keymap: Allow modifiers as keys (#12047)

It is sometimes desirable to allow modifers to serve as keys themselves
for the purposes of keybinds. For example, the popular keybind in
jetbrains IDEs `shift shift` which opens the file finder.

This change treats modifers in the keymaps as keys themselves if they
are not accompanied by a key they are modifying.

Further this change wires up they key dispatcher to treat modifer change
events as key presses which are considered for matching against
keybinds.


Release Notes:

- Fixes #6460

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/gpui/src/platform/keystroke.rs

@@ -94,6 +94,27 @@ impl Keystroke {
             }
         }
 
+        //Allow for the user to specify a keystroke modifier as the key itself
+        //This sets the `key` to the modifier, and disables the modifier
+        if key.is_none() {
+            if shift {
+                key = Some("shift".to_string());
+                shift = false;
+            } else if control {
+                key = Some("control".to_string());
+                control = false;
+            } else if alt {
+                key = Some("alt".to_string());
+                alt = false;
+            } else if platform {
+                key = Some("platform".to_string());
+                platform = false;
+            } else if function {
+                key = Some("function".to_string());
+                function = false;
+            }
+        }
+
         let key = key.ok_or_else(|| anyhow!("Invalid keystroke `{}`", source))?;
 
         Ok(Keystroke {
@@ -186,6 +207,10 @@ impl std::fmt::Display for Keystroke {
             "right" => '→',
             "tab" => '⇥',
             "escape" => '⎋',
+            "shift" => '⇧',
+            "control" => '⌃',
+            "alt" => '⌥',
+            "platform" => '⌘',
             key => {
                 if key.len() == 1 {
                     key.chars().next().unwrap().to_ascii_uppercase()
@@ -241,6 +266,15 @@ impl Modifiers {
         }
     }
 
+    /// How many modifier keys are pressed
+    pub fn number_of_modifiers(&self) -> u8 {
+        self.control as u8
+            + self.alt as u8
+            + self.shift as u8
+            + self.platform as u8
+            + self.function as u8
+    }
+
     /// helper method for Modifiers with no modifiers
     pub fn none() -> Modifiers {
         Default::default()

crates/gpui/src/window.rs

@@ -549,6 +549,7 @@ pub struct Window {
     pub(crate) focus: Option<FocusId>,
     focus_enabled: bool,
     pending_input: Option<PendingInput>,
+    pending_modifiers: Option<Modifiers>,
     pending_input_observers: SubscriberSet<(), AnyObserver>,
     prompt: Option<RenderablePromptHandle>,
 }
@@ -823,6 +824,7 @@ impl Window {
             focus: None,
             focus_enabled: true,
             pending_input: None,
+            pending_modifiers: None,
             pending_input_observers: SubscriberSet::new(),
             prompt: None,
         })
@@ -3161,23 +3163,76 @@ impl<'a> WindowContext<'a> {
             .dispatch_tree
             .dispatch_path(node_id);
 
+        let mut bindings: SmallVec<[KeyBinding; 1]> = SmallVec::new();
+        let mut pending = false;
+        let mut keystroke: Option<Keystroke> = None;
+
+        if let Some(event) = event.downcast_ref::<ModifiersChangedEvent>() {
+            if let Some(previous) = self.window.pending_modifiers.take() {
+                if event.modifiers.number_of_modifiers() == 0 {
+                    let key = match previous {
+                        modifiers if modifiers.shift => Some("shift"),
+                        modifiers if modifiers.control => Some("control"),
+                        modifiers if modifiers.alt => Some("alt"),
+                        modifiers if modifiers.platform => Some("platform"),
+                        modifiers if modifiers.function => Some("function"),
+                        _ => None,
+                    };
+                    if let Some(key) = key {
+                        let key = Keystroke {
+                            key: key.to_string(),
+                            ime_key: None,
+                            modifiers: Modifiers::default(),
+                        };
+                        let KeymatchResult {
+                            bindings: modifier_bindings,
+                            pending: pending_bindings,
+                        } = self
+                            .window
+                            .rendered_frame
+                            .dispatch_tree
+                            .dispatch_key(&key, &dispatch_path);
+
+                        keystroke = Some(key);
+                        bindings = modifier_bindings;
+                        pending = pending_bindings;
+                    }
+                }
+            } else if event.modifiers.number_of_modifiers() == 1 {
+                self.window.pending_modifiers = Some(event.modifiers);
+            }
+            if keystroke.is_none() {
+                self.finish_dispatch_key_event(event, dispatch_path);
+                return;
+            }
+        }
+
         if let Some(key_down_event) = event.downcast_ref::<KeyDownEvent>() {
-            let KeymatchResult { bindings, pending } = self
+            self.window.pending_modifiers.take();
+            let KeymatchResult {
+                bindings: key_down_bindings,
+                pending: key_down_pending,
+            } = self
                 .window
                 .rendered_frame
                 .dispatch_tree
                 .dispatch_key(&key_down_event.keystroke, &dispatch_path);
 
