Does a line contain a point

Question

I want the user to be able to drag the edges of a square around the canvas. With my current solution it works but has glitches, sometimes an edge cannot be selected. Is ther

Answer 1

use the line equation y = mx + b to find out if the point is on a line

float EPSILON = 0.001f;

public boolean isPointOnLine(Point linePointA, Point linePointB, Point point) {
    float m = (linePointB.y - linePointA.y) / (linePointB.x - linePointA.x);
    float b = linePointA.y - m * linePointA.x;
    return Math.abs(point.y - (m*point.x+b)) < EPSILON);
}