expose main-loop file descriptor hooks

plugins/python/python.py

@@ -304,6 +304,28 @@ def _on_timer_hook(userdata):
     return 0
 
 
+@ffi.def_extern()
+def _on_fd_hook(fd, flags, userdata):
+    hook = ffi.from_handle(userdata)
+    keep = False
+    try:
+        keep = bool(hook.callback(fd, flags, hook.userdata))
+    except Exception:
+        traceback.print_exc()
+    if not keep:
+        # The C watch removes itself on return; do not unhook it a second time.
+        try:
+            hook.is_unload = True
+            # from_handle() yields a weak proxy: id(proxy) is not id(Hook).
+            for existing in hook.plugin.hooks:
+                if existing == hook:
+                    hook.plugin.remove_hook(id(existing))
+                    break
+        except ReferenceError:
+            pass  # the callback already unhooked itself
+    return int(keep)
+
+
 @ffi.def_extern()
 def _on_say_command(word, word_eol, userdata):
     """Handle input in the special >>python<< tab.