Rename PointCollection::Borrow to Point

Author: 38

src/element/basic_shapes.rs

@@ -18,7 +18,7 @@ impl<Coord> Pixel<Coord> {
 }
 
 impl<'a, Coord> PointCollection<'a, Coord> for &'a Pixel<Coord> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> Self::IntoIter {
         std::iter::once(&self.pos)
@@ -81,7 +81,7 @@ impl<Coord> PathElement<Coord> {
 }
 
 impl<'a, Coord> PointCollection<'a, Coord> for &'a PathElement<Coord> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = &'a [Coord];
     fn point_iter(self) -> &'a [Coord] {
         &self.points
@@ -153,7 +153,7 @@ impl<Coord> Rectangle<Coord> {
 }
 
 impl<'a, Coord> PointCollection<'a, Coord> for &'a Rectangle<Coord> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = &'a [Coord];
     fn point_iter(self) -> &'a [Coord] {
         &self.points
@@ -245,7 +245,7 @@ impl<Coord, Size: SizeDesc> Circle<Coord, Size> {
 }
 
 impl<'a, Coord, Size: SizeDesc> PointCollection<'a, Coord> for &'a Circle<Coord, Size> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> std::iter::Once<&'a Coord> {
         std::iter::once(&self.center)
@@ -306,7 +306,7 @@ impl<Coord> Polygon<Coord> {
 }
 
 impl<'a, Coord> PointCollection<'a, Coord> for &'a Polygon<Coord> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = &'a [Coord];
     fn point_iter(self) -> &'a [Coord] {
         &self.points

src/element/boxplot.rs

@@ -180,8 +180,8 @@ impl<K, O: BoxplotOrient<K, f32>> Boxplot<K, O> {
 impl<'a, K: Clone, O: BoxplotOrient<K, f32>> PointCollection<'a, (O::XType, O::YType)>
     for &'a Boxplot<K, O>
 {
-    type Borrow = (O::XType, O::YType);
-    type IntoIter = Vec<Self::Borrow>;
+    type Point = (O::XType, O::YType);
+    type IntoIter = Vec<Self::Point>;
     fn point_iter(self) -> Self::IntoIter {
         self.values
             .iter()

src/element/candlestick.rs

@@ -62,7 +62,7 @@ impl<X: Clone, Y: PartialOrd> CandleStick<X, Y> {
 }
 
 impl<'a, X: 'a, Y: PartialOrd + 'a> PointCollection<'a, (X, Y)> for &'a CandleStick<X, Y> {
-    type Borrow = &'a (X, Y);
+    type Point = &'a (X, Y);
     type IntoIter = &'a [(X, Y)];
     fn point_iter(self) -> &'a [(X, Y)] {
         &self.points

src/element/composable.rs

@@ -36,7 +36,7 @@ where
 }
 
 impl<'a, Coord, DB: DrawingBackend> PointCollection<'a, Coord> for &'a EmptyElement<Coord, DB> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = Once<&'a Coord>;
     fn point_iter(self) -> Self::IntoIter {
         once(&self.coord)
@@ -64,7 +64,7 @@ pub struct BoxedElement<Coord, DB: DrawingBackend, A: Drawable<DB>> {
 impl<'b, Coord, DB: DrawingBackend, A: Drawable<DB>> PointCollection<'b, Coord>
     for &'b BoxedElement<Coord, DB, A>
 {
-    type Borrow = &'b Coord;
+    type Point = &'b Coord;
     type IntoIter = Once<&'b Coord>;
     fn point_iter(self) -> Self::IntoIter {
         once(&self.offset)
@@ -132,7 +132,7 @@ where
     A: Drawable<DB>,
     B: Drawable<DB>,
 {
-    type Borrow = &'b Coord;
+    type Point = &'b Coord;
     type IntoIter = Once<&'b Coord>;
     fn point_iter(self) -> Self::IntoIter {
         once(&self.offset)

src/element/dynelem.rs

@@ -36,7 +36,7 @@ where
 impl<'a, 'b: 'a, DB: DrawingBackend, Coord: Clone> PointCollection<'a, Coord>
     for &'a DynElement<'b, DB, Coord>
 {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = &'a Vec<Coord>;
     fn point_iter(self) -> Self::IntoIter {
         &self.points

src/element/errorbar.rs

@@ -97,8 +97,8 @@ impl<K, V> ErrorBar<K, V, ErrorBarOrientH<K, V>> {
 impl<'a, K: Clone, V: Clone, O: ErrorBarOrient<K, V>> PointCollection<'a, (O::XType, O::YType)>
     for &'a ErrorBar<K, V, O>
 {
-    type Borrow = (O::XType, O::YType);
-    type IntoIter = Vec<Self::Borrow>;
+    type Point = (O::XType, O::YType);
+    type IntoIter = Vec<Self::Point>;
     fn point_iter(self) -> Self::IntoIter {
         self.values
             .iter()

