ui: Add functions for generating textual representations of key bindings (#15287)

This PR adds some helper functions in the `ui` crate that can be used to
get textural representations of keystrokes or key bindings.

Release Notes:

- N/A

crates/gpui/src/platform/keystroke.rs

@@ -237,14 +237,15 @@ pub struct Modifiers {
 }
 
 impl Modifiers {
-    /// Returns true if any modifier key is pressed
+    /// Returns whether any modifier key is pressed.
     pub fn modified(&self) -> bool {
         self.control || self.alt || self.shift || self.platform || self.function
     }
 
-    /// Whether the semantically 'secondary' modifier key is pressed
-    /// On macos, this is the command key
-    /// On windows and linux, this is the control key
+    /// Whether the semantically 'secondary' modifier key is pressed.
+    ///
+    /// On macOS, this is the command key.
+    /// On Linux and Windows, this is the control key.
     pub fn secondary(&self) -> bool {
         #[cfg(target_os = "macos")]
         {
@@ -257,7 +258,7 @@ impl Modifiers {
         }
     }
 
-    /// How many modifier keys are pressed
+    /// Returns how many modifier keys are pressed.
     pub fn number_of_modifiers(&self) -> u8 {
         self.control as u8
             + self.alt as u8
@@ -266,12 +267,12 @@ impl Modifiers {
             + self.function as u8
     }
 
-    /// helper method for Modifiers with no modifiers
+    /// Returns [`Modifiers`] with no modifiers.
     pub fn none() -> Modifiers {
         Default::default()
     }
 
-    /// helper method for Modifiers with just the command key
+    /// Returns [`Modifiers`] with just the command key.
     pub fn command() -> Modifiers {
         Modifiers {
             platform: true,
@@ -279,7 +280,7 @@ impl Modifiers {
         }
     }
 
-    /// A helper method for Modifiers with just the secondary key pressed
+    /// A Returns [`Modifiers`] with just the secondary key pressed.
     pub fn secondary_key() -> Modifiers {
         #[cfg(target_os = "macos")]
         {
@@ -298,7 +299,7 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with just the windows key
+    /// Returns [`Modifiers`] with just the windows key.
     pub fn windows() -> Modifiers {
         Modifiers {
             platform: true,
@@ -306,7 +307,7 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with just the super key
+    /// Returns [`Modifiers`] with just the super key.
     pub fn super_key() -> Modifiers {
         Modifiers {
             platform: true,
@@ -314,7 +315,7 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with just control
+    /// Returns [`Modifiers`] with just control.
     pub fn control() -> Modifiers {
         Modifiers {
             control: true,
@@ -322,7 +323,15 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with just shift
+    /// Returns [`Modifiers`] with just control.
+    pub fn alt() -> Modifiers {
+        Modifiers {
+            alt: true,
+            ..Default::default()
+        }
+    }
+
+    /// Returns [`Modifiers`] with just shift.
     pub fn shift() -> Modifiers {
         Modifiers {
             shift: true,
@@ -330,7 +339,7 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with command + shift
+    /// Returns [`Modifiers`] with command + shift.
     pub fn command_shift() -> Modifiers {
         Modifiers {
             shift: true,
@@ -339,7 +348,7 @@ impl Modifiers {
         }
     }
 
-    /// helper method for Modifiers with command + shift
+    /// Returns [`Modifiers`] with command + shift.
     pub fn control_shift() -> Modifiers {
         Modifiers {
             shift: true,
@@ -348,7 +357,7 @@ impl Modifiers {
         }
     }
 
-    /// Checks if this Modifiers is a subset of another Modifiers
+    /// Checks if this [`Modifiers`] is a subset of another [`Modifiers`].
     pub fn is_subset_of(&self, other: &Modifiers) -> bool {
         (other.control || !self.control)
             && (other.alt || !self.alt)