From ca1a98e7a2d4e029fa3ece888221d9c23a093ec3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Camilla=20L=C3=B6wy?= <elmindreda@elmindreda.org>
Date: Tue, 1 Feb 2022 22:05:55 +0100
Subject: [PATCH] X11: Fix event polling when event fd > 1023

This replaces select with poll for checking for data on event file
descriptors, as select cannot handle file descriptors larger than 1023.

Closes #2024

(cherry picked from commit d3e4fcf8b7608e7b6f6cf1c102b1e28c478f5a6c)
---
 CONTRIBUTORS.md  |  1 +
 README.md        |  2 ++
 src/x11_window.c | 30 ++++++++++++------------------
 3 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 4526e5b2..b35d2428 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -81,6 +81,7 @@ video tutorials.
  - Paul Holden
  - Warren Hu
  - Charles Huber
+ - illustris
  - InKryption
  - IntellectualKitty
  - Aaron Jacobs
diff --git a/README.md b/README.md
index d0deac37..da0fc03d 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,8 @@ information on what to include when reporting a bug.
 
  - [Cocoa] Bugfix: `kUTTypeURL` was deprecated in macOS 12.0 (#2003)
  - [X11] Bugfix: Dynamic loading on OpenBSD failed due to soname differences
+ - [X11] Bugfix: Waiting for events would fail if file descriptor was too large
+   (#2024)
  - [Wayland] Added support for key names via xkbcommon
  - [Wayland] Bugfix: Key repeat could lead to a race condition (#1710)
  - [Wayland] Bugfix: Activating a window would emit two input focus events
diff --git a/src/x11_window.c b/src/x11_window.c
index 356572d8..f328c297 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -32,7 +32,7 @@
 #include <X11/cursorfont.h>
 #include <X11/Xmd.h>
 
-#include <sys/select.h>
+#include <poll.h>
 
 #include <string.h>
 #include <stdio.h>
@@ -57,37 +57,31 @@
 #define _GLFW_XDND_VERSION 5
 
 
-// Wait for data to arrive using select
+// Wait for event data to arrive on any relevant file descriptor
 // This avoids blocking other threads via the per-display Xlib lock that also
 // covers GLX functions
 //
 static GLFWbool waitForEvent(double* timeout)
 {
-    fd_set fds;
-    const int fd = ConnectionNumber(_glfw.x11.display);
-    int count = fd + 1;
-
-#if defined(__linux__)
-    if (_glfw.linjs.inotify > fd)
-        count = _glfw.linjs.inotify + 1;
-#endif
     for (;;)
     {
-        FD_ZERO(&fds);
-        FD_SET(fd, &fds);
+        nfds_t count = 1;
+        struct pollfd fds[2] =
+        {
+            { ConnectionNumber(_glfw.x11.display), POLLIN }
+        };
+
 #if defined(__linux__)
         if (_glfw.linjs.inotify > 0)
-            FD_SET(_glfw.linjs.inotify, &fds);
+            fds[count++] = (struct pollfd) { _glfw.linjs.inotify, POLLIN };
 #endif
 
         if (timeout)
         {
-            const long seconds = (long) *timeout;
-            const long microseconds = (long) ((*timeout - seconds) * 1e6);
-            struct timeval tv = { seconds, microseconds };
+            const int milliseconds = (int) (*timeout * 1e3);
             const uint64_t base = _glfwPlatformGetTimerValue();
 
-            const int result = select(count, &fds, NULL, NULL, &tv);
+            const int result = poll(fds, count, milliseconds);
             const int error = errno;
 
             *timeout -= (_glfwPlatformGetTimerValue() - base) /
@@ -98,7 +92,7 @@ static GLFWbool waitForEvent(double* timeout)
             if ((result == -1 && error == EINTR) || *timeout <= 0.0)
                 return GLFW_FALSE;
         }
-        else if (select(count, &fds, NULL, NULL, NULL) != -1 || errno != EINTR)
+        else if (poll(fds, count, -1) != -1 || errno != EINTR)
             return GLFW_TRUE;
     }
 }