src/element/image.rs

@@ -193,7 +193,7 @@ impl<'a, Coord> From<(Coord, DynamicImage)> for BitMapElement<'a, Coord, BGRXPix
 }
 
 impl<'a, 'b, Coord> PointCollection<'a, Coord> for &'a BitMapElement<'b, Coord> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> Self::IntoIter {
         std::iter::once(&self.pos)

src/element/mod.rs

@@ -30,7 +30,7 @@
 
     // For any reference to RedX, we can convert it into an iterator of points
     impl <'a> PointCollection<'a, (i32, i32)> for &'a RedBoxedX {
-        type Borrow = &'a (i32, i32);
+        type Point = &'a (i32, i32);
         type IntoIter = Once<&'a (i32, i32)>;
         fn point_iter(self) -> Self::IntoIter {
             once(&self.0)
@@ -192,13 +192,40 @@ pub use self::image::BitMapElement;
 mod dynelem;
 pub use dynelem::{DynElement, IntoDynElement};
 
-/// A type which is logically a collection of points, under any given coordinate system
+/// A type which is logically a collection of points, under any given coordinate system.
+/// Note: Ideally, a point collection trait should be any type of which coordinate elements can be
+/// iterated. This is similar to `iter` method of many collection types in std.
+///
+/// ```ignore
+/// trait PointCollection<Coord> {
+///     type PointIter<'a> : Iterator<Item = &'a Coord>;
+///     fn iter(&self) -> PointIter<'a>;
+/// }
+/// ```
+///
+/// However,
+/// [Generic Associated Types](https://github.com/rust-lang/rfcs/blob/master/text/1598-generic_associated_types.md)
+/// is far away from stablize.
+/// So currently we have the following workaround:
+///
+/// Instead of implement the PointCollection trait on the element type itself, it implements on the
+/// reference to the element. By doing so, we now have a well-defined lifetime for the iterator.
+///
+/// In addition, for some element, the coordinate is computed on the fly, thus we can't hard-code
+/// the iterator's return type is `&'a Coord`.
+/// `Borrow` trait seems to strict in this case, since we don't need the order and hash
+/// preservation properties at this point. However, `AsRef` doesn't work with `Coord`
+///
+/// This workaround also leads overly strict lifetime bound on `ChartContext::draw_series`.
+///
+/// TODO: Once GAT is ready on stable Rust, we should simplify the design.
+///
 pub trait PointCollection<'a, Coord> {
     /// The item in point iterator
-    type Borrow: Borrow<Coord>;
+    type Point: Borrow<Coord> + 'a;
 
     /// The point iterator
-    type IntoIter: IntoIterator<Item = Self::Borrow>;
+    type IntoIter: IntoIterator<Item = Self::Point>;
 
     /// framework to do the coordinate mapping
     fn point_iter(self) -> Self::IntoIter;

src/element/points.rs

@@ -26,7 +26,7 @@ impl<Coord, Size: SizeDesc> Cross<Coord, Size> {
 }
 
 impl<'a, Coord: 'a, Size: SizeDesc> PointCollection<'a, Coord> for &'a Cross<Coord, Size> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> std::iter::Once<&'a Coord> {
         std::iter::once(&self.center)
@@ -69,7 +69,7 @@ impl<Coord, Size: SizeDesc> TriangleMarker<Coord, Size> {
 }
 
 impl<'a, Coord: 'a, Size: SizeDesc> PointCollection<'a, Coord> for &'a TriangleMarker<Coord, Size> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> std::iter::Once<&'a Coord> {
         std::iter::once(&self.center)

src/element/text.rs

@@ -29,7 +29,7 @@ impl<'a, Coord, T: Borrow<str>> Text<'a, Coord, T> {
 }
 
 impl<'b, 'a, Coord: 'a, T: Borrow<str> + 'a> PointCollection<'a, Coord> for &'a Text<'b, Coord, T> {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> Self::IntoIter {
         std::iter::once(&self.coord)
@@ -216,7 +216,7 @@ impl<'a, Coord> MultiLineText<'a, Coord, String> {
 impl<'b, 'a, Coord: 'a, T: Borrow<str> + 'a> PointCollection<'a, Coord>
     for &'a MultiLineText<'b, Coord, T>
 {
-    type Borrow = &'a Coord;
+    type Point = &'a Coord;
     type IntoIter = std::iter::Once<&'a Coord>;
     fn point_iter(self) -> Self::IntoIter {
         std::iter::once(&self.coord)