Welcome to the Lounge

class image {
public:
    virtual gfx::gfx_result initialize()=0;
    virtual bool initialized() const=0;
    virtual void deinitialize()=0;
    virtual gfx::size16 dimensions() const=0;
    virtual gfx::rect16 bounds() const;
    virtual gfx::gfx_result draw(const gfx::rect16& bounds, image_draw_callback callback, void* callback_state=nullptr) const=0;
};

// we're within the destination
if((x2>=st.bounds->x1 && x1<=st.bounds->x2) && 
    (y2>=st.bounds->y1 && y1<=st.bounds->y2)) {
    const int offsx = -st.bounds->x1;
    const int offsy = -st.bounds->y1;
    const bool left_edge = x2>=st.bounds->x1 && x1<st.bounds->x1;
    const bool top_edge = y2>=st.bounds->y1 && y1<st.bounds->y1;
    int xs=0,xpe=w,xc=w;
    if(left_edge) {
        xs=st.bounds->x1-x1;
        xc = w-xs;
    }
    int ys=0,ype=h,yc=h;
    if(top_edge) {
        ys=st.bounds->y1-y1;
        yc = h-ys;
    }
    const uint8_t* pbs = (const uint8_t*)bmp;
    uint8_t* pbd = ( uint8_t*)st.bmp;
    for(int y=0;y<yc;++y) {
        const uint8_t* ps = pbs+(((y+ys)*w*3)+(xs*3));
        uint8_t* pd = pbd+(y*xc*4);
        for(int x=0;x<xc;++x) {
            *pd++=*ps++;
            *pd++=*ps++;
            *pd++=*ps++;
            *pd++=0xFF;
        }
    }
    image_data data;
    data.is_fill = false;
    const const_bitmap<rgba_pixel<32>> csrc(size16(xc,yc),st.bmp);
    data.bitmap.region = &csrc;
    data.bitmap.location = point16(x1+offsx,y1+offsy);
    gfx_result r =st.cb(data,st.cb_state);
    if(gfx_result::success!=r) {
        st.error = r;
        return 0;
    }
        
} else {
    if(y1>st.bounds->y2) {
        st.error = gfx_result::success;
        // don't need to display any more...
        return 0;
    } 
}

Quote:

Thanks for switching on for our first Free Electricity session on Thursday 15th August. Together, you stopped 180 wind turbine's worth of clean, green power from going to waste. Pretty cool ey? And here's how you did:

You used 94p worth of Free Electricity ⚡️

Not a fortune, but not too bad for an hour's free extra power! Collectively, you guys saved £126,000 by making the most of 531 megawatt hours' surplus green power.