Add support for asymmetrical padding

core/src/lib.rs

@@ -22,6 +22,7 @@ mod background;
 mod color;
 mod font;
 mod length;
+mod padding;
 mod point;
 mod rectangle;
 mod size;
@@ -32,6 +33,7 @@ pub use background::Background;
 pub use color::Color;
 pub use font::Font;
 pub use length::Length;
+pub use padding::Padding;
 pub use point::Point;
 pub use rectangle::Rectangle;
 pub use size::Size;

core/src/padding.rs

@@ -0,0 +1,65 @@
+/// An amount of space to pad for each side of a box
+#[derive(Debug, Hash, Copy, Clone)]
+pub struct Padding {
+    /// Top padding
+    pub top: u16,
+    /// Right padding
+    pub right: u16,
+    /// Bottom padding
+    pub bottom: u16,
+    /// Left padding
+    pub left: u16,
+}
+
+impl Padding {
+    /// Padding of zero
+    pub const ZERO: Padding = Padding {
+        top: 0,
+        right: 0,
+        bottom: 0,
+        left: 0,
+    };
+
+    /// Create a Padding that is equal on all sides
+    pub const fn new(padding: u16) -> Padding {
+        Padding {
+            top: padding,
+            right: padding,
+            bottom: padding,
+            left: padding,
+        }
+    }
+}
+
+impl std::convert::From<u16> for Padding {
+    fn from(p: u16) -> Self {
+        Padding {
+            top: p,
+            right: p,
+            bottom: p,
+            left: p,
+        }
+    }
+}
+
+impl std::convert::From<[u16; 2]> for Padding {
+    fn from(p: [u16; 2]) -> Self {
+        Padding {
+            top: p[0],
+            right: p[1],
+            bottom: p[0],
+            left: p[1],
+        }
+    }
+}
+
+impl std::convert::From<[u16; 4]> for Padding {
+    fn from(p: [u16; 4]) -> Self {
+        Padding {
+            top: p[0],
+            right: p[1],
+            bottom: p[2],
+            left: p[3],
+        }
+    }
+}

core/src/size.rs

@@ -1,4 +1,4 @@
-use crate::Vector;
+use crate::{Padding, Vector};
 use std::f32;
 
 /// An amount of space in 2 dimensions.
@@ -28,10 +28,10 @@ impl Size {
     pub const INFINITY: Size = Size::new(f32::INFINITY, f32::INFINITY);
 
     /// Increments the [`Size`] to account for the given padding.
-    pub fn pad(&self, padding: f32) -> Self {
+    pub fn pad(&self, padding: Padding) -> Self {
         Size {
-            width: self.width + padding * 2.0,
-            height: self.height + padding * 2.0,
+            width: self.width + (padding.left + padding.right) as f32,
+            height: self.height + (padding.top + padding.bottom) as f32,
         }
     }
 }