From faf331fdaddb690e1020f6af680c6cdced1c8f92 Mon Sep 17 00:00:00 2001
From: Daniel Rainer <daniel.rainer@localhost>
Date: Fri, 10 Apr 2026 19:12:52 +0200
Subject: [PATCH] refactor: use macro for special key char def

Reduce verbosity of const definitions. Define a dedicated const for the
base of the special key encoding range. This range is 256 bytes wide, so
by defining consts via an u8 offset from the base, we can guarantee that
the consts fall into the allocated range. Ideally, we would also check
for collisions, but Rust's const capabilities don't allow for that as
far as I'm aware.

Having `SPECIAL_KEY_ENCODE_BASE` in the `rust-widestring` crate allows
getting rid of the dependency on `key::Backspace` in the
`fish_reserved_codepoint` function, which unblocks code extraction.

Part of #12625
---
 crates/widestring/src/lib.rs |  3 +-
 src/key.rs                   | 67 +++++++++++++++++++++++-------------
 2 files changed, 45 insertions(+), 25 deletions(-)

diff --git a/crates/widestring/src/lib.rs b/crates/widestring/src/lib.rs
index 1efc34b5d..86ad45e3f 100644
--- a/crates/widestring/src/lib.rs
+++ b/crates/widestring/src/lib.rs
@@ -16,6 +16,7 @@ pub mod prelude {
 /// The character to use where the text has been truncated.
 pub const ELLIPSIS_CHAR: char = '\u{2026}'; // ('…')
 
+pub const SPECIAL_KEY_ENCODE_BASE: char = '\u{F500}';
 // These are in the Unicode private-use range. We really shouldn't use this
 // range but have little choice in the matter given how our lexer/parser works.
 // We can't use non-characters for these two ranges because there are only 66 of
@@ -28,7 +29,7 @@ pub mod prelude {
 // Note: We don't use the highest 8 bit range (0xF800 - 0xF8FF) because we know
 // of at least one use of a codepoint in that range: the Apple symbol (0xF8FF)
 // on Mac OS X. See http://www.unicode.org/faq/private_use.html.
-pub const ENCODE_DIRECT_BASE: char = '\u{F600}';
+pub const ENCODE_DIRECT_BASE: char = char_offset(SPECIAL_KEY_ENCODE_BASE, 256);
 pub const ENCODE_DIRECT_END: char = char_offset(ENCODE_DIRECT_BASE, 256);
 
 /// Encode a literal byte in a UTF-32 character. This is required for e.g. the echo builtin, whose
diff --git a/src/key.rs b/src/key.rs
index ec65cab26..adc937d06 100644
--- a/src/key.rs
+++ b/src/key.rs
@@ -7,31 +7,50 @@
 use fish_common::{EscapeFlags, EscapeStringStyle};
 use fish_fallback::fish_wcwidth;
 use fish_feature_flags::{FeatureFlag, feature_test};
-use fish_widestring::{L, WExt as _, WString, decode_byte_from_char, wstr};
+use fish_widestring::{
+    L, SPECIAL_KEY_ENCODE_BASE, WExt as _, WString, char_offset, decode_byte_from_char, wstr,
+};
 
-pub(crate) const Backspace: char = '\u{F500}'; // below ENCODE_DIRECT_BASE
-pub(crate) const Delete: char = '\u{F501}';
-pub(crate) const Escape: char = '\u{F502}';
-pub(crate) const Enter: char = '\u{F503}';
-pub(crate) const Up: char = '\u{F504}';
-pub(crate) const Down: char = '\u{F505}';
-pub(crate) const Left: char = '\u{F506}';
-pub(crate) const Right: char = '\u{F507}';
-pub(crate) const PageUp: char = '\u{F508}';
-pub(crate) const PageDown: char = '\u{F509}';
-pub(crate) const Home: char = '\u{F50A}';
-pub(crate) const End: char = '\u{F50B}';
-pub(crate) const Insert: char = '\u{F50C}';
-pub(crate) const Tab: char = '\u{F50D}';
-pub(crate) const Space: char = '\u{F50E}';
-pub(crate) const Menu: char = '\u{F50F}';
-pub(crate) const PrintScreen: char = '\u{F510}';
-pub(crate) const MAX_FUNCTION_KEY: u32 = 12;
-pub(crate) fn function_key(n: u32) -> char {
-    assert!((1..=MAX_FUNCTION_KEY).contains(&n));
-    char::from_u32(u32::from('\u{F5FF}') - MAX_FUNCTION_KEY + (n - 1)).unwrap()
+const fn special_key_char(offset: u8) -> char {
+    // TODO: use `u32::from(offset)` once that's available in const fn
+    char_offset(SPECIAL_KEY_ENCODE_BASE, offset as u32)
+}
+
+macro_rules! define_special_keys {
+    ($($key_name:ident: $offset:expr)*) => {
+        $(
+            pub(crate) const $key_name: char = special_key_char($offset);
+        )*
+    };
+}
+
+define_special_keys! {
+    Backspace: 0
+    Delete: 1
+    Escape: 2
+    Enter: 3
+    Up: 4
+    Down: 5
+    Left: 6
+    Right: 7
+    PageUp: 8
+    PageDown: 9
+    Home: 10
+    End: 11
+    Insert: 12
+    Tab: 13
+    Space: 14
+    Menu: 15
+    PrintScreen: 16
+
+    Invalid: 255
+}
+
+pub(crate) const MAX_FUNCTION_KEY: u8 = 12;
+pub(crate) fn function_key(n: u8) -> char {
+    assert!((1..=MAX_FUNCTION_KEY).contains(&n));
+    special_key_char(254 - MAX_FUNCTION_KEY + n)
 }
-pub(crate) const Invalid: char = '\u{F5FF}';
 
 pub(crate) const KEY_NAMES: &[(char, &wstr)] = &[
     ('-', L!("minus")),
@@ -297,7 +316,7 @@ pub(crate) fn parse_keys(value: &wstr) -> Result<Vec<Key>, WString> {
                 let num = key_name.strip_prefix('f').unwrap();
                 let codepoint = match fish_wcstoul(num) {
                     Ok(n) if (1..=u64::from(MAX_FUNCTION_KEY)).contains(&n) => {
-                        function_key(u32::try_from(n).unwrap())
+                        function_key(u8::try_from(n).unwrap())
                     }
                     _ => {
                         return Err(wgettext_fmt!(