Fixed destination of _NET_WM_PING reply.

README.md

@@ -72,6 +72,7 @@ GLFW bundles a number of dependencies in the `deps/` directory.
  - [Cocoa] Bugfix: Resizing a window to its minimum size would segfault
  - [Cocoa] Bugfix: Creating or showing a window would make its context current
  - [X11] Bugfix: `glfwInit` would segfault on systems without RandR
+ - [X11] Bugfix: The response to `_NET_WM_PING` was sent to the wrong window
  - [WGL] Removed `GLFW_USE_DWM_SWAP_INTERVAL` compile-time option
  - [WGL] Bugfix: Swap interval was ignored when DWM was enabled
  - [GLX] Added dependency on `libdl` on systems where it provides `dlopen`

src/x11_window.c

@@ -1132,12 +1132,14 @@ static void processEvent(XEvent *event)
                     // The window manager is pinging the application to ensure it's
                     // still responding to events
 
-                    event->xclient.window = _glfw.x11.root;
+                    XEvent reply = *event;
+                    reply.xclient.window = _glfw.x11.root;
+
                     XSendEvent(_glfw.x11.display,
-                               event->xclient.window,
+                               _glfw.x11.root,
                                False,
                                SubstructureNotifyMask | SubstructureRedirectMask,
-                               event);
+                               &reply);
                 }
             }
             else if (event->xclient.message_type == _glfw.x11.XdndEnter)