Adding a function to find the triangle containing a point

[mllobera]

Based on what I have seen in your code I was wondering about the possibility of inserting the following functions into triangulator.cpp and *.h in order to extend your code to be able to get the location of the triangle containing a point. I do no have much of C++ experience hence why I am not making a pull request.

Here are the functions,

// Private Function to check if a point is inside a triangle using barycentric coordinates
bool PointInTriangle(const glm::ivec2 p, const glm::ivec2 a, const glm::ivec2 b, const glm::ivec2 c) const {
    auto sign = [](const glm::ivec2 p1, const glm::ivec2 p2, const glm::ivec2 p3) {
        return (p1.x - p3.x) * (p2.y - p3.y) - (p2.x - p3.x) * (p1.y - p3.y);
    };

    bool d1 = sign(p, a, b) < 0.0f;
    bool d2 = sign(p, b, c) < 0.0f;
    bool d3 = sign(p, c, a) < 0.0f;

    return ((d1 == d2) && (d2 == d3));
}

// Public  function to triangle contianing point pt
int locatePoint(const glm::ivec2 pt) const {
    for (int i = 0; i < m_Queue.size(); ++i) {
        const int t = m_Queue[i];
        const int e0 = t * 3;
        const int e1 = e0 + 1;
        const int e2 = e0 + 2;

        const int p0 = m_Triangles[e0];
        const int p1 = m_Triangles[e1];
        const int p2 = m_Triangles[e2];

        const glm::ivec2 a = m_Points[p0];
        const glm::ivec2 b = m_Points[p1];
        const glm::ivec2 c = m_Points[p2];

        if (PointInTriangle(pt, a, b, c)) {
            return t;
        }
    }
    return -1;  // Point is not inside any triangle
}

Thank you for considering these.