fix(custom): avoid blocking child reaps in interval worker

Stop the interval worker from waiting synchronously on every pid in pid_children_ before it refreshes the module.

Switching this reap pass to waitpid(..., WNOHANG) keeps the worker responsive when an older event-triggered child is still running, while still removing children that have already exited.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

src/modules/custom.cpp

@@ -2,6 +2,7 @@
 
 #include <spdlog/spdlog.h>
 
+#include <cerrno>
 #include <stdexcept>
 #include <utility>
 
@@ -50,13 +51,21 @@ void waybar::modules::Custom::delayWorker() {
   }
 
   thread_ = [this] {
-    for (int i : this->pid_children_) {
-      int status;
-      waitpid(i, &status, 0);
+    for (auto it = this->pid_children_.begin(); it != this->pid_children_.end();) {
+      int status = 0;
+      const auto pid = static_cast<pid_t>(*it);
+      const auto waited = waitpid(pid, &status, WNOHANG);
+      if (waited == 0) {
+        ++it;
+        continue;
+      }
+      if (waited == -1 && errno != ECHILD) {
+        ++it;
+        continue;
+      }
+      it = this->pid_children_.erase(it);
     }
 
-    this->pid_children_.clear();
-
     bool can_update = true;
     if (config_["exec-if"].isString()) {
       output_ = util::command::execNoRead(config_["exec-if"].asString());