Add is_* and as_* methods to the event enums (#949)

* Add is_ and as_ methods to the event enums

Often application code only cares about a small subset of possible
events. These methods make it simpler to write code which checks whether
an event is a particular event type or converts events into the specific
type (returning an Option).

This can help simplify some nested match blocks. E.g.:

```rust
match event {
    Event::Key(key) if key.kind == KeyEventKind::Press => { ... }
}
```

becomes:

```rust
if let Some(key) = event.as_key_press() { ... }
```

Similar flexible methods are aded across all the event enums:

- `Event::is_focus_gained()`
- `Event::is_focus_lost()`
- `Event::is_key()`
- `Event::is_mouse()`
- `Event::is_paste()`
- `Event::is_resize()`
- `Event::is_key_press()`
- `Event::as_key_press() -> Option<&KeyEvent>`
- `MouseEventKind::is_*()`
- `MouseButton::is_*()`
- `KeyEventKind::is_*()`
- `KeyEvent::is_press()`
- `KeyEvent::is_release()`
- `KeyEvent::is_repeat()`
- `KeyCode::is_*()`
- `KeyCode::is_function_key(n)`
- `KeyCode::is_char(c)`
- `KeyCode::as_char() -> Option<char>`
- `KeyCode::is_media_key(media)`
- `KeyCode::is_modifier(modifier)`
- add is_key_release() and is_key_repeat() checks
- add as_key_event()
- rename as_key_press() to as_key_press_event()
- add as_key_repeat_event()
- add as_key_release_event()
- add as_mouse_event()
- add as_paste_event()
- more tests
- update event-match and key-display examples

Cargo.toml

@@ -46,6 +46,7 @@ use-dev-tty = ["filedescriptor", "rustix/process"]
 
 [dependencies]
 bitflags = { version = "2.3" }
+derive_more = { version = "1.0.0", features = ["is_variant"] }
 document-features = "0.2.10"
 futures-core = { version = "0.3", optional = true, default-features = false }
 parking_lot = "0.12"

examples/event-match-modifiers.rs

@@ -4,43 +4,42 @@
 
 use crossterm::event::{Event, KeyCode, KeyEvent, KeyModifiers};
 
-fn match_event(read_event: Event) {
-    match read_event {
-        // Match one one modifier:
-        Event::Key(KeyEvent {
-            modifiers: KeyModifiers::CONTROL,
-            code,
-            ..
-        }) => {
-            println!("Control + {:?}", code);
-        }
-        Event::Key(KeyEvent {
-            modifiers: KeyModifiers::SHIFT,
-            code,
-            ..
-        }) => {
-            println!("Shift + {:?}", code);
-        }
-        Event::Key(KeyEvent {
-            modifiers: KeyModifiers::ALT,
-            code,
-            ..
-        }) => {
-            println!("Alt + {:?}", code);
-        }
+fn match_event(event: Event) {
+    if let Some(key) = event.as_key_press_event() {
+        match key {
+            KeyEvent {
+                modifiers: KeyModifiers::CONTROL,
+                code,
+                ..
+            } => {
+                println!("Control + {:?}", code);
+            }
+            KeyEvent {
+                modifiers: KeyModifiers::SHIFT,
+                code,
+                ..
+            } => {
+                println!("Shift + {:?}", code);
+            }
+            KeyEvent {
+                modifiers: KeyModifiers::ALT,
+                code,
+                ..
+            } => {
+                println!("Alt + {:?}", code);
+            }
 
-        // Match on multiple modifiers:
-        Event::Key(KeyEvent {
-            code, modifiers, ..
-        }) => {
-            if modifiers == (KeyModifiers::ALT | KeyModifiers::SHIFT) {
-                println!("Alt + Shift {:?}", code);
-            } else {
-                println!("({:?}) with key: {:?}", modifiers, code)
+            // Match on multiple modifiers:
+            KeyEvent {
+                code, modifiers, ..
+            } => {
+                if modifiers == (KeyModifiers::ALT | KeyModifiers::SHIFT) {
+                    println!("Alt + Shift {:?}", code);
+                } else {
+                    println!("({:?}) with key: {:?}", modifiers, code)
+                }
             }
         }
-
-        _ => {}
     }
 }
 

examples/key-display.rs

@@ -7,9 +7,9 @@
 
 use std::io;
 
-use crossterm::event::{KeyEventKind, KeyModifiers};
+use crossterm::event::KeyModifiers;
 use crossterm::{
-    event::{read, Event, KeyCode},
+    event::{read, KeyCode},
     terminal::{disable_raw_mode, enable_raw_mode},
 };
 
@@ -29,20 +29,17 @@ fn main() -> io::Result<()> {
 }
 
 fn print_events() -> io::Result<()> {
-    loop {
-        let event = read()?;
-        match event {
-            Event::Key(event) if event.kind == KeyEventKind::Press => {
-                print!("Key pressed: ");
-                if event.modifiers != KeyModifiers::NONE {
-                    print!("{}+", event.modifiers);
-                }
-                println!("{}\r", event.code);
-                if event.code == KeyCode::Esc {
-                    break;
-                }
-            }
-            _ => {}
+    while let Ok(event) = read() {
+        let Some(event) = event.as_key_press_event() else {
+            continue;
+        };
+        let modifier = match event.modifiers {
+            KeyModifiers::NONE => "".to_string(),
+            _ => format!("{:}+", event.modifiers),
+        };
+        println!("Key pressed: {modifier}{code}\r", code = event.code);
+        if event.code == KeyCode::Esc {
+            break;
         }
     }
     Ok(())