Change remove_event logic

We defer the removal of entries until after the poll loop has finished.
Otherwise we may end up adjusting the poll array while we're still
reading from it, causing us to skip events.

swaybar/event_loop.c

@@ -72,24 +72,18 @@ void add_event(int fd, short mask,
 }
 
 bool remove_event(int fd) {
-	int index = -1;
+	/*
+	 * Instead of removing events immediately, we mark them for deletion
+	 * and clean them up later. This is so we can call remove_event inside
+	 * an event callback safely.
+	 */
 	for (int i = 0; i < event_loop.fds.length; ++i) {
 		if (event_loop.fds.items[i].fd == fd) {
-			index = i;
+			event_loop.fds.items[i].fd = -1;
+			return true;
 		}
 	}
-	if (index != -1) {
-		free(event_loop.items->items[index]);
-
-		--event_loop.fds.length;
-		memmove(&event_loop.fds.items[index], &event_loop.fds.items[index + 1],
-				sizeof(struct pollfd) * event_loop.fds.length - index);
-
-		list_del(event_loop.items, index);
-		return true;
-	} else {
-		return false;
-	}
+	return false;
 }
 
 static int timer_item_timer_cmp(const void *_timer_item, const void *_timer) {
@@ -126,6 +120,21 @@ void event_loop_poll() {
 		}
 	}
 
+	// Cleanup removed events
+	int end = 0;
+	int length = event_loop.fds.length;
+	for (int i = 0; i < length; ++i) {
+		if (event_loop.fds.items[i].fd == -1) {
+			free(event_loop.items->items[i]);
+			list_del(event_loop.items, i);
+			--event_loop.fds.length;
+		} else if (end != i) {
+			event_loop.fds.items[end++] = event_loop.fds.items[i];
+		} else {
+			end = i + 1;
+		}
+	}
+
 	// check timers
 	// not tested, but seems to work
 	for (int i = 0; i < event_loop.timers->length; ++i) {