Make UserInput generic over the maximum number of chord inputs

RELEASES.md

@@ -11,6 +11,13 @@
 ### Usability
 
 - Implemented `Eq` for `Timing` and `InputMap`.
+- `UserInput` is now generic over the maximum size of inputs for a `Chord` (the default is still `8`).
+  - If an iterator with too many inputs is passed to `UserInput::chord`, the rest of the inputs are now ignored instead of panicing.
+  - If you want to react to this case, the new `UserInput::try_make_chord` function returns a `Result` instead.
+
+### Breaking changes
+
+- `UserInput::chord` does not panic anymore if you provide an iterator with more inputs than the maximum allowed number. Instead, the rest of the elements are silently ignored.
 
 ## Version 0.5
 

src/user_input.rs

@@ -11,32 +11,41 @@ use crate::{
     buttonlike::{MouseMotionDirection, MouseWheelDirection},
 };
 
+/// An [`UserInput::Chord`] could not be created because there were too many input elements
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub struct ChordCreationError;
+
 /// Some combination of user input, which may cross [`Input`]-mode boundaries
 ///
 /// Suitable for use in an [`InputMap`](crate::input_map::InputMap)
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
-pub enum UserInput {
+pub enum UserInput<const CHORD_MAX_SIZE: usize = 8> {
     /// A single button
     Single(InputKind),
     /// A combination of buttons, pressed simultaneously
     ///
-    /// Up to 8 (!!) buttons can be chorded together at once.
+    /// The number of buttons you can chord together is configurable via the `CHORD_MAX_SIZE` generic (8 by default).
     /// Chords are considered to belong to all of the [InputMode]s of their constituent buttons.
-    Chord(PetitSet<InputKind, 8>),
+    Chord(PetitSet<InputKind, CHORD_MAX_SIZE>),
     /// A virtual DPad that you can get an [`AxisPair`] from
     VirtualDPad(VirtualDPad),
 }
 
-impl UserInput {
+impl<const CHORD_MAX_SIZE: usize> UserInput<CHORD_MAX_SIZE> {
     /// Creates a [`UserInput::Chord`] from an iterator of [`InputKind`]s
     ///
     /// If `inputs` has a length of 1, a [`UserInput::Single`] variant will be returned instead.
+    ///
+    /// If `inputs` contains more than `CHORD_MAX_SIZE` elements, the rest of the elements are ignored.
+    /// If you want to react to this case with a [`Result`], use [`UserInput::try_make_chord`] instead.
     pub fn chord(inputs: impl IntoIterator<Item = impl Into<InputKind>>) -> Self {
         // We can't just check the length unless we add an ExactSizeIterator bound :(
-        let mut length: u8 = 0;
+        let mut length: usize = 0;
+
+        let mut set: PetitSet<InputKind, CHORD_MAX_SIZE> = PetitSet::default();
 
-        let mut set: PetitSet<InputKind, 8> = PetitSet::default();
-        for button in inputs {
+        // If the iterator contains more than the maximum number of elements, ignore the rest
+        for button in inputs.into_iter().take(CHORD_MAX_SIZE) {
             length += 1;
             set.insert(button.into());
         }
@@ -47,6 +56,38 @@ impl UserInput {
         }
     }
 
+    /// Creates a [`UserInput::Chord`] from an iterator of [`InputKind`]s
+    ///
+    /// If `inputs` has a length of 1, a [`UserInput::Single`] variant will be returned instead.
+    ///
+    /// If `inputs` contains more than `CHORD_MAX_SIZE` elements, a [`ChordCreationError`] is returned.
+    /// If you want to silently ignore the rest of the elements, use the [`UserInput::chord`] function instead.
+    pub fn try_make_chord(
+        inputs: impl IntoIterator<Item = impl Into<InputKind>>,
+    ) -> Result<Self, ChordCreationError> {
+        // We can't just check the length unless we add an ExactSizeIterator bound :(
+        let mut length: usize = 0;
+
+        let mut set: PetitSet<InputKind, CHORD_MAX_SIZE> = PetitSet::default();
+
+        // If the iterator contains more than the maximum number of elements, ignore the rest
+        for button in inputs.into_iter().take(CHORD_MAX_SIZE) {
+            length += 1;
+
+            if length >= CHORD_MAX_SIZE {
+                return Err(ChordCreationError);
+            }
+            set.insert(button.into());
+        }
+
+        let user_input = match length {
+            1 => UserInput::Single(set.into_iter().next().unwrap()),
+            _ => UserInput::Chord(set),
+        };
+
+        Ok(user_input)
+    }
+
     /// The number of logical inputs that make up the [`UserInput`].
     ///
     /// - A [`Single`][UserInput::Single] input returns 1