fix: constrain Line.contains() to its endpoints

packages/melonjs/CHANGELOG.md

@@ -24,6 +24,7 @@
 
 ### Fixed
 - Input: a child cropped out of view by a container with `clipping`, or scrolled out of a `UIPanel`, no longer gets pointer events where it is not drawn
+- Geometry: `Line#contains()` checks the segment endpoints as well as collinearity; a point on the line beyond either endpoint was reported as contained (thanks @mmporong)
 - UI: a `UITextButton` moved after it was built draws its background where it is, not where it was first put
 - UI: a blocking `UIPanel` stays opaque to hover for as long as the pointer is on it, not only on the frame the pointer enters
 - UI: a draggable `UIBaseElement` pressed with no hover first, as a touch tap is, no longer throws, and drags by touch; in the world, rather than floating, it no longer jumps by the camera position when dragged

packages/melonjs/src/geometries/line.ts

@@ -48,7 +48,12 @@ export class Line extends Polygon {
 
 		//(Cy - Ay) * (Bx - Ax) = (By - Ay) * (Cx - Ax)
 		return (
-			(_y - start.y) * (end.x - start.x) === (end.y - start.y) * (_x - start.x)
+			(_y - start.y) * (end.x - start.x) ===
+				(end.y - start.y) * (_x - start.x) &&
+			_x >= Math.min(start.x, end.x) &&
+			_x <= Math.max(start.x, end.x) &&
+			_y >= Math.min(start.y, end.y) &&
+			_y <= Math.max(start.y, end.y)
 		);
 	}
 

packages/melonjs/tests/line.spec.ts

@@ -60,6 +60,11 @@ describe("Shape : Line", () => {
 			expect(line.contains(29, 61)).toEqual(false);
 		});
 
+		it("does not contain collinear points beyond its endpoints", () => {
+			expect(line.contains(56, 120)).toEqual(false);
+			expect(line.contains(-28, -60)).toEqual(false);
+		});
+
 		it("Line Bounding Rect width is 28", () => {
 			expect(bounds.width).toEqual(28);
 		});