Files · Explorer: a folder as a list, tiles or columns, with one path and one order

FileExplorer shows the folder at the end of a path three ways: the
directory listing, a grid of tiles, or a column per folder along the
path with the next folder lit. Its name, its count and a switch of views
sit above one path bar that climbs. A folder opens in place; a file goes
to the host, which lists each folder it goes to. A pick in an earlier
column closes the columns past it, and a new deepest column scrolls into
view. The directory listing takes its pick from its owner and reports
it, so the pick carries across views; its path bar and its first order
are shared. The gallery walks a small file system and shows the tree,
the context menu, renaming in place and a drop zone in use.

src/theme/files.rs

@@ -7,12 +7,18 @@ use super::{Theme, tokens::px_to_rems};
 pub struct FileSizes {
     /// A tile in a grid of files, wide.
     pub tile: Rems,
+    /// A column of a folder along a path, wide.
+    pub column: Rems,
+    /// The columns view, tall.
+    pub columns: Rems,
 }
 
 impl Theme {
     pub fn files(&self) -> FileSizes {
         FileSizes {
             tile: px_to_rems(96.0),
+            column: px_to_rems(200.0),
+            columns: px_to_rems(288.0),
         }
     }
 }