From d0ce905d1bc3fff6e9ca8e61e589f5e3d2219fbb Mon Sep 17 00:00:00 2001
From: q3k <q3k@q3k.org>
Date: Wed, 21 May 2025 12:54:38 +0200
Subject: [PATCH] Do not respond to right alt (Alt Gr) keyboard events.
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On some keyboard layouts (eg. pl) the right alt key (a.k.a. Alt Gr) is
used in combination with letters to type special characters, eg. AltGr-C
makes a 'ć' on a pl keyboard layout.

At least on Firefox on macOS it seems like events that would otherwise
result in a special character still get passed to keydown and friends.
This means that if etherpad handles alt-c, it might swallow someone's
intent to type in 'ć' and instead open up the chat window.

This could arguably be a bug in Firefox or macOS, as the same doesn't
happen in Firefox on Linux/X11. But before I bring the discussion to a
wider audience I'd like to at least make the issue go away at etherpad
level.
---
 src/static/js/ace2_inner.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/static/js/ace2_inner.ts b/src/static/js/ace2_inner.ts
index 709840f80..654042d69 100644
--- a/src/static/js/ace2_inner.ts
+++ b/src/static/js/ace2_inner.ts
@@ -2526,7 +2526,15 @@ function Ace2Inner(editorInfo, cssManagers) {
 
   const handleKeyEvent = (evt) => {
     if (!isEditable) return;
-    const {type, charCode, keyCode, which, altKey, shiftKey} = evt;
+    const {type, charCode, keyCode, which, shiftKey} = evt;
+
+    // If DOM3 support exists, ensure that the left ALT key was pressed. This
+    // allows keyboard layouts with special meaning for right-alt-char to
+    // continue working on Firefox / macOS.
+    let altKey = evt.altKey;
+    if (evt.originalEvent.location !== undefined) {
+        altKey = altKey && evt.originalEvent.location === evt.originalEvent.DOM_KEY_LOCATION_LEFT;
+    }
 
     // Don't take action based on modifier keys going up and down.
     // Modifier keys do not generate "keypress" events.