From aff98d7f2af466f4b066ac9a019b8ca1e450c5cd Mon Sep 17 00:00:00 2001
From: Jacek <acejacek@gmail.com>
Date: Sun, 4 Sep 2022 10:39:03 +0200
Subject: [PATCH] Check collision point polygon (#2685)

* Update raylib.h

* CheckCollisionPointPolygon()

* typo
---
 src/raylib.h  |  1 +
 src/rshapes.c | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/raylib.h b/src/raylib.h
index 0746ca2a3..1f0ee8f32 100644
--- a/src/raylib.h
+++ b/src/raylib.h
@@ -1213,6 +1213,7 @@ RLAPI bool CheckCollisionCircleRec(Vector2 center, float radius, Rectangle rec);
 RLAPI bool CheckCollisionPointRec(Vector2 point, Rectangle rec);                                         // Check if point is inside rectangle
 RLAPI bool CheckCollisionPointCircle(Vector2 point, Vector2 center, float radius);                       // Check if point is inside circle
 RLAPI bool CheckCollisionPointTriangle(Vector2 point, Vector2 p1, Vector2 p2, Vector2 p3);               // Check if point is inside a triangle
+RLAPI bool CheckCollisionPointPolygon(Vector2 point, Vector2* vertices, int verticesCount);              // Check if point is within a polygon described by array of vertices
 RLAPI bool CheckCollisionLines(Vector2 startPos1, Vector2 endPos1, Vector2 startPos2, Vector2 endPos2, Vector2 *collisionPoint); // Check the collision between two lines defined by two points each, returns collision point by reference
 RLAPI bool CheckCollisionPointLine(Vector2 point, Vector2 p1, Vector2 p2, int threshold);                // Check if point belongs to line created between two points [p1] and [p2] with defined margin in pixels [threshold]
 RLAPI Rectangle GetCollisionRec(Rectangle rec1, Rectangle rec2);                                         // Get collision rectangle for two rectangles collision
diff --git a/src/rshapes.c b/src/rshapes.c
index 955f056d4..8018bbdef 100644
--- a/src/rshapes.c
+++ b/src/rshapes.c
@@ -1631,6 +1631,28 @@ bool CheckCollisionPointTriangle(Vector2 point, Vector2 p1, Vector2 p2, Vector2
     return collision;
 }
 
+// Check if point is within a polygon described by array of vertices
+bool CheckCollisionPointPolygon(Vector2 point, Vector2* vertices, int verticesCount)
+{
+    // http://jeffreythompson.org/collision-detection/poly-point.php
+    
+    bool collision = false;
+    
+    if (verticesCount > 2)
+    {
+        for (int i = 0; i < verticesCount; i++)
+        {
+            Vector2 vc = vertices[i];
+            Vector2 vn = vertices[i + 1];
+            
+            if ((((vc.y >= point.y) && (vn.y < point.y)) || ((vc.y < point.y) && (vn.y >= point.y))) &&
+                 (point.x < ((vn.x - vc.x)*(point.y - vc.y)/(vn.y - vc.y) + vc.x))) collision = !collision;
+        }
+    }
+    
+    return collision;
+}
+
 // Check collision between two rectangles
 bool CheckCollisionRecs(Rectangle rec1, Rectangle rec2)
 {