1 files changed, 83 insertions, 0 deletions
diff --git a/src/geom/dir.rs b/src/geom/dir.rs
new file mode 100644
index 00000000..cfcb4c09
--- /dev/null
+++ b/src/geom/dir.rs
@@ -0,0 +1,83 @@
+use super::*;
+
+/// The four directions into which content can be laid out.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum Dir {
+    /// Left to right.
+    LTR,
+    /// Right to left.
+    RTL,
+    /// Top to bottom.
+    TTB,
+    /// Bottom to top.
+    BTT,
+}
+
+impl Dir {
+    /// The side this direction starts at.
+    pub fn start(self) -> Side {
+        match self {
+            Self::LTR => Side::Left,
+            Self::RTL => Side::Right,
+            Self::TTB => Side::Top,
+            Self::BTT => Side::Bottom,
+        }
+    }
+
+    /// The side this direction ends at.
+    pub fn end(self) -> Side {
+        match self {
+            Self::LTR => Side::Right,
+            Self::RTL => Side::Left,
+            Self::TTB => Side::Bottom,
+            Self::BTT => Side::Top,
+        }
+    }
+
+    /// The specific axis this direction belongs to.
+    pub fn axis(self) -> SpecAxis {
+        match self {
+            Self::LTR | Self::RTL => SpecAxis::Horizontal,
+            Self::TTB | Self::BTT => SpecAxis::Vertical,
+        }
+    }
+
+    /// Whether this direction points into the positive coordinate direction.
+    ///
+    /// The positive directions are left-to-right and top-to-bottom.
+    pub fn is_positive(self) -> bool {
+        match self {
+            Self::LTR | Self::TTB => true,
+            Self::RTL | Self::BTT => false,
+        }
+    }
+
+    /// The factor for this direction.
+    ///
+    /// - `1.0` if the direction is positive.
+    /// - `-1.0` if the direction is negative.
+    pub fn factor(self) -> f64 {
+        if self.is_positive() { 1.0 } else { -1.0 }
+    }
+
+    /// The inverse direction.
+    pub fn inv(self) -> Self {
+        match self {
+            Self::LTR => Self::RTL,
+            Self::RTL => Self::LTR,
+            Self::TTB => Self::BTT,
+            Self::BTT => Self::TTB,
+        }
+    }
+}
+
+impl Display for Dir {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.pad(match self {
+            Self::LTR => "ltr",
+            Self::RTL => "rtl",
+            Self::TTB => "ttb",
+            Self::BTT => "btt",
+        })
+    }
+}