/**
* \brief Subtract a rectangle \a b from a rectangle \a a.
* \param a The target.
* \param b The rectangle to remove in \a a.
* \param boxes The subparts of \a a after the subtraction.
*/
void bear::visual::screen::subtract
( const rectangle_type& a, const rectangle_type& b,
rectangle_list& result ) const
{
if ( !a.intersects(b) )
result.push_front(a);
else
{
const rectangle_type inter = a.intersection(b);
if ( (inter.width() <= 8) || (inter.height() <= 8) )
result.push_front(a);
else
{
if ( a.left() != inter.left() )
result.push_front
( rectangle_type( a.left(), a.bottom(), inter.left(), a.top() ) );
if ( a.top() != inter.top() )
result.push_front
( rectangle_type
( inter.left(), inter.top(), inter.right(), a.top() ) );
if ( a.right() != inter.right() )
result.push_front
( rectangle_type
( inter.right(), a.bottom(), a.right(), a.top() ) );
if ( a.bottom() != inter.bottom() )
result.push_front
( rectangle_type
( inter.left(), a.bottom(), inter.right(), inter.bottom() ) );
}
}
} // screen::subtract()
/**
* \brief Tell if a rectangle intersects a rectangle from a list.
* \param r The rectangle to check.
* \param boxes The boxes to compare to.
*/
bool bear::visual::screen::intersects_any
( const rectangle_type& r, const rectangle_list& boxes ) const
{
bool result=false;
rectangle_list::const_iterator it;
for (it=boxes.begin(); !result && (it!=boxes.end()); ++it)
if ( r.intersects(*it) )
{
const rectangle_type inter = r.intersection(*it);
result = (inter.width() > 0) && (inter.height() > 0);
}
return result;
} // screen::intersects_any()
