Add immut! macros

src/lib.rs

@@ -103,12 +103,14 @@ pub mod event;
 #[macro_use]
 pub mod view;
 
+#[macro_use]
+pub mod utils;
+
 pub mod align;
 pub mod direction;
 pub mod menu;
 pub mod rect;
 pub mod theme;
-pub mod utils;
 pub mod vec;
 pub mod views;
 

src/utils/immutify.rs

@@ -0,0 +1,135 @@
+/*
+
+// TODO: replace the 3 macros with 3 functions once they work correctly with
+// reference arguments.
+// (The returned closure must implement the for<'a> Fn(T, U<'a>)...
+
+
+// TODO: replace the 3 macros/functions with a generic function when it can
+// accept any number of arguments.
+
+/// Wraps a `FnMut` into a `Fn`
+///
+/// This can be used to use a `FnMut` when a callack expects a `Fn`.
+///
+/// # Note
+///
+/// If the resulting `Fn` is called recursively, subsequent calls will be
+/// no-ops.
+pub fn immutify<F: FnMut(&mut Cursive)>(
+    f: F,
+) -> impl for<'s> Fn(&'s mut Cursive) {
+    let callback = RefCell::new(f);
+    move |s| {
+        // Here's the weird trick: if we're already borrowed,
+        // just ignored the callback.
+        if let Ok(mut f) = callback.try_borrow_mut() {
+            // Beeeaaah that's ugly.
+            // Why do we need to manually dereference here?
+            (&mut *f)(s);
+        }
+    }
+}
+
+*/
+
+/// Macro to wrap a `FnMut` with 1 argument into a `Fn`.
+///
+/// This can wrap any `FnMut` with a single arguments (for example `&mut Cursive`).
+///
+/// See [`immut2!`] and [`immut3!`] to support a different number of arguments.
+///
+/// # Note
+///
+/// If this function tries to call itself recursively (for example by
+/// triggering an event in `Cursive`), the second call will be a no-op.
+/// Enabling recursive calls would break the `FnMut` contract.
+///
+/// In addition, due to weird interaction between Higher-rank trait bounds and
+/// closures, you should use the result from the macro directly, and not
+/// assign it to a variable.
+///
+/// # Examples
+///
+/// ```rust
+/// # #[macro_use]
+/// # extern crate cursive;
+/// # use cursive::Cursive;
+/// # fn main() {
+/// # let mut siv = Cursive::dummy();
+/// let mut i = 0;
+/// // `Cursive::add_global_callback` takes a `Fn(&mut Cursive)`
+/// siv.add_global_callback('q', immut1!(move |s: &mut Cursive| {
+///     // But here we mutate the environment! Crazy!
+///     i += 1;
+///     if i == 5 {
+///         s.quit();
+///     }
+/// }));
+/// # }
+/// ```
+#[macro_export]
+macro_rules! immut1 {
+    ($f:expr) => {{
+        let callback = ::std::cell::RefCell::new($f);
+        move |s| {
+            if let Ok(mut f) = callback.try_borrow_mut() {
+                (&mut *f)(s)
+            }
+        }
+    }};
+}
+
+/// Macro to wrap a `FnMut` with 2 arguments into a `Fn`.
+///
+/// This can wrap any `FnMut` with two arguments.
+///
+/// See [`immut1!`] and [`immut3!`] to support a different number of arguments.
+///
+/// # Note
+///
+/// If this function tries to call itself recursively (for example by
+/// triggering an event in `Cursive`), the second call will be a no-op.
+/// Enabling recursive calls would break the `FnMut` contract.
+///
+/// In addition, due to weird interaction between Higher-rank trait bounds and
+/// closures, you should use the result from the macro directly, and not
+/// assign it to a variable.
+#[macro_export]
+macro_rules! immut2 {
+    ($f:expr) => {{
+        let callback = ::std::cell::RefCell::new($f);
+        move |s, t| {
+            if let Ok(mut f) = callback.try_borrow_mut() {
+                (&mut *f)(s, t)
+            }
+        }
+    }};
+}
+
+/// Macro to wrap a `FnMut` with 3 arguments into a `Fn`.
+///
+/// This can wrap any `FnMut` with three arguments.
+///
+/// See [`immut1!`] and [`immut2!`] to support a different number of arguments.
+///
+/// # Note
+///
+/// If this function tries to call itself recursively (for example by
+/// triggering an event in `Cursive`), the second call will be a no-op.
+/// Enabling recursive calls would break the `FnMut` contract.
+///
+/// In addition, due to weird interaction between Higher-rank trait bounds and
+/// closures, you should use the result from the macro directly, and not
+/// assign it to a variable.
+#[macro_export]
+macro_rules! immut3 {
+    ($f:expr) => {{
+        let callback = ::std::cell::RefCell::new($f);
+        move |s, t, u| {
+            if let Ok(mut f) = callback.try_borrow_mut() {
+                (&mut *f)(s, t, u)
+            }
+        }
+    }};
+}

src/utils/mod.rs

@@ -1,6 +1,8 @@
 //! Toolbox to make text layout easier.
 
 mod counter;
+#[macro_use]
+mod immutify;
 pub mod lines;
 pub mod markup;
 mod reader;

src/views/edit_view.rs

@@ -236,16 +236,7 @@ impl EditView {
     where
         F: FnMut(&mut Cursive, &str, usize) + 'static,
     {
-        let callback = RefCell::new(callback);
+        self.set_on_edit(immut3!(callback));
-        // Here's the weird trick: if we're already borrowed,
-        // just ignored the callback.
-        self.set_on_edit(move |s, text, cursor| {
-            if let Ok(mut f) = callback.try_borrow_mut() {
-                // Beeeaaah that's ugly.
-                // Why do we need to manually dereference here?
-                (&mut *f)(s, text, cursor);
-            }
-        });
     }
 
     /// Sets a callback to be called whenever the content is modified.