Cleanup of XKB detection code.

src/x11_window.c

@@ -615,6 +615,36 @@ static void processEvent(XEvent *event)
             const int key = translateKey(event->xkey.keycode);
             const int mods = translateState(event->xkey.state);
 
+            if (!_glfw.x11.xkb.detectable)
+            {
+                // XKB detectable key repeat is not supported on this server
+                // For key repeats we will get KeyRelease/KeyPress pairs with
+                // similar or identical time stamps.  User selected key repeat
+                // filtering is handled in _glfwInputKey/_glfwInputChar.
+                if (XEventsQueued(_glfw.x11.display, QueuedAfterReading))
+                {
+                    XEvent nextEvent;
+                    XPeekEvent(_glfw.x11.display, &nextEvent);
+
+                    if (nextEvent.type == KeyPress &&
+                        nextEvent.xkey.window == event->xkey.window &&
+                        nextEvent.xkey.keycode == event->xkey.keycode)
+                    {
+                        // This last check is a hack to work around key repeats
+                        // leaking through due to some sort of time drift
+                        // Toshiyuki Takahashi can press a button 16 times per
+                        // second so it's fairly safe to assume that no human is
+                        // pressing the key 50 times per second (value is ms)
+                        if ((nextEvent.xkey.time - event->xkey.time) < 20)
+                        {
+                            // This is a server-generated key repeat event
+                            // Do not report anything for this event
+                            break;
+                        }
+                    }
+                }
+            }
+
             _glfwInputKey(window, key, event->xkey.keycode, GLFW_RELEASE, mods);
             break;
         }