateRenderer() failed! %s\n", SDL_GetError());
        return -1;
    }

    return 0; // success
}

void setUpPaddles(SDL_Rect *player1, SDL_Rect *player2){
    // Define paddle width and height
    int pW = 30;
    int pH = 100;

    player1->x = pW * 2; // Position P1 paddle 2 paddle-widths away from screen edge
    player1->y = (SCR_H / 2) - (pH / 2); // Position Paddle in direct centre
    player1->w = pW; // Paddle Width
    player1->h = pH; // Paddle Height

    player2->x = SCR_W - (pW * 3); // Position P2 paddle 2 paddle-widths away from screen edge
    player2->y = (SCR_H / 2) - (pH / 2); // Position Paddle in direct centre
    player2->w = pW; // Paddle Width
    player2->h = pH; // Paddle Height
}