C++ Tutorials - Absolute n00b spoonfeed

For those there who know a little bit of allegro, I need some information.

I made a class 'Level', public of class 'Buffer', with a SetLevel function that mask blits the "walls" of the game to the buffer. Well, it actually doesn't, the sprite is not visible in the window. I tried then mask bliting it in the main function by making functions that return the buffer and the 'wall' variables ... and it worked.

Now I'm just confused. The masked_blit() can't blit from inside a class? The blit function can.

Here are the classes:

Code: Select all

// CreateBuffer.h

class CreateBuffer {

    protected:
        BITMAP* Buffer;

    public:
        CreateBuffer();
        ~CreateBuffer();

        BITMAP* GetBuffer() { return Buffer; }
        void BlitBuffer();
        void ClearBuffer();
};

CreateBuffer::CreateBuffer() {

    Buffer = create_bitmap( 800, 600 );
}

CreateBuffer::~CreateBuffer() {

    destroy_bitmap( Buffer );
}

void CreateBuffer::BlitBuffer() {

    blit( Buffer, screen, 0, 0, 0, 0, 800, 600 );
}

void CreateBuffer::ClearBuffer() {

    clear_bitmap( Buffer );
}


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// Level.h

class Level: public CreateBuffer {

  private:
        BITMAP* Wall;

  public:
        Level();
        void SetLevel();

        BITMAP* GetWall() { return Wall; }

        ~Level();

};


Level::Level() {

    Wall = load_bitmap( "data/castle.bmp", NULL );
}


void Level::SetLevel() {

    masked_blit ( Wall, Buffer, 0, 0, 0, 0, 96, 28 );
}


Level::~Level() {

    destroy_bitmap( Wall );
}



And here is the main function that works:

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#include "Library.h"


int main() {

    AllegroSetup cInitialized(1);

    CreateBuffer cBuffer;

    Level cLevel;

    masked_blit( cLevel.GetWall(), cBuffer.GetBuffer(), 0, 0, 0, 0, 800, 600 );

    cBuffer.BlitBuffer();

    readkey();

    return 0;
}
END_OF_MAIN();


But when I try to use the SetLevel function inside of the Level class I get no sprite on the buffer

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#include "Library.h"


int main() {

    AllegroSetup cInitialized(1);

    CreateBuffer cBuffer;

    Level cLevel;

    cLevel.SetLevel();

    cBuffer.BlitBuffer();

    readkey();

    return 0;
}
END_OF_MAIN();


All my header files are included in a 'library' header which I include in all .cpp files. The AllegroSetup class just initializes allegro.
I did, redid, rerererereredid it all, tried different ways to do it, and that's the single think that won't work, mask blitting from inside a class!

I read the docs' about masked_blit and there's nothing about 'not working in a class', it kind of sounds unreal, why wouldn't it work in a class ? :\

Just give me a straight answer, even if it's 'YOU ARE IDIOT !". Thanks. :-<


Side note: I used Moosader's sprites for this project, thank you.

The code below should work. In the comments I explained why.

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    #include "Library.h"


    int main() {

        AllegroSetup cInitialized(1);

        //CreateBuffer cBuffer; Level inherits from CreateBuffer

        Level cLevel;

        cLevel.SetLevel(); // This mask_blit uses the buffer bitmap of the base class of Level, which is CreateBuffer

        cLevel.BlitBuffer(); // CreateBuffer class has no knowledge of classes that derive from it, so you need to use Level here

        readkey();

        return 0;
    }
    END_OF_MAIN();


That way it works.

So there's nothing wrong with the masked_blit function, it was all about the inheritance.

I somehow thought about that too, but I came up with: the inherited classes configure the buffer and it doesn't matter if it knows of the other classes because he's modified before output.

Thanks for your answer, now it's all clearer.


Late edit:
Is it then good to make a class that inherits all the game-specific classes ( Level, Player, Objects ) so that I can blit them?