From 7b9cafd528ab82311ca676a4d35796fb9c9ccbf1 Mon Sep 17 00:00:00 2001
From: Ruben Vereecken <ruben@20tech.io>
Date: Wed, 22 Apr 2026 09:39:12 +0100
Subject: [PATCH] XInput keyboard: dispatch via XTestFakeDeviceKeyEvent

GDK3 (used by Firefox/Camoufox) selects XI2 for the seat keyboard at
startup and ignores core-protocol KeyPress events. XTestFakeKeyEvent
produces core events, so typed characters from the Neko viewer silently
never reach Firefox.

Fix: discover the "Virtual core XTEST keyboard" XInput1 device at
startup, cache it, and dispatch key events via XTestFakeDeviceKeyEvent
which goes through the XI path. Falls back to the old core XTest path
if the device isn't found.

Requires -lXi (libxi-dev at build, libxi6 at runtime).
---
 server/pkg/xorg/xorg.c  | 56 +++++++++++++++++++++++++++++++++++++++--
 server/pkg/xorg/xorg.go |  2 +-
 server/pkg/xorg/xorg.h  |  1 +
 3 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/server/pkg/xorg/xorg.c b/server/pkg/xorg/xorg.c
index e2c04dcc2..a796e3748 100644
--- a/server/pkg/xorg/xorg.c
+++ b/server/pkg/xorg/xorg.c
@@ -1,17 +1,61 @@
 #include "xorg.h"
 
 static Display *DISPLAY = NULL;
+// XTEST virtual keyboard XInput1 device handle — cached so XKey() can dispatch
+// via XTestFakeDeviceKeyEvent (XI-aware) instead of XTestFakeKeyEvent (core-only).
+// GDK3 selects XI2 for the seat keyboard at startup and ignores core-protocol
+// KeyPress events, so core XTest silently drops every key into Firefox.
+static XDevice *XTEST_KEYBOARD = NULL;
 
 Display *getXDisplay(void) {
   return DISPLAY;
 }
 
+// Discover and open the "Virtual core XTEST keyboard" XInput1 device.
+// Must be called after XOpenDisplay. Returns NULL on failure; callers fall back
+// to XTestFakeKeyEvent (which doesn't work against modern GDK3, but at least
+// doesn't crash).
+static XDevice *openXTestKeyboardDevice(Display *display) {
+  int ndev = 0;
+  XDeviceInfo *devs = XListInputDevices(display, &ndev);
+  if (devs == NULL)
+    return NULL;
+
+  XDevice *dev = NULL;
+  for (int i = 0; i < ndev; i++) {
+    if (devs[i].name == NULL)
+      continue;
+    // Exact match against the XTEST extension's virtual keyboard. X.Org spawns
+    // this device at server startup. Use strstr to tolerate naming variations
+    // across X servers — e.g. "Virtual core XTEST keyboard" vs "XTEST keyboard".
+    if (strstr(devs[i].name, "XTEST") != NULL && strstr(devs[i].name, "keyboard") != NULL) {
+      dev = XOpenDevice(display, devs[i].id);
+      if (dev != NULL)
+        break;
+    }
+  }
+
+  XFreeDeviceList(devs);
+  return dev;
+}
+
 int XDisplayOpen(char *name) {
   DISPLAY = XOpenDisplay(name);
-  return DISPLAY == NULL;
+  if (DISPLAY == NULL)
+    return 1;
+
+  // Best-effort: cache the XTEST keyboard device. If this fails we still return
+  // success — XKey falls back to core XTest, which at least preserves the old
+  // behaviour (broken, but not a crash).
+  XTEST_KEYBOARD = openXTestKeyboardDevice(DISPLAY);
+  return 0;
 }
 
 void XDisplayClose(void) {
+  if (XTEST_KEYBOARD != NULL) {
+    XCloseDevice(DISPLAY, XTEST_KEYBOARD);
+    XTEST_KEYBOARD = NULL;
+  }
   XCloseDisplay(DISPLAY);
 }
 
@@ -225,7 +269,15 @@ void XKey(KeySym keysym, int down) {
   if (down)
     XKeyEntryAdd(keysym, keycode);
 
-  XTestFakeKeyEvent(display, keycode, down, CurrentTime);
+  // Prefer XTestFakeDeviceKeyEvent: it dispatches via the XTEST XInput device,
+  // so XI2 listeners (GDK3 inside Firefox) actually receive the event. The core
+  // XTestFakeKeyEvent path produces core-protocol events that GDK3's XI2 keyboard
+  // path silently drops.
+  if (XTEST_KEYBOARD != NULL) {
+    XTestFakeDeviceKeyEvent(display, XTEST_KEYBOARD, keycode, down, NULL, 0, CurrentTime);
+  } else {
+    XTestFakeKeyEvent(display, keycode, down, CurrentTime);
+  }
   XSync(display, 0);
 }
 
diff --git a/server/pkg/xorg/xorg.go b/server/pkg/xorg/xorg.go
index a6a387995..33447391a 100644
--- a/server/pkg/xorg/xorg.go
+++ b/server/pkg/xorg/xorg.go
@@ -1,7 +1,7 @@
 package xorg
 
 /*
-#cgo LDFLAGS: -lX11 -lXrandr -lXtst -lXfixes -lxcvt
+#cgo LDFLAGS: -lX11 -lXrandr -lXtst -lXfixes -lXi -lxcvt
 
 #include "xorg.h"
 */
diff --git a/server/pkg/xorg/xorg.h b/server/pkg/xorg/xorg.h
index 781bcef81..833bdda79 100644
--- a/server/pkg/xorg/xorg.h
+++ b/server/pkg/xorg/xorg.h
@@ -6,6 +6,7 @@
 #include <X11/extensions/Xrandr.h>
 #include <X11/extensions/XTest.h>
 #include <X11/extensions/Xfixes.h>
+#include <X11/extensions/XInput.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>