+            keystroke = Some(key_down_event.keystroke.clone());
+
+            bindings = key_down_bindings;
+            pending = key_down_pending;
+        }
+
         if pending {
             let mut currently_pending = self.window.pending_input.take().unwrap_or_default();
-                if currently_pending.focus.is_some() && currently_pending.focus != self.window.focus
+            if currently_pending.focus.is_some() && currently_pending.focus != self.window.focus {
-                {
                 currently_pending = PendingInput::default();
             }
             currently_pending.focus = self.window.focus;
-                currently_pending
+            if let Some(keystroke) = keystroke {
-                    .keystrokes
+                currently_pending.keystrokes.push(keystroke.clone());
-                    .push(key_down_event.keystroke.clone());
+            }
             for binding in bindings {
                 currently_pending.bindings.push(binding);
             }
@@ -3189,8 +3244,8 @@ impl<'a> WindowContext<'a> {
                     let Some(currently_pending) = cx.window.pending_input.take() else {
                         return;
                     };
-                        cx.pending_input_changed();
                     cx.replay_pending_input(currently_pending);
+                    cx.pending_input_changed();
                 })
                 .log_err();
             }));
@@ -3199,7 +3254,6 @@ impl<'a> WindowContext<'a> {
             self.pending_input_changed();
 
             self.propagate_event = false;
-
             return;
         } else if let Some(currently_pending) = self.window.pending_input.take() {
             self.pending_input_changed();
@@ -3223,8 +3277,15 @@ impl<'a> WindowContext<'a> {
                 return;
             }
         }
+
+        self.finish_dispatch_key_event(event, dispatch_path)
     }
 
+    fn finish_dispatch_key_event(
+        &mut self,
+        event: &dyn Any,
+        dispatch_path: SmallVec<[DispatchNodeId; 32]>,
+    ) {
         self.dispatch_key_down_up_event(event, &dispatch_path);
         if !self.propagate_event {
             return;

crates/ui/src/components/keybinding.rs

@@ -30,7 +30,7 @@ impl KeyBinding {
         Some(Self::new(key_binding))
     }
 
-    fn icon_for_key(keystroke: &Keystroke) -> Option<IconName> {
+    fn icon_for_key(&self, keystroke: &Keystroke) -> Option<IconName> {
         match keystroke.key.as_str() {
             "left" => Some(IconName::ArrowLeft),
             "right" => Some(IconName::ArrowRight),
@@ -45,6 +45,11 @@ impl KeyBinding {
             "escape" => Some(IconName::Escape),
             "pagedown" => Some(IconName::PageDown),
             "pageup" => Some(IconName::PageUp),
+            "shift" if self.platform_style == PlatformStyle::Mac => Some(IconName::Shift),
+            "control" if self.platform_style == PlatformStyle::Mac => Some(IconName::Control),
+            "platform" if self.platform_style == PlatformStyle::Mac => Some(IconName::Command),
+            "function" if self.platform_style == PlatformStyle::Mac => Some(IconName::Control),
+            "alt" if self.platform_style == PlatformStyle::Mac => Some(IconName::Option),
             _ => None,
         }
     }
@@ -80,7 +85,7 @@ impl RenderOnce for KeyBinding {
             .gap(Spacing::Small.rems(cx))
             .flex_none()
             .children(self.key_binding.keystrokes().iter().map(|keystroke| {
-                let key_icon = Self::icon_for_key(keystroke);
+                let key_icon = self.icon_for_key(keystroke);
 
                 h_flex()
                     .flex_none()

docs/src/key-bindings.md

@@ -50,12 +50,12 @@ Zed has the ability to match against not just a single keypress, but a sequence
 Each key press is a sequence of modifiers followed by a key. The modifiers are:
 
 - `ctrl-` The control key
-- `cmd-` On macOS, this is the command key
+* `cmd-`, `win-` or `super-` for the platform modifier (Command on macOS, Windows key on Windows, and the Super key on Linux).
-- `alt-` On macOS, this is the option key
+- `alt-` for alt (option on macOS)
 - `shift-` The shift key
 - `fn-` The function key
 
-The keys can be any single unicode codepoint that your keyboard generates (for example `a`, `0`, `£` or `ç`).
+The keys can be any single unicode codepoint that your keyboard generates (for example `a`, `0`, `£` or `ç`), or any named key (`tab`, `f1`, `shift`, or `cmd`).
 
 A few examples:
 
@@ -64,10 +64,15 @@ A few examples:
    "cmd-k cmd-s": "zed::OpenKeymap", // matches ⌘-k then ⌘-s
    "space e": "editor::Complete", // type space then e
    "ç": "editor::Complete", // matches ⌥-c
+   "shift shift": "file_finder::Toggle", // matches pressing and releasing shift twice
  }
 ```
 
-NOTE: Keys on a keyboard are not always the same as the character they generate. For example `shift-e` actually types `E` (or `alt-c` types `ç`). Zed allows you to match against either the key and its modifiers or the character it generates. This means you can specify `alt-c` or `ç`, but not `alt-ç`. It is usually better to specify the key and its modifiers, as this will work better on different keyboard layouts.
+The `shift-` modifier can only be used in combination with a letter to indicate the uppercase version. For example `shift-g` matches typing `G`. Although on many keyboards shift is used to type punctuation characters like `(`, the keypress is not considered to be modified and so `shift-(` does not match.
+
+The `alt-` modifier can be used on many layouts to generate a different key. For example on macOS US keyboard the combination `alt-c` types `ç`. You can match against either in your keymap file, though by convention Zed spells this combination as `alt-c`.
+
+It is possible to match against typing a modifier key on its own. For example `shift shift` can be used to implement JetBrains search everywhere shortcut. In this case the binding happens on key release instead of key press.
 
 ### Remapping keys