void gClearScreen(CColor* color)
{
    float r = (float)color->r / 255;
    float g = (float)color->g / 255;
    float b = (float)color->b / 255;

    glClearColor(r, g, b, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
}

#define GL_UNSIGNED_SHORT_5_6_5 0x8363
#define TEXTURE_COLORKEY 63519

void gPrepareBitmap(CBitmap* bmp)
{
    GLuint tex[1];
    glGenTextures(1, &tex);

    sysLogf("Uploading texture %dx%d\n", bmp->width, bmp->height);

    unsigned char* data = (unsigned char*)malloc(bmp->width * bmp->height * 4);

    // Quick endian flip & color-space conversion
    for (int i = 0; i < bmp->width * bmp->height; i++)
    {
        unsigned short pixel = *((unsigned short*)&bmp->pixels[i * 2]);

        float r = (float)(pixel & 31) / 32;
        float g = (float)((pixel >> 5) & 63) / 64;
        float b = (float)(pixel >> 11) / 32;

        data[i * 4 + 2] = (unsigned char)(r * 255);
        data[i * 4 + 1] = (unsigned char)(g * 255);
        data[i * 4] = (unsigned char)(b * 255);

        data[i * 4 + 3] = pixel == TEXTURE_COLORKEY ? 0 : 255;
    }

    glBindTexture(GL_TEXTURE_2D, tex[0]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bmp->width, bmp->height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);

    free(data);

    bmp->_platData = tex[0];
}

void gDrawBitmap(CBitmap* bmp, int x, int y)
{
    gDrawBitmapEx(bmp, x, y, 0, 0);
}

void gDrawBitmapEx(CBitmap* bmp, int x, int y, CColor* colorKey, CColor* mulColor)
{
    if (!bmp->_platData)
        gPrepareBitmap(bmp);

    glBindTexture(GL_TEXTURE_2D, (GLuint)bmp->_platData);

    glBegin(GL_QUADS);
    glTexCoord2f(0, 0);
    glVertex2i(x, y);
    glTexCoord2f(1, 0);
    glVertex2i(x + bmp->width, y);
    glTexCoord2f(1, 1);
    glVertex2i(x + bmp->width, y + bmp->height);
    glTexCoord2f(0, 1);
    glVertex2i(x, y + bmp->height);
    glEnd();
}