feat(layout): add Rect -> Size conversion methods (#789)

- add Size::new() constructor
- add Rect::as_size()
- impl From<Rect> for Size
- document and add tests for Size

src/layout/rect.rs

@@ -8,6 +8,7 @@ use crate::prelude::*;
 
 mod offset;
 
+use layout::Size;
 pub use offset::*;
 
 /// A simple rectangle used in the computation of the layout and to give widgets a hint about the
@@ -325,6 +326,14 @@ impl Rect {
             current_column: self.x,
         }
     }
+
+    /// Converts the rect into a size struct.
+    pub fn as_size(self) -> Size {
+        Size {
+            width: self.width,
+            height: self.height,
+        }
+    }
 }
 
 #[cfg(test)]
@@ -548,7 +557,7 @@ mod tests {
     }
 
     #[test]
-    fn test_rows() {
+    fn rows() {
         let area = Rect::new(0, 0, 3, 2);
         let rows: Vec<Rect> = area.rows().collect();
 
@@ -558,7 +567,7 @@ mod tests {
     }
 
     #[test]
-    fn test_columns() {
+    fn columns() {
         let area = Rect::new(0, 0, 3, 2);
         let columns: Vec<Rect> = area.columns().collect();
 
@@ -570,4 +579,15 @@ mod tests {
 
         assert_eq!(columns, expected_columns);
     }
+
+    #[test]
+    fn as_size() {
+        assert_eq!(
+            Rect::new(1, 2, 3, 4).as_size(),
+            Size {
+                width: 3,
+                height: 4
+            }
+        );
+    }
 }

src/layout/size.rs

@@ -1,12 +1,59 @@
+#![warn(missing_docs)]
+use crate::prelude::*;
+
 /// A simple size struct
+///
+/// The width and height are stored as `u16` values and represent the number of columns and rows
+/// respectively.
 #[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash)]
 pub struct Size {
+    /// The width in columns
     pub width: u16,
+    /// The height in rows
     pub height: u16,
 }
 
+impl Size {
+    /// Create a new `Size` struct
+    pub fn new(width: u16, height: u16) -> Self {
+        Size { width, height }
+    }
+}
+
 impl From<(u16, u16)> for Size {
     fn from((width, height): (u16, u16)) -> Self {
         Size { width, height }
     }
 }
+
+impl From<Rect> for Size {
+    fn from(rect: Rect) -> Self {
+        rect.as_size()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn new() {
+        let size = Size::new(10, 20);
+        assert_eq!(size.width, 10);
+        assert_eq!(size.height, 20);
+    }
+
+    #[test]
+    fn from_tuple() {
+        let size = Size::from((10, 20));
+        assert_eq!(size.width, 10);
+        assert_eq!(size.height, 20);
+    }
+
+    #[test]
+    fn from_rect() {
+        let size = Size::from(Rect::new(0, 0, 10, 20));
+        assert_eq!(size.width, 10);
+        assert_eq!(size.height, 20);
+    }
+}