fix x/y/xy ops; remove button_2/3

src/layout.rs

@@ -96,6 +96,76 @@ impl Sizer {
     }
 }
 
+/// Some layout operations exist in multiple variants that take a single argument.
+/// Their handling in [eval_view] is uniform and goes like this:
+macro_rules! eval_enum ((
+    $name:literal, $output:ident, $state:ident, $value:expr, $Enum:ident {
+        $($v:literal => $V:ident),* $(,)?
+    }
+) => {{
+    match $value {
+        $(Some($v) => $Enum::$V,)*
+        frag => return Err(format!("invalid variant: {}/{frag:?}", $name).into())
+    }
+}});
+
+/// Some layout operations exist in XY, X, and Y variants that take 3 or 2 arguments.
+/// Their handling in [eval_view] is uniform and goes like this:
+macro_rules! eval_xy (
+    // Valueless variant:
+    //     (fill/x ...)
+    //     (fill/y ...)
+    //     (fill/xy ...)
+    (
+        $name:expr => $expr:expr, $head:expr, $output:ident, $state:ident,
+        $variant:expr, $xy:ident, $x:ident, $y:ident, $arg:expr,
+    ) => {{
+        // frags.next(): 2nd slash-delimited fragment: /x, /y, /xy
+        let variant = $variant;
+        let thunk = draw(move|screen|$state.interpret(screen, &$arg));
+        match variant {
+            // X variant
+            Some("x") => thunk.$x().draw($output),
+            // Y variant
+            Some("y") => thunk.$y().draw($output),
+            // XY variant (can be omitted)
+            Some("xy") | None => thunk.$xy().draw($output),
+            // Other namespace members are invalid
+            frag => invalid_variant($name, frag, $expr, $head)
+        }
+    }};
+
+    // Variadic variant:
+    //     (push/x n ...)
+    //     (push/y n ...)
+    //     (push/xy n m ...)
+    (
+        $name:expr => $expr:expr, $head:expr, $output:ident, $state:ident,
+        $variant:expr, $xy:ident, $x:ident, $y:ident, $arg0:expr, $arg1:expr, $arg2:expr,
+    ) => {{
+        // frags.next(): 2nd slash-delimited fragment: /x, /y, /xy
+        let variant = $variant;
+        let thunk = draw(move|screen|$state.interpret(screen, &match variant {
+            Some("x")  | Some("y") => $arg1,
+            Some("xy") | None => $arg2,
+            _ => panic!("{}: unsupported axis {variant:?}; try /x, /y, /xy", $name)
+        }));
+        match variant {
+            // X variant
+            Some("x") => thunk.$x($state.namespace($arg0?)?)
+                .draw($output),
+            // Y variant
+            Some("y") => thunk.$y($state.namespace($arg0?)?)
+                .draw($output),
+            // XY variant (can be omitted)
+            Some("xy") | None => thunk.$xy($state.namespace($arg0?)?, $state.namespace($arg1?)?)
+                .draw($output),
+            // Other namespace members are invalid
+            frag => invalid_variant($name, frag, $expr, $head)
+        }
+    }};
+);
+
 macro_rules! def_layout_modifier {
     (
         $Trait:ident ($fn_x:ident $fn_y:ident $fn_xy:ident),
@@ -126,7 +196,7 @@ macro_rules! def_layout_modifier {
         fn_kw_layout!($kw_name |state, output, expr| {
             let head = expr.head()?;
             let mut frags = head.src()?.unwrap_or_default().split("/");
-            Ok(matches!(expr.head()?, Some("exact")).then(||{
+            Ok(matches!(frags.next(), Some($name)).then(||{
                 let args  = expr.tail();
                 let arg0  = args.head();
                 let tail0 = args.tail();