refresh icons at the same period interval as command_output

Reload icons specified by a filesystem path after command execution
completes. This allows dynamic icons such as album art to update on
the widget refresh interval while preserving the original behavior
for static theme icons.

Author: mrsteve0924

src/panel/widgets/command-output.cpp

@@ -14,7 +14,8 @@
 #include "command-output.hpp"
 
 static sigc::connection label_set_from_command(std::string command_line,
-    Gtk::Label& label)
+    Gtk::Label& label, Gtk::Image* icon = nullptr,
+    const std::string& icon_name = "")
 {
     command_line = "/bin/sh -c \"" + command_line + "\"";
 
@@ -23,6 +24,7 @@ static sigc::connection label_set_from_command(std::string command_line,
     Glib::spawn_async_with_pipes("", Glib::shell_parse_argv(command_line),
         Glib::SpawnFlags::DO_NOT_REAP_CHILD | Glib::SpawnFlags::SEARCH_PATH_FROM_ENVP,
         Glib::SlotSpawnChildSetup{}, &pid, nullptr, &output_fd, nullptr);
+
     return Glib::signal_child_watch().connect([=, &label] (Glib::Pid pid, int exit_status)
     {
         FILE *file = fdopen(output_fd, "r");
@@ -43,6 +45,14 @@ static sigc::connection label_set_from_command(std::string command_line,
         }
 
         label.set_markup(output);
+
+        if (icon &&
+    	    !icon_name.empty() &&
+    	    (icon_name[0] == '/' ||
+     	     icon_name.rfind("~/", 0) == 0))
+	{
+    	    IconProvider::image_set_icon(*icon, icon_name);
+	}
     }, pid);
 }
 
@@ -102,7 +112,7 @@ WfCommandOutputButtons::CommandOutput::CommandOutput(const std::string & name,
     const auto update_output = [=] ()
     {
         command_sig.disconnect();
-        command_sig = label_set_from_command(command, main_label);
+        command_sig = label_set_from_command(command, main_label, &icon, icon_name);
     };
 
     signals.push_back(signal_clicked().connect(update_output));