move macros into relevant modules

tek/src/view_sizes.rs

@@ -1,4 +1,17 @@
 use crate::*;
+
+/// Define a type alias for iterators of sized items (columns).
+macro_rules! def_sizes_iter {
+    ($Type:ident => $($Item:ty),+) => {
+        pub(crate) trait $Type<'a> =
+            Iterator<Item=(usize, $(&'a $Item,)+ usize, usize)> + Send + Sync + 'a;}}
+
+def_sizes_iter!(ScenesSizes  => Scene);
+def_sizes_iter!(TracksSizes  => Track);
+def_sizes_iter!(InputsSizes  => JackMidiIn);
+def_sizes_iter!(OutputsSizes => JackMidiOut);
+def_sizes_iter!(PortsSizes   => Arc<str>, [PortConnect]);
+
 impl Tek {
     /// Spacing between tracks.
     pub(crate) const TRACK_SPACING: usize = 0;