1 files changed, 113 insertions, 0 deletions
diff --git a/src/coord/ranged1d/combinators/partial_axis.rs b/src/coord/ranged1d/combinators/partial_axis.rs
new file mode 100644
index 0000000..b778ee2
--- /dev/null
+++ b/src/coord/ranged1d/combinators/partial_axis.rs
@@ -0,0 +1,113 @@
+use crate::coord::ranged1d::{
+    AsRangedCoord, DefaultFormatting, DiscreteRanged, KeyPointHint, Ranged,
+};
+use std::ops::Range;
+
+/// This axis decorator will make the axis partially display on the axis.
+/// At some time, we want the axis only covers some part of the value.
+/// This decorator will have an additional display range defined.
+#[derive(Clone)]
+pub struct PartialAxis<R: Ranged>(R, Range<R::ValueType>);
+
+/// The trait for the types that can be converted into a partial axis
+pub trait IntoPartialAxis: AsRangedCoord {
+    /// Make the partial axis
+    ///
+    /// - `axis_range`: The range of the axis to be displayed
+    /// - **returns**: The converted range specification
+    fn partial_axis(
+        self,
+        axis_range: Range<<Self::CoordDescType as Ranged>::ValueType>,
+    ) -> PartialAxis<Self::CoordDescType> {
+        PartialAxis(self.into(), axis_range)
+    }
+}
+
+impl<R: AsRangedCoord> IntoPartialAxis for R {}
+
+impl<R: Ranged> Ranged for PartialAxis<R>
+where
+    R::ValueType: Clone,
+{
+    type FormatOption = DefaultFormatting;
+    type ValueType = R::ValueType;
+
+    fn map(&self, value: &Self::ValueType, limit: (i32, i32)) -> i32 {
+        self.0.map(value, limit)
+    }
+
+    fn key_points<Hint: KeyPointHint>(&self, hint: Hint) -> Vec<Self::ValueType> {
+        self.0.key_points(hint)
+    }
+
+    fn range(&self) -> Range<Self::ValueType> {
+        self.0.range()
+    }
+
+    fn axis_pixel_range(&self, limit: (i32, i32)) -> Range<i32> {
+        let left = self.map(&self.1.start, limit);
+        let right = self.map(&self.1.end, limit);
+
+        left.min(right)..left.max(right)
+    }
+}
+
+impl<R: DiscreteRanged> DiscreteRanged for PartialAxis<R>
+where
+    R: Ranged,
+    <R as Ranged>::ValueType: Eq + Clone,
+{
+    fn size(&self) -> usize {
+        self.0.size()
+    }
+
+    fn index_of(&self, value: &R::ValueType) -> Option<usize> {
+        self.0.index_of(value)
+    }
+
+    fn from_index(&self, index: usize) -> Option<Self::ValueType> {
+        self.0.from_index(index)
+    }
+}
+
+/// Make a partial axis based on the percentage of visible portion.
+/// We can use `into_partial_axis` to create a partial axis range specification.
+/// But sometimes, we want to directly specify the percentage visible to the user.
+///
+/// - `axis_range`: The range specification
+/// - `part`: The visible part of the axis. Each value is from [0.0, 1.0]
+/// - **returns**: The partial axis created from the input, or `None` when not possible
+pub fn make_partial_axis<T>(
+    axis_range: Range<T>,
+    part: Range<f64>,
+) -> Option<PartialAxis<<Range<T> as AsRangedCoord>::CoordDescType>>
+where
+    Range<T>: AsRangedCoord,
+    T: num_traits::NumCast + Clone,
+{
+    let left: f64 = num_traits::cast(axis_range.start.clone())?;
+    let right: f64 = num_traits::cast(axis_range.end.clone())?;
+
+    let full_range_size = (right - left) / (part.end - part.start);
+
+    let full_left = left - full_range_size * part.start;
+    let full_right = right + full_range_size * (1.0 - part.end);
+
+    let full_range: Range<T> = num_traits::cast(full_left)?..num_traits::cast(full_right)?;
+
+    let axis_range: <Range<T> as AsRangedCoord>::CoordDescType = axis_range.into();
+
+    Some(PartialAxis(full_range.into(), axis_range.range()))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    #[test]
+    fn test_make_partial_axis() {
+        let r = make_partial_axis(20..80, 0.2..0.8).unwrap();
+        assert_eq!(r.size(), 101);
+        assert_eq!(r.range(), 0..100);
+        assert_eq!(r.axis_pixel_range((0, 100)), 20..80);
+    }
+}