From 9b9bfeb02d43b4f6d2946b8ba3455b9062dd1aac Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 22 Mar 2026 02:09:42 +0000
Subject: [PATCH] Fix XI_BadDevice crash on USB device disconnect (#9723)

When a USB HID device (keyboard/mouse) is disconnected, X11 fires an
XI_HierarchyChanged event, which triggers read_xi_scroll_devices().
That function calls XIGetProperty() on devices from XIQueryDevice().
There is a race condition: if a device is removed between these calls,
X11 generates an XI_BadDevice error. Without a custom error handler, the
default X11 handler calls exit(), killing kitty.

Fix: wrap the device query loop in read_xi_scroll_devices() with
_glfwGrabErrorHandlerX11() / _glfwReleaseErrorHandlerX11() so that any
XI_BadDevice error is captured by kitty's own handler rather than the
default fatal one.

Fixes #9723
Fixes #9724
---
 glfw/x11_init.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/glfw/x11_init.c b/glfw/x11_init.c
index fd09fec56..44385df0e 100644
--- a/glfw/x11_init.c
+++ b/glfw/x11_init.c
@@ -156,8 +156,11 @@ read_xi_scroll_devices(void) {
     if (!xi.available || xi.major < 2 || (xi.major == 2 && xi.minor < 1) || !xi.LIBINPUT_SCROLL_METHOD_ENABLED) return;
 #undef xi
     int deviceCount;
+    // Grab the error handler to prevent XI_BadDevice errors from killing kitty
+    // when a device is removed between XIQueryDevice and XIGetProperty calls.
+    _glfwGrabErrorHandlerX11();
     XIDeviceInfo* devices = XIQueryDevice(_glfw.x11.display, XIAllDevices, &deviceCount);
-    if (!devices) return;
+    if (!devices) { _glfwReleaseErrorHandlerX11(); return; }
     for (int i = 0; i < deviceCount; i++) {
         XIDeviceInfo* device = &devices[i];
         if (device->use == XIMasterPointer) _glfw.x11.xi.master_pointer_id = device->deviceid;
@@ -251,6 +254,7 @@ read_xi_scroll_devices(void) {
         }
     }
     XIFreeDeviceInfo(devices);
+    _glfwReleaseErrorHandlerX11();
 }
 
 // Look for and initialize supported X11 extensions