Xcode与Visual Studio-SDL C ++

Question

I'm self learning programming using various online tutorials and a couple of books. Currently it's C++. I've done a bit of OpenGL and SDL in the last few days.

I have a small program that creates a wall to stop a small square from passing through it.

Here's my code:

    //
    //  main.cpp
    //  SDL_Template
    //

    // The headers
    #include <stdlib.h>
    #include <string>

    // SDL headers
    #include <SDL/SDL.h>
    #include "SDL_image/SDL_image.h"
    //#include "SDL/SDL_ttf.h"
    //#include "SDL/SDL_mixer.h"

    // Other headers
    #include <OpenGL/gl3.h>


    // Screen attributes
    const int SCREEN_WIDTH = 640;
    const int SCREEN_HEIGHT = 480;
    const int SCREEN_BPP = 32;

    // The frame rate
    const int FRAMES_PER_SECOND = 20;

    // The attributes of the square
    const int SQUARE_WIDTH = 20;
    const int SQUARE_HEIGHT = 20;

    // The surfaces
    SDL_Surface *square = NULL;
    SDL_Surface *screen = NULL;

    // The event structure
    SDL_Event event;

    // The wall
    SDL_Rect wall;

    // The square
    class Square
    {
        private:
            // The collision box of the square
            SDL_Rect box;

            // The velocity of the square
            int xVel, yVel;

        public:
            // Initializes the variables
            Square();

            // Takes key presses and adjusts the square's velocity
            void handle_input();

            // Moves the square
            void move();

            // Shows the square on the screen
            void show();
    };

    //The timer
    class Timer
    {
        private:
            // The clock time when the timer started
            int startTicks;

            // The ticks stored when the timer was paused
            int pausedTicks;

            // The timer status
            bool paused;
            bool started;

        public:
            // Initializes variables
            Timer();

            // The various clock actions
            void start();
            void stop();
            void pause();
            void unpause();

            // Gets the timer's time
            int get_ticks();

            // Checks the status of the timer
            bool is_started();
            bool is_paused();
    };

    SDL_Surface *load_image(std::string filename)
    {
        // The image that's loaded
        SDL_Surface* loadedImage = NULL;

        // The optimized surface that will be used
        SDL_Surface* optimizedImage = NULL;

        // Load the image
        loadedImage = IMG_Load(filename.c_str());

        // If the image loaded
        if (loadedImage != NULL)
        {
            // Create an optimized surface
            optimizedImage = SDL_DisplayFormat(loadedImage);

            // Free the old surface
            SDL_FreeSurface(loadedImage);

            // If the surface was optimized
            if (optimizedImage != NULL)
            {
                //  Color key surface
                SDL_SetColorKey(optimizedImage, SDL_SRCCOLORKEY, SDL_MapRGB(optimizedImage->format, 0, 0xFF, 0xFF));
            }
        }

        // Return the optimized surface
        return optimizedImage;
    }

    void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL)
    {
        // Holds offsets
        SDL_Rect offset;

        // Get offsets
        offset.x = x;
        offset.y = y;

        // Blit
        SDL_BlitSurface(source, clip, destination, &offset);
    }

    bool check_collision(SDL_Rect A, SDL_Rect B)
    {
        // The sides of the rectangles
        int leftA, leftB;
        int rightA, rightB;
        int topA, topB;
        int bottomA, bottomB;

        // Calculate the sides of rect A
        leftA = A.x;
        rightA = A.x + A.w;
        topA = A.y;
        bottomA = A.y + A.h;

        // Calculate the sides of rect B
        leftB = B.x;
        rightB = B.x + B.w;
        topB = B.y;
        bottomB = B.y + B.h;

        // If any of the sides from A are outside of B
        if( bottomA <= topB )
        {
            return false;
        }

        if( topA >= bottomB )
        {
            return false;
        }

        if( rightA <= leftB )
        {
            return false;
        }

        if( leftA >= rightB )
        {
            return false;
        }

        // If none of the sides from A are outside B
        return true;
    }

    bool init()
    {
        // Initialize all SDL subsystems
        if (SDL_Init( SDL_INIT_EVERYTHING ) == -1)
        {
            return false;
        }

