Question

我试图用两个函数展示两个不同的动画，一个渲染和两个线程。

每次运行代码时都会遇到不同类型的错误。如：刷新功能中的分段默认（行SDL_RenderPresent（w1.renderer）;）和其他奇怪的错误。每次都不同。

我知道它在两个不同的线程中使用渲染。但我不知道如何解决这个问题。

当我只使用其中一个线程运行时，一切正常。但不是他们两个。

我只是想在窗户周围播放不同的图形。（总是使用sdl2）。

这是我的代码：

window.h中：

class Window
{
public:
SDL_Window *window1;
int background,windowWidth,windowHeight,windowXcoord,windowYcoord;
SDL_Renderer * renderer;
SDL_Renderer * renderer2;
Window();
};

void refresh();
extern Window w1;

window.cpp：

Window w1;
Window::Window()
{
window1=nullptr;
background = 0xffffff;
windowWidth=700;      windowHeight=500;
windowXcoord = 650;  windowYcoord = 0;

this->window1 = 
SDL_CreateWindow("Window",windowXcoord,windowYcoord, 
windowWidth,windowHeight, SDL_WINDOW_SHOWN);
  this->renderer =  SDL_CreateRenderer( this->window1, -1 ,  
SDL_RENDERER_ACCELERATED);

SDL_SetRenderDrawColor( this->renderer, 255, 255, 255, 255 );
SDL_RenderClear( this->renderer );
SDL_RenderPresent(this->renderer);
}

// this function is called everytime an object or function want to "refresh" the window.

void refresh(){

// clearing the window
  SDL_SetRenderDrawColor( w1.renderer, 255, 255, 255,0 );
  SDL_RenderClear( w1.renderer );

// r1, the first Rects object to animate.
  SDL_SetRenderDrawColor( w1.renderer,255,0,0,255);
  SDL_RenderFillRect( w1.renderer, &r1.rect );

// r2, the second Rects.
  SDL_SetRenderDrawColor( w1.renderer,255,0,255,255);
  SDL_RenderFillRect( w1.renderer, &r2.rect );
  SDL_RenderPresent(w1.renderer);
}

rects.h：

class Rects
{
public:
SDL_Rect rect;

Rects();
};
extern Rects r1, r2;

void moveR1();
void moveR2();

rects.cpp：

Rects::Rects()
{ }
Rects r1,r2;

// moveR1 and moveR2, (just some dumm animations-example)
void moveR1(){
r1.rect.x=400; r1.rect.y=100;
r1.rect.w =40; r1.rect.h =10;
SDL_SetRenderDrawColor( w1.renderer,255,0,0,255);
SDL_RenderFillRect( w1.renderer, &r1.rect );
{
for (int u = 1; u<=5;u++){
r1.rect.x=200; r1.rect.y=100;
r1.rect.w =50; r1.rect.h =50;
refresh();
for (int i = 1; i <=200; i++){

r1.rect.x-=1;
usleep (7000);
refresh();
}
}
}
}
void moveR2(){
  r2.rect.x=200; r2.rect.y=100;
  r2.rect.w =40; r2.rect.h =10;
  SDL_SetRenderDrawColor( w1.renderer,255,255,0,255);
  SDL_RenderFillRect( w1.renderer, &r2.rect );
  {
     for (int u = 1; u<=5;u++){
           check
           r2.rect.x=200; r2.rect.y=100;
           r2.rect.w =50; r2.rect.h =50;
           refresh();
           for (int i = 1; i <=200; i++){

                 r2.rect.x+=1; r2.rect.y+=1;
                 usleep (7000);
              refresh();
              }
        }
  }
}

和主要：

int main()
{
  thread t1(moveR1);
  t1.detach();

  thread t2(moveR2);
  t2.detach();

  // sleep instead of showing a loop.

  sleep (10);

  return 0; 
}

欢迎任何礼貌的帮助，我在这里学习。

Answer 1

当我只使用其中一个线程运行时，一切正常。但不是他们两个。

根据 2D加速渲染的documentation （也称为SDL_render.h，换句话说，SDL_RenderPresent所居住的地方：

此API不适用于多个线程，有关详细信息，请参阅SDL bug #1995。

你很快就无法做到这一点。通过查看错误的描述，它看起来像一个UB，并且bug的链接可能会为您提供所有细节。

我只是想在窗户周围播放不同的图形。

你不需要使用两个线程来做到这一点您可以更新图形所需的位置，动画和任何内容，并从同一个线程中显示它们。在调用SDL_RenderCopy之前，没有什么能阻止您多次调用相同的函数（例如SDL_RenderPresent）。
如果你需要每个图形的一个主题，那么在视频中有数千个多边形的游戏呢？

Answer 2

// thanks to skypjack, i am able to solve the problem
// HOW TO PRESENT TWO (OR MORE) GRAPHICS WITH SDL_RENDERER WITHOUT USING THREADS.
// The two rectangle animation are just and example. 
// It could be whatever we want to show.
// In this case, just two rectangles moving around.
#include <unistd.h>
#include <SDL.h>
using namespace std;

SDL_Window *window1;
int background, windowWidth, windowHeight,windowXcoord,
windowYcoord;

SDL_Rect rectangle1;
SDL_Rect rectangle2;
SDL_Renderer *renderer;
int sequence1;
int sequence2;
void moveRectangle1(), moveRectangle2();

int main()
{
  window1=nullptr;
  background = 0xffffff;
  windowWidth=700;      windowHeight=500;
  windowXcoord = 650;  windowYcoord = 0;
  window1 = SDL_CreateWindow("Main
  Window",windowXcoord,windowYcoord, windowWidth,windowHeight,
 SDL_WINDOW_SHOWN);
  renderer =  SDL_CreateRenderer( window1, -1 ,
SDL_RENDERER_ACCELERATED);

  SDL_SetRenderDrawColor( renderer, 255, 255, 255, 255 );
  SDL_RenderClear( renderer );
  SDL_RenderPresent(renderer);

  rectangle1.x = 100; rectangle1.y = 100; rectangle1.h = 40;
 rectangle1.w = 40;
  rectangle2.x = 100; rectangle2.y = 100; rectangle2.h = 40;
rectangle2.w = 40;

  for (int i = 1;i<500;i++){
              SDL_SetRenderDrawColor( renderer, 255, 255, 255,0 );
              SDL_RenderClear( renderer );
              // chequear return (cerrar programa)
              moveRectangle1();
              moveRectangle2();
              SDL_RenderPresent(renderer);
              usleep (12000);
        }
  return 0;
}

void moveRectangle1(){
    sequence1++;
  if (sequence1 <= 50){ rectangle1.x++; }
  else if (sequence1 <= 100){ rectangle1.x--; }
  else { sequence1 = 0; }

  SDL_SetRenderDrawColor(renderer,255,0,0,255);
  SDL_RenderFillRect(renderer, &rectangle1 );

}
void moveRectangle2(){
  sequence2++;
  if (sequence2 <= 100){ rectangle2.y++; }
  else if (sequence2 <= 200){ rectangle2.y--; }
  else { sequence2 = 0; }

  SDL_SetRenderDrawColor(renderer,0,200,0,255);
  SDL_RenderFillRect( renderer, &rectangle2 );
}

在两个不同的线程中显示两个或多个具有SDL2渲染的不同动画（解决方案中没有线程）。 C ++

2 个答案: