X11: Fix glfwWaitEvents* ignoring joystick events

The data available on the X11 connection may be a reply or an internal
event for an X11 extension.  Previously the check for whether an event
was available for us was done outside waitForEvent.  This prevented data
available on other file descriptors from breaking the outer wait loop.

This commit moves the check for whether an event is available into the
wait functions, where there is enough knowledge to limit the check to
the X11 connection.

Related to #932

README.md

@@ -271,6 +271,7 @@ information on what to include when reporting a bug.
  - [X11] Bugfix: Waiting for events would fail if file descriptor was too large
    (#2024)
  - [X11] Bugfix: Joystick events could lead to busy-waiting (#1872)
+ - [X11] Bugfix: `glfwWaitEvents*` did not continue for joystick events
  - [Wayland] Added dynamic loading of all Wayland libraries
  - [Wayland] Added support for key names via xkbcommon
  - [Wayland] Removed support for `wl_shell` (#1443)

src/x11_window.c

@@ -98,7 +98,14 @@ static GLFWbool waitForData(struct pollfd* fds, nfds_t count, double* timeout)
 static GLFWbool waitForX11Event(double* timeout)
 {
     struct pollfd fd = { ConnectionNumber(_glfw.x11.display), POLLIN };
-    return waitForData(&fd, 1, timeout);
+
+    while (!XPending(_glfw.x11.display))
+    {
+        if (!waitForData(&fd, 1, timeout))
+            return GLFW_FALSE;
+    }
+
+    return GLFW_TRUE;
 }
 
 // Wait for event data to arrive on any event file descriptor
@@ -115,7 +122,19 @@ static GLFWbool waitForAnyEvent(double* timeout)
         fds[count++] = (struct pollfd) { _glfw.linjs.inotify, POLLIN };
 #endif
 
-    return waitForData(fds, count, timeout);
+    while (!XPending(_glfw.x11.display))
+    {
+        if (!waitForData(fds, count, timeout))
+            return GLFW_FALSE;
+
+        for (int i = 1; i < count; i++)
+        {
+            if (fds[i].revents & POLLIN)
+                return GLFW_TRUE;
+        }
+    }
+
+    return GLFW_TRUE;
 }
 
 // Waits until a VisibilityNotify event arrives for the specified window or the
@@ -2794,20 +2813,13 @@ void _glfwPollEventsX11(void)
 
 void _glfwWaitEventsX11(void)
 {
-    while (!XPending(_glfw.x11.display))
-        waitForAnyEvent(NULL);
-
+    waitForAnyEvent(NULL);
     _glfwPollEventsX11();
 }
 
 void _glfwWaitEventsTimeoutX11(double timeout)
 {
-    while (!XPending(_glfw.x11.display))
-    {
-        if (!waitForAnyEvent(&timeout))
-            break;
-    }
-
+    waitForAnyEvent(&timeout);
     _glfwPollEventsX11();
 }