        // Set up the screen
        screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);

        // If there was an error in setting up the screen
        if (screen == NULL)
        {
            return false;
        }

        // Set the window caption
        SDL_WM_SetCaption("Move the Square", NULL);

        // If everything initialized fine
        return true;
    }

    bool load_files()
    {
        // Load the square image
        square = load_image("square.bmp");

        // If there was a problem in loading the square
        if (square == NULL)
        {
            return false;
        }

        // If everything loaded fine
        return true;
    }

    void clean_up()
    {
        // Free the surface
        SDL_FreeSurface(square);

        // Quit SDL
        SDL_Quit();
    }

    Square::Square()
    {
        // Initialize the offsets
        box.x = 0;
        box.y = 0;

        // Set the square's dimentions
        box.w = SQUARE_WIDTH;
        box.h = SQUARE_HEIGHT;

        // Initialize the velocity
        xVel = 0;
        yVel = 0;
    }

    void Square::handle_input()
    {
        // If a key was pressed
        if (event.type == SDL_KEYDOWN)
        {
            //Adjust the velocity
            switch (event.key.keysym.sym)
            {
                case SDLK_UP: yVel -= SQUARE_HEIGHT / 2; break;
                case SDLK_DOWN: yVel += SQUARE_HEIGHT / 2; break;
                case SDLK_LEFT: xVel -= SQUARE_WIDTH / 2; break;
                case SDLK_RIGHT: xVel += SQUARE_WIDTH / 2; break;
            }
        }
        // If a key was released
        else if (event.type == SDL_KEYUP)
        {
            //Adjust the velocity
            switch (event.key.keysym.sym)
            {
                case SDLK_UP: yVel += SQUARE_HEIGHT / 2; break;
                case SDLK_DOWN: yVel -= SQUARE_HEIGHT / 2; break;
                case SDLK_LEFT: xVel += SQUARE_WIDTH / 2; break;
                case SDLK_RIGHT: xVel -= SQUARE_WIDTH / 2; break;
            }
        }
    }

    void Square::move()
    {
        // Move the square left or right
        box.x += xVel;

        // If the square went too far to the left or right or has collided with the wall
        if (( box.x < 0 ) || ( box.x + SQUARE_WIDTH > SCREEN_WIDTH ) || ( check_collision(box, wall)))
        {
            // Move back
            box.x -= xVel;
        }

        // Move the square up or down
        box.y += yVel;

        // If the square went too far up or down or has collided with the wall
        if (( box.y < 0 ) || ( box.y + SQUARE_HEIGHT > SCREEN_HEIGHT) || (check_collision(box, wall)))
        {
            // Move back
            box.y -= yVel;
        }
    }

    void Square::show()
    {
        // Show the square
        apply_surface(box.x, box.y, square, screen);
    }

    Timer::Timer()
    {
        // Initialize the variables
        startTicks = 0;
        pausedTicks = 0;
        paused = false;
        started = false;
    }

    void Timer::start()
    {
        // Start the timer
        started = true;

        // Unpause the timer
        paused = false;

        // Get the current clock time
        startTicks = SDL_GetTicks();
    }

    void Timer::stop()
    {
        // Stop the timer
        started = false;

        // Unpause the timer
        paused = false;
    }

    void Timer::pause()
    {
        // If the timer is running and isn't already paused
        if ((started == true) && (paused == false))
        {
            // Pause the timer
            paused = true;

            // Calculate the paused ticks
            pausedTicks = SDL_GetTicks() - startTicks;
        }
    }

    void Timer::unpause()
    {
        // If the timer is paused
        if (paused == true)
        {
            // Unpause the timer
            paused = false;

            // Reset the starting ticks
            startTicks = SDL_GetTicks() - pausedTicks;

