Implement Mul for Transform

Seems like it is implemented in SFML like such, so I copied the behavior
from SFML to here.

Author: dogunbound

src/graphics/transform.rs

@@ -1,3 +1,5 @@
+use std::ops::{Mul, MulAssign};
+
 use crate::{ffi::graphics as ffi, graphics::FloatRect, system::Vector2f};
 
 /// Define a 3x3 transform matrix.
@@ -195,3 +197,58 @@ impl Default for Transform {
         Self::IDENTITY
     }
 }
+
+impl Mul for Transform {
+    type Output = Self;
+
+    fn mul(self, rhs: Self) -> Self::Output {
+        let mut clone_self = self;
+        clone_self.combine(&rhs);
+        clone_self
+    }
+}
+
+impl MulAssign for Transform {
+    fn mul_assign(&mut self, rhs: Self) {
+        self.combine(&rhs);
+    }
+}
+
+impl Mul<Vector2f> for Transform {
+    type Output = Vector2f;
+
+    fn mul(self, rhs: Vector2f) -> Self::Output {
+        self.transform_point(rhs)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_mul() {
+        let test_transform = Transform::new(1., 2., 3., 4., 5., 6., 7., 8., 9.);
+        let result = Transform::new(30., 36., 42., 66., 81., 96., 102., 126., 150.);
+
+        assert_eq!(test_transform * test_transform, result);
+    }
+
+    #[test]
+    fn test_mulassign() {
+        let mut test_transform = Transform::new(1., 2., 3., 4., 5., 6., 7., 8., 9.);
+        let result = Transform::new(30., 36., 42., 66., 81., 96., 102., 126., 150.);
+
+        test_transform *= test_transform;
+        assert_eq!(test_transform, result);
+    }
+
+    #[test]
+    fn test_mul_vector() {
+        let test_transform = Transform::new(1., 2., 3., 4., 5., 6., 7., 8., 9.);
+        let test_point = Vector2f::new(2., 3.);
+        let result = Vector2f::new(11., 29.);
+
+        assert_eq!(test_transform * test_point, result);
+    }
+}