On macOS, fix assertion when pressing Fn key

CHANGELOG.md

@@ -16,6 +16,7 @@ Unreleased` header.
 - On Windows, fix `set_control_flow` in `AboutToWait` not being taken in account.
 - On macOS, send a `Resized` event after each `ScaleFactorChanged` event.
 - On Wayland, fix `wl_surface` being destroyed before associated objects.
+- On macOS, fix assertion when pressing `Fn` key.
 
 # 0.29.3
 

src/platform_impl/macos/event.rs

@@ -156,13 +156,11 @@ pub(crate) fn create_key_event(
             // Also not checking if this is a release event because then this issue would
             // still affect the key release.
             Some(text) if !has_ctrl => Key::Character(text.clone()),
-            _ => {
+            _ => match key_without_modifiers.as_ref() {
-                let modifierless_chars = match key_without_modifiers.as_ref() {
+                Key::Character(ch) => get_logical_key_char(ns_event, ch),
-                    Key::Character(ch) => ch,
+                // Don't try to get text for events which likely don't have it.
-                    _ => "",
+                _ => key_without_modifiers.clone(),
-                };
+            },
-                get_logical_key_char(ns_event, modifierless_chars)
-            }
         };
 
         (logical_key, key_without_modifiers)

src/platform_impl/macos/view.rs

@@ -74,8 +74,8 @@ enum ImeState {
 bitflags! {
     #[derive(Debug, Clone, Copy, PartialEq)]
     struct ModLocationMask: u8 {
-        const LEFT = 1;
+        const LEFT     = 0b0001;
-        const RIGHT = 2;
+        const RIGHT    = 0b0010;
     }
 }
 impl ModLocationMask {
@@ -88,13 +88,13 @@ impl ModLocationMask {
     }
 }
 
-fn key_to_modifier(key: &Key) -> ModifiersState {
+fn key_to_modifier(key: &Key) -> Option<ModifiersState> {
     match key {
-        Key::Named(NamedKey::Alt) => ModifiersState::ALT,
+        Key::Named(NamedKey::Alt) => Some(ModifiersState::ALT),
-        Key::Named(NamedKey::Control) => ModifiersState::CONTROL,
+        Key::Named(NamedKey::Control) => Some(ModifiersState::CONTROL),
-        Key::Named(NamedKey::Super) => ModifiersState::SUPER,
+        Key::Named(NamedKey::Super) => Some(ModifiersState::SUPER),
-        Key::Named(NamedKey::Shift) => ModifiersState::SHIFT,
+        Key::Named(NamedKey::Shift) => Some(ModifiersState::SHIFT),
-        _ => unreachable!(),
+        _ => None,
     }
 }
 
@@ -924,6 +924,7 @@ impl WinitView {
         // event, thus we can't generate regular presses based on that. The `ModifiersChanged`
         // later will work though, since the flags are attached to the event and contain valid
         // information.
+        'send_event: {
             if is_flags_changed_event && ns_event.key_code() != 0 {
                 let scancode = ns_event.key_code();
                 let physical_key = PhysicalKey::from_scancode(scancode as u32);
@@ -932,7 +933,11 @@ impl WinitView {
                 let mut event = create_key_event(ns_event, false, false, Some(physical_key));
 
                 let key = code_to_key(physical_key, scancode);
-            let event_modifier = key_to_modifier(&key);
+                // Ignore processing of unkown modifiers because we can't determine whether
+                // it was pressed or release reliably.
+                let Some(event_modifier) = key_to_modifier(&key) else {
+                    break 'send_event;
+                };
                 event.physical_key = physical_key;
                 event.logical_key = key.clone();
                 event.location = code_to_location(physical_key);
@@ -974,7 +979,6 @@ impl WinitView {
                     }
                     *phys_mod = ModLocationMask::empty();
                 } else {
-                // is_active
                     if *phys_mod == location_mask {
                         // Here we hit a contradiction:
                         // The modifier state was "changed" to active,
@@ -1011,6 +1015,7 @@ impl WinitView {
                     self.queue_event(event);
                 }
             }
+        }
 
         if prev_modifiers == current_modifiers {
             return;