            // Reset the paused ticks
            pausedTicks = 0;
        }
    }

    int Timer::get_ticks()
    {
        // If the timer is running
        if (started == true)
        {
            // If the timer is paused
            if (paused == true)
            {
                // Return the number of ticks when the timer was paused
                return pausedTicks;
            }
            else
            {
                // Return the current time minus the start time
                return SDL_GetTicks() - startTicks;
            }
        }

        // If the timer isn't running
        return 0;
    }

    bool Timer::is_started()
    {
        return started;
    }

    bool Timer::is_paused()
    {
        return paused;
    }

    int main(int argc, char* args[])
    {
        // Quit flag
        bool quit = false;

        // The square
        Square mySquare;

        // The frame rate regulator
        Timer fps;

        // Initialize
        if( init() == false )
        {
            return 1;
        }

        // Load the files
        if (load_files() == false)
        {
            return 1;
        }

        // Set the wall
        wall.x = 300;
        wall.y = 40;
        wall.w = 40;
        wall.h = 400;

        // While the user hasn't quit
        while (quit == false)
        {
            // Start the frame timer
            fps.start();

            // While there are events to handle
            while (SDL_PollEvent(&event))
            {
                // Handle events for the square
                mySquare.handle_input();

                // If the user has Xed out the window
                if (event.type == SDL_QUIT)
                {
                    // Quit the program
                    quit = true;
                }
            }

            // Move the square
            mySquare.move();

            // Fill the screen white
            SDL_FillRect(screen, &screen->clip_rect, SDL_MapRGB(screen->format, 0xFF, 0xFF, 0xFF));

            // Show the wall
            SDL_FillRect (screen, &wall, SDL_MapRGB(screen->format, 0x77, 0x77, 0x77));

            // Show the square on the screen
            mySquare.show();

            // Update the screen
            if (SDL_Flip(screen) == -1)
            {
                return 1;
            }

            // Cap the frame rate
            if (fps.get_ticks() < 1000 / FRAMES_PER_SECOND)
            {
                SDL_Delay((1000 / FRAMES_PER_SECOND) - fps.get_ticks());
            }
        }

        // Clean up
        clean_up();

        return 0;
    }

I completely understand how this site works, so I'm not asking you to check my code. My code compiles in both Xcode 4.5 and Visual Studio 2010. In Xcode it compiles, but throws some warnings up (although it still builds), but nothing happens when it's run. However in Visual Studio 2012, it compiles, with no warnings and runs successfully.

I have searched here and the C++/SDL forums/help pages, but I haven't found any similar cases.

Why may this be? Seems it runs in Visual Studio 2010, I'm confident it isn't the code...

In case you were wondering the warnings flagged up in Xcode are:

229 enumeration values not handled in switch: 'SDLK_UNKNOWN','SDLK_BACKSPACE','SDLK_TAB'...

This is highlighted on the switch (event.key.keysym.sym) line of code.

So my questions are:

• What kind of problems could case this warning error?

• Are there any commonly know issues with programs working in Visual Studio and not Xcode?

I'm guessing (it seems I can't find anything about it) it's a setting somewhere that I haven't spotted...

I apologise for the length of this.

Answer 1

You are not handling all the possible choices in your switch statement. If this is what you intended then you can remove the warning by using the default case like the following:

switch (event.key.keysym.sym)
{
     case SDLK_UP:    yVel -= SQUARE_HEIGHT / 2; break;
     case SDLK_DOWN:  yVel += SQUARE_HEIGHT / 2; break;
     case SDLK_LEFT:  xVel -= SQUARE_WIDTH  / 2; break;
     case SDLK_RIGHT: xVel += SQUARE_WIDTH  / 2; break;
     default: break;
}

Answer 2

Xcode is simply warning you that you are not handling all possible values for the event.key.keysym.sym enumeration. Since I doubt you want to handle ever single different type of key press, this isn't a problem, as I would maybe see if I could turn down the warning level to suppress these warnings.

As for the program not running successfully when built by Xcode, I don't know. Perhaps SDL is set up in a different way?