Programming 2D Games

The official forum for "Programming 2D Games" the book by: Charles Kelly

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PostPosted: Sun Oct 15, 2017 5:35 am 

Joined: Thu Oct 05, 2017 6:53 am
Posts: 13
Currently, the TextureManager class is able to contain many separate textures from separate files, but the only way to take advantage of this is by calling initialize() and passing it a text file of all texture files to load.

I added an addTexture() function to the TextureManager class to be able to add a new texture to an already-initialized TextureManager object:
bool TextureManager::addTexture(std::string file) {
    initialized = false;
    bool success = true;
    try {
        for (UINT i = 0; i<file.size(); i++)    // convert to lowercase
   = tolower(;
        fileNames.push_back(file);      // put one file name in files
        width.push_back(0);         // make room for width
        height.push_back(0);        // make room for height
        texture.push_back(NULL);    // make room for texture

        // load texture files
        UINT i = fileNames.size() - 1;
        hr = graphics->loadTexture(fileNames[i].c_str(),
            graphicsNS::TRANSCOLOR, width[i], height[i], texture[i]);
        if (FAILED(hr))
            success = false;    // texture failed to load
    catch (...) { return false; }
    initialized = true;                    // set true when initialized
    return success;

Another issue I ran into is that the draw() function in the Image class requires you to provide the texture number (default 0) every time you drew an image.
If a particular image (or entity) object always uses the same non-zero texture number from its TextureManager, it's a little bit awkward to structure the game so that it calls that object's draw() function and passes it the right textureN every time.

A better solution in my opinion is to store the textureNum in the Image object itself:
    Graphics *graphics;     // pointer to graphics
    TextureManager *textureManager; // pointer to texture manager
    // spriteData contains the data required to draw the image by Graphics::drawSprite()
    SpriteData spriteData;  // SpriteData is defined in "graphics.h"
    COLOR_ARGB colorFilter; // applied as a color filter (use WHITE for no change)
    UINT textureNum;        // which texture from textureManager is currently being used
    int     cols;           // number of cols (1 to n) in multi-frame sprite

And also add a getter and setter for textureNum.
Then change the draw() function prototype to this:
virtual void draw(COLOR_ARGB color = graphicsNS::WHITE) { draw(color, -1); }

And the function implementation to this:
void Image::draw(COLOR_ARGB color, UINT textureN)
    if (!visible || graphics == NULL)
    // set texture to draw
    if (textureN != -1)
        spriteData.texture = textureManager->getTexture(textureN);
        spriteData.texture = textureManager->getTexture(textureNum);
    if(color == graphicsNS::FILTER)                     // if draw with filter
        graphics->drawSprite(spriteData, colorFilter);  // use colorFilter
        graphics->drawSprite(spriteData, color);        // use color as filter

This way, the textureN arg defaults to -1, which results in the Image property `textureNum` being used to draw the Image. But a different textureN can always be passed and used instead.

I also added a textureN arg to Image::initialize() and Entity::initialize() so that the a textureNum can be specified during initialization.
I also re-ordered the args to Image::initialize() and Entity::initialize() so that width, height, and ncols are optional and default to 0.
The prototype for Image::initialize() is now:
    virtual bool Image::initialize(Graphics *g, TextureManager *textureM, UINT textureN = 0,
                                   int width = 0, int height = 0, int ncols = 0);

The implementation is now:
bool Image::initialize(Graphics *g, TextureManager *textureM, UINT textureN,
                       int width, int height, int ncols)
        graphics = g;                               // the graphics object
        textureManager = textureM;                  // pointer to texture object

        textureNum = textureN;
        spriteData.texture = textureManager->getTexture(textureN);
        if(width == 0)
            width = textureManager->getWidth(textureN);     // use full width of texture
        spriteData.width = width;
        if(height == 0)
            height = textureManager->getHeight(textureN);   // use full height of texture
        spriteData.height = height;
        cols = ncols;
        if (cols == 0)
            cols = 1;                               // if 0 cols use 1

        // configure spriteData.rect to draw currentFrame
        spriteData.rect.left = (currentFrame % cols) * spriteData.width;
        // right edge + 1
        spriteData.rect.right = spriteData.rect.left + spriteData.width; = (currentFrame / cols) * spriteData.height;
        // bottom edge + 1
        spriteData.rect.bottom = + spriteData.height;
    catch(...) {return false;}
    initialized = true;                                // successfully initialized
    return true;

Similar changes were made to the Entity class.

I also added a very simple getSize() function to textureManager.h:
UINT getSize() const
    return texture.size();

Which has been useful for me when I want to set an Image/Entity to use a TextureManager's last texture (size - 1).

The last thing to note on this subject is Entity::collidePixelPerfect(). That function includes these lines:
// get fresh texture because they may have been released, maybe a bad idea
ent.spriteData.texture = ent.textureManager->getTexture();
spriteData.texture = textureManager->getTexture();

I think this code has always been problematic, because it assumes that both entities should use texture 0 from their TextureManager when considering pixel perfect collision.
If you want to perform pixel perfect collision using any texture from either TextureManager, these lines need to be changed to:
// get fresh texture because they may have been released
ent.spriteData.texture = ent.textureManager->getTexture(ent.getTextureNum());
spriteData.texture = textureManager->getTexture(getTextureNum());

Last edited by Danny-E 33 on Mon Oct 16, 2017 3:59 am, edited 1 time in total.

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PostPosted: Sun Oct 15, 2017 10:23 pm 
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Joined: Sat Jan 28, 2012 4:36 pm
Posts: 547
Thanks for sharing your code changes. It looks like some nice additions.

Professor Kelly

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PostPosted: Mon Oct 16, 2017 4:22 am 

Joined: Thu Oct 05, 2017 6:53 am
Posts: 13
You're welcome! Many thanks for making the engine and writing the book!

I just realized that the Image::draw() function takes a UINT for the textureN arg.. and I made it default to -1...
and then in the implementation compare the arg to -1 to decide if the object's textureNum property should be used instead.
Of course since the arg is unsigned, using -1 causes it to get treated as 4294967295 (ULONG_MAX), and then the comparison 'if (4294967295 != -1)' "correctly" evaluates to false.
I suppose I should change the default value and the comparison value from -1 to ULONG_MAX to be more proper, even though the behavior is identical.

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