Implement Lens directly on a pair (#1654)

* Implement Lens directly on a pair
* Implement Lens for tuples of length 3 to 7
* Update Changelog

CHANGELOG.md

@@ -30,7 +30,7 @@ You can find its changes [documented below](#070---2021-01-01).
 - `Notification`s can be submitted while handling other `Notification`s ([#1640] by [@cmyr])
 - Added ListIter implementations for OrdMap ([#1641] by [@Lejero])
 - `Padding` can now use `Key<Insets>` ([#1662] by [@cmyr])
-- `LifeCycle::DisabledChanged`, `InternalLifeCycle::RouteDisabledChanged` and the `set_disabled()` and `is_disabled()` 
+- `LifeCycle::DisabledChanged`, `InternalLifeCycle::RouteDisabledChanged` and the `set_disabled()` and `is_disabled()`
   context-methods to implement disabled ([#1632] by [@xarvic])
 - `LifeCycle::BuildFocusChain` to update the focus-chain ([#1632] by [@xarvic])
 - `DisabledIf` widget wrapper to disable based on the state of Data and Env ([#1702] by [@xarvic])
@@ -45,6 +45,7 @@ You can find its changes [documented below](#070---2021-01-01).
 - Update to piet v0.4.0 (rich text on linux!) ([#1677] by [@cmyr])
 - `register_for_focus()` should from now on be called from `LifeCycle::BuildFocusChain` instead of `LifeCycle::WidgetAdded` ([#1632] by [@xarvic])
 - Flex values that are less than 0.0 will default to 0.0 and warn in release. It will panic in debug mode. ([#1691] by [@arthmis])
+- Lens implemented for tuples of Lenses of length 2-8, Tuple2 removed ([#1654] by [@Maan2003])
 
 ### Deprecated
 
@@ -667,6 +668,7 @@ Last release without a changelog :(
 [#1640]: https://github.com/linebender/druid/pull/1640
 [#1641]: https://github.com/linebender/druid/pull/1641
 [#1647]: https://github.com/linebender/druid/pull/1647
+[#1654]: https://github.com/linebender/druid/pull/1654
 [#1660]: https://github.com/linebender/druid/pull/1660
 [#1662]: https://github.com/linebender/druid/pull/1662
 [#1677]: https://github.com/linebender/druid/pull/1677

druid/src/lens/lens.rs

@@ -568,30 +568,65 @@ impl<A, B: Clone> Lens<A, B> for Constant<B> {
     }
 }
 
-/// A lens that combines two lenses into a tuple.
-#[derive(Debug, Copy, Clone)]
-pub struct Tuple2<L1, L2>(pub L1, pub L2);
-
-impl<A, L1B, L2B, L1, L2> Lens<A, (L1B, L2B)> for Tuple2<L1, L2>
-where
-    L1B: Clone,
-    L2B: Clone,
-    L1: Lens<A, L1B>,
-    L2: Lens<A, L2B>,
-{
-    fn with<V, F: FnOnce(&(L1B, L2B)) -> V>(&self, data: &A, f: F) -> V {
-        let l1b = self.0.with(data, |v| v.clone());
-        let l2b = self.1.with(data, |v| v.clone());
-        f(&(l1b, l2b))
-    }
-    fn with_mut<V, F: FnOnce(&mut (L1B, L2B)) -> V>(&self, data: &mut A, f: F) -> V {
-        let l1b = self.0.with(data, |v| v.clone());
-        let l2b = self.1.with(data, |v| v.clone());
-        let mut tuple = (l1b, l2b);
-        let out = f(&mut tuple);
-        let (l1b, l2b) = tuple;
-        self.0.with_mut(data, |v| *v = l1b);
-        self.1.with_mut(data, |v| *v = l2b);
-        out
-    }
+macro_rules! impl_lens_for_tuple {
+    ($(($Lens:ident, $B:ident, $i:tt)),*) => {
+        #[allow(non_snake_case)]
+        impl<A, $($Lens,)* $($B,)*> Lens<A, ($($B,)*)> for ($($Lens,)*)
+        where
+            $($B: Clone,)*
+            $($Lens: Lens<A, $B>,)*
+        {
+            fn with<V, F: FnOnce(&($($B,)*)) -> V>(&self, data: &A, f: F) -> V {
+                $(let $B = self.$i.with(data, |v| v.clone());)*
+                let tuple = ($($B,)*);
+                f(&tuple)
+            }
+            fn with_mut<V, F: FnOnce(&mut ($($B,)*)) -> V>(&self, data: &mut A, f: F) -> V {
+                $(let $B = self.$i.with(data, |v| v.clone());)*
+                let mut tuple = ($($B,)*);
+                let out = f(&mut tuple);
+                let ($($B,)*) = tuple;
+                $(self.$i.with_mut(data, |v| *v = $B);)*
+                out
+            }
+        }
+    };
 }
+
+impl_lens_for_tuple!((L0, L0B, 0), (L1, L1B, 1));
+impl_lens_for_tuple!((L0, L0B, 0), (L1, L1B, 1), (L2, L2B, 2));
+impl_lens_for_tuple!((L0, L0B, 0), (L1, L1B, 1), (L2, L2B, 2), (L3, L3B, 3));
+impl_lens_for_tuple!(
+    (L0, L0B, 0),
+    (L1, L1B, 1),
+    (L2, L2B, 2),
+    (L3, L3B, 3),
+    (L4, L4B, 4)
+);
+impl_lens_for_tuple!(
+    (L0, L0B, 0),
+    (L1, L1B, 1),
+    (L2, L2B, 2),
+    (L3, L3B, 3),
+    (L4, L4B, 4),
+    (L5, L5B, 5)
+);
+impl_lens_for_tuple!(
+    (L0, L0B, 0),
+    (L1, L1B, 1),
+    (L2, L2B, 2),
+    (L3, L3B, 3),
+    (L4, L4B, 4),
+    (L5, L5B, 5),
+    (L6, L6B, 6)
+);
+impl_lens_for_tuple!(
+    (L0, L0B, 0),
+    (L1, L1B, 1),
+    (L2, L2B, 2),
+    (L3, L3B, 3),
+    (L4, L4B, 4),
+    (L5, L5B, 5),
+    (L6, L6B, 6),
+    (L7, L7B, 7)
+);

druid/src/lens/mod.rs

@@ -49,6 +49,6 @@
 #[allow(clippy::module_inception)]
 #[macro_use]
 mod lens;
-pub use lens::{Constant, Deref, Field, Identity, InArc, Index, Map, Ref, Then, Tuple2, Unit};
+pub use lens::{Constant, Deref, Field, Identity, InArc, Index, Map, Ref, Then, Unit};
 #[doc(hidden)]
 pub use lens::{Lens, LensExt};