Fix Rectangle::from_point_and_size

It was setting the wrong size/pixels.

src/main.rs

@@ -449,7 +449,7 @@ pub fn update(state_ptr: *mut State, dt_ms: u32) {
             }
 
             &engine::Draw::Rectangle(top_left, dimensions, color) => {
-                if dimensions.x > 0 && dimensions.y > 0 {
+                if dimensions.x >= 1 && dimensions.y >= 1 {
                     let rect = rect::Rectangle::from_point_and_size(top_left, dimensions);
                     for pos in rect.points() {
                         assert!(pos.x >= 0 && pos.x < 255);

src/rect.rs

@@ -13,7 +13,7 @@ impl Rectangle {
         assert!(size > (0, 0));
         Rectangle {
             top_left,
-            bottom_right: top_left + size,
+            bottom_right: top_left + size - (1, 1),
         }
     }
 
@@ -31,7 +31,7 @@ impl Rectangle {
     }
 
     pub fn dimensions(self) -> Point {
-        self.bottom_right - self.top_left
+        self.bottom_right - self.top_left + (1, 1)
     }
 
     /// Returns `true` if the point is within the areas specified by
@@ -105,3 +105,32 @@ impl Iterator for RectangleIterator {
         }
     }
 }
+
+#[cfg(test)]
+mod tests{
+    use super::Rectangle;
+    use point::Point;
+
+    #[test]
+    fn smallest_rect() {
+        let rect = Rectangle::from_point_and_size((0, 0).into(), (1, 1).into());
+        assert_eq!(rect.dimensions(), Point::new(1, 1));
+        assert_eq!(rect.points().collect::<Vec<_>>().len(), 1);
+
+        let rect = Rectangle::from_point_and_size((5, 7).into(), (1, 1).into());
+        assert_eq!(rect.dimensions(), Point::new(1, 1));
+        assert_eq!(rect.points().collect::<Vec<_>>().len(), 1);
+    }
+
+    #[test]
+    fn rect_size_2() {
+        let rect = Rectangle::from_point_and_size((0, 0).into(), (2, 2).into());
+        assert_eq!(rect.dimensions(), Point::new(2, 2));
+        assert_eq!(rect.points().collect::<Vec<_>>().len(), 4);
+
+        let rect = Rectangle::from_point_and_size((5, 7).into(), (2, 2).into());
+        assert_eq!(rect.dimensions(), Point::new(2, 2));
+        assert_eq!(rect.points().collect::<Vec<_>>().len(), 4);
+    }
+
+}