How to compare positions in sfml? - c++

Question

I'm new to sfml and I'm making a simple game. I need to compare 2 positions and I can't find how to do it.
How can I do it? I though that I can do it somehow like this:
if (somesprite.getPosition() < (some x,some y)) { some code}
So I just need to find out how to compare two positions.
Thank you in advance for answers that will get me closer to finding the right way to do it.
- Torsmel

Answer 1

getPosition() returns a sf::Vector2<T> which has overloads for subtraction.
Subtract one sf::Vector2<T> from another and the length of the resulting sf::Vector2<T> will be the distance between the positions.
#include <SFML/System/Vector2.hpp>
#include <cmath>
template<typename T>
T Vector2length(const sf::Vector2<T>& v) {
return std::sqrt(v.x * v.x + v.y * v.y);
}
void some_func() {
auto spos = somesprite.getPosition();
decltype(spos) xy(some_x, some_y);
auto distance_vec = spos - xy;
if( Vector2length(distance_vec) < max_distance ) {
// do stuff
}
}
Since sf::Vector2<T> is lacking length() and other common functions usually associated with Cartesian vectors, an alternative to the above is to inherit sf::Vector2<T> and extend it:
#include <SFML/System/Vector2.hpp>
#include <cmath>
// extending sf::Vector2<T> with functions that could be nice to have
template<typename T>
struct Vector2_ext : sf::Vector2<T> {
using sf::Vector2<T>::Vector2;
// converting from a sf::Vector2
Vector2_ext(const sf::Vector2<T>& o) : sf::Vector2<T>(o) {}
// converting back to a sf::Vector2
operator sf::Vector2<T>&() { return *this; }
operator sf::Vector2<T> const&() const { return *this; }
// your utility functions
T length() const { return std::sqrt(this->x * this->x + this->y * this->y); }
};
// deduction guide
template<typename T>
Vector2_ext(T, T)->Vector2_ext<T>;
With this, you can convert back and forth between sf::Vector2<T> and Vector2_ext<T> when needed.
int some_func(sf::Sprite& somesprite, float some_x, float some_y, float max_distance) {
auto distance =
// somesprite.getPosition() - sf::Vector2(some_x, some_y) returns a sf::Vector2<T>
// that we convert to a temporary Vector2_ext<T> and call its length() function:
Vector2_ext(somesprite.getPosition() - sf::Vector2(some_x, some_y)).length();
if(distance < max_distance) {
// do stuff
}
}