SDL_Surface向量

Question

我正在尝试创建一个曲面矢量，它将包含用户输入的消息(它是一个聊天框)。但每当我向矢量中添加新曲面并显示它们时，其他曲面就会显示在曲面矢量中。我不知道为什么会这样。我假设这是因为向量不断地用.push_Back();调整大小，而计算机在其他表面移动之前没有这样做，所以它们被“卡在中间”，并显示在表面的位置。但是当我检查它的时候，它根本没有添加任何东西！我甚至尝试过.reserve( myVect.size() + 1);，但遗憾的是，这只给了我同样的问题。

我认为问题出在handle_input();和消息的显示方式上。我在网上任何地方都找不到关于这个问题的任何东西！

这是我的资料来源：

    ofstream logFile;


    SDL_Surface *text = NULL;


void apply_surface (int x, int y, SDL_Surface *source, SDL_Surface *destination, SDL_Rect *clip = NULL) {

    SDL_Rect offset;
    offset.x = x;
    offset.y = y;

    SDL_BlitSurface(source, clip, screen, &offset);
}


vector <SDL_Surface*> surface_vect;

bool handle_input() {

if (event.type == SDL_KEYDOWN) {

   std::string temp = str;

   if ( str.length() <= 48) {
      logFile << "str's length is <=48.\n";
      if ( event.key.keysym.unicode == (Uint16) ' ' ) {

         str += (char)event.key.keysym.unicode;
         logFile << "Space bar was pressed.\n";
         charcount += 1;
      }
      else if ( ( event.key.keysym.unicode >= (Uint16)'0') && (event.key.keysym.unicode <= (Uint16) '9' ) ) //Finally works!
      {
         charcount += 1;
         str += (char)event.key.keysym.unicode;
         logFile << "Number key: " <<(char)event.key.keysym.unicode << " pressed, and added to str.\n";
      }
      else if (( event.key.keysym.unicode >= (Uint16)'A' )&& (event.key.keysym.unicode <= (Uint16) 'Z') )
      {
         charcount += 1;
         str += (char)event.key.keysym.unicode;
         logFile << "Number key: " <<(char)event.key.keysym.unicode << " pressed, and added to str.\n";
      }
      else if ( (event.key.keysym.unicode >= (Uint16)'a' )&& (event.key.keysym.unicode <= (Uint16) 'z' ) )
      {
         charcount += 1;
         str += (char)event.key.keysym.unicode;
         logFile << "Number key: " <<(char)event.key.keysym.unicode << " pressed, and added to str.\n";
      }
      else if ( (event.key.keysym.unicode == SDLK_RETURN ) )
      {
         str = "";
         surface_vect.reserve ( surface_vect.size() + 1);

         if ( surface_vect.size() < surface_vect.capacity() ) { //PREVENTS AN ACCESS READING VIOLATION ERROR! THE ELEMENTS IN THE VECTOR WERE BECOMING TOO LARGE FOR THE VECTOR!!
         surf_count += 1;
         surface_vect.push_back ( text );
         logFile << "surface_vect has: " << surf_count << " surfaces!";
     }

     }
      if (event.key.keysym.unicode == SDLK_BACKSPACE && str.length() != 0) {
            charcount -= 1;
        str.erase(str.length() - 1);
         logFile << "Backspace was pressed.\n";
      }
      if (str != temp) {
          SDL_FreeSurface ( text );  //This frees up the text surface whenever the str changes.

          text = TTF_RenderText_Solid(font, str.c_str(), textcolor); //Renders the text whenever that change occurs.

         logFile << "Full text rendered: " << str.c_str() << " Number of surfaces in existence: " << c << " Number of characters in current surface: " << charcount  << "\n"; 
      }


      //OK SO: the program separates the surfaces! Now to just make each surface different for each different message! To do this, we will put the "text" surface into the top of surface_vect, because that vector will be our messages body. Text will display all messages being typed, only when return is pressed is it added to the message surfaces body!
   }
}
return true;
}


int main ( int argc, char* args[] )
{
    time(&currentTime);

    int count = 0;

    text = TTF_RenderText_Solid(font, "First surface message!", textcolor);

    surface_vect.push_back( text );

    Timer myTime;
    Timer fps;

    if (init() == false ) {
        return false;
    }

    logFile << "Everything initialized fine. \n" ;
    if (load_files() == false) {

        return false;
    }

    logFile << "All files loaded successfully.\n";

myTime.start(); //The time the loop started. Keeps track of the time.

while (quit == false )
{
    fps.start(); //Frame timer.
    std::stringstream time; //Something to convert the time into a string, along with a message.
    while (SDL_PollEvent( &event ) ) {
        count += 1;
    if ( handle_input() == false ) {
        logFile << "Handle_input() returned false on the: " << count << "th run through the while loop!";
        return false;
    }

        if ( event.type  == SDL_QUIT ) {
            fps.stop();
            myTime.stop();
            quit = true; //Duh.
        }

    }

    apply_surface(0,0, background, screen);
    apply_surface ( 25, 435, text, screen ); //Render the text surface because its separate from the other surfaces! It needs its own render command.

for ( int c = 0; c <= surface_vect.size() - 1; c+=1 ) {
        apply_surface(25, newY - (13 * c), surface_vect.at(c), screen);
    }

    if (SDL_Flip (screen) == - 1) {
        return false;
    }
    frame += 1; //Frame counter. Used to 
        if( fps.get_ticks() < 1000 / FRAMES_PER_SECOND )
        {
            SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() );
        }

}
clean_up();
return 0;

}

有没有更好的方法来做这件事？它应该只是将用户的文本放入一个曲面矢量中，并在上面显示它们。

Answer 1

我不理解你对症状的描述，但是看一下代码，我猜你推入surface_vect向量的文本之后不会显示出来，因为当用户按下return键时，你实际上是在做这件事(我只保留了相关的行)：

surface_vect.push_back ( text );
SDL_FreeSurface ( text );
text = TTF_RenderText_Solid(font, str.c_str(), textcolor);

请记住，text变量和surface_vect向量并不包含实际的曲面，而是指向曲面的指针，所以当您执行push_back操作时，您不会将曲面的副本放入向量中，而只是指针的副本。当你SDL_FreeSurface(text)的时候，表面本身就被清除了，这意味着你刚刚插入到向量中的指针现在正指向一个清除的表面，这个表面不会显示任何东西……您可以通过在push_back之后执行text=NULL来解决此问题(SDL_FreeSurface(text)接受NULL，不做任何事情)

注意在你的代码中还有很多其他的小问题(比如你使用vector就好像它是一个C数组，或者你应该改用list )，但这不在问题的范围内;)