Add Key::Cut, Key::Copy, Key::Paste (#3725)

The comment added in commit 8a0bc97 ("[egui_glium] Fix paste") seems to
assume that `winit` "should have translated" common "paste" keyboard
combos to a `Cut`/`Copy`/`Paste` "KeyCode", but completely glossed over
the fact that this `KeyCode` (now also `NamedKey`) maps to a special key
dedicated to this purpose found on some keyboards and OSes. Make sure
that this key is still handled in addition to the combo that is
detected.

---

Note that this PR does not compile as it is (and I have hence not tested
this nor even ran into this limitation), just noticed this inconsistency
while failing to understand a code comment. We'd have to decide if the
variants should be added to `egui::Key` or if these helper functions
need to take `winit` keys (`ScanCode` or `NamedKey`) directly?

I should have an old keyboard with a physical paste key in a drawer
somewhere. And on Android there are special copy/paste events that can
be sent by a virtual keyboard or the debug shell, so that this can be
properly tested before it is merged.
(Except that the current `clipboard` implementation is not supported on
Android)

crates/egui-winit/src/lib.rs

@@ -691,8 +691,6 @@ impl State {
 
         if let Some(logical_key) = logical_key {
             if pressed {
-                // KeyCode::Paste etc in winit are broken/untrustworthy,
-                // so we detect these things manually:
                 if is_cut_command(self.egui_input.modifiers, logical_key) {
                     self.egui_input.events.push(egui::Event::Cut);
                     return true;
@@ -946,17 +944,20 @@ fn is_printable_char(chr: char) -> bool {
 }
 
 fn is_cut_command(modifiers: egui::Modifiers, keycode: egui::Key) -> bool {
-    (modifiers.command && keycode == egui::Key::X)
+    keycode == egui::Key::Cut
+        || (modifiers.command && keycode == egui::Key::X)
         || (cfg!(target_os = "windows") && modifiers.shift && keycode == egui::Key::Delete)
 }
 
 fn is_copy_command(modifiers: egui::Modifiers, keycode: egui::Key) -> bool {
-    (modifiers.command && keycode == egui::Key::C)
+    keycode == egui::Key::Copy
+        || (modifiers.command && keycode == egui::Key::C)
         || (cfg!(target_os = "windows") && modifiers.ctrl && keycode == egui::Key::Insert)
 }
 
 fn is_paste_command(modifiers: egui::Modifiers, keycode: egui::Key) -> bool {
-    (modifiers.command && keycode == egui::Key::V)
+    keycode == egui::Key::Paste
+        || (modifiers.command && keycode == egui::Key::V)
         || (cfg!(target_os = "windows") && modifiers.shift && keycode == egui::Key::Insert)
 }
 
@@ -983,47 +984,50 @@ fn key_from_named_key(named_key: winit::keyboard::NamedKey) -> Option<egui::Key>
     use egui::Key;
     use winit::keyboard::NamedKey;
 
-    match named_key {
-        NamedKey::Enter => Some(Key::Enter),
-        NamedKey::Tab => Some(Key::Tab),
-        NamedKey::Space => Some(Key::Space),
-        NamedKey::ArrowDown => Some(Key::ArrowDown),
-        NamedKey::ArrowLeft => Some(Key::ArrowLeft),
-        NamedKey::ArrowRight => Some(Key::ArrowRight),
-        NamedKey::ArrowUp => Some(Key::ArrowUp),
-        NamedKey::End => Some(Key::End),
-        NamedKey::Home => Some(Key::Home),
-        NamedKey::PageDown => Some(Key::PageDown),
-        NamedKey::PageUp => Some(Key::PageUp),
-        NamedKey::Backspace => Some(Key::Backspace),
-        NamedKey::Delete => Some(Key::Delete),
-        NamedKey::Insert => Some(Key::Insert),
-        NamedKey::Escape => Some(Key::Escape),
-        NamedKey::F1 => Some(Key::F1),
-        NamedKey::F2 => Some(Key::F2),
-        NamedKey::F3 => Some(Key::F3),
-        NamedKey::F4 => Some(Key::F4),
-        NamedKey::F5 => Some(Key::F5),
-        NamedKey::F6 => Some(Key::F6),
-        NamedKey::F7 => Some(Key::F7),
-        NamedKey::F8 => Some(Key::F8),
-        NamedKey::F9 => Some(Key::F9),
-        NamedKey::F10 => Some(Key::F10),
-        NamedKey::F11 => Some(Key::F11),
-        NamedKey::F12 => Some(Key::F12),
-        NamedKey::F13 => Some(Key::F13),
-        NamedKey::F14 => Some(Key::F14),
-        NamedKey::F15 => Some(Key::F15),
-        NamedKey::F16 => Some(Key::F16),
-        NamedKey::F17 => Some(Key::F17),
-        NamedKey::F18 => Some(Key::F18),
-        NamedKey::F19 => Some(Key::F19),
-        NamedKey::F20 => Some(Key::F20),
+    Some(match named_key {
+        NamedKey::Enter => Key::Enter,
+        NamedKey::Tab => Key::Tab,
+        NamedKey::Space => Key::Space,
+        NamedKey::ArrowDown => Key::ArrowDown,
+        NamedKey::ArrowLeft => Key::ArrowLeft,
+        NamedKey::ArrowRight => Key::ArrowRight,
+        NamedKey::ArrowUp => Key::ArrowUp,
+        NamedKey::End => Key::End,
+        NamedKey::Home => Key::Home,
+        NamedKey::PageDown => Key::PageDown,
+        NamedKey::PageUp => Key::PageUp,
+        NamedKey::Backspace => Key::Backspace,
+        NamedKey::Delete => Key::Delete,
+        NamedKey::Insert => Key::Insert,
+        NamedKey::Escape => Key::Escape,
+        NamedKey::Cut => Key::Cut,
+        NamedKey::Copy => Key::Copy,
+        NamedKey::Paste => Key::Paste,
+        NamedKey::F1 => Key::F1,
+        NamedKey::F2 => Key::F2,
+        NamedKey::F3 => Key::F3,
+        NamedKey::F4 => Key::F4,
+        NamedKey::F5 => Key::F5,
+        NamedKey::F6 => Key::F6,
+        NamedKey::F7 => Key::F7,
+        NamedKey::F8 => Key::F8,
+        NamedKey::F9 => Key::F9,
+        NamedKey::F10 => Key::F10,
+        NamedKey::F11 => Key::F11,
+        NamedKey::F12 => Key::F12,
+        NamedKey::F13 => Key::F13,
+        NamedKey::F14 => Key::F14,
+        NamedKey::F15 => Key::F15,
+        NamedKey::F16 => Key::F16,
+        NamedKey::F17 => Key::F17,
+        NamedKey::F18 => Key::F18,
+        NamedKey::F19 => Key::F19,
+        NamedKey::F20 => Key::F20,
         _ => {
             log::trace!("Unknown key: {named_key:?}");
-            None
+            return None;
         }
-    }
+    })
 }
 
 fn key_from_key_code(key: winit::keyboard::KeyCode) -> Option<egui::Key> {
@@ -1054,6 +1058,10 @@ fn key_from_key_code(key: winit::keyboard::KeyCode) -> Option<egui::Key> {
         // KeyCode::Colon => Key::Colon, // NOTE: there is no physical colon key on an american keyboard
         KeyCode::Semicolon => Key::Semicolon,
 
+        KeyCode::Cut => Key::Cut,
+        KeyCode::Copy => Key::Copy,
+        KeyCode::Paste => Key::Paste,
+
         KeyCode::Minus | KeyCode::NumpadSubtract => Key::Minus,
 
         // Using Mac the key with the Plus sign on it is reported as the Equals key

crates/egui/src/data/input.rs

@@ -879,6 +879,10 @@ pub enum Key {
     PageUp,
     PageDown,
 
+    Copy,
+    Cut,
+    Paste,
+
     // ----------------------------------------------
     // Punctuation:
     /// `:`
@@ -1005,6 +1009,9 @@ impl Key {
         Self::End,
         Self::PageUp,
         Self::PageDown,
+        Self::Copy,
+        Self::Cut,
+        Self::Paste,
         // Punctuation:
         Self::Colon,
         Self::Comma,
@@ -1102,6 +1109,10 @@ impl Key {
             "PageUp" => Self::PageUp,
             "PageDown" => Self::PageDown,
 
+            "Copy" => Self::Copy,
+            "Cut" => Self::Cut,
+            "Paste" => Self::Paste,
+
             "Colon" | ":" => Self::Colon,
             "Comma" | "," => Self::Comma,
             "Minus" | "-" | "−" => Self::Minus,
@@ -1209,6 +1220,10 @@ impl Key {
             Key::PageUp => "PageUp",
             Key::PageDown => "PageDown",
 
+            Key::Copy => "Copy",
+            Key::Cut => "Cut",
+            Key::Paste => "Paste",
+
             Key::Colon => "Colon",
             Key::Comma => "Comma",
             Key::Minus => "